All a glow. Real kit really does glow in the dark

my SoH all a glow

http://inlinethumb33.webshots.com/43...600x600Q85.jpg

Another angle

http://inlinethumb21.webshots.com/43...600x600Q85.jpg

and my PL-7 too

http://inlinethumb49.webshots.com/17...600x600Q85.jpg

Ooh, nice.

My wife just leaned over my shoulder and said 'Frankenstein things!'
Followed by 'You'll need to get a proper stand before you can get some of them' :eyebrows:

That's one of the coolest valve glows I've seen in a while - nice one, Steve :smoking:

Btw, what does "SoH" stand for?

Marco.

Ah yes, SoH stands for Son of Heffa. Heffa was a first valve amp design that aimed to provide a reasonable tube amp for under £100.
This was an Anglo Swedish project to provide the chassis and parts to help interested folk build a great valve amp.
That was back in around 2000. The Heffa bit comes from the huge mains transformer in Swedish called 'Heffa Klump'. Named so due to it's weight.
It was found in a surplus store in Sweden and cost 100SEK ~about £8 back then.
It's size and flexibility meant the chance for a very good power supply.
Heffa featured cheap mains transformers as audio output transformers!

Here a pic of a Heffa transformer in situ
http://inlinethumb02.webshots.com/41...600x600Q85.jpg

Here's a link to a site with an original Heffa in use in Sweden.
Cool with the HT lead tubes.
http://images.google.co.uk/imgres?im...%3D63%26um%3D1


Heffa sounded pretty good, was around 10W p/c. I borrowed one for a week or so and found it easily outperformed my MF A3 integrated / Power amp combo bi amping.

SoH was a development of this. Using 6SN7's as Spliter / input stage and drivers & a pair of KT88's in familiar push pull class A operation.
Heffa uses two 20W tail resistors with big heat sinks to achieve class A.

The same mains transformer was used and the audio output transformers were Lundahl. Again most of the big stuff was sourced in Sweden as we worked / travelled there a lot. Exchange rate was favourable too.

Total cost back then about £350.
Cases were made at a metal box factory in Sweden and I brought most of them them over ~20 or so and transformers on my many business trips (Business class and special baggage is a wonder thing).
The deal was Dave got to use the CNC / metal box machine in return for a built amp;)

In the UK we used good quality passives / active parts from Farnell.

I was one of the early ones to put one together and install the Heffa.
Dave the Project leader had to help me a lot to commission it,
smoke test and fix a few things.
It was quite a feeling connecting it up to a cheap pair of speakers and portable CD player to smoke test. Both of these components were expendable. When you have 480V DC whizzing about inside you need to be careful. Always work with one hand behind you back is good advice.
The original Svetlana KT88's were quite aggressive on current and we needed a 2nd PSU.
The PSU's are soft start Silicon devices and are VERY quiet.

I had roped a mate of mine iinto building one at the time. He copied mine and we tested it ourselves. Didn't work. Another mate also built one independantly and his didn't work either. After some badgering I got them together and using mine a working example we worked through the problems and both have been working since. The dual PSU was the heart of the problem.
All these things come together to give a very authoritative, etched, powerful amp that seems to handle any speakers, any loads and once sorted is extremely reliable.
I have learned a bit about valve amps, got a scope and can easily replace all the passives in the amp for about £40 and the actives for a further £30 should it need a refresh.

Since 2002 I have changed the sig wire, speaker wire, tried some other sig caps. I've done a lot of tube rolling of both the 6SN7's and KT88's.
Only last night I wondered what the Kenrad black glass 6SN7's (rear ones i the photo's above) would sound like vs the Sylvania browns.

I have bought a lot of 6SN7's 2nd hand on ebay. All have worked / are still working.
There is something rather magical about obtaining a tube from the 1940's, 50's or 60's, plugging it in and then hearing what a subtle yet different sound it has.
The modern Electro Harmonix 6SN7's are pretty good too - esp the gold pin ones. My mate recommends the cryo treated ones. I remain on the fence as to this procedure.
KT88's I have settled on Electro Harmonix's over the Svetlana's or Tesla's.
I just prefer the sound.

The tubes are pretty unstressed - I've never had a failure yet.

So that is pretty much it.
I have no plans to change this amp. It probably equals or betters a Berning (I've heard 2 now - both through big Tannoys incidentally).
Plus side is I can fix this one should anything go wrong.

This site shows some of Dave's other projects / his tech view on tube amps
http://en.wikipedia.org/wiki/Valve_a...hnical#Biasing

His teflon cap and film resistor version sounded good but not enough to make me want to change to those components...

Thanks, Steve.

Now that's what I call a thorough answer! - Very interesting.

I get good vibes from that amp - I can just 'sense' that it sounds good... :)

How are the Berkleys liking it?

Btw, do you mind if I move this thread to the Blank Canvas, as that's where it really belongs :cool:

Marco.

Oh yes please move - I put it hear as it had a pic of the PL-71.

The Tannoys love it. Very easy to drive.
I keep thinking to recab them but then listen and think - this is good, very good.

Took the photo's last night on wife's Canon 20D (best birthday present I ever got her:-) using a 15 to 30sec exposure. Tripod it not brilliant though.
On the PL-71 pic you can see the arm sway has cause a little blur.

Sorry for resurrecting an old thread but just have to say WOW - those valves look fantastic - is it wrong to feel strangely aroused after seeing pictures like those? :lol:

Lovelly work Steve and Imagine the Tannoys loving them

Yes, all is working very well.
Oddly my hifi ownership cycle sees my loving a setup then has a slight dip over a few weeks (familiarity perhaps) now I'm coming out the other end of that dip thinking it's better than ever.

Next step DIY GRF's - I have been saying this for months but WILL start them soon. 2nd daughter is a keen DIY'er so will be on at me again soon.