Which valve amp do I keep?

[Richard (Wales)]

Hi everyone.

I have been into valve equipment for many years, mainly radios.
Recently I bought a job lot of stuff, which turned out to be mainly audio stuff.

This included a pair of Quad ESL57 speakers - WOW what a revelation they were.

This has got me interested, and so I now need to sort out and keep a valve amp to go with them, the choices are:-

Leak stereo 20
Radford STA15 mk III
Radford STA25 mk III
Pair of Leak TL50+

Any opinions on which one will best go with the 57s, which one is best etc??

With thanks

Richard

[Shoog]

I believe the leak TL50's should outperform the Leak stereo 20, which suffers from a flabby bass and high colouration (in a nice way though).

Shoog

[andyjevans]

Leak stereo 20
Radford STA15 mk III
Radford STA25 mk III
Pair of Leak TL50+

I've had quite a few Leak amps and modified a lot of them, and I would say with confidence that the stock Leaks, with the exception of the TL10 and earlier ones, can be easily outperformed by most valve amps. The TL50 in stock form is not very interesting sounding either. So as far as Leaks go, I'd say modify them or leave them. Now, since the Stereo 20 is not so collectible as the others, it's a good candidate for modification. I could give you some instant tips on this if I can dig them out of my files - briefly, a 6N30 DC coupled into a 6N1P phase splitter is a huge improvement, and you could also rewire the output transformers as suggested on this site in previous threads. A modified Leak can sound quite good. Now we come to the collectibles. The TL50s and the Radfords should be left original. Good news - they're worth money, bad news if you don't update the parts you are losing performance.
So my conclusion is that if you want sound that is at least one level up from these old classics, you either modify the Stereo 20 or use something else entirely. I recently built a PPP 6V6 triode amp (using 7C5, the loctal equivalent) with a 6J5 DC to 6SN7 front end (using 7A4 and 7AF7 which are round plate). This sounds absolutely delightful, and is better than any version of rebuilt Leaks (including radical ones like my all-triode PPP 6S4 one) and no doubt all the Radfords too. It's simple to build, cheap, and will give you another level up of quality (built with good parts). Alternatives are 2a3 and 300b amps. with what the Leaks and Radfords are worth, you could sell one or two if you don't want to do a build, and just buy a good push pull DHT amp.
Classics are wonderful to collect, but not really for serious day to day listening. Andy

[andyjevans]

Looking through your post again, maybe you are saying you have narrowed down your wish list to the four you mention - I'd assumed you had all four, so I may be in error. In fact I come from Bridgend, but live up in London. Shame I'm not still in Wales - (unless I pay a nostalgic visit) I have a few amps you could demo. Andy

[Richard (Wales)]

Hi

Thanks for the replies.

Andy - yes I have got the 4 options listed.

I am working on the stereo 20 at the moment, will see what it sounds like stock before considering any mods.

Anyone used the Radfords?

Richard.

[barretter]

Both the Radfords are superior to either of the Leaks in terms of accuracy and noise level. I have restored (in terms of new parts but no circuit changes) both a pair of Leak TL12+s and a Radford STA25 for a friend who has a pair of large Klipschorn speakers (i.e very sensitive). When you connect the Leaks to them you can hear their noise in all its glory ; when you connect the Radford, there is virtual silence except for a little hiss at the tweeter if you put your head close to it. The Leaks have an inferior power supply with no choke and are much too sensitive. You can change the sensitivity in the TL12+s by wiring the input EF86 as a triode and changing the feedback components but I don't know how to alter the Stereo 20 front end. If I were you I would keep one of the Radfords and flog the rest on eBay. You'll make a lot of money.

[andyjevans]

If you have all four amps, then you are in the best position to tell us what they sound like with the Quads, not vica versa. What are your ears telling you so far?
My brother once had all the Radfords up to the ST100 and the best sounding of all was the ST15 (or its mono versions). Andy

[EC8010]

Originally posted by andyjevans
If you have all four amps, then you are in the best position to tell us what they sound like with the Quads, not vica versa. What are your ears telling you so far?

Of course, that rather assumes that each amplifier is working properly and doesn't have leaky coupling capacitors, resistors that have gone high in value, failing smoothing capacitors, dirty contacts, or dry joints. Oh, and tired valves.

[ray_moth]

Agreed, get rid of the Leaks unless you plan to improve them significantly. Even then, it's doubtful which, if any, of the original Leak parts are worth retaining - in the case of the Stereo 20, probably only the chassis!

I don't know about the Radfords, except that they have a good reputation. However, the circuit uses a peculiar triode-pentode LTP splitter, apparently to minimize its input capacitance (or so I've been told).

[Shoog]

I sold a Leak stereo 20 a few years ago and got £330 on Ebay. £330 buys a hell of a lot of good components for a cooking modern amp.

Shoog