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View Full Version : Valves, I think I'm starting to understand what the fuss is about.



HighFidelityGuy
09-03-2011, 22:47
Yesterday I took delivery of a WD KEL84 amp which I purchased off Martin (smurfbrain). Up until now I've never used a valve amp in my system other than a Chinese valve preamp which was a bit crap. :lol: I've heard some very nice valve amps in other systems and liked what I heard, so I decided the KEL84 seemed like a inexpensive but well respected amp to try out.

I wasn't really sure what to expect from the KEL84 in my system as my speakers are fairly difficult to drive and I listed to a lot of powerful, dynamic music. So in switching between my 550W solid state monoblocks to a tiny 15W valve amp I was at least expecting to have less bass punch and extension and less dynamics. I was quite wrong. In some ways the KEL84 seems to provide more punch and just as much bass extension. It does perhaps lack the level of dynamics that my monoblocks are capable of but there's not a huge difference if I'm honest.

I was half expecting the valves to improve the midrange over my monoblocks seen as this is one area that valve are supposed to excel. The KEL84 definitely provided a different tonal balance in the midrange, with male voices seeming more detailed and emotive. Stereo imaging in this department was also improved. There is however a little more warmth in the lower midrange which I'm not sure whether I like. This warmth reminds me of difference between my Alps Blue Velvet based passive attenuator and my LDR based attenuator. As I plan to use the KEL84 with my LDR attenuator I think that removing the volume control and input selector from the KEL84 will yield some improvements in the midrange.

As I hear a lot of people saying that valve amps sound less bright/harsh that solid state amps I was expecting the KEL84 to be more subdued in the treble department. This doesn't seem to be the case but the treble does seem to be slightly more airy and possibly less fatiguing, although I didn't really find my solid state amps fatiguing. The only negative in this area seems to be that the timing seems a little off on some fast sparkly cymbal passages. I have one track where every hi-hat tish constantly swaps from left to right on every hit. This channel swapping is very obvious with my monoblocks whereas the KEL84 seems to smear the effect. This is probably another area that will improve once the amp is converted to a power amp. If not I guess some better valves may help.

So in summary, I've found the KEL84 to be a very capable amp which can hold it's own against a pair of solid state monoblocks which are technically worth over three times as much based on rrp. While I've found the KEL84 to be slightly lacking in a couple of areas I feel this can be improved on with some very simple tweaks. The main eye opener for me has been that I do seem to be able to drive my speakers off a low powered valve amp with surprisingly good results, with the big surprise being that I actually seem to be getting a better bass sound which is completely opposite to what I expected.

So my first proper valve experience has been a good one and it's given me a taste of what valves have to offer. I like what I'm hearing and I want more. I think I might be a valve convert. :eek: Now look what you've gone and done. :lol:

Thanks again to Martin for packing the amp up so well. :cool:

Ali Tait
10-03-2011, 07:09
Yes, the KEL is a great little amp and a real giant killer. Has yours been modded?

tubehunter
10-03-2011, 07:14
Just a little;)

John
10-03-2011, 08:15
Welcome to the world of valves. A lot of us really like them

HighFidelityGuy
10-03-2011, 09:22
Yes, the KEL is a great little amp and a real giant killer. Has yours been modded?

I was going to say "I don't think so as Martin didn't mention it". However it seems Duncan (who built it) knows otherwise. :eyebrows:


Just a little;)

Hi Duncan. Would you be able to list the mods you did please? :)


Welcome to the world of valves. A lot of us really like them

Cheers John. I think I'm starting to like them too. I need to do some better A/B testing between this amp and my solid state's. I think I'll get one of Stan's speaker switch boxes so I can do faster switching. That should then give me a more accurate idea of the areas where they differ. I can then find out if any extra mods or valve upgrades would be worthwhile. It should be an interesting project. :)

SPS
10-03-2011, 09:53
the kel84 is not a bad amp, most el84 based amps have that sound, its quite similar to the leak stereo 20 in many ways.. very nice

my view... is the valve amp is will be letting more of the finer detail through.

and in my view, that results in more of the harmonics being heard.. that tends to sweeten the sound and make it more musical, and can give more a room filling sound stage. What can sound like better seperation with the SS amp, could be due to the higher harmonics being missed, when they should bring the sounds together more.
in saying that, in most cases there should still be pinpoint seperation of all the sounds within the music, and a sense of space and air,

That in turn can change what you hear and how it sounds,
my 1st valve amp was a single ended el84 amp driving yam ns1000's

I quickly sold a 3 months old quite expensive SS pre/ power amp. and a few months later changed to higher effeciency speakers.

back then i used a swich box to change over the amps and speakers.. when i though 'that not right' i swapped the amp over.. the valve's won every time

Many modern solid state amps tend have a slight grey/ grainy sound , after that the valve amp tends to sound like there's something missing at first... until you get used to it.
When you do get used to it, I hard to believe why any one would want a SS amp.... but the strange thing is when one lives with it, its not heard. ...I've been there !

This point was demonstrated to mark grant the other week when he brought some kit round. your not too far away from me.. your very welcome to do the same.

its a slipery slope... and everyone has different tastes.
best of luck with it..

anthonyTD
10-03-2011, 10:17
hi Dave,
mono block amps whether valve or solid state will almost always give a better definition on right and left source recorded information than a stereo unit that shares the same power supply and chassis etc, other than that i think from what you have desribed, you have had a positive and pleasant surprise with your first adventure into Valve power amps.:)
Anthony,TD...

Clive
10-03-2011, 10:37
Hi Dave,

Our individual sensitivities help us define our views of the sounds and equipment we like or dislike. I'm unfortunately someone who greatly dislikes unnatural or over-emphasised sibilance. I find a great many solidstate amps are harsh in reproducing sibilance. There are other reasons for my liking valve amps but this harshness issue is a big reason for why I don't get on with many solidstate amps, I can hear the effect as soon as I enter a room with music playing. Of course you can get it wrong with valve amps too but that's harder to do.

HighFidelityGuy
10-03-2011, 11:28
my view... is the valve amp is will be letting more of the finer detail through.

and in my view, that results in more of the harmonics being heard.. that tends to sweeten the sound and make it more musical, and can give more a room filling sound stage. What can sound like better seperation with the SS amp, could be due to the higher harmonics being missed, when they should bring the sounds together more.
in saying that, in most cases there should still be pinpoint seperation of all the sounds within the music, and a sense of space and air,


I think you might be right about harmonics etc. I definitely got a sence that the harmonic content was different but I couldn't put my finger on the exact difference. I think I'll be able to tell better once I get the switch box and can switch between the amps quicker. I've heard that the harmonics that valve amps produce are mure musical sounding and more pleasing to the ear. So I guess to a certain extent I need to get used to this difference but at the same time I do like the sound I get from my solid-state's. I think I just need to pin down the differences and then decided which areas of each I prefer. I can then attempt to get the best of both through tweaking..


hi Dave,
mono block amps whether valve or solid state will almost always give a better definition on right and left source recorded information than a stereo unit that shares the same power supply and chassis etc, other than that i think from what you have desribed, you have had a positive and pleasant surprise with your first adventure into Valve power amps.:)
Anthony,TD...

I did suspect that. I do really like the extra channel seperation that monoblocks bring. I'm hoping that some tweaking will improve this area. It may not actual be a big issue, I've so far only noticed the smearing on one dubstep track that I only use for testing bass and chanel seperation. I don't have much music that will really highlight the weakness. So some extra chanel seperation and a wider stereo image would just be a bonus. I've seen some E80CF valves that are supposed to excel in this area, so I might try a pair of them. It's also another area where I think the power amp conversion may help as I think this will reduce crosstalk.

It's definitely been a pleasent supprise so far. I was expecting to have more issues that couldn't be solved without buying new speakers. That would have been a deal breaker as I love my speakers and I can't afford a bigger valve amp yet. Luckily it seems that the weak areas should be relatively easy and inexpensive to improve. So I'm felling quite positive about the whole thing. :)


Hi Dave,

Our individual sensitivities help us define our views of the sounds and equipment we like or dislike. I'm unfortunately someone who greatly dislikes unnatural or over-emphasised sibilance. I find a great many solidstate amps are harsh in reproducing sibilance. There are other reasons for my liking valve amps but this harshness issue is a big reason for why I don't get on with many solidstate amps, I can hear the effect as soon as I enter a room with music playing. Of course you can get it wrong with valve amps too but that's harder to do.

I know what you mean. I also dislike sibilance (although I suspect you are more sensitive to this than me), it gives me a headache. As does nasally or quacky sounding upper midrange and/or harsh treble. I've usually found speakers are to blame for this. Some PA speakers are intolerable in this respect. I guess solid state amps will emphasise this further.

My speakers have a seperate soft dome midrange driver that covers almost the entire vocal range and I find this helps as there's no crossover distortion in that important frequency band. Speakers with a crossover point around 3KHz tend to fall down in this area. That's not something your Bastanis will suffer from though. ;)

Clive
10-03-2011, 12:10
I know what you mean. I also dislike sibilance (although I suspect you are more sensitive to this than me), it gives me a headache. As does nasally or quacky sounding upper midrange and/or harsh treble. I've usually found speakers are to blame for this. Some PA speakers are intolerable in this respect. I guess solid state amps will emphasise this further.

My speakers have a seperate soft dome midrange driver that covers almost the entire vocal range and I find this helps as there's no crossover distortion in that important frequency band. Speakers with a crossover point around 3KHz tend to fall down in this area. That's not something your Bastanis will suffer from though. ;)
There are all sorts of ways of masking the effect, finding the source of it is important as masking isn't the best way. For sure it can be speakers, it's very often also CD players too - actually usually these are the worst culprits. As you say the Bastanis get around the xover are problem very well.

Sibilance annoys me the most when it invades the entire soundstage because it's totally over-blown. I don't get a headache but I do stop listening to music - which is probably why I don't get a headache!

smurfbrain
10-03-2011, 13:59
As far as i remember kel has jensen output caps. Not sure if there were other mods to the amp as I deleted original email from Duncan.:scratch: Surely he will correct me if I'm wrong.
One thing that I have noticed is that once you have properly setup listening room the amp was excellent in details retrieval better than cambridge amp I had.
All valves are almost new so give them a bit of time run in. I have exaggerated number of hours the valves were used. Enjoy:)

tubehunter
10-03-2011, 18:02
Hi Dave


No I didn't build this one, but have built this model before.
The amp is fairly old and I just replaced the psu caps.Think I upgraded them and increased the capacity.

Yes valves are the only valid way of enjoying music.

http://i514.photobucket.com/albums/t350/halx00/IMG_5602.jpg

selfaddict
10-03-2011, 18:14
Nice to hear of you positive experience with the valves. I like the option to modify the sound to suit my taste and the surroundings with valves. I am still a newbie with the valves, but have enjoyed the whole time with big grin in my face. Tube rolling :bulb: rocks

Other thing I have noticed is that I am able to keep on listening different kind of music much longer, I mean hours after hours without becoming fatigued or needing a break. When I have the time I can just flip the records one after another and enjoy the music without concentrating what is missing.

Enjoy.

greenhomeelectronics
10-03-2011, 18:47
I love valves. I got hold of a Yaqin which rekindled my fascination for the "glowing bottle". Even quite a basic amp can produce an atmosphere that many solid state amps just don't seem to have.

Reid Malenfant
10-03-2011, 18:56
Yes valves are the only valid way of enjoying music.
:scratch: :rolleyes:

That is rather a bit of a sweeping statement, perhaps if you had added "imo" it might not get people a bit touchy ;)

Welder
10-03-2011, 19:01
“Yes valves are the only valid way of enjoying music.”

Isatso :rolleyes:

Tim
10-03-2011, 19:02
Yes valves are the only valid way of enjoying music.

http://i514.photobucket.com/albums/t350/halx00/IMG_5602.jpg

See, this picture here has got me convinced I want to try valves - a thing of beauty :)

Marco
10-03-2011, 19:47
Lovely pic, Dunc - you need to make it into your avatar! ;)

Marco.

Ali Tait
10-03-2011, 20:39
I found it very worthwhile changing the coupling caps im my KEL. Easy to do and makes a big difference IMHO. I put ClarityCaps in mine when I had it, and I found them a big improvement. Not expensive either.

anthonyTD
10-03-2011, 21:53
Hi all,
something i feel i have to share my opinion and experience on.
And so my opinion is,,,valves done right and implimented into the right area of the audio reproduction chain ie; power amps and pre's etc, are far more rewarding than most solid state designs as far as musicality etc, however, solid state when done correctly can also be' and are' a god send when used in the enviroment best suited for eg, where would we be as far as modern source equipment is concerned without op amps etc, these devices have opened up a whole new world in terms of us being able to experience new music formats ie; CD, SACD, music streaming etc, etc. in fact these devices are and have been in main stream recording equipment for many decades now, so most of the recordings we listen to and cherish for their quality have indeed been amplified prior to the final mix by many opamps in mixing desks microphone preamps and recording effects etc.
so, i for one am very glad that solid state devices like opamps, bipolar transistors, and mosfets were developed, and as i have stated when used within their optimum roles can and do perform with excelence.
Anthony,TD...

HighFidelityGuy
11-03-2011, 15:42
Hi Dave


No I didn't build this one, but have built this model before.
The amp is fairly old and I just replaced the psu caps.Think I upgraded them and increased the capacity.

Yes valves are the only valid way of enjoying music.

http://i514.photobucket.com/albums/t350/halx00/IMG_5602.jpg

Hi Duncan, thanks for the info. That's a lovely photo. I love the blue glow, very sexy.

I've had a look inside and I can see that it's the original spec with the exception of the power caps. I'm starting to make a list of tweaks starting with the power amp conversion. I'll then probably try new coupling caps.

I noticed that the ECF80's have a non-regulated DC heater supply and the EL84's an AC heater supply. Does anyone think upgrading either of these to regulated DC might provide any benefits? Other than that I've read that the cathode caps can be upgraded along with a few of the other caps. Feedback can also be reduced but I don't know what difference that will make. Then of course I could try upgrading the valves but as the current ones a new I'll probably leave that for a while.

I think I'll just gradually try a few of the above and see what improvements can be made. It should be a good learning process.


I found it very worthwhile changing the coupling caps im my KEL. Easy to do and makes a big difference IMHO. I put ClarityCaps in mine when I had it, and I found them a big improvement. Not expensive either.

Thanks Ali,

I've heard ClarityCaps are supposed to be good. Mundorf Supreme's (non silver) are also supposed to be good vallue and I've seen some Russian Teflon caps on ebay that aren't too expensive. I know Teflon caps are theoretically the best but I don't know if they'll be any better than polyprop's in this application. :scratch:

lurcher
11-03-2011, 16:43
Beware, badly done DC heating can do more harm than good.

anthonyTD
11-03-2011, 16:52
DC heaters should only realy be necesary when the gain of a paticular stage is so high[ phono stages etc] where the AC heater noise/hum can be a problem, beware though as standard DC heating ie; with no means of reversing the voltage polarity can cause premature loss of emision.
output valves in a push-pull design rarely need their heaters DC'd due to natural cancelation of hum within the push-pull operation.
as for coupling caps, if the circuit has been designed properly then polyprop caps should be all thats needed.
Good power supply caps are a must, rectifier diodes can also have quite an impact on sonics.
Anthony,TD...

lurcher
11-03-2011, 17:03
beware though as standard DC heating ie; with no means of reversing the voltage polarity can cause premature loss of emision.

Not saying you are wrong, but how does that occur with an indirectly heated valve?

6.3v was originally the heater voltage for DC heated valves after all (3 Lead Acid cells 2.1 * 3 = 6.3v)

HighFidelityGuy
11-03-2011, 17:09
Thanks chaps. Very interesting stuff.
I understood most of what you said Anthony with the exception of this bits about polarity. I knew there was difference in the way some valve needed to be heated from the point of view of direct vs indirect, current source vs voltage source but I don't understand how polarity comes into this. My knowledge on this subject is quite limited. Would you be able to explain a bit further?

I think all the valves in the KEL84 are indirectly heated. It has 2x ECF80 and 4x EL84. What heating method would you use with these valves?

Here's the schematic (page 6): http://www.world-designs.co.uk/acatalog/kel84.pdf

Cheers. :cool:

Ali Tait
11-03-2011, 18:49
What valves are in it Dave?

HighFidelityGuy
11-03-2011, 19:10
What valves are in it Dave?

See my last post, second paragraph. ;)

Ali Tait
11-03-2011, 19:36
I know what valves are in it, I used to have one!

I meant what make. :lol:

smurfbrain
11-03-2011, 19:46
jj el84, mullard ecf80

HighFidelityGuy
11-03-2011, 19:51
Doh. :doh: Sorry.

ECF80's are Mullards. I'm not sure when they were made.
EL84's are the standard JJ's.

What makes did you find gave the best results?

I fancy trying some E80CF (http://www.watfordvalves.com/product_detail.asp?id=575)'s and maybe some Shuguang Psvane EL84's (http://psvanetube.com/wordpress/?page_id=12&category=8&product_id=4) but they're all a bit pricey. Which I don't mind if they're quite a bit better but that's the bit I don't know. :scratch:

Cheers.

Ali Tait
11-03-2011, 20:10
I had some Valvo e80cf's and I bought a matched set of Philips NOS from Langrex, which I thought were very good without paying silly money for Mullard etc.

anthonyTD
11-03-2011, 22:33
Not saying you are wrong, but how does that occur with an indirectly heated valve?

6.3v was originally the heater voltage for DC heated valves after all (3 Lead Acid cells 2.1 * 3 = 6.3v)

hi Nick,
i was refering to indirectly heated cathode valves the types that are in the amp in question.:)
anyway,,,here is one theory why it is a good idea to have the option of reversing the polarity of DC supplied heaters.

There have been never-ending arguments for valve heater filaments (including output valves) to be supplied with DC rather than AC. High current DC has a disadvantage similar to the Electrolytic corrosion caused by vehicle batteries. Electrolytic corrosion effects cable, connectors and valve filaments resulting in reduced filament life. However, Cathode emission life is less than the reduced life caused by DC corrosion of the filament. Therefore, DC for valve filaments is not a real problem. A simple solution to minimise DC electrolytic corrosion is to switch (reverse) the polarity of the DC to the filaments approx each month

I also have a theory that constantly running a valve heater on one polarity [+ or -] can cause a similar effect as leaving the valve heaters on full power for long intervals without any HT voltage on the anode/plates,[standby mode] ie; a coating is formed that prevents electron flow hence reduced emision.
just my ramblings though.;)

As for directly heated triodes...
Where the cathode is directly heated (the filament has the oxide coatings directly applied), DC operation is mandatory, or hum would be inevitable .however directly heated cathodes will always emit electrons unevenly, because of the voltage gradient across the filament. The most positive end will have the greatest emission, since the negative voltage between cathode and grid is lowest.

Anthony,TD...

Clive
11-03-2011, 22:42
The easy way if you have 2 identical valves is to wire them in opposite polarities and swap the valves every so often.

lurcher
11-03-2011, 22:49
There have been never-ending arguments for valve heater filaments (including output valves) to be supplied with DC rather than AC. High current DC has a disadvantage similar to the Electrolytic corrosion caused by vehicle batteries. Electrolytic corrosion effects cable, connectors and valve filaments resulting in reduced filament life. However, Cathode emission life is less than the reduced life caused by DC corrosion of the filament. Therefore, DC for valve filaments is not a real problem. A simple solution to minimise DC electrolytic corrosion is to switch (reverse) the polarity of the DC to the filaments approx each month


I am not sure we are reading that the same way. To me that seems to be saying that DC heater power will reduce the life of the heater, but it will still be less than the life of the cathode so it doesn't matter. Not how you seem to be reading it as the DC heater supply will reduce the life of the cathode.

anthonyTD
11-03-2011, 23:01
I am not sure we are reading that the same way. To me that seems to be saying that DC heater power will reduce the life of the heater, but it will still be less than the life of the cathode so it doesn't matter. Not how you seem to be reading it as the DC heater supply will reduce the life of the cathode.


hi Nick,
i was refering to indirectly heated cathode valves the types that are in the amp in question.
anyway,,,here is one theory why it is a good idea to have the option of reversing the polarity of DC supplied heaters
:)
Anthony, TD...

anthonyTD
12-03-2011, 10:44
hi Dave,
sorry for deviating [slightly] off topic something that rarely happens here on AOS :eyebrows :eek:
anyway, i think what we are all trying to say is, concentrate on improving on the the things that are imediate, ie; power supply caps, Diodes, coupling caps, bypass caps etc, the AC heaters in this amp should be sufficient as far hum and noise are concerned as long as they are either center tapped or have one end fixed to earth/chassis. better valves are always a choice of the end user, NOS valves [on the whole] do tend to be made better than most of the current production, however, original old stock valves like EL84 etc are becoming very scarce now so dont be surprised if you see for eg Mullard versions fetching upwards of £60-00 each!
hope this helps.
Anthony,TD...

Ali Tait
12-03-2011, 11:26
These might be worth a try, they are cheap and I've read they are good-

http://cgi.ebay.co.uk/EL84-7189-6BQ5-6P14P-NOS-8-pcs-/260750451474?pt=Vintage_Electronics_R2&hash=item3cb5f02312#ht_506wt_1139

HighFidelityGuy
12-03-2011, 13:03
Thanks for all the input and suggestions chaps. You've come up with some very interesting points.

From what's been said I'll definitely stick with AC heaters on the output valves as the standard supply is centre tapped and I can't hear any hum what so ever through the speakers.

On the subject of the input valve DC heaters; I'll definitely upgrade the diodes on this. I've seen a good guide that shows how to do this including a pi filter to keep the correct 6.3V output.

Would there be any benefit to using a regulated supply here instead of the above?

Cheers.

lurcher
12-03-2011, 15:39
I dont think there is enough headroom for a regulator. Maybe if you use low Vf diodes in the bridge.

HighFidelityGuy
12-03-2011, 15:58
I was wondering if this would be suitable: http://www.tentlabs.com/Components/Tubeamp/Tubeheater/index.html

It can can supply 1.5A and the two ECF80's only need <500mA each. So I should have over 500mA headroom.

Do you think this would work and more importantly could it provide an audible benefit over the standard non-regulated DC heater supply?

Cheers.

tubehunter
12-03-2011, 16:21
I think nick means voltage from the 6.3 winding on the transformer.

lurcher
12-03-2011, 16:45
Yes I did, but also yes, that Tent Labs supply would work fine.

Can't say it would make any difference though, I haven't tried it in a kel84. TBH, I never though it suffered from the heater supplies anyway.

Jonboy
12-03-2011, 16:52
Forget Mullards unless you have money burning a hole in your pocket try these (http://cgi.ebay.co.uk/EL84M-RUSSIA-6BQ5-TUBE-VALVE-NOS-MATCHED-PAIR-/390283331716?pt=UK_Consumer_VintageAudio_RL&hash=item5adeb30884) Russians which are very good, i used them in my Leak Stereo 20 to good effect

HighFidelityGuy
12-03-2011, 16:57
Ah, I see. The heater winding on the power transformer is 6A so there should be enough headroom. I think.

The reason I thought of using this is that upgrading the diodes and adding the pi filter is supposed to increase the increase the s/n ratio quite a bit. So I thought if I'm going to change all that I may as well just use this module instead and get regulation on top.

Apparently low loss diodes also help the HT supply but seen as this will increase the voltage would I need to compensate for this?

Cheers.

lurcher
12-03-2011, 18:05
No, it was voltage headroom I meant. 6.3v windings have a peak voltage of 8.9v, a normal silicon bridge will drop about 1.2v, so that leaves 7.7v into the regulator. If you want 6.3v out that only leaves 1.4v across the regulator. Most regulators need 2v across them to regulate. Its doable, and thats what the Tent Labs unit does, but you need to use either a discreet reg, or a LDO regulator and low voltage drop diodes.

HighFidelityGuy
12-03-2011, 18:59
No, it was voltage headroom I meant. 6.3v windings have a peak voltage of 8.9v, a normal silicon bridge will drop about 1.2v, so that leaves 7.7v into the regulator. If you want 6.3v out that only leaves 1.4v across the regulator. Most regulators need 2v across them to regulate. Its doable, and thats what the Tent Labs unit does, but you need to use either a discreet reg, or a LDO regulator and low voltage drop diodes.

I see what you mean. The Tent Labs website says the module will work off a 6.3V heater winding so I guess it should be fine. Although it does seem to suggest that it can only supply 1A like this, so that might not leave enough headroom.

I'll give this some thought.

HighFidelityGuy
15-04-2011, 13:39
It's been a few weeks since I had my first experience with the KEL84, so I thought I'd give a bit of an update on what I've been doing with it.

After doing a lot of research into all the mods available for the KEL84 and some general reading up on valve amp design, I decided that I would see how far I could push it's performance in the hope that I could improve the slightly weak areas when compared against my mono-blocks.

As my KEL84 is an early version it lacks several improvements that were added later and also has a couple of minor design flaws. The flaws are in the wattage ratings of a few resistors which need to be increased. Also on the subject of resistors; I need to swap a couple to convert it into a power amp, I want to swap a few for Mills wirewound's and a few others for Kiwame carbon films. So in the end all the resistors are getting swapped. Some of the grid resistors are also a bit too far away from the valve bases, so I'm going to improve that. I'm hoping these changes will lower the amps distortion and clean up the sound a bit. Other users seem to have found improvements using these resistors, so hopefully I will too.

After that I'm going to swap the orange drop coupling caps for Mundorf Silver/Oil, polystyrene caps for silver mica and Jensen electrolytic bypass caps for Elna Silmic II. I'm hoping these changes improve the tonal balance and detail retrieval. I did a lot of research into coupling caps and the Mundorf Silver/Oil's seemed to be highly regarded as very good but not stupidly expensive like some Teflon caps. I'm hoping their slight brightness will compliment the Kiwame resistor's slight warmth to provide a nice balance. That's the theory anyway.

I'm also going to swap the HT supply caps but I've not decided what to use there yet. Possibly some Panasonic high ripple, low ESR caps. I also can't decide what values to use as there are lots of conflicting opinions on which should be increased and which shouldn't. I'm going to mull this over while I work on the other parts.

I decided to not bother with the Tent regulated heater supply as I couldn't guarantee that it would work properly with the existing heater winding. So I'm going to stick with the upgraded design that WAD recommended that involves swapping the standard diodes with Schottkies and dropping the extra voltage they allow through in a simple pi filter. I'll also swap the HT supply diodes for Schottkies at the same time.

After running the amp in it's standard form for a while I noticed that the mains transformer ran quite hot and made an audible mechanical buzz. So I picked up some silicone tubing off eBay that I'm going to use to make some dampening bushes to reduce the buzz. I don't think the heat of the transformer is a major issue as it's not too bad but I'm going to keep an eye on it. I could probably attach a heatsink using thermal adhesive I guess.

I have most of the parts I need now and I've removed all the old parts from the PCB. So I'm hoping to get the board populated with everything I have over the weekend and finish it all off next week. I'll try to post some photos soon. :cool:

Reid Malenfant
15-04-2011, 13:52
Hi Dave, i think you'll have a very difficult if not impossible job finding Schottky diodes rated high enough (voltage wise) to replace the HT supply diodes ;)

Some kind of Fred would be fine (fast recovery epitaxial diode).

HighFidelityGuy
15-04-2011, 13:55
Hi Dave, i think you'll have a very difficult if not impossible job finding Schottky diodes rated high enough (voltage wise) to replace the HT supply diodes ;)

Really. I'm sure I ordered the ones that WAD recommended. :scratch: Perhaps they're not Schottkies and just some other type of ultra fast diodes. :confused: I'll check my RS order and let you know what I've got......

HighFidelityGuy
15-04-2011, 13:58
Ok, here's what I ordered: LINK (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=625-5357)
And here's the amps schematic: LINK (http://www.world-designs.co.uk/acatalog/kel84.pdf) Page 6

Have I got the right thing? Cheers.

Reid Malenfant
15-04-2011, 14:34
Aye, a FRED :eyebrows: They'll do nicely ;)

In reply to your possible changing of PSU capacitors, if it was me i'd change C1 as that will be subject to the most ripple ;)

lurcher
15-04-2011, 14:59
Yes, as said those will be fine. The confusion was that they are not schottky
But I just noticed that RS now stock the Cree high voltage schottky diodes.

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7027453

I must give them a try.

HighFidelityGuy
15-04-2011, 15:02
Aye, a FRED :eyebrows: They'll do nicely ;)

In reply to your possible changing of PSU capacitors, if it was me i'd change C1 as that will be subject to the most ripple ;)

Awesome, thanks Mark.
I was thinking the same thing with the caps. C1 had already been swapped for a 220uF so I might use a similar capacity to remove extra ripple over the standard 100uF. It's mainly C2 and C3 I can't decide on. I've heard C3 has a bigger impact on the sound than the other two and that a film cap should work well but that would seriously limit the capacity I could use due to space and cost restrictions. Do you have any recommendations on what caps to use in those positions?

My other idea is to use some smaller film caps (maybe around 3uF) after C3, one for each Channel of the amp as close to point B on the schematic as possible. My idea is that it would provide small energy supply close to the area of demand to smooth things out. What do you think to that idea?

Cheers. :cool:

Reid Malenfant
15-04-2011, 15:28
I'm not sure i'd change the value of C3 very much if at all ;) It appears that it's just being fed by a resistor & the circuit along with another bleeding resistor looks to be maintaining a fairly stable DC for the front end. You could bypass the 100uf with something of better quality or go the whole hog & regulate the front end with a discrete voltage regulator using a power Mosfet. As i say though, looking at it as is i'd keep to around 100uf.

That leaves you with C1 & 2, as i have already mentioned C1 will have the largest ripple voltage so that to my mind is the one to focus on in the way of chucking capacitance at it. C2 should be worth bypassing as it directly feeds the output stage..

Just remember i know diddly squat about valves though :eyebrows:

Ali Tait
15-04-2011, 15:30
Dave, just MHO, the Mundorf silver oils are quite good, but I found them a little too much at the top end. If you are prepared to spend a few quid, I'd go for either SCR teflons or AN coppers. These two are the best I've tried so far.

HighFidelityGuy
15-04-2011, 15:51
I'm not sure i'd change the value of C3 very much if at all ;) It appears that it's just being fed by a resistor & the circuit along with another bleeding resistor looks to be maintaining a fairly stable DC for the front end. You could bypass the 100uf with something of better quality or go the whole hog & regulate the front end with a discrete voltage regulator using a power Mosfet. As i say though, looking at it as is i'd keep to around 100uf.

That leaves you with C1 & 2, as i have already mentioned C1 will have the largest ripple voltage so that to my mind is the one to focus on in the way of chucking capacitance at it. C2 should be worth bypassing as it directly feeds the output stage..

Just remember i know diddly squat about valves though :eyebrows:

Ok, thanks Mark. What would you use for bypassing C2?


Dave, just MHO, the Mundorf silver oils are quite good, but I found them a little too much at the top end. If you are prepared to spend a few quid, I'd go for either SCR teflons or AN coppers. These two are the best I've tried so far.

Thanks Ali. I'm slightly worried about the Silver/Oil's sound too bright. I think some people perceive them that way while others think they sound detailed and airy. I guess it also depends on what they're used in. I decided it was worth the risk as they're pretty much at the top of my price range. I've already spent about the same on components as I did on the amp, so I'd prefer not to go any further. I've heard the standard Mundorf Supreme version sounds similar to the Silver/Oil but a bit less bright, so that's a possibility. I was just a bit worried that with the Kiwame resistors and the the warmer sounding caps that I'd end up too much warmth. I guess I'll have to wait and see if my theory works in practice. :)

Reid Malenfant
15-04-2011, 16:01
Some kind of high voltage Polypropylene or similar film capacitor :) Depending on what you can fit in i'd go for 0.47uf or bigger if possible. 500V DC rating or higher to be on the safe side :eyebrows:

HighFidelityGuy
15-04-2011, 16:16
Some kind of high voltage Polypropylene or similar film capacitor :) Depending on what you can fit in i'd go for 0.47uf or bigger if possible. 500V DC rating or higher to be on the safe side :eyebrows:

Thanks Mark. I might look at getting some Solen FastCap's (http://www.falconacoustics.co.uk/alcap-solen-loudspeaker-crossover-network-polypropylene-polyester-polycarbonate-audio-capacitors/capacitors-audio-crossover-nonpolarised-electrolytic-polypropylene-polycarbonate-polythene-01uf-082uf/solen-scr-0-47uf-630v-dc-fastcap-polyprop.html) to experiment with bypassing. Or maybe some Evox-Rifa (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=5441399) Pulse caps. :hmm:I'll have to check on the dimensions.

Ali Tait
15-04-2011, 17:10
Dave, I've found the Takman resistors very good. Cheap too.

Reid Malenfant
15-04-2011, 17:15
I'd go for the Solens out of the two, they are a little more specialised where as the Evox-Rifa are more general purpose as far as i'm aware ;)

I'm sure there are a bucket full more out there though so take your time. Whilst it won't have any audio signal passing directly through it it still one of the most important caps in the amp keeping the voltage on the front end stable.

HighFidelityGuy
16-04-2011, 14:23
Dave, I've found the Takman resistors very good. Cheap too.

Thanks Ali. I've used them before and found them to be good. I'm actually using a couple in this project as I couldn't get Kiwame's in a certain value. I'm also using some tantalum resistors in another place for the same reason.


I'd go for the Solens out of the two, they are a little more specialised where as the Evox-Rifa are more general purpose as far as i'm aware ;)

I'm sure there are a bucket full more out there though so take your time. Whilst it won't have any audio signal passing directly through it it still one of the most important caps in the amp keeping the voltage on the front end stable.

Thanks Mark. I've ordered some 0.6uF Solen caps as they were the biggest that would fit on the back of the PCB. I think they'll be easier to fit than the Evox ones as well.

I've now got all of the components mounted other than the few power supply related caps that I'm ordering now and the parts relating to the heater supply. The heater supply is proving tricky as there's not much room to mount the extra components required for the Schottky diode upgrade. So I'm just trying to puzzle that out. I'll post some photo's ASAP but I seem to have mis-placed my camera at the moment. :doh:

HighFidelityGuy
17-04-2011, 11:04
I found my camera last night, so here's a photo of what I've done so far:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_PCB_01.jpg

I've now installed the DC heater supply parts and wired up the AC heater supply. As you can see the PCB is getting rather busy. All the components I've used are physically larger than those they replaced which has presented some challenges. The DC heater supply was particularly tricky which this photo attempts to show:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/DC_Heater_01.jpg

I've used 4700uF Rubycon YXF high ripple, long life caps for the DC heater. I wrapped these in heat shrink to prevent shorts caused my the tight packaging. I just hope I've wired this bit up correctly. I've tried to make it so it's not too tricky to swap the resistor just in case I need to tweak the value to get 6.3V.

Here you can see how the brown Elna Silmic II electrolytic and black Mundorf axial cap's on the right are much bigger than the spaces on the PCB which forced me to do some stacking and packing. You can also see how I've directly soldered a grid resistor to the valve base to get it as close as possible. I've done the same thing with all the grid resistors.:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/Tight_Fit.jpg

I've now ordered the last few caps I need. I'll be using a 220uF Panasonic high ripple cap in position C1 and 100uF Vishay low ESR caps in position C2 and C3. So while I'm waiting for them to arrive I've started some work on the case and cabling related stuff. I've removed the input selector, volume control, input sockets and speaker binding posts. I'm going to fit a pair of WBT Nextgen copper RCA sockets for the input and some Eichmann Tellurium Copper speaker binding posts. I'm also upgrading the Zobel network components to Mills wirewound resistors and Mundorf Supreme caps which will be soldered directly to the back of the binding posts. All the internal wiring will be replaced too. Probably with 5N silver wire in Teflon sheathing but I've not quite decided yet. That's all for now. :)

colinB
17-04-2011, 16:44
Have you tried Ampohm oil paper caps? They appear to be going for good prices at the moment and have a big selection including copper.

HighFidelityGuy
17-04-2011, 21:45
Have you tried Ampohm oil paper caps? They appear to be going for good prices at the moment and have a big selection including copper.

I did consider them early on but I guess they didn't score as highly as the Mundorf Silver/Oil's in the reviews I read so I discounted them. There are so many makes and models out there I'll probably never try them all. I'm fairly new to DIY Hi-Fi, so as I've not tried many makes I'm quite reliant on recommendations I read online. I guess eventually as I try more I'll settle on on some favorites.

Have you compared the Ampohm's against any other caps?

colinB
17-04-2011, 23:28
I havent Dave. There is a mod for my tube amp but it involves Jensen caps and they cost a bomb. Always looking for a cheap oil/paper alternative.

HighFidelityGuy
21-04-2011, 22:10
All the parts I was waiting for arrived earlier this week and I managed to finish building the amp back up tonight. After a thorough check over to make sure I'd not made any obvious errors I fired her up to check some voltages. No bangs, no smoke and I didn't get electrocuted, so it's all good so far! :eyebrows: Some voltages seem a bit high, some a bit low but hopefully they're within tolerance. I'll have to check that out further but for now it seems to be working. So I'm going to tidy all the crap off my workbench (or "the dining room table" as my wife calls it :lol:) and hook the amp up to some cheap speakers for the first listening test. I'll then break out the oscilloscope and check out some waveforms. I'll try and take some photos too. They're jobs for tomorrow though. Now it's time for a beer, then bed. :cool:

HighFidelityGuy
22-04-2011, 09:46
Well it makes sound. :champagne:
I can't really tell what the sound quality is like yet as the £10 Argos speakers I use for testing are offensively crap. I'm going to leave it running through them for at least a couple of hour just to make sure the amp seems stable. I'll then take a few photos and hook the amp up to my main system. :)

DSJR
22-04-2011, 10:44
Yes please to pics.

I do have to say that after listening to the Albarry power amps the other day, I should confirm that solid state CAN do it with careful design and a beefy power supply - not to get oodles of Watts, but to put some inertia behind the Watts that DO come out, if you see what I mean. Hobby-ists that can make their own (valve) gear using good circuits and components for not too much dosh can grin from ear to ear IMO :)

HighFidelityGuy
22-04-2011, 11:36
Yes please to pics.

I do have to say that after listening to the Albarry power amps the other day, I should confirm that solid state CAN do it with careful design and a beefy power supply - not to get oodles of Watts, but to put some inertia behind the Watts that DO come out, if you see what I mean. Hobby-ists that can make their own (valve) gear using good circuits and components for not too much dosh can grin from ear to ear IMO :)

I know what you mean and I've come to the same conclusion. The power supply seems to play a massive role in determining the end results. My 550W solid state mono-blocks sound great to me but the tiny 15W KEL84 in bottom of the range spec sounded almost as good overall and better in some areas. So I really can't wait to here what it sounds like with all the power supply and signal path mods I've done. :eyebrows:

As requested, here are a few photo's of the amp:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Testing01.jpg

The bottom box is my old MD player that's currently looping Jamiroquai. The box at the back is my Lighter Note passive attenuator. The blue LCD is a mains voltage display that I got off eBay recently. It's been calibrated with a Fluke meter that can just be seen in the bottom right.

I couldn't resist doing a valve glow closeup. It'll look better at night but never quite as impressive as the bigger output valves like KT88's. Oh well, they still looks nice and are chucking out a fair amount of heat, as is the mains transformer. This has been mounted of some silicon bushes that I made to raise it up a bit to allow better air flow and dampen the slight hum it makes. The hum has definitely been reduced, so I'm happy about that as this was one of my only real criticisms of the amp. The valve dampers were bought of ebay and seem very good quality even if they do look a bit daft.

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Testing02.jpg

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Testing03.jpg

Once the amp's been running for another hour or two I'll let it cool down so I can take some photo's of the inside. :cool:

EDIT: I forgot to mention that I've left the front panel off for now. I need to sort it out so I can mount the control knobs back on to preserve the aesthetics. The knobs won't actually control anything as the amp's been converted to a single input power amp.

EDIT2: I probably ought to apologise for the blue power LED that I fitted. The original was an orange one that just didn't match my other equipment that all came with blue LED's. I know some people hate them but you can't please everyone. :ner:

HighFidelityGuy
22-04-2011, 12:13
I've just checked for audible hum and hiss and I can't hear any hum and just a slight bit of hiss when the volume is cranked all the way up. So I'm happy with that.

The only slight cause for concern so far is that the mains transformer is almost too hot to touch. I've read that they run hot in the KEL84 but I'd prefer to lower the temp if possible. Does anyone know if attaching heatsinks to the transformer sides with heat conductive epoxy will affect the working of the transformer at all? I wouldn't have thought so as aluminium isn't ferrous but I thought I better check to be on the safe side. Cheers.

Reid Malenfant
22-04-2011, 14:54
I've just checked for audible hum and hiss and I can't hear any hum and just a slight bit of hiss when the volume is cranked all the way up. So I'm happy with that.

The only slight cause for concern so far is that the mains transformer is almost too hot to touch. I've read that they run hot in the KEL84 but I'd prefer to lower the temp if possible. Does anyone know if attaching heatsinks to the transformer sides with heat conductive epoxy will affect the working of the transformer at all? I wouldn't have thought so as aluminium isn't ferrous but I thought I better check to be on the safe side. Cheers.
That'll be fine Dave, though it's the windings that you want to keep cool really ;)

HighFidelityGuy
22-04-2011, 16:16
That'll be fine Dave, though it's the windings that you want to keep cool really ;)

Ok thanks Mark. I might look into that later.

It looks like I spoke too soon about hum. I've just connected the amp up to my main speakers and I get a hum through both channels. :( I guess the cheapo Argos speakers weren't sensitive enough to pick it up. So I need to look into that issue. It sounds like it's about 100Hz, so I don't know if that's anything to go on. :scratch: I've got a feeling it's going to be either the signal input wiring or the feedback wiring that's at fault. The original wire was shielded but I've used twin solid core twisted together. So perhaps it's picking up interference from one of the rectifiers or something. :scratch:

Reid Malenfant
22-04-2011, 16:27
Try using shielded wire where it was used previously, it was probably used for a reason :)

HighFidelityGuy
22-04-2011, 16:48
Ok thanks. I always struggle to find good quality but reasonably priced wire to use for internal hookup. We spend tons of money on good quality cables to go between equipment so it seems only sensible to use cables of the same quality inside equipment. It would be great if Mark Grant sold his G1000HD cable unterminated as I'd use that. Up until now I've not had a problem using 5N silver wire off eBay but I guess this amp creates more EMI than other things I've worked with. It could just be a wire routing issue though. I had to run the left channel feed back wire quite close to the heater supply rectifier as I ran out of cable.

I've tried moving the input wire further away and that hasn't helped so It might be the feedback wire. It's going to be a real pain to get to the place on the PCB where this connects now so I think what I'm going to try first is sheathing the existing cable from the other end. I have some shielded microphone cable that I should be able to strip the internal cores out of. I'll try that and report back in a bit....

Reid Malenfant
22-04-2011, 17:02
It would be great if Mark Grant sold his G1000HD cable unterminated as I'd use that..
So i'm guessing you haven't PM'd him to find out if he would then :scratch:

Don't ask & you certainly won't get :eyebrows:

He's a nice chap to deal with & after a bit of discussion supplied me with 20M (i think) of unterminated DSP 2.5 mains cable ;)

DSJR
22-04-2011, 18:30
I get wonderful results from van damme screened cables. The single double screened has a handful of silver strands in it from memory and this seems to work well. The wire costs less than £1.50m and is really good - honest!

HighFidelityGuy
22-04-2011, 19:26
So i'm guessing you haven't PM'd him to find out if he would then :scratch:

Don't ask & you certainly won't get :eyebrows:

He's a nice chap to deal with & after a bit of discussion supplied me with 20M (i think) of unterminated DSP 2.5 mains cable ;)

I've not asked Mark. I decided to just use what I had seen as I'd had good results before. I'll send him a PM and see what he says.


I get wonderful results from van damme screened cables. The single double screened has a handful of silver strands in it from memory and this seems to work well. The wire costs less than £1.50m and is really good - honest!

Thanks, I'll keep that in mind. :)

Well I tried shielding the existing cable and that didn't work. There wasn't enough room inside the microphone cable. So I decided to just use the microphone cable for the feedback wire. Unfortunately it hasn't changed anything. So I need to try something else. First I'm going to do some searching on the Word Design forum to see if anyone else has had a similar problem.

HighFidelityGuy
22-04-2011, 19:49
Aaaaaaaarrrrgggg, I don't believe it, I think I've just wasted ages replacing the feedback wire when there was nothing wrong with the amp. :steam::doh:

I decided to double check that the hum wasn't being caused by a ground loop, so I started pulling out cables going into my attenuator and when I got to the one that comes from my AV amp the hum disappeared. So it was a fecking ground loop all along. :steam: What a ball ache. :rolleyes:

I've got an idea how to fix this by plugging the AV amp into a different socket but for now it's staying unplugged the fecking fecker. Right I'm off to Burger King for a belated dinner as I can't be arsed to cook.....

HighFidelityGuy
27-04-2011, 14:02
I've now lived with my modded KEL84 for a few days and I must say that I'm really enjoying the sound it's making. I didn't do any critical listening for the first couple of days but during that time it sounded very good but a bit uneven, with a slightly bright top end and slightly too much mid-bass punch. These areas have now calmed down and the overall sound seems very balanced. I haven't done any direct A/B test between this amp and my solid-state mono-blocks but I had become quite accustomed to the solid-state sound. It seems at the moment that I can hear more detail through the KEL84, with the main improvement being that there seems to be more space around the notes, as if they were getting blended together a bit more by the solid state amps. This has produced a more airy sound that I like a lot. Bass is also improved, with a nice mid-bass punch and seemingly more control and clarity in the lower bass. The mid-range also seems clearer somehow which has made vocals slightly more realistic sounding. Overall the sound seems to be more detailed and even handed and just generally easier to listen to. Which is nice.

So the upgrades seem to have filled the main gaps I was hearing between my solid-state amps and the un-modded KEL84. Hopefully this really is the case and it's not just that I'm making myself believe it. :doh: I'll know better when I get one of Stan's switch boxes to do some proper A/B testing. I'll leave that for a while though so the KEL84 can run in a bit more. I think I'll have to look into getting some better EL84's to try as well. :eyebrows:

I've really been surprised by just how much performance the KEL84 has to offer. I never thought a 15W valve amp could work this well with my speakers. Especially in the bass department. I thought 15W would be way too little to get this much bass but I was very wrong. :eek:

DSJR
27-04-2011, 20:09
Does the mains transformer still run very hot?

I tried the top models Graaf preamp at home a good few years ago (the sample KK wet himself over). On switch-on, the transformer buzzed like a swarm of angry bees, but was silent 20 minutes later. The thing was, that he casework got very hot and I really feared for the row of expensive oil-filled capacitors visible along the back of the case. A few years of regular baking this way must have shortened their lives I'd have thought.

HighFidelityGuy
27-04-2011, 23:50
Yep, the mains transformer still runs rather hot. It must reach over 40 degrees C. I've ordered an infrared thermometer so I can make some proper readings. I do however seem to have cured the mechanical buzzing the transformer made by mounting it on silicon bushes. I think I'll try attaching some heatsinks to it but it'll be a but tricky as the sides aren't flat.

Other than the hot transformer, the only negative thing I've been able to think of with the amp is that the power LED is too bright. I was just going to add an extra resistor but I think I might connect a pot in series instead and mount this where the volume pot went. I need to mount something there anyway to fill the hole so I may as well give it a purpose. :)

wee tee cee
02-05-2011, 08:45
I had my first experience of valves last night.My friend has very kindly loaned me a Art Audio pre/power combo.Had a really good listen to it last night and was very impressed.I am a tad obsessive about sibilance and have pointed the finger at everything apart from my naim5i amp.The valve combo was much more forgiving.Female vocals are fantastic,symbals sound lovely.I was suprised at the lovely bass.I listen to a lot of rock and found the combo lacked some of the attack of the naim but overall a far less fatiguing sound.Iam quite interested to hear what a combination of valves and ss would sound like.

Marco
02-05-2011, 08:58
I'll bring my Croft and Copper amp with me, Tony, next time I'm coming up to Glasgow, and you'll be able to hear both combinations :)

Marco.

wee tee cee
02-05-2011, 09:13
Lord help me....This could get awfy expensive.....

Marco
02-05-2011, 09:23
Lol - it'll give you an 'interesting' benchmark from which to judge.... :eyebrows:

Marco.

wee tee cee
02-05-2011, 10:19
Marco,
Thanks for the offer,Id be delighted to have you over.Ill make yer tea and provide plenty of red to wash it down.Let me know whenever your planning to come back home.

Marco
02-05-2011, 10:53
No worries, dude. It'll be next time I'm up visiting Snapper, whom I think you should also meet, as (like me) he was born just around the corner from you :)

Marco.

DSJR
02-05-2011, 13:58
ANYTHING compared to mid-period Naim is going to sound more laid back and refined IMO...

I repeat, Glenn Croft's new integrated (£1K inc phono stage) will sound just what you'd need - the atmosphere and 3-D of good valves, with some control and power from solid-state. A highly addictive combination IMO... and the new control knobs make it look far more expensive than it actually is IMO.

Alex_UK
02-05-2011, 18:20
Yep, the new Croft integrated is a fine sounding amp. And agree the new knobs look much nicer. You just know the money is being spent where it matters - pretty much like a Caterham 7 - everything is about performance and not much frippery. Just be aware there is no remote control, which might be important for you.

wee tee cee
03-05-2011, 08:32
Or a KTM,deletes the two extra wheels......

Alex_UK
03-05-2011, 08:42
Or a KTM,deletes the two extra wheels......

Unless its a X-Bow (http://www.ktm-x-bow.com/) of course ;)

wee tee cee
03-05-2011, 08:47
Unless its a X-Bow (http://www.ktm-x-bow.com/) of course ;)

Aye,That would do for your work......

HighFidelityGuy
04-05-2011, 09:57
I realised yesterday that I hadn't posted any photos of the amp now that it's mostly finished.

Here's the insides:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Finished01.jpg

Here's a closer look at the PCB:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Finished02.jpg

And here's a closeup of the Zobel network:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Zobel.jpg

My next jobs are to mount a dummy input selector switch and volume control pot and then re-attach the front panel and knobs. I intend to wire the dummy volume control so that it controls the brightness of the power LED. I have all the parts for this so I'm hoping to get that done later this week. The only other thing left to do is to block up all the input connector holes on the back that are now empty. I think I noticed some suitable plugs on eBay a while ago that should do the job. I'll post some more photos once I've got the whole thing finished off. :)

wee tee cee
07-05-2011, 19:02
Have been playing the lap top/squeezebox directly through the valve power amp utilising the volume controls on both as the pre amp.Must admit,I think it sounds better without the pre amp.
Tried going back to my Naim 5i,didnt last long.
Maybe try a t amp as a half way house,saving some sheckels along the way.....

Jonboy
07-05-2011, 19:31
Tried going back to my Naim 5i,didnt last long.


anything is better than a Naim amp :sofa:


I'm glad you have cured your sibilance problems in all seriousness

wee tee cee
07-05-2011, 20:36
Had a wee listen to the Naim again.....I think I might have to go down the valve route.I will wait till the bantum arrives and give it a good listen.We must be getting quite drunk because my wife told me the Naim is like a pair of loubitans-great to walk from a venue straight into a taxi,but you wouldnt want to walk about in them all day.....I sort of understood
either way I reckon its going to cost me in amps or shoes......

Alex_UK
07-05-2011, 21:54
either way I reckon its going to cost me in amps or shoes......

Both, I suspect! :lol:

HighFidelityGuy
12-05-2011, 02:11
I installed a matched quad of cryo treated E84L's tonight. First impressions are that they've improved the bass and the detail retrieval in the higher frequencies. The bass seems to drop lower and with more authority and I heard subtle details in one track that I'd never heard before. So I'm looking forward to doing hearing how they improve as they run in. I also have a pair of E80CF gold pins on the way that I found for a reasonable price on eBay. :eyebrows:

I also managed to find some grommets to fill the unused input socket holes in the chassis. So they've tidied up the rear panel nicely. Now I just need to sort out the power LED and front panel. Once I've done them I'll post some photo's. :)

HighFidelityGuy
23-05-2011, 22:08
I finally got round to finishing of this project today. I've fitted a new input selector switch which is purely to allow me to keep the knob for aesthetic reasons. I've also fitted a 4.7K pot where the volume control used to be and wired this in series with the existing LED resistor to allow me to fine tune the LED brightness. This has allowed me to tone down the brightness to a much more acceptable level. At 20mA it was enough to give you a migrain. :lol:

Unfortunately in my rush to get it connected back up again I forgot to take photos, so here's one of the amp in situ. I'll try to remember to more photos tomorrow as I plan to try adding some more tube damper rings then as an experiment:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/KEL84/KEL84_Done.jpg

I've got a cunning idea of a way to tame the transformer heat, so I'll be experimenting with that soon. :eyebrows:

Yoga
01-06-2011, 20:38
Nice!

I quite fancy a tube preamp/headphone amp combo, but most (in my limited experience) are in the U.S (Shiit, Woo etc.).

Any UK versions about guys?

Edit: promoted question to a new thread (http://theartofsound.net/forum/showthread.php?p=220545)

AlexM
02-06-2011, 13:07
I wouldn't worry about the hot transformer - if it's surface temperature is 40-50c then the windings will still be a long, long way below critical temps. Adding a heatsink to the core laminations probably won't cause any issues, but won't really help much either. When I had to replace a transformer thermal fuse with a thermal diode, the recommended temperature rating was 140c!.

The mechanical buzzing is more of an issue, but your decoupling grommets will help prevent transmission. You may want to check your wiring to ensure that there is no potential diff between neutral and earth. If it isn't audible then I wouldn't worry too much.

BTW, I think that you can find a better EL84 then your current JJs... the Gold Lion EL84 reissues might be just the ticket. I have a quad of the GL KT-88s and they are the best I have tried by far and hold bias perfectly. The price is very reasonable and quality/consistency of the product is very good (more than can be said for JJ IMHO).

Regards,
Alex

Ali Tait
02-06-2011, 13:27
The new Genelex EL84's are very good.