Thanks for the sujestions. I have a bleeder resistor (to stop turn on noise), but didn't put in the circuit.
This circuit is working well enough for me to be reluctant to mess with it too much. It been my first tube project, I'am quite please with the result.
I am collecting the components together to try some other simple line amps with different valves. I just was given a bag of tubes from a TV repair man. Most are totally useless TV tubes, but there are a few that might perform. There are a rake of UY41's and one each of ECC83,ECC84 and ECC85. Unforntunately the rest are mostly "U" type versions of the more useful "E" type.
Thanks Shoog
This circuit is working well enough for me to be reluctant to mess with it too much. It been my first tube project, I'am quite please with the result.
I am collecting the components together to try some other simple line amps with different valves. I just was given a bag of tubes from a TV repair man. Most are totally useless TV tubes, but there are a few that might perform. There are a rake of UY41's and one each of ECC83,ECC84 and ECC85. Unforntunately the rest are mostly "U" type versions of the more useful "E" type.
Thanks Shoog
Try changing that 1M resistor to about 1K on the grid of the lower 6922. This will lower the effect of any grid current to neglible and also greatly improve the performance of this circuit as a cc load on the upper triode.
Your cascode connected source follower is running very close to saturation, and would be ineffective with output voltages above about 1Vpk where the follower is saturated. The -3dB corner of your follower is 160Hz, below which it becomes less and less effective.. I would increase the value of that 10K resistor to say 100K which would drop about 10% of the supply across the mosfet (+bias say 5V) keeping it out of saturation at reasonable output voltages, lower the load on the output and move the -3dB corner down to 16Hz so that the follower actually works at low frequencies.. Alternately I would eliminate it altogether if you cannot boost the supply to at least +/-80V.
Your cascode connected source follower is running very close to saturation, and would be ineffective with output voltages above about 1Vpk where the follower is saturated. The -3dB corner of your follower is 160Hz, below which it becomes less and less effective.. I would increase the value of that 10K resistor to say 100K which would drop about 10% of the supply across the mosfet (+bias say 5V) keeping it out of saturation at reasonable output voltages, lower the load on the output and move the -3dB corner down to 16Hz so that the follower actually works at low frequencies.. Alternately I would eliminate it altogether if you cannot boost the supply to at least +/-80V.
Hi there,
I checked the mosfet for clipping today - no sign. My gainclone main amp runs at high gain so headroom problems have never been a problem. I might try the 1K for 1M substitution.
At this stage I am working on a +/-90V supply version with a bias point of -2V which should be safe. I was thinking of changing the Fet for a bipolar so that I am not losing 4V of supply.
Shoog
I checked the mosfet for clipping today - no sign. My gainclone main amp runs at high gain so headroom problems have never been a problem. I might try the 1K for 1M substitution.
At this stage I am working on a +/-90V supply version with a bias point of -2V which should be safe. I was thinking of changing the Fet for a bipolar so that I am not losing 4V of supply.
Shoog
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