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-   -   Replacing Valves Leak Stereo 20 (http://www.diyaudio.com/forums/tubes-valves/113618-replacing-valves-leak-stereo-20-a.html)

pubrunner2000 14th December 2007 08:54 AM

Replacing Valves Leak Stereo 20
 
Hi there,

I have a Leak Stereo 20 valve amp which was working fine. Unfortunately, my three year old managed to bypass my defence system to pull out and damage three of the valves. The pins on the valves aren't bent at all, but where they go to a point at the top, he has broken the tip off. (When he did all this, the amp was switched off).

I am NOT in any way technically minded so my queries may seem somewhat naive.

What I would like to know is -

Should I now replace all the valves ?

Which valves should I buy ? - It currently has Mullards, which have been in it for at least 10 years. (The amp has had very little use in the last 4 or 5 years). Should I replace like with like, or are there other valves which would be better suited ?

Where in the UK can I purchase these valves ? What should I expect to pay (ish) ?

Ta very much for any advice !

Andy

fauxpas 14th December 2007 10:17 AM

http://www.hi-fiworld.co.uk/hfw/hfwI...akstereo20.gif

To quote from here

At the end of the 1950s, Leak redesigned the range and added to it. There was the TL12+ with its EL84s, the TL25+ with the larger EL34s, and the most powerful of the three, the TL50+ which used a pair of KT88s. No prizes for guessing the output power of each!

The sad thing is, the bigger they get, the worse they sound. The TL12+ is the best of the bunch, the 50 the worst by far. As for the TL25+, it has the same basic output transformer as the TL12 and sounds hardly any more powerful.

At the same time in 1958, Leak launched two stereo amplifier chassis, the Stereo 20 (EL84) and the Stereo 50 (EL34). The same sonic rule applies here - the smaller 20 floors the larger 50 and is far more reliable to boot.

Out of the entire range, in standard form, the Stereo 20 has the best sound, followed by the TL12+. There are a couple of potential problems in the Stereo 20 - the mains transformer is a little marginal although it's fine in normal operation, and, as was usual for the time, the input sensitivity is very high at 100mV for 10watts output. On the whole however, the Stereo 20 is an excellent design well executed.

SY 14th December 2007 11:32 AM

May as well totally retube it- the replacements aren't very expensive. For ECC83 and EL84, I've had very positive experience with JJ; avoid fashionable NOS tubes. I don't know JJ's pricing in the UK, but here, a replacement set of all the tubes for your amp will run about $100.

If any of your Mullards are intact, you could Ebay them to pay for the new set.

Shoog 14th December 2007 05:50 PM

This may be a silly question, but has the silvering on the inside of the tube gone white. If its still silver then the valves may just be OK.

Shoog

Eli Duttman 14th December 2007 11:24 PM

I agree with SY on the use of JJ EL84s, as they are the best sounding current production variety.

I would use a Sovtek 12AX7LPS in the slot that's shared between the 2 channels, for good S/N performance. Saratov, Russia, made "reissue" Mullard long plate ECC83s get my nod for the other 'X7 positions, for tonal reasons.

DigitalJunkie 15th December 2007 12:23 AM

Re: Replacing Valves Leak Stereo 20
 
Quote:

Originally posted by pubrunner2000
(When he did all this, the amp was switched off).

I hope you keep an eye on him when the amp is switched on!
There are Hot tubes and High Voltages present. Tube amps are best kept out of reach of children,and animals. ;)

frankwm 15th December 2007 01:01 AM

I've a couple of Leak 20's - never really use 'em though.
Did get a stock of valves and also try some types out 'a few' years back.
You don't mention exactly which are damaged but, my 2cents:..

Mullard GZ34 rectifier: - you could replace with Sovtek equivalent with no appreciable (to my ear) quality-loss.

Mullard EL84: - I've a supply of 'Edicron' - & Googling will give you UK suppliers. I can recommend this valve - & 4 from, eg, "rapidonline", would cost 22.

Mullard ECC83: - is a problem.
The "original's" are definitely superior - in terms of 'speed'/translucency - compared to Sovtek 12AX7LPS - itself a rather better version of the 'bog-standard' Sovtek 12AX7 (ECC83).

Unfortunately, original Mullard or the UK 'military' type must now be almost unavailable/hideously expensive (10years ago they were just over a Tenner).

Frank


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