Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jammied on December 28, 2021, 07:37:16 pm
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Hello
I have been playing around with my laney cub 10. They have a hard wired fender type tmb tone circuit with pre selected and set values.
Recently I bypassed the the pre-set tone stack by by running the end of the volume pot to v1b then running the middle of the volume pot to a .0047 capacitor that connects to the phase inverter pin7. The problem with this is putting high voltage dc on the volume pot.
Is there a way to nail that tone without putting the high voltage on the volume control?
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Is there a way to nail that tone without putting the high voltage on the volume control?
Yes. Put a cap between the tube and the volume control.
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The fender type tmb tone circuit hides a DC-block function. Leo designed-out a dime here. Bypass the tone-shape, you still have to block the DC.
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Thanks for your help Sluckey and PRR
If I put the .0047 on v1b and to the end of the volume pot. The run the center of the pot to v2a it should work?
I'm pretty sure I tried that but it kept crackling and loosing volume. So would I also have to use a resistor and capacitor on v2a in line with the center of the volume?
I was trying for a tweed champ volume control.
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If I put the .0047 on v1b and to the end of the volume pot. The run the center of the pot to v2a it should work?
You must also have a cap between the pot and V2A.
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Thank you I appreciate the help. What values would you recommend as a starting point to keep the tone about the same? .002 on each side? Or maybe a capacitor bypassing a resistor on v2a. I really like the character and tone with .0047
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Experiment. Tell us what you like.
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Will do.
I see that the 18watt minimalist is using a .0047 into the volume pot and a .022 for a phase inverter input so. Maybe I will start there. The 18watt minimalist is using a 500k volume pot. But a 1meg should also work
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Plagiarize is good. All of my best ideas were plagiarized from somewhere. :l2:
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Well that added some treble fizzy nonsense! Don't like that! Would rather take my chances with high voltage on the volume pot! Before it was bright but not fizzy and harsh. Sounded like a good tweed amp
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There put it back to high voltage on volume pot and back to brassy bright blues. Not treble fizzy spiky bright. Guess maybe try it again tomorrow. With .0047 and .022 it has a jcm800 fizzy treble on the notes. I already have a jcm800.
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There's an easier/more popular way to bypass the tone stack without involving any dc on the volume pot or extra caps. You can easily try it to see if you like it. Simply disconnect R17 from ground. Done. If you like the results install a switch.
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Thank you. That was the first way I bypassed it..
I may try bridging pins 2 and 7 on v1 to get rid of the marshall style preamp gain system then add some local nfb
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Maybe this simple tone control tied to the .0047 will do enough to get rid of the excess treble?
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By crackey that tone control worked!! It got rid of the fizzy, buzzy and fuzzy sound. But you can still dial it back in. Doesn't seem to take away from the overall tone. Between this tone pot and the cub tone control it can get a wide variety of sounds..
Very pleased :icon_biggrin: