Edwar65

[edwar65]

Hi, newbie to group, I'm based in Wales in the uk and I'm in process of firing up a leak stereo 20 with a home brew passive pre amp and a rega planar 2 turntable, plus an arcam cd 73 CD player.
Like to know more about the solid state rectifier/input stage mods that have been mentioned by a member and moderator by name of dtaylor from the uk?

Any help much appreciated
Tom.

[AlfaGTV]

Welcome Tom!
Cant help you with the LEAK issues though, but i'm sure someone will be able to answer your questions!

What kind'a music gets played on the kit then?

Regards /Mike

[John]

Welcome to AOS Tom

[edwar65]

Hi, into all sorts of music from female vocal, jazz, uk 80,s bands, all sorts really?
Tom

[The Grand Wazoo]

Hi Tom,
Welcome to AoS. Nice to have you here.
Cheers

[MartinT]

Hi Tom and welcome to AoS. About the Leak Stereo 20, I think you might mean me? Unfortunately I've now sold it, although that brought a tear to my eye. Wonderful amp with the most glorious midrange ever.

Yes, I did perform some input stage mods published in Hi-Fi World many years ago. I also swapped the GZ34 rectifier for a RATA solid state module, now no longer available. I can't find any reference to the HFW article online, unfortunately, and don't seem to have the supplement any more either :(

[edwar65]

Hi,thanks for all the replies everyone.Martin there was a link marked 'notes' in the mail where you advertised your amp up for sale, for some unknown reason,
it takes you to a link which is not found?
I'd really like to know more about the mods available,mine is running in triode mode and for some reason the guy who runs Servicesound in East Sussex,has suggested that its not a good idea to do this with this amp,although I can't remember why.
He seems a genuine guy and very helpful and has suggested very similar mods done to martins amp,check out his website for the leak mods he does and anyone let me know what you think,I think his fee for the mods is around £300 to include a new set of electro harmonix valves,as he suggests these are very reliable?
thanks again
tom

[MartinT]

Tom - from my old website (now no longer online):


This involves essentially changing the biasing of the phase splitter stage to allow direct coupling from the primary stage, reducing gain and fitting the more linear ECC82 valve for the original ECC83 type. I also added the resistors to isolate the transformer windings from the output valve screens.

Take R6 and R11 (the only 3.3M resistors in the circuit) and join them together in the air, isolating them from R8 & R9. Now remove R9 (22k) and replace with a link, remove R8 (1k) and replace with one of 100k. This last one is between the valve socket and circuit board. Remove C3 (0.1u) and replace with a link. Add the 100R resistors to the transformer connections (on my unit, the white and purple wires should be removed from the transformer solder tags and the 100R resistors inserted in line). Replace V2R and V2L with ECC82 valves.

The above will give you a significant improvement for very little expense. The source for this design improvement is Hi-Fi World magazine. Other improvements, depending on how much you want to spend: 1) Replace the two electrolytic reservoir caps with RATA 32+32uF Ansar polypropylene types. The old caps will be good for nothing if they are original. The RATA units are physically much larger. You must use cap clips and drill two holes in the base plate to mount each one. This gives a useful improvement in dynamics and transparency and much greater bass impact. This is (in my opinion) the single best mod you can make after the above circuit change. 2) Replace the GZ34 rectifier valve with a RATA fast recovery solid state module (this plugs into the valve socket). This improves the focus of the sound stage. 3) Replace all the 47uF (or 50uF) 25V electrolytic capacitors. Use 47uF 50V Black Gates for the output valve bypass caps and Sanyo Os-Con 47uF 25V types for the other two. This cleans up the transparency a lot. 4) Replace all the remaining 0.1u (or 0.22u) caps with Kimber Kaps (expensive). This cleans up the transparency a little. The combination of all these mods gives you a valve amp with incredible transparency and detail, and power which defies its 20W per channel rating.

The RATA caps and rectifier are no longer available, so you would need to substitute as appropriate. Good luck!