Valves, I think I'm starting to understand what the fuss is about.

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:

Yes, the KEL is a great little amp and a real giant killer. Has yours been modded?

Just a little;)

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

Quote:

---

Originally Posted by Ali Tait

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:

Quote:

---

Originally Posted by tubehunter

Just a little;)

---

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

Quote:

---

Originally Posted by John

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. :)

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..

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...

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.

Quote:

---

Originally Posted by SPS

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..

Quote:

---

Originally Posted by anthonyTD

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. :)

Quote:

---

Originally Posted by Clive

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. ;)

Quote:

---

Originally Posted by HighFidelityGuy

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!

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:)

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/t...0/IMG_5602.jpg

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.

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.

Quote:

---

Originally Posted by tubehunter

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 ;)

“Yes valves are the only valid way of enjoying music.”

Isatso :rolleyes:

Quote:

---

Originally Posted by tubehunter

Yes valves are the only valid way of enjoying music.

http://i514.photobucket.com/albums/t...0/IMG_5602.jpg

---

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

Lovely pic, Dunc - you need to make it into your avatar! ;)

Marco.

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.

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...

Quote:

---

Originally Posted by tubehunter

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/t...0/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.

Quote:

---

Originally Posted by Ali Tait

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:

Beware, badly done DC heating can do more harm than good.

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...

Quote:

---

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)

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:

What valves are in it Dave?

Quote:

---

Originally Posted by Ali Tait

What valves are in it Dave?

---

See my last post, second paragraph. ;)

I know what valves are in it, I used to have one!

I meant what make. :lol:

jj el84, mullard ecf80

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's and maybe some Shuguang Psvane EL84's 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.

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.

Quote:

---

Originally Posted by lurcher

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...

The easy way if you have 2 identical valves is to wire them in opposite polarities and swap the valves every so often.

Quote:

---

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.

Quote:

---

Originally Posted by lurcher

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.

---

Quote:

---

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...

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...

These might be worth a try, they are cheap and I've read they are good-

http://cgi.ebay.co.uk/EL84-7189-6BQ5...#ht_506wt_1139

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.

I dont think there is enough headroom for a regulator. Maybe if you use low Vf diodes in the bridge.

I was wondering if this would be suitable: http://www.tentlabs.com/Components/T...ter/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.

I think nick means voltage from the 6.3 winding on the transformer.

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.

Forget Mullards unless you have money burning a hole in your pocket try these Russians which are very good, i used them in my Leak Stereo 20 to good effect

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.

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.

Quote:

---

Originally Posted by lurcher

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.

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:

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).

Quote:

---

Originally Posted by Reid Malenfant

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......

Ok, here's what I ordered: LINK
And here's the amps schematic: LINK Page 6

Have I got the right thing? Cheers.