Leak Stereo 20 and a Thank You

[Alex S]

It's impossible for in line attenuators to do any wrong. Every passive IS one.

Different resistors, doubling of resistors, another plug/connection, possible impedance issue, etc. Anyway, they don't work for me (in 2 completely different systems) and that's what matters.

I very strongly disagree!!!! In fact that's nonsense. Any engineer who cannot use modern components and techniques to improve on what was possible in 1958 is in the wrong business.

I presume by 'sympathetically restored' GT means using modern equivalent components to replace worn parts. That's what Mike so carefully did with mine. If you want to hotrod the Leak go ahead. It is not what I was looking for. Just as I was not wanting a hotrodded/supercharched Honda S2000. I accept both items as they are and if I want something different then I will buy something different.

As for valves, I am agnostic and will try things and use my ears. If I find something better than Mullard with the same reliability for less money I will be delighted.

 

[Amormusic]

I've read this stream with interest as I'm thinking a nice ST20 should be something to grace my living room, soon. I have a bonus incoming and thinking I'd like to assign a portion of it to laying my hands on one.

FWIW Alex, although not specifically related to the Leak (as I've never owned one, yet), I've recently moved on a maxed out modded Jolida DAC, and I spent quite a bit of time tube rolling. The EI Yugoslavia tubes mentioned above are special indeed and I rate them v.highly.

If/when I pick up a Leak that's the first thing I'll try to pick back up for it.

The Leak rebuild, looks awesome.

 

[Alex S]

Returning to valve options and ECC83s, the Mullards I bought are starting to look almost cheap. A scan round eBay and other sellers puts just about any valve recommendations here well over £50, including the fancier Chinese offerings.

So what of the usual JJ, Harma, Sovtek etc do people consider good as ‘daily drivers’? For example, what do people think of this lot: https://www.hificollective.co.uk/valves/12ax7.html

 

[Tony L]

The Sovtek 12AX7LPS always used to be my favourite current production ECC83 type, though the JJs aren’t horrible either. Both Croft and EAR fit JJs as stock, so they can’t be too bad as they’d get a lot of returns. Back when I had the Prima Luna I felt the Sovteks were the best in that (phase splitter I think) position, and that was up against some expensive Mullards etc (I actually shared Jez’s view back then, but wider experience has shown context is everything and I’ve since heard Mullards sound astonishing in the Leaks).

The valve market is very odd and I admit I have been exceptionally lucky. I now have a huge stash and a lot of that has found its way to me from other equipment, random auction lots, even given to me. Even so if I still don’t think paying £50-100, even more for a really good Mullard or whatever ECC83 isn’t bad value assuming it lasts 3-4 or more times longer than a Russian or Chinese valve. They usually do. As I say I have never yet had a Mullard ECC83 fail or test as ‘worn’ on my tester. Some of mine are pulls from old and obviously high-use kit, e.g. I was given an old mono Ferrograph Series 4 broadcast tape deck by a neighbour (it is in my kitchen and I have no idea what to do with it!) that was obviously high use as the controls and heads are worn, the long-plate Blackburn F91 ECC83 tests strong and sounds great, as did the EL84! I can’t test the EF86s as my valve tester doesn’t do them, but they sound fine in the TL12 Plus. These are all well used 1959 valves. All are still fine! You can’t expect EL84s to last forever, but the ECC83s and GZ34 should have a very long life ahead. I’d really not be afraid to use them.

PS Same story with the lovely vintage Tektronix scope I’m currently restoring as best I can. The few valves in that I can test with my little tester are the Mullard ECC82s and 83s. All test as strong as a new Sovtek, JJ or whatever, ‘good’ and about 7-8 on the gain matching indicator. This is a very expensive piece of lab kit that would likely have been run all day every day for a decade or more. All the valves I am properly able to identify/date (mainly the Mullards as I understand the codes) date to the point I think the scope was made (1967). Good valves in a piece of kit that doesn’t hammer them have a very, very long life. Likely more than capacitors (though the vast majority of those seem fine in the Tek too!).

 

[Fatmarley]

Different resistors, doubling of resistors, another plug/connection, possible impedance issue, etc. Anyway, they don't work for me (in 2 completely different systems) and that's what matters.

I tried it directly in my Naim preamp years ago (just the resistors), and it killed the sound. The dynamics and life was sucked out of the music.

EDIT: I did bypass the buffer stage of the preamp a while before this mod, so I don't know if that had something to do with it.

 

[Alex S]

Tony, can you please post a link to the Sovteks I’m looking for.

 

[Tony L]

Tony, can you please post a link to the Sovteks I’m looking for.

Sovtek 12AX7LPS, some here at Watford Valves. As with everything else they’ve gone up, I still think of them as £10 valves, but they are good. I think you will prefer the Mullards though. These are the JJ ECC83s that the likes of EAR, Croft etc fit as stock. Again reasonable (maybe nicer in the mid than the Sovteks, but less deep and grippy in the bass). At £30 or so a throw I’d personally prefer to pay say £90 for decent tested vintage stuff that will likely work out cheaper as they just keep going so long.

PS Prices are without VAT and I think delivery is £4.

 

[Alex S]

Thanks. I am restricting my Leak playing as you know. I have the valves that Mike supplied so I’ll wait to see how long my Mullards last in my case before deciding. The only spanner in that works is valve prices are only going one way.

 

[Marchbanks]

Can’t live with each other and can’t live without every forum needs its pantomime side.

Or as Norm famously said on Cheers - ‘Women, eh? Can’t live with ’em... [pause] pass the peanuts, please.’

 

[chiily]

I've a set of sovtek 12ax7LPS in my ST20, and yes they have shot up in price. I paid £15 each delivered from here https://valvetubeguitaramps.com/product/sovtek-12ax7lps/

 

[Alex S]

Thanks, that’s about the same as Watford after add-ons. Not sure how they can charge £26-something for SD.

 

[Tony L]

The only spanner in that works is valve prices are only going one way.

I suspect they are a bit hyped-up due to the war in Ukraine so I’d certainly not stockpile Sovteks, JJs etc at this point. The vintage stuff will keep going up as that supply is obviously finite. Whenever you buy-in will seem good after a year or two. I can’t ever see prices dropping as it isn’t just the audiophile world, the guitarists are hunting exactly the same Mullards, RCAs, GEs, Telefunkens etc.

If you wanted to gamble a couple of £k I suspect you could buy several sets of say nice 60s Mullards at 2022 prices, run each set for 5 years, and sell it for more than you paid assuming they all still tested good.

My thinking is kind of related to that except I don’t sell. I have multiple sets of nice valves and I tend to rotate them, say a year in (my usage is pretty light), then flip another set in, then another etc. That way I should still have multiple good sets with similar ages on them from which additional sets could be made if one or two valves failed. There is a school of thought with power valves to buy two or more sets and do exactly this as you aren’t ever left with three good valves because one died prematurely. It should mean you get a heck of a lot more actual mileage/hours by the time you do eventually get down to that final working quad. I’ve done this with the Russian 6P14P-ERs and I have seven similar enough Mullard EL84s (one perfect date-matched quad and three random loose ones).

 

[Alex S]

I have family in Russia. It’s not easy for them, but perhaps I can give them a project to take their mind off things.

 

[Tony L]

I have family in Russia. It’s not easy for them, but perhaps I can give them a project to take their mind off things.

If so get them hunting for military 6P14P-E* types. I can’t remember the specific one off the top of my head (I’ll dig some out later). There are several and the Russian letters are not always translated correctly (ER, EV, EP etc) which adds to my confusion, but the one you really want has gold pins and twice the rated lifespan of the standard version. Very good valves indeed.

PS It is the 6П14П-EP (usually translated as ER in English) you want, these have a 10,000 hour lifespan. The others are 3000 (no suffix) or 5000 (EB). Some details here. I’ve examples of all of them. I stockpiled a bit when they were £40 or less a quad delivered (i.e. well prior to Brexit!).

 

[Alex S]

Tony, ValveampUK have stock of those at £28 each (90's date codes). The 5000 hr ones for £15 (80's date codes). Doesn't seem that bad. Do you think they sound much the same?

 

[Mike P]

Tony, ValveampUK have stock of those at £28 each (90's date codes). The 5000 hr ones for £15 (80's date codes). Doesn't seem that bad. Do you think they sound much the same?

Alex, the valve set that the amp came with includes a quad of matched NOS 6P14P. Given that you've also got the Mullard el84's you're pretty well sorted now I would think.

 

[GT]

I presume by 'sympathetically restored' GT means using modern equivalent components to replace worn parts.

I am aware that some doing servicing, don't have any choice using new parts if they don't have a stock of NOS mil spec parts to hand, but in most cases new parts can ruin the sound of the amplifier like the ST20, as in using metal film resistors for example.

 

[Alex S]

Alex, the valve set that the amp came with includes a quad of matched NOS 6P14P. Given that you've also got the Mullard el84's you're pretty well sorted now I would think.

I agree. Really I'm broadening my knowledge rather than trying to spend money.

I am aware that some doing servicing, don't have any choice using new parts if they don't have a stock of NOS mil spec parts to hand, but in most cases new parts can ruin the sound of the amplifier like the ST20, as in using metal film resistors for example.

GT, Mike, who posted above you, restored my ST20. I believe he used like for like wherever possible.

 

[Mike P]

It's impossible for in line attenuators to do any wrong. Every passive IS one.

Jez makes a very good point Alex. You can think of the inline attenuators as just a passive with only one setting and no source selector. Adding them just achieves the same thing as if someone opened up your Khozmo and changed the resistor values inside. No more, no less (assuming all brands of resistors sound the same, which is an debate for another day).

 

[Tony L]

Though by saying that if it sounds different, it is different. Passive preamps do sound different from one another, it may not be night and day, but it is there and a Stereo 20 is more than good enough to hear it.