Hi,
Long time reader first time poster. I've been searching google and forums for a few days
I'm relatively new to modding amps but comfortable around higher voltages.
My friend asked me to help him with his AC4TV (schem attached). He's looking to replace the voltage selector knob with a bass roll off.
Snipping out the attenuator network seems straightforward and repurposing the chassis hole seems easy enough.
The tone control reads to me like a variable bright bypass for the volume control, but I could well be wrong and it's not that useful for him and having control of the bottom would make the amp more versatile.
Is it possible to change R12 for a 1M pot and replace the whole stack with a "normal" Fender or Vox TB (ie Princeton or AC15 top-boost)?
Also the function of R15/C12 just plain confuse me.
Thanks,
Lukas
Long time reader first time poster. I've been searching google and forums for a few days
I'm relatively new to modding amps but comfortable around higher voltages.
My friend asked me to help him with his AC4TV (schem attached). He's looking to replace the voltage selector knob with a bass roll off.
Snipping out the attenuator network seems straightforward and repurposing the chassis hole seems easy enough.
The tone control reads to me like a variable bright bypass for the volume control, but I could well be wrong and it's not that useful for him and having control of the bottom would make the amp more versatile.
Is it possible to change R12 for a 1M pot and replace the whole stack with a "normal" Fender or Vox TB (ie Princeton or AC15 top-boost)?
Also the function of R15/C12 just plain confuse me.
Thanks,
Lukas
Attachments
My suggestion. You will be reusing C6 22n (for C3), as well as C4 220p (for C1) and C3 6.8n (for C2) in the Fender tonestack. The volume pot you can use for RB, the bass control. Also the tone pot you have for the treble pot RT. You will also need a 75k for R1 and a 6.8k one for RM. The response will be similar to the Marshal/Bassman EQ.
TSC in the web
There will be a substantial loss of gain as compared to before, about as much as a Blackface Champ. R15 and C5 cuts a little bass and biases the triode a little cold. C15 also rolls of a little of the highs, so this stage give a little more midrange type of sound as well as biases the stage a little cold giving it more of a Marshall sound. You could remove these parts afterward and either go with a 220k and 2.2k resistors with C11 or 100k and 1.5k like what Fender uses.
I don't know how possible it is physically but if your buddy likes a full cranked sound you could always just have the volume control where it is and stick the tone stack behind the second triode. This is how the guys at AX84 did theirs. See current materials. Not having the master volume after the tone stack just has you not overdriving the triodes at low volumes.
AX84.com - The Cooperative Tube Guitar Amp Project
https://www.youtube.com/watch?v=gaFrj_lE5mA
TSC in the web
There will be a substantial loss of gain as compared to before, about as much as a Blackface Champ. R15 and C5 cuts a little bass and biases the triode a little cold. C15 also rolls of a little of the highs, so this stage give a little more midrange type of sound as well as biases the stage a little cold giving it more of a Marshall sound. You could remove these parts afterward and either go with a 220k and 2.2k resistors with C11 or 100k and 1.5k like what Fender uses.
I don't know how possible it is physically but if your buddy likes a full cranked sound you could always just have the volume control where it is and stick the tone stack behind the second triode. This is how the guys at AX84 did theirs. See current materials. Not having the master volume after the tone stack just has you not overdriving the triodes at low volumes.
AX84.com - The Cooperative Tube Guitar Amp Project
https://www.youtube.com/watch?v=gaFrj_lE5mA
Last edited:
Thanks for the help
Wow, thanks for the help, exactly what I was after.
I'll order some bits and try it out.
Thanks again
Wow, thanks for the help, exactly what I was after.
I'll order some bits and try it out.
Thanks again
I defiantly had other things in mind for the morning but sometimes a question gets under my skin and I need to know the answer. I was going to try the Vox circuit just to keep the lineage but once I saw the 220 pF capacitor I just went down the Fender route. Let us know how it turns out.