What is the suggested operating point for GM70 in class A (not A2 or A3)?
What is the loaded impedance for that?
What is the loaded impedance for that?
About 80mA is OK for this triode.
A-C should be about 1000-1100V,
Anode load 6-8k. Don't try to get
the highest possible power from
the tube, output about 15-18W
is OK.
A-C should be about 1000-1100V,
Anode load 6-8k. Don't try to get
the highest possible power from
the tube, output about 15-18W
is OK.
I've tried 10K loaded but some recommended 8K loaded. What do you think?
Also, what's wrong with highest possible power?
Also, what's wrong with highest possible power?
I'm running at 1kV, 100 - 120mA and 7K plate load. I get roughly 20W output.
Long ago load line calculations indicated 20W @ 7K, and maybe 25W @ 6K if I recall correctly, I also considered a 5K load line, but decided the added power came with too much distortion attached. I choose the higher impedance in order to reduce distortion. Many people have run them into loads as high as 10K with good results.
I'd say at minimum the output transformer insulation should be rated for continuous operation at a combined 2kV - 2.5kV ac+dc, this will prevent failure. (My amp swings 1kVac p-p with 1kVdc, and is insulated for 2.5kV. ) And please ground the secondary for safety.
Over time I have come to prefer the graphic plate version, although others prefer the copper plate version of the GM70.
For the 1kV supply I used solid state FW bridge rectifier with silicon carbide rectifiers into CLCLC filters.
Long ago load line calculations indicated 20W @ 7K, and maybe 25W @ 6K if I recall correctly, I also considered a 5K load line, but decided the added power came with too much distortion attached. I choose the higher impedance in order to reduce distortion. Many people have run them into loads as high as 10K with good results.
I'd say at minimum the output transformer insulation should be rated for continuous operation at a combined 2kV - 2.5kV ac+dc, this will prevent failure. (My amp swings 1kVac p-p with 1kVdc, and is insulated for 2.5kV. ) And please ground the secondary for safety.
Over time I have come to prefer the graphic plate version, although others prefer the copper plate version of the GM70.
For the 1kV supply I used solid state FW bridge rectifier with silicon carbide rectifiers into CLCLC filters.
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