View Full Version : Head Amp of the glowy kind.
Firebottle
08-04-2016, 09:58
Can you guess what it is yet?
http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1050368.jpg
Built yesterday into an old analogue satellite receiver case, which actually turned out to be about the right size.
I wanted to make a valve based head amp so I can test sound differences with various output caps, but with more than a couple of volts across the caps.
Experimental valve head amp:
http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1050369.jpg
Based around a 9V transformer (bottom left in the photo) to feed the heater regulator, plus a 17V/230V transformer (top left) to give approx 110V AC for the HT rectifier.
Ignore the transistors, links and resistors on the PCB, they were just part of the satellite power supply. The heater regulator is on the heatsink, rather OTT for the dissipation needed.
The third piece of iron is another transformer used as a choke, about 33 Henrys, then followed by a MOSFET capacitance multiplier, essential to reduce hum to acceptable levels.
The business end, simplicity in itself:
http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1050370.jpg
How does it sound I hear you ask, pretty bl**y fabulous :D
There is some tube rush but not bad at all, about the same as surface noise you might get on some vinyl. I'm very happy with the choice of valve, I had to swap one that was a bit noisier.
Valves are from my 'stock box' so have cost next to nothing, they are miniature 7 pin single triodes, EC900:
http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1050371.jpg
Gain is a useful x21, is it microphonic? Of course it is :eyebrows:, though within acceptable limits.
Very pleased with the outcome.
:)
Wow didn't expect you to go down this route Alan.
Firebottle
08-04-2016, 10:49
I won't be offering any for sale, hence the post is under 'The Drawing Board'.
I suppose it is/was a bit of an itch I had to scratch. I'll bring it over next time we are in the UK.
:)
I won't be offering any for sale, hence the post is under 'The Drawing Board'.
I suppose it is/was a bit of an itch I had to scratch. I'll bring it over next time we are in the UK.
:)
Great, look forward to hearing that. How do you think it compares to the tranny head amp?
awkwardbydesign
08-04-2016, 12:50
Not much room in there for "proper" caps!
Firebottle
08-04-2016, 17:01
Compared to the FET amp it is definitely noisier, but I would say they are equal in their transparency.
Plenty of room for 'proper' caps. That is part of the reason for the build, to try with a selection of output caps.
To be continued............
You could always fit anti-microphonic valve bases, if you can find some B7G type. What is the output impedance?
Ali Tait
08-04-2016, 17:22
How about a hybrid to get the noise floor down?:eyebrows:
Firebottle
08-04-2016, 18:41
I'll measure the output impedance tomorrow Barry.
I've done the hybrid Ali with the KIN design and it's a lot quieter, but I just wanted to try valve only approach.
:)
Ali Tait
08-04-2016, 18:44
So there's a hybrid head amp in the KIN?
Firebottle
08-04-2016, 20:47
Not a separate head amp as such, but the KIN is a hybrid design.
:)
Firebottle
09-04-2016, 05:54
What is the output impedance?
Just measured it Barry and it is 3K ohm :)
Firebottle
09-04-2016, 16:21
Well there is definitely something gelling here.
This valve head amp has been built as a bit of an experiment but it's blowing my socks off ;)
It's remarkably low noise and there is a bit of a hum (probably need a quieter heater supply) but you don't hear it when the music is playing.
I've been spinning some albums from Dire Straits and a Strauss Gala on Decca (very well recorded) and there is a real wow factor.
Nothing I can really describe that will make much sense unless you hear it, but there is a better placement of instruments and a greater fullness to the whole sound.
Not something I really expected with a change of head amp/input method, but I'm enjoying it immensely.
:D
Valves doing their magic again.;)
This valve head amp has been built as a bit of an experiment but it's blowing my socks off
I did say some time ago that a valve is the best by far, if you can get the noise down enough :-). TBH, one of the reasons I designed the reference phono stage with its 53dB of gain, its front end is just about quiet enough for a 0.3mv cartridge directly into it. Some hiss, but its less than the noise floor of clean vinyl. No hum of course, the two box layout and shunt regs sort that. I would suggest you try the power supply separate from the valves. Chokes are good things in power supplies, but can be a mixed bag for phono stages as they will emit a fair amount of RFI.
Firebottle
10-04-2016, 07:28
Cheers Nick :thumbsup:
No doubt I'll continue to meddle with it.
Firebottle
10-04-2016, 16:26
Valves doing their magic again.;)
That's what it is James, magic.
I've cured the hum by fitting a steel shield between the valves and the PSU end :yay:
Been doing a comparison between the cascode JFET MC input on the KIN and using the valve head amp into the MM input (direct to the first valve).
There is a difference and neither is bad in any sense, but the valve head amp offers more space and definition to my ears.
YMMV ;)
So there's a hybrid head amp in the KIN?
Just a gut feeling, but I think there's something special about surrounding valves with sand...
Never heard better, put it that way.
Alan,
get on the case....! (or Nick)
Make something affordable to the masses and it'll be a game changer.
Ali Tait
10-04-2016, 17:03
Yep, I'd buy one!
Just a gut feeling, but I think there's something special about surrounding valves with sand...
Never heard better, put it that way.
Alan,
get on the case....! (or Nick)
Make something affordable to the masses and it'll be a game changer.
Sharp or building :D
Maybe now you have SS, Valve and hybrid options of the head amp!:)
That's what it is James, magic...
Been doing a comparison between the cascode JFET MC input on the KIN and using the valve head amp into the MM input (direct to the first valve).
There is a difference and neither is bad in any sense, but the valve head amp offers more space and definition to my ears.
Hehe... What did I say to you at my place about head amps? ;)
Valves or no valves (although I accept that the latter add another dimension of their own), a GOOD head amp used with a GOOD MM phono stage often sounds better/more musically enjoyable than a standalone MC stage, valve or SS... With the latter, used on its own, there's a certain 'magic' missing with vinyl replay.
Nice one, Alan. If you decide to loan out a sample unit, please put my name on the list :cool:
Marco.
Firebottle
28-05-2016, 14:54
is it microphonic? Of course it is :eyebrows:, though within acceptable limits.
Well a development on this. I've fitted mechanical isolation to the business end.
I've used a couple of medium sized rubber 'O' rings, one at each end to support the valve socket angle bracket.
They are stretched out into an 'X' from each corner of the bracket onto some M3 support pillars.
This has cut the microphony to almost nothing. :D
Just listening to some Vivaldi and it's wonderful.
Arkless Electronics
28-05-2016, 15:37
I seem to have missed this thread.... Interesting stuff. I built a valve head amp years ago which I still have. 2 x ECC88 per channel. It sounds wonderful but valve head amps are a bit like classic cars... high maintenance!
Unfortunately there seems to be very little interest in head amps, even though if decent they generally beat SUT's ;)
Firebottle
29-05-2016, 11:12
Pictures of the 'O' ring anti vibration support for those that ere interested:
http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1050462.jpg
Close up of one end showing the fitment:
http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1050463.jpg
:)
So when can we get a listen to it? I'd certainly be interested :)
Marco.
Firebottle
30-05-2016, 07:22
I'll bring it along on my next visit Marco ;)
337alant
30-05-2016, 21:14
Sounds like another great project Al , I was listening to Steve's Fire bottle the other day and it was superb.
Just one personal preference though Valves are a beautiful thing and should always be on display
Alan
Firebottle
31-05-2016, 05:58
Thanks Alan, tend to agree on the display part :)
I am happier having them hidden away from little fingers.
I would love to hear the head amp if an opportunity were to arise soon.
Yeah, I'm surprised the head amp isn't doing the 'round robin' the same as your phono stages have? :)
I think you should get a demo sample made up, if indeed its not the one you're currently using, because I suspect you'd sell a few! Hint, hint... ;)
Marco.
Arkless Electronics
31-05-2016, 09:51
Yeah, I'm surprised the head amp isn't doing the 'round robin' the same as your phono stages have? :)
I think you should get a demo sample made up, if indeed its not the one you're currently using, because I suspect you'd sell a few! Hint, hint... ;)
Marco.
I doubt it somehow..... There appears to be zero demand for head amps....
I doubt it somehow..... There appears to be zero demand for head amps....
Main issue I had when trying a head amp was that it didn't make any difference (in my setup)
So, what does that mean?
Can a headamp improve a cheaper/poorer MM stage/input or do you need a 'good' stage/input to hear the difference?
Now I'm not asking this to 'diss' headamps, I'm asking because I don't know.
Firebottle
31-05-2016, 11:09
A head amp gives MC capability to an MM only stage. The better the MM stage the better the performance including MC via the head amp.
If you had no difference then it's very likely you have a good MC stage already.
Arkless Electronics
31-05-2016, 12:09
Main issue I had when trying a head amp was that it didn't make any difference (in my setup)
So, what does that mean?
Can a headamp improve a cheaper/poorer MM stage/input or do you need a 'good' stage/input to hear the difference?
Now I'm not asking this to 'diss' headamps, I'm asking because I don't know.
Like Alan says there....
A head amp is not meant to make a MM only phono amp better than a phono stage with MC input. Some MM/MC phono stages actually work by switching in a built in head amp so as it is added before the MM stage anyway! The most common use for a head amp is to allow MC carts to be used with MM only valve phono stages.... this has nothing to do with the MM stage being valved but simply because many valve stages don't have MC capability.
Personally I reckon the greater popularity of SUT's over head amps is to do with the fact that an SUT is far more likely to have colourations which some like the sound of, i.e due to electrical resonances in the SUT, in combination with the loading of the cartridge itself and any capacitive and resistive loading, there is more likely to be false sheen or bass boost etc whereas a head amp is far more likely to be low colouration and accurate. Not always of course and the degree of this varies hugely depending on the exact set up. This tends to make an SUT much more system and cartridge matching sensitive than a head amp. A SUT should win on low noise but the noise from a good head amp won't be an issue anyway.
I doubt it somehow..... There appears to be zero demand for head amps....
I totally disagree; it's simply that those here who make them lack sufficient imagination to sell them properly! :eyebrows:;)
In any successful hi-fi business, two main skill sets are required: 1) Someone with the technical knowledge and skill to build the equipment itself, and 2) Someone with the skill to market it and sell it!
Sadly, most small hi-fi manufacturers are badly lacking the latter - and it's that which makes the business money, which in turn makes the whole thing go round....!
Marco.
Arkless Electronics
31-05-2016, 13:58
I totally disagree; it's simply that those here who make them don't have sufficient imagination to sell them properly! :eyebrows:;)
In any successful hi-fi business, two main skill sets are required: 1) Someone with the technical knowledge and skill to build the equipment itself, and 2) Someone with the skill to market it and sell it!
Sadly, most small hi-fi manufacturers are badly lacking the latter - and it's that which makes the business money, which in turn makes the whole thing go round....!
Marco.
Whilst I certainly lack marketing skills, I'd be interested as to where there is all this interest in head amps? On here it seems to be only if a second hand Lentek unit comes up.... which can be easily beaten by units from Alan or myself.... (no doubt those who would bid on a Lecson are thinking "he would say that, wouldn't he" without any inclination to find out for themselves)
As folks will have realised, I just don't get the whole having to "market", "push", "pimp" ones products to customers... just doesn't seem British if you know what I mean;) It doesn't sit easy with me.... Life would be so much easier if people would just go "I need a head amp, these guys on AOS seem to really know their stuff and have head amps for sale, hand made, at a very reasonable price. I'll try one and then BUY IT if I like it". Instead it appears to all revolve around some sort of obscure politics (with a small p), "branding" and probably strange incantations or something :scratch:
Lol... I'll get to that later. Right now, the weather's too nice and I'm too full of Prosecco! :cheers:
All I'll say in the meantime is that a little imagination/lateral thinking, coupled with people skills, can be a wonderful thing... ;)
Marco.
Arkless Electronics
31-05-2016, 14:20
Lol... I'll get to that later. Right now, the weather's too nice and I'm too full of Prosecco! :cheers:
All I'll say in the meantime is that a little imagination/lateral thinking, coupled with people skills, can be a wonderful thing... ;)
Marco.
How the other half live..... weathers bad, no prosecco (at this time!?:cool:) and about to dive into a dud Quad 306 and slave over a hot soldering iron :D
Lol... Enjoy. It's half term, so Del's off and we're enjoying the sunshine and fresh air outside in the garden (beautiful sunny and warm day here in Wrexham), and I've just cut the grass (our lawn is like a small park), so we're just chilling out and having a wee drinky! :)
Laters...
Marco.
Firebottle/Arkless ...
Thanks for the info, I'm still learning even at my age.
I've just listened to the Amused To Death LP by Roger Waters (Analogue Productions Reissue) and oh boy oh boy it sounds superb.
Hosepipe ban be in force here soon 😂
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