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Leak Stereo 20

The quality of the transformers would go a long way to differentiate products using similar circuits. An amp isn't just the schematic.
 
Tony L said:
Loads of modern amps are very conceptually similar e.g. the Leben CS300, World Audio Deign KEL84 etc etc, in fact you could argue the Vox AC15 guitar amp is very similar!
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True. But there’s the fact this is pretty much an exact visual copy of the Stereo 20 too.
 
John_73 said:
True. But there’s the fact this is pretty much an exact visual copy of the Stereo 20 too.
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No doubt, the English Acoustics is unquestionably a Stereo 20 clone, and what looks to be a very nice one. There is obviously a huge precedent for cloning in the guitar/musical instrument market with infinite numbers of pretty much identical copies of the Les Paul, Stratocaster, Telecaster etc. This all went through the courts way back in the 1970s when the Japanese were producing far better guitars than these American companies and selling them cheaper. The result of huge amounts of litigation was the only protectable aspects were the product name, brandname, logo and headstock shape. The rest was viewed as public domain.

The LS3/5A is another fascinating example. One where you could easy write a book about what exactly is and isn’t one, and why some are marketed as such when logically they can’t be to my mind! I guess one view being that it is a tight BBC measurement specification rather than a particular subset of components and assembly processes.
 

This is a truly fascinating look inside the Mullard Blackburn factory and details the steps and processes involved in making an EL84, four 1965 examples of which currently reside in my Stereo 20. The scale of production along with the complexity and sheer amount of labour involved really is astonishing. Worth half an hour of anyone’s time!
 
Great story...."It got pretty murky though: http://ukhhsoc.torrens.org/makers/Leak/Dinsdale_HFNLetter.txt"

and I read a story once that HJ Leak tried to emulate the sound of the Stereo 20 through the Leak Stereo 30....obviously did nothing of the sort!
Although I shouldn't be knocking Harold, I've had the pleasure of owning a pair of TL50's (In Triode mode...now somewhere on the IofW),
TL12+'s and Stereo 20: the Stereo 20, 120V version is still with me after 30 years...
Love it!
 
Just dusted off my Stereo 20 and replaced the coupling capacitors with the K40-Y. I am really enjoying this amp again plugged into my Tannoys (HPD315 in custom built 100 liter bass reflex) Also someone mention the Armstrong A20/A220.. I rebuilt one of these rarities a few years back and must put it up against the Stereo 20 for a shootout! Not sure if mine has Partridge OPTs, but it is another very neat little EL84 PP amp from the same period.

20210126_165705 by Jonathan Chiles, on Flickr

20210126_112648 by Jonathan Chiles, on Flickr

20210126_165847 by Jonathan Chiles, on Flickr
 
The Armstrong looks interesting. I assume that isn’t it’s factory paint?! Is it the same valve line-up and similar gain to the Leak?
 
Tony,

You may be surprised to know that the early version of the A20 did indeed come with a very trendy pinky / red finish. However, when the power amplifier was rebranded as the A220 , the colour changed to a more conservative green. The carrying 'hoops' are a real bonus when servicing . The A20 / 220 is a vintage valve amplifier that has been somewhat overlooked. I actually marginally preferred mine to the Leak equivalent.

IIRC, the valve line-up is identical. I have an original sales 'flyer' somewhere.
 
There is a surprising amount of very interesting early UK valve amps which have sadly been lost to history. I’ve got quite a bit of reading material from the mid-50s through to the dawn of the transistor era and there are lots I’d love to try. One problem is most were mono, so even if one turns up on eBay the chances of a matching pair is exceptionally unlikely. The Armstrong stuff has certainly been on my radar, there were some nice chunky mono amps in their range too.

I’m pleased to hear yours was pink/red originally, the current trend for black of blingy CNC alloy is remarkably boring. Some of the ‘50s stuff was really cool, I’m often surprised seeing real examples of stuff I’d only ever seen in black and white images in HiFi Yearbook, Gramophone etc.
 
If you don't already own any issues, early copies of HI-Fi News are a great source of period adverts relating to rare / odd-ball audio gear. As you are no doubt aware,this magazine was first published in 1956. Sadly by 1961, many smaller manufacturers had fallen by the wayside leaving the ' big-boys' such as Leak, Quad, Radford etc. to dominate the market.
 
I’ve a fair few early to mid-60s copies and a few years from the ‘70s. A fascinating magazine at that time.
 
brecklandboy said:
If you don't already own any issues, early copies of HI-Fi News are a great source of period adverts relating to rare / odd-ball audio gear. As you are no doubt aware,this magazine was first published in 1956. Sadly by 1961, many smaller manufacturers had fallen by the wayside leaving the ' big-boys' such as Leak, Quad, Radford etc. to dominate the market.
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I have an almost complete set from the 50s to, I think, the mid 90s. I don't think I have the first issue, but I'm sure there are a few from 1956.

And before anyone asks, they're all currently packed up so I'm not in a position to copy any articles.
 
Re the Armstrong, and according to Jim LeSurfs info the slightly later A220 did in fact come in a almost postbox red colour with the black handles, my amp was originally olive green but you could only tell by looking on the inside as the outside was corroded and had been given a rattle can job in grey, the valve bases had not even been masked over :( After a complete strip down I thought I would try to nail the red colour. If I had to do it again now I would have stayed with the olive drab) I think the colour balance is a bit off in the photo I posted making it appear more pink. I was going off the photos here from Jims site:

http://www.audiomisc.co.uk/Armstrong/200/200page3.html

There is so little info available on this unit and mine came in such poor neglected condition, I was very happy to be able to get it up and running again. Sensitivity again from Jims page is shown at 410mV for 12W, same valve compliment as ST20. So a slightly better candidate for an active pre but not by much!
 
Looks good. Sensitivity is very similar to a Quad 303 (0.5V for 45W) so certainly usable with an active pre. I’m using a 303 with a Verdier valve pre into my Tannoys, though thankfully it has internal output settings. The gain-reduced Croft 25 would be a great match too.
 
Has anybody got any experience using polishes or waxing the Stereo 20 finish? I have a 1967 grey unit, and despite a thorough clean the main chassis finish has evidently oxidised over the decades and it's now a satin finish rather than gloss. The issue I have is that (long story short!) I'm currently getting a paint match done so I can respray the transformer cowls, and the dual F&T 32uF+32uF caps (only, the main chassis retains it's original paint).

I'm not sure whether to use a satin clear coat for those items being newly painted, or a gloss clear coat. If I want it all to match as-is, then a satin coat would seem the way forward for the cowls and caps. If I go for a 'how it would have looked new', then a gloss coat for those repainted parts, but I'd then need to wax the main chassis to bring up the shine there. Not sure which direction to go currently, though maintaining a satin finish for everything would mean I wouldn't have to bother re-waxing the main chassis periodically to keep up the shine I guess. Yes, undoubtedly overthinking all this..... ;)
 
My charcoal ST20 was dull when I first got it. I used car cleaner and silicone polish (Simonize) to get the shine/sheen back. It stays shiny for ages and just needs a quick application on a cloth if I feel it needs it. Dust does not stick to it as much either. Be careful though, they were given a lacquer (?) coating which can easily be rubbed off or damaged. Don't be tempted to use any abrasive or cutting 'polish'. That leaves a much less shiny paint surface.


IMG-7117.jpg


I used off the shelf paint for my caps and touch ups. Quote from #340:
''For the Charcoal / Grey paint I chose Toyota Decuma Grey.
It is not exact, but good enough when the rest reflects back.
Another close colour was Peugeot Steel Grey metallic, but I had to decide from the colour on the can and Decuma had the similar metal fleck finish.''



Anyway they are more than 50 years old so just do not look right if they are 'perfect'...
Alan
 
Thanks for that Alan! Yours cleaned up really nicely, and your reply has helped crystalise a plan of action. I used Auto Glym 'Show Shine' yesterday, but that didn't really add any shine so much as made the best of the satin finish. Have just ordered the spray version of the Simonize wax following your comments. Will definitely not use any abrasive cleaner. I'll see how well that works, and then can make a decision on whether to go for a satin or gloss topcoat for the cowl and dual caps paint job.

It's been a pain in the neck really, but a huge chunk of paint had flaked off one of the output transformer cowls (Leak used no undercoating for the cowls!), and I then had the decision to make about whether to strip and repaint just that one cowl, or the full lot. Decided having one potentially a different colour to the rest would look too odd, so sent them all off to an 'expert' to get them paint matched and resprayed. The match was atrocious and was a flat (not metallic!) medium grey. I wish now I'd never bothered but have to follow it through now with the painting, but this time I'll do it myself. Fortunately both the original dual caps have their original paint, so sent one of those off to get a match to 'paints4u'. Touch wood they'll be able to provide a decent enough match, otherwise I will just say to hell with it and go for a standard can from Halfords.
 
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