Hi friends,
I recently finished a hybrid circlotron amplifier, schematic you can see on attachment.
Is my first attempt in solid state, I only have experience in tubes, but I liked the idea of this topology.
My first listening test was very impressive unfortunately protection circuit at the output shut down when high level music applied.
I connect my signal generator at the input and a dummy load at the output to take some measurements.
When there is no signal in the input there is no DC offset at the output.
When I start raise the signal in the input, there is DC offset at the output and raise as the input raise until shut down from the protection circuit at 500mV DC. input about 300mV AC 1KHz sine wave.
What may cause this problem?
Some information:
input transformer sowter 3575,
tube ECC82 in PP with LL1660 interstage, at 250V power Supply, cathode bias 1K each triode, 8mA each
Output mosfets Exicon ECX10N20, Matched for Idss, bias 1,5VDC , Power supply 42VDC, run at 1A each one
I recently finished a hybrid circlotron amplifier, schematic you can see on attachment.
Is my first attempt in solid state, I only have experience in tubes, but I liked the idea of this topology.
My first listening test was very impressive unfortunately protection circuit at the output shut down when high level music applied.
I connect my signal generator at the input and a dummy load at the output to take some measurements.
When there is no signal in the input there is no DC offset at the output.
When I start raise the signal in the input, there is DC offset at the output and raise as the input raise until shut down from the protection circuit at 500mV DC. input about 300mV AC 1KHz sine wave.
What may cause this problem?
Some information:
input transformer sowter 3575,
tube ECC82 in PP with LL1660 interstage, at 250V power Supply, cathode bias 1K each triode, 8mA each
Output mosfets Exicon ECX10N20, Matched for Idss, bias 1,5VDC , Power supply 42VDC, run at 1A each one
Last edited:
If the applied signal is AC then it can have a dc offset but shouldn't trigger your circuit as it keeps passing through zero volts. If your circuit detects average DC throughout the signal then perhaps the two triodes aren't putting out same size signal and need balancing ? Or maybe one is clipping before the other ? I designed my own DC speaker protect circuit but it only fires if DC above/below +/- 2 volts is there for > 500mS. It doesn't look for average dc level. So if the signal passes through zero then DC level count is zeroed.
The only thing came in my mind also, is the unbalance amplification from the two triodes.
Is very hard to find matched triodes in the same glass.
I made a simple current source with a jfet for each triode, for double source ac about 600mV the protection cut again at 500mV DC. The result is better but not best. I still can’t run the amp for full power
Any recommendation to have almost zero DC at the output?
Is very hard to find matched triodes in the same glass.
I made a simple current source with a jfet for each triode, for double source ac about 600mV the protection cut again at 500mV DC. The result is better but not best. I still can’t run the amp for full power
Any recommendation to have almost zero DC at the output?
The rest current in 1A for each mosfet, calculated from voltage drop in 1ohm resistors at the power supply
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.