Lowering Bass

[lpd]

Hi guys. Picked up a Dynacord Hall Jazz three seperate inputs. The reverb input is very loud way too much gain with a 12AX7s. Reverb was pulled from the circuit on this channel no tank no reverb circuit. I put a 12Au7 in lieu of 12AX7s much better gain. I find the amp has a little too much bass even with tone dimed on treble side. Any idea how to balance the bass out and perhaps lower gain on reverb channel?

[xtian]

PI-to-power tube coupling caps are already pretty small. I'd clip in some bright caps on the volume controls as an experiment.

[modman]

R43 is the resistor of the negative feedback loop
Adding a pot after this resistor, with the wiper connected to a 100nF capacitor which in turn goes to ground, makes a presence control. It will allow you to vary the amount of bass that is 'fed back'.
You could also play with C16 the tone stack cap... better still you could change it James tonestack or Fender/Vox is you like scooped mids.
I would also lower the resistance on the input, or even jumper all that shit and plug in at the 1M resistor to ground, easier still: convert input 2 and 1 for guitar.

[jjman]

I agree with eliminating that mumbo jumbo on the input. If changing the leak to a 1meg you'll want to add cathode bias. You could then reduce bass by selecting an appropriate value for the cathode cap. Although a conversion may eliminate the need to reduce bass.

[lpd]

R43 is the resistor of the negative feedback loop
Adding a pot after this resistor, with the wiper connected to a 100nF capacitor which in turn goes to ground, makes a presence control. It will allow you to vary the amount of bass that is 'fed back'.
You could also play with C16 the tone stack cap... better still you could change it James tonestack or Fender/Vox is you like scooped mids.
I would also lower the resistance on the input, or even jumper all that shit and plug in at the 1M resistor to ground, easier still: convert input 2 and 1 for guitar.

Bypassed the mess on the front end into the 1m resistor and the tone is more balanced however I find the volume on the input 1 low and idea how to boost gain a little?

[modman]

R43 is the resistor of the negative feedback loop
Adding a pot after this resistor, with the wiper connected to a 100nF capacitor which in turn goes to ground, makes a presence control. It will allow you to vary the amount of bass that is 'fed back'.
You could also play with C16 the tone stack cap... better still you could change it James tonestack or Fender/Vox is you like scooped mids.
I would also lower the resistance on the input, or even jumper all that shit and plug in at the 1M resistor to ground, easier still: convert input 2 and 1 for guitar.

Bypassed the mess on the front end into the 1m resistor and the tone is more balanced however I find the volume on the input 1 low and idea how to boost gain a little?

Jumper the resistors in front of the volume pot: R17/18. Don't jumper those 0.025µF capacitors -- they are used to block HV DC from the next stage.
As is you always will have the 220k in the signal path, even if the pot is turned all the way up, i.e. 0 ohm resistance.

[Stevem]

Before you even bother to heat up a iron for circuit mods have you tryed out the amp thru a different speaker in terms of the unneeded Bass issue?

Spent old surrounds and spiders on speakers can make for large amounts of cone movement without much bass being applied!
Soft near flacking apart cones near the voice coil cover can make for very receded highs also!

[lpd]

R43 is the resistor of the negative feedback loop
Adding a pot after this resistor, with the wiper connected to a 100nF capacitor which in turn goes to ground, makes a presence control. It will allow you to vary the amount of bass that is 'fed back'.
You could also play with C16 the tone stack cap... better still you could change it James tonestack or Fender/Vox is you like scooped mids.
I would also lower the resistance on the input, or even jumper all that shit and plug in at the 1M resistor to ground, easier still: convert input 2 and 1 for guitar.

Bypassed the mess on the front end into the 1m resistor and the tone is more balanced however I find the volume on the input 1 low and idea how to boost gain a little?

Jumper the resistors in front of the volume pot: R17/18. Don't jumper those 0.025µF capacitors -- they are used to block HV DC from the next stage.
As is you always will have the 220k in the signal path, even if the pot is turned all the way up, i.e. 0 ohm resistance.

Tried soldering a 1m from input one 1/4 jack to c4 but no sound any idea why? I jumpered input 2 to the 1 meg resistor no problem. Any ideas?

[modman]

Bypassed the mess on the front end into the 1m resistor and the tone is more balanced however I find the volume on the input 1 low and idea how to boost gain a little?

Jumper the resistors in front of the volume pot: R17/18. Don't jumper those 0.025µF capacitors -- they are used to block HV DC from the next stage.
As is you always will have the 220k in the signal path, even if the pot is turned all the way up, i.e. 0 ohm resistance.

Tried soldering a 1m from input one 1/4 jack to c4 but no sound any idea why? I jumpered input 2 to the 1 meg resistor no problem. Any ideas?

Don't put a 1M resistor in line with signal, it will kill it completely. Just connect input to the front of that capacitor with a jumper/alligator clip.

This amp?

[lpd]

Jumper the resistors in front of the volume pot: R17/18. Don't jumper those 0.025µF capacitors -- they are used to block HV DC from the next stage.
As is you always will have the 220k in the signal path, even if the pot is turned all the way up, i.e. 0 ohm resistance.

Tried soldering a 1m from input one 1/4 jack to c4 but no sound any idea why? I jumpered input 2 to the 1 meg resistor no problem. Any ideas?

Don't put a 1M resistor in line with signal, it will kill it completely. Just connect input to the front of that capacitor with a jumper/alligator clip.

This amp?

Mine is that amp plus a triode for a reverb stage. The first input is low volume. Second input sounds great and third is way too much gain as the reverb circuit was pulled from the amp. I jumpered both input 1&2 with alligator clips to the 1 M resistor bypassing the rest of the input circuit and it was a much cleaner signal. When i soldered a permanent jumper things stopped working on input 1 ?? I tried to bypass the 1m resistor and go from input to c4 with 1m but it killed the signal. Also noticed lowering Guitar pickups improved things immensely in bass output. It has a Princeton type clean not a lot of gain except the third input. Will test more today