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Leak Stereo 20

John_73 said:
Does anybody know the real-world operating voltages for C3 and C5 please? From the circuit diagram it seems C3 would be 160V max, but nothing is there for C5. I have 0.1uF 400V sets and 200V sets of the K40Y-9 Russian paper in oil types, and would prefer to use the 200V ones if possible as they’re less bulky, but wasn’t sure if the voltage rating was a tad too low. Cheers.
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Real world, Leak used 350 volt types originally, so use the 400 volt ones you have. There is room.
C3 'sees' more than 260 volts before the EL84s start to conduct fully and pull the HT down. Then it depends on the ECC83 you have in V1. Expect more than the diagram voltage with modern digital meters - you could well measure 200+ volts.
C5 max will be somewhere near 30 volts (V2 cathode voltages at 37 off diagram) so actually could be lower voltage.

Just measured mine, C3 202 volts (Mullard ECC83), 218 volts (Sovtek 12AX7LPS) with ref to chassis. So 200 volt caps would be just good enough once all the valves are conducting...
C3 measures about 28 volts the instant you put the meter on it and falls to 20 due to the load of my meter.

Cross posts, I was busy with my meter...
 
Thanks very much Jez and Al! Appreciate you taking those measurements too Al, useful to have some hard data. I think I'd better stick with the 400V items then just to be on the safe side, and as Tony says once fitted they'll likely be one of the last things to ever need replacing again, they're built so well.

Still deciding what resistors to go for. For keeping (pretty much at least) close to the visual looks of the originals I'm tempted to use the 2W set of TE carbon films I have, with *perhaps* a little modernising with Dale metal film types (which also look the part) just for the input resistors to keep noise low in that first valve only. So R1, R2 and - perhaps - the plate load R5. I know some don't mind what is underneath, but I do like to maintain a bit of visual eye-candy continuity with what was in there before. A balanced restoration rather than going too far in one direction (all metal films and bright yellow polys) or the other (sourcing in-tolerance carbon comps and NOS TCC PIOs etc). Have discounted Kiwames as the leads on the 2W ones are unfortunately too short in some instances and I hate adding on bits of wire. Takmans to be frank I'm not sure about as I'm no longer a fan of fancy boutique components from companies I don't know anything about, and their data sheets seem designed by marketeers! Though Tony seems extremely happy with his ST20 containing Takmans. Pretty sure there's barely any audible difference between those and the TE connectivity carbon films though. The R7s, R9s and the R4s were the only resistors that still measured comfortably well within spec, so will be keeping those where they are. Nice to keep a few original components in there.
 
John_73 said:
Takmans to be frank I'm not sure about as I'm no longer a fan of fancy boutique components from companies I don't know anything about, and their data sheets seem designed by marketeers!
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Are they really any more ‘boutique’ than any other carbon-film resistor in a metal-film world? They don’t have an especially boutique price and being made in Japan I’m inclined to trust them. They seem to have a good reputation in the restoration community though I agree the marketing is a bit out-there! The ones I’ve measured seem bang on too. I’ve no view on sound as I’ve never compared them to anything. One thing I like is they have a complete set for the Leak aside from the four 3m3, so it is almost possible to get everything in one order and the 1W ones will span the widest tags.
 
Yep you will usually need to extend the wires on modern resistors... or what I do which is cut the old ones out leaving an inch or so of the original wire still soldered in place and then solder the new ones to those ends.
 
Tony L said:
Are they really any more ‘boutique’ than any other carbon-film resistor in a metal-film world? They don’t have an especially boutique price and being made in Japan I’m inclined to trust them. They seem to have a good reputation in the restoration community though I agree the marketing is a bit out-there! The ones I’ve measured seem bang on too. I’ve no view on sound as I’ve never compared them to anything. One thing I like is they have a complete set for the Leak aside from the four 3m3, so it is almost possible to get everything in one order and the 1W ones will span the widest tags.
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My opinion of them soured a tad when I saw this contraption (top of the list):

http://solidgreen.co.jp/products/takman.html

They have been making resistors since 1997 from what Google Translate makes of their web pages, so as you say likely nothing wrong with them, and many satisfied users out there:

https://translate.google.com/translate?sl=auto&tl=en&u=http://www.takman-e.co.jp

Think on reflection I'll stick with the TEs though. They look the part, constructions seems sound from the data sheets plus I have at least 10 of each value so should be able to match them to within 2% or better with a bit of luck.
 
I usually avoid boutique parts also. Manufacturing electronic components of precision and reliability generally demands a huge factory with money no object resources and therefore boutique parts are often just standard ones bought in from a major company and re-badged... so you pay maybe 5 X as much for a fancy looking logo on them...

I would not trust parts made by some small outfit that's not been around for long, is maybe using worn out equipment bought in when mainstream companies have abandoned something as obsolete, and who are not used to building to military or aerospace quality standards with all the testing regimes involved in that. With major manufacturers it is often the case that even non mil spec gear is built to the same standards as mil spec but just isn't tested as comprehensively to be sure of mil compliance.
 
John_73 said:
My opinion of them soured a tad when I saw this contraption (top of the list):

http://solidgreen.co.jp/products/takman.html
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I have to admit I’ve read that three times now and I still don’t know what it is!

I suspect the resistors are good though, mine have been in several years now with no issue and this amp really is quiet - I can stick my ear up against the JR149 tweeters and barely hear even the slightest hint of hiss. It certainly does the ‘black silence’ soundstage thing.
 
Just to further comment on the above post I stuck it and the ProPassion down in the Tannoy system for a couple of days and there just isn’t any hiss or hum I can hear short of sticking my ear right up to the compression horn of the Tannoy.

The Leak sounds great with the Tannoys (8 Ohm tap); just tons of headroom, that 10 Watts could easy blow the windows out. It has a wonderfully coherent and open sound, yet really grippy, tight and punchy in the bass with plenty of weight too - nothing stodgy or boring here at all, it can really groove. It really is a superb amp IMO.
 
Tony L said:
Just to further comment on the above post I stuck it and the ProPassion down in the Tannoy system for a couple of days and there just isn’t any hiss or hum I can hear short of sticking my ear right up to the compression horn of the Tannoy.

The Leak sounds great with the Tannoys (8 Ohm tap); just tons of headroom, that 10 Watts could easy blow the windows out. It has a wonderfully coherent and open sound, yet really grippy, tight and punchy in the bass with plenty of weight too - nothing stodgy or boring here at all, it can really groove. It really is a superb amp IMO.
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Must admit I always thought it a bit odd that you didn't use the Leak with the Tannoy's... it's a better amp than the 303 and historically correct for old Tannoy's plus the greater 8R power of the 303 would better suit the low efficiency of the 149's... and I'd guess the 303 and JR149's just about overlapped historically too!
 
Arkless Electronics said:
Must admit I always thought it a bit odd that you didn't use the Leak with the Tannoy's... it's a better amp than the 303 and historically correct for old Tannoy's plus the greater 8R power of the 303 would better suit the low efficiency of the 149's... and I'd guess the 303 and JR149's just about overlapped historically too!
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Its a preamp thing! My turntable is in the Tannoy system, the Leak is just too high-gain to use with my JC Verdier valve preamp even on its lowest output setting, and that’s where my phono stage is (and its a nice one)!

The Verdier/303 makes for a very nice sounding combo with the Tannoys, plus the 303/Lockwood Tannoys is pure studio monitor pedigree so I’m not too bothered really. I’ll obviously have to rethink if I retire/move and downsize to a single system, but I don’t need to worry about that for a good while yet.
 
Tony L said:
Its a preamp thing! My turntable is in the Tannoy system, the Leak is just too high-gain to use with my JC Verdier valve preamp even on its lowest output setting, and that’s where my phono stage is (and its a nice one)!

The Verdier/303 makes for a very nice sounding combo with the Tannoys, plus the 303/Lockwood Tannoys is pure studio monitor pedigree so I’m not too bothered really. I’ll obviously have to rethink if I retire/move and downsize to a single system, but I don’t need to worry about that for a good while yet.
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In line attenuators or a passive set to say "3" out of 10 between Verdier and St20 would sort it of course... but I'm sure you know that:)
 
Tony L said:
Just to further comment on the above post I stuck it and the ProPassion down in the Tannoy system for a couple of days and there just isn’t any hiss or hum I can hear short of sticking my ear right up to the compression horn of the Tannoy.
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Reading this post again today got me thinking as I've been getting some hum from my setup. Nothing too bad that has any real impact on listening pleasure but there was certainly an audible hum coming from the speakers that could be heard from the listening position with the volume set at normal level.

It was a 50Hz type hum so my initial thought was that I had a ground loop. I tried some poking around with an earth lead but nothing made a difference.

My amp is freshly rebuilt to the same spec as Tony's (well almost) so I was confident that the amp wasn't to blame.

Then I tried moving the passive pre and....Bingo! I found the cause of the hum. It turns out that the passive pre (a Glasshouse TVC) is really quite sensitive to picking up hum if it is too close to the Leak. In particular the area towards the back of the amp around the transformers seems to be broadcasting a lot of 50Hz EMI.

I've now rejigged my rack to put the pre several shelves above the Leak and the hum has dropped right off.
 
Excellent, that makes sense. I keep my ProPassion a fair distance away and it is hooked up with nice screened vdH D102. The Leak is so sensitive it will find any noise upstream. You need a damn good quiet ECC83 in that first position too, and a clean valve base!

I’d like to try a TVC properly one day, I’ve always been curious. I’ve heard them before and liked them, but never really lived with one.

PS When putting it all back today I grounded the ProPassion’s case as I noticed it had an earth terminal on the back. I just hooked a thin lead from one of the Leak’s speaker returns to it as that’s just chassis/mains earth according to my multimeter. Don’t think I can hear a blind bit of difference, but it cost nowt!
 
TVC's are an autotransformer and so will be rather sensitive to magnetic hum fields.

St20's are really quiet on background noise though yes. In standard form you will normally hear a very audible mains hum come up in volume as it warms up and then fade out again... this is normal for a St20.
 
Mike P said:
What do you recommend?
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I use Blackburn Mullards of a similar date to the amp as they seem to suit my taste, though any good valve will do. That first input position really will show any noise, e.g. I have a couple of otherwise very nice sounding long silver-plate communist-era EIs that are way too noisy and microphonic to use there, but are usually ok in other positions.

I’d not be afraid of spending the extra for really good NOS in this amp as the ECC83s and GZ34 do seem to last pretty much forever. I’m pretty sure the pair of Mullards I have in the phase splitter position of my amp at present are actually original to the amp, they came with it and the date codes are in range. They measure fine despite being older than me! I do have a perfect set of ‘65 Mullard EL84s which are worth serious cash, and I’d not personally pay the extra over the Russian military 6P14P-E* types (which are excellent), but I would for the ‘83s and GZ34.
 
Thanks Tony.

I've already sorted myself with a quad of NOS 6P14P-EV and I've got a used but 'tested good' Mullard GZ34 on the way. I still need to get a spare set of ECC83's sorted though.
 
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