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Leak Stereo 20

Discussion in 'classic' started by Tony L, Jan 31, 2012.

  1. Arkless Electronics

    Arkless Electronics Trade: Arkless

    I've done all sorts of modifications to mine to pretty good effect, all reversible of course.
    I designed and built a regulated PSU for it a few years back but never got round to fitting it... One of these days!
    I also of course offer a commercial service in the repairing and refurbing of these and all similar valve amps.
  2. Tony L

    Tony L Administrator

    As a rule of thumb keep them as short as possible and as low capacitance as possible. Not a huge issue with the Leak as its input impedance is very high at 1mOhm, but I'd still stick to sensible low capacitance cable. Van den Hul cable tends to be very low capacitance and is good with passive pres IME.
  3. Mr.Nic

    Mr.Nic pfm Member

    Thanks Tony, appreciate your input!
  4. Tony L

    Tony L Administrator

    I now have two! The local auction came good again today...


    A rather tidy 1965 grey Stereo 20 complete with box, manual and leads. I paid way more than I was hoping as there was one other punter in the room that obviously knew what it was and drove it right up. Without him I’d have had it for £30, with I ended up payng £473 including auction fees, which was very, very close to my own red-line of £500.


    The reason I paid quite a hefty wedge for something I already own is it looks totally stock, maybe even NOS even though it has a couple of minor cosmetic issues (one scratch and some slight discolouration where the octal cable was coiled on top which won’t come off). The reason I suspect it may be NOS is the tube set is certainly original, all the date codes match, the three Mullard ECC83s and EL84s being a proper matched trio/quad when it comes to date codes and batch numbers, and more significantly there is not even the slightest hint of any heat marking on the circuit board around the green ‘drop’ resistor. I’ve never seen a Stereo 20 this clean underneath.

    Leak Stereo 20 prices seem to be rocketing at the moment, some good examples going over £1k, so really I bought this as an investment. I’m just going to keep it as-is as people seem to pay the most money for really good unrestored originals so they can choose their own rebuild strategy. I can certainly understand this as I ended up ripping out the previous rebuild of my bronze one and doing it with what I view as more sympathetic components. I’ll try out some of these lovely tubes though!

    PS Anyone know if it is possible to check the transformers with a multimeter without powering it up (which I obviously can’t do)? I have no reason to suspect any issues, but it would be nice to know they were ok.
  5. Barrymagrec

    Barrymagrec pfm Member

    Are you the same Tony L who keeps saying he has too much kit?......

    Looks very clean indeed, probably hardly used, pretty good investment I should think.
  6. Tony L

    Tony L Administrator

    Ha, indeed! Not too hard to stash a box though, especially if it may potentially double the investment! I know where I could get a Wharfdale SFB3 for not a lot of cash, but I’ve nowhere to put that!

    PS Here’s another underneath shot, I’ve never seen any Stereo 20 with no heat marking at all under the green resistor!

  7. Arkless Electronics

    Arkless Electronics Trade: Arkless

    Looks NOS. I've never seen one that clean. Not even a hint of wax leaking from the transformers. It's a pity it will need a complete rebuild to be any use....

    You can only do basic tests on the transformers with a multimeter. ie test they are not open circuit or shorting to ground. You could remove the GZ34 and power it up and test the AC voltages from the mains TX of course.
  8. Robert

    Robert Tapehead

    Looks lovely Tony. I prefer this chassis colour to the beige/sand one that is more common.
  9. Dowser

    Dowser Learning to bodge again..

  10. Dark Energy

    Dark Energy pfm Member

    WOW! That's amazing! ST20 is truly a great amp, far better than most would imagine. £473 I don't think that's a high price these days, they were going for £300 back in the 90s (and that's for normal worn types). Nice!

  11. Tony L

    Tony L Administrator

    Well the 1965 ‘four notch’ Blackburn Mullard GZ34 rectifier certainly works! I’ll try the ECC83s and EL84s later. I’m rather curious to hear the Mullard EL84s assuming they are ok as I’ve never compared them to the Russian 6P14P-EV I run in mine. In a way I hope they aren’t hugely better as they are a hard to find and therefore expensive tube these days. I’ve been running similar period Mullard ECC83s and a slightly later (‘seven notch’) GZ34 in my Stereo 20 for a good while now, just chickening out of finding a set of Mullard EL84s.
  12. Tony L

    Tony L Administrator

    ...now got the full tube-set running in ‘my’ Stereo 20 and they are certainly fine. I stuck the EL84s in before taking a break for food, now the three ECC83s. FWIW I don’t feel the Mullard 84s are better than the Russian 6P14P-EV, just slightly different; a little more airy and 3d in the treble, but a little less punchy and dynamic too. Swings and roundabouts really, both being really nice. I’d not personally pay 3x or more the price for NOS Mullards, whereas I would with the ECC83s and GZ34, and have done!

    The more I look at this amp the more I suspect it really is NOS. Things like the speaker terminal screws just look mint with no indication anyone has ever taken a screwdriver to them, then as commented abve the total lack of heat evidence. The negative being it does have some cosmetic blemishes through bad storage, the most annoying being the marking to the top painted area between the two rows of tubes where the paint has I think reacted to the octal lead being coiled there, so its NOS, but certainly not mint! You’d not notice it in use though, it still looks nice and the sides and back are all very clean and tidy. (I uploaded the pics straight from my iPhone with no post-processing and they are rather flattering and make ut look far too dark, it is the charcoal grey one would expect).

    The potential NOS aspect is obviously very good news for the valves. This is obviously an collectable/expensive set of tubes and very likely worth what I paid for the amp. All 1964 yellow-print Blackburn Mullards with matching date codes on the trio of 83s and quad of 84s. I’ll run them for a few hours tonight, which may actually do them some good as it should get any rogue particles that need sticking to the getter stuck to the getter, and then I’ll just put everything back in its box and sit on it a few years until it is time to move it on!

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