GM 70 Schematic needed!

[enzoastro]

Yeah stayed cool at roughly 280-300ma draw the heater transformers and diodes were another thing!
Enzo

 

[widowmaker]

I used an antek 400-400 500ma toride for my gm70 amp, choke input gave mw 670v with the gm70's drawing 120ma each and 45ma for the driver stage, which is mu follower with 6e5p at 22.5ma/180v/3.7Vgk.
fitting a few small value caps at the ps input got me to 800v.

i now have the antek 500-500v 400ma to give 900v with very little capacitence, i like to think of it as choke input with snubbing caps ;-)

hope that may be of helkp
enzo

The value of 670V (and even 800V) is too low for GM-70.
If you want to get the best from GM-70 you have to use at least 1000V supply and anode current not more than 80-90mA.
Higher drawn current means also higher ripple in power supply, regardless of how big chokes and caps are used there.
The difference is quite big, it is tested already, believe me.
In my case I'm using for each channel one 400VA transformer with secondary 1.05kV AC (1050-0-1050 full wave).
Russian damping diodes 6C10P as a rectifier, then RC(100R+20uF) and two LC filter(20H+80uF) in series. Ua-c is about 1150V (Ia=85mA),
about 120V at cathode resistor and about 30V at output transformer.
Anode load is 10k.
Dampers 6D22S are not suitable for high end amplifiers due to their very low internal resistance (this is not a solid state device, right ).
For sure russian 5C4S/M is one of the best rectifiers for high end audio, but in our case it is useless because of its relatively low reverse anode voltage.

 

[enzoastro]

Thanks for the advice;-)

Its running at 930v 85ma/gm70 now

i found whats made the biggest difference so far was the coleman filiment regulators and power supply caps, and have to say i like low impeadence power supply sound, not fasionable i know!

I do have a few 10h 350ma chokes so may try another LC stage after the cLC or even a ss regulator. Size and heat is the limiter for me, im trying to keep to 60 x 30 cm for a 2 channel chassis, not inc the heater supplies.

enzo

 

[djn]

Dampers 6D22S are not suitable for high end amplifiers due to their very low internal resistance (this is not a solid state device, right ).

Can you say more about this. I am planning on using the 6D22s.