Hi,
I just built this 100w tube amp, and the preamp section has a lot of static.
The amp section is clean. Only hums a bit when the master volume is all the way up.
This is a 3 stage 12ax7 circuit.
Plate follower - Pot - cathode follower - tone stack - plate follower - Pot
The static increase when turning up the first pot, and you can hear it being adjusted by the tone stack.
I have built this circuit twice before, and it is my cleanest build yet. But this time it has major static. The only thing different is I am using can caps for the power filtering, and one of them is under the first part of the preamp.
Have tried different tubes but no change.
All parts are new
Brian
I just built this 100w tube amp, and the preamp section has a lot of static.
The amp section is clean. Only hums a bit when the master volume is all the way up.
This is a 3 stage 12ax7 circuit.
Plate follower - Pot - cathode follower - tone stack - plate follower - Pot
The static increase when turning up the first pot, and you can hear it being adjusted by the tone stack.
I have built this circuit twice before, and it is my cleanest build yet. But this time it has major static. The only thing different is I am using can caps for the power filtering, and one of them is under the first part of the preamp.
Have tried different tubes but no change.
All parts are new
Brian
It is possible your pot's wiper is losing contact intermittently that the grid is floating. Do you have a high value resistor, say 1M or higher, between wiper and ground?
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Tubes used: JJ's and EH It is not the tubes. I pulled the EH's out of another amp with the same circuit, that had no problem
Resistor: just a 27K that I am using to cut the gain down a bit. it originally had none.
Only differents now is volume.
Will try that.
Resistor: just a 27K that I am using to cut the gain down a bit. it originally had none.
Only differents now is volume.
Will try that.
if power amp sensitivity is high ...and use another gain stage with 12ax7 white noise come to speaker and tone control can make increase the white noise of first stage 12ax7.
different is just gain in your new amp project !!!!😉
this is guitar amp ?😕
Here is the schematic. My pdf printer sucks so it wont print the whole thing.
The part cut off is just the power amp section, and that is fine.
I made some changes since last post. Lowered the voltage on the cathode follower stage.
It seems a little more tamed as long as I dont crank it up a lot.
Although I have a 47k res on the last pot to bring down the volume.
this 100w is insane
I now have a wooshy sounds when turning the first pot. Always in the same place on the wiper.
Is it normal to have negative 140mv DC on the pot when turned all the way up, and no input signal?
The part cut off is just the power amp section, and that is fine.
I made some changes since last post. Lowered the voltage on the cathode follower stage.
It seems a little more tamed as long as I dont crank it up a lot.
Although I have a 47k res on the last pot to bring down the volume.
this 100w is insane
I now have a wooshy sounds when turning the first pot. Always in the same place on the wiper.
Is it normal to have negative 140mv DC on the pot when turned all the way up, and no input signal?
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. some 12ax7 will make noise more than other, . . . Tubes in high gain operation can makes more background noise. bad tube and Plate resistors make more noise and hiss. try good 12ax7 or changing circuit to lower gain or add low capacitance to plate resistor.
I see that your using a LTspice sim why don't you post the *.ASC file with the include files ( libs ) you are using in a zip file
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