Volume/Tone pot interaction affecting voltage & creating noise
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- yello
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Re: Volume/Tone pot interaction affecting voltage & creating noise
Looks like my two el84 power tubes are at 14+ watts each and 120%+ plate dissipation.
Stock cathode resistor was 130, but I used 150 ohm.
Looking at my voltage chart, to compare this amp to its twin (same amp circuit but different power transformer as built in different countries, Canada versus Japan) that Bill Krinard modded, the voltages produced by each PT are different. I used the same B+ cap/resistor scheme, so not surprised I'm getting different results.
What is the best approach to address my higher voltages? Zener? Higher B+ node A resistor? Higher Cathode resistor? Some combo of those?
Stock cathode resistor was 130, but I used 150 ohm.
Looking at my voltage chart, to compare this amp to its twin (same amp circuit but different power transformer as built in different countries, Canada versus Japan) that Bill Krinard modded, the voltages produced by each PT are different. I used the same B+ cap/resistor scheme, so not surprised I'm getting different results.
What is the best approach to address my higher voltages? Zener? Higher B+ node A resistor? Higher Cathode resistor? Some combo of those?
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Re: Volume/Tone pot interaction affecting voltage & creating noise
Correct. Shoot between 180 to 220 for the cathode, and figure out what you want your B+ to be, then drop it there. Take some new voltages, do some more math, and play some guitar.
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Re: Volume/Tone pot interaction affecting voltage & creating noise
The math is my new frontier, learning better how to calculate the needed value of parts, especially on the B+.JMPGuitars wrote: ↑Mon 01/30/23 2:38 pmCorrect. Shoot between 180 to 220 for the cathode, and figure out what you want your B+ to be, then drop it there. Take some new voltages, do some more math, and play some guitar.
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Re: Volume/Tone pot interaction affecting voltage & creating noise
You can cheat for your dissipation here: https://robrobinette.com/Tube_Bias_Calculator.htmyello wrote: ↑Mon 01/30/23 2:46 pmThe math is my new frontier, learning better how to calculate the needed value of parts, especially on the B+.JMPGuitars wrote: ↑Mon 01/30/23 2:38 pmCorrect. Shoot between 180 to 220 for the cathode, and figure out what you want your B+ to be, then drop it there. Take some new voltages, do some more math, and play some guitar.
For B+, well, that's usually determined by how the circuit behaves at different values.
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'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Modern Ground Schemes
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Re: Volume/Tone pot interaction affecting voltage & creating noise
That's the exact tool I use for dissipation.JMPGuitars wrote: ↑Mon 01/30/23 2:50 pmYou can cheat for your dissipation here: https://robrobinette.com/Tube_Bias_Calculator.htmyello wrote: ↑Mon 01/30/23 2:46 pmThe math is my new frontier, learning better how to calculate the needed value of parts, especially on the B+.JMPGuitars wrote: ↑Mon 01/30/23 2:38 pm
Correct. Shoot between 180 to 220 for the cathode, and figure out what you want your B+ to be, then drop it there. Take some new voltages, do some more math, and play some guitar.
For B+, well, that's usually determined by how the circuit behaves at different values.
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- yello
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Re: Volume/Tone pot interaction affecting voltage & creating noise
This one is wrapped up and sounding nice. Got the bias set at a good level, and my friend and I both like how it sounds, so he is getting it back to enjoy.
Thanks for the great guidance - I learn more with every one, and each amp I work on I feel more skilled and confident, and can get things done more efficiently. Certainly makes it more fun!
On to the next one...
Thanks for the great guidance - I learn more with every one, and each amp I work on I feel more skilled and confident, and can get things done more efficiently. Certainly makes it more fun!
On to the next one...
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