Princeton Reverb Blackface tonestack bypass

[TurboGuitarMelton]

Hi,


I want to add the tonestack bypass mod or "raw" switch. However, the gain jump is so large that I can't even turn the amp up past 2 or else its overly loud and has a very nasty Overdrive.


I am aware that I can put a 100k resistor on the switch to help with gain but I feel like at that point the tonestack is still influencing the sound and sucking gain.


In the 5e3 there are two bypassed gain stages and the OD isnt crazy. Is the third gainstage after the reverb the reason there is such a crazy amount of gain?


If I lifted the cathode bypass cap on the second or the third gainstage do you think it would balance better?


Whats the purpose of the 3rd gain stage? Is it the reverb recovery? Or another bump before the phase inverter. The Princeton nonreverb amp doesn't have it.

[sluckey]

Put a 250K pot ***AND*** a switch between the tonestack and ground. Set the raw gain for what you like.

[shooter]

once you have what sluckey said working n smiling;
gain manipulation is a fun  to play with, scope n signal source are prerequisites though.  I like the simple Vac out / Vac in = Vgain.  gets fun when you can make it asymmetrical, compressed, kinked, on the scope, then test image with loud guitar

[jjasilli]

Whats the purpose of the 3rd gain stage? Is it the reverb recovery? Or another bump before the phase inverter. The Princeton nonreverb amp doesn't have it.

See, e.g.: https://reverb.com/news/a-nerds-guide-to-the-fender-princeton-reverb

[d95err]

In the 5e3 there are two bypassed gain stages and the OD isnt crazy. Is the third gainstage after the reverb the reason there is such a crazy amount of gain?

The 5e3 has a 12AY7 for the first gain stage, which has about half the gain of a 12AX7. So, if you lift the tonestack on the PR, you get more gain going into the second stage than on a 5e3.

On a 5e3, the whole amp (poweramp and probably the PI) will be clipping by the time the second gain stage starts to distort. On the PR with a tonestack lift, the distortion will probably mainly be from the second gain stage.

To get better distortion, I would experiment with cutting bass when activating the tone-stack lift. E.g. having the switch also change the cathode of the first gain stage to e.g. 2k7/0.68u (á la Marshall).

[MFowler]

Like Slucky said the 250k pot as shown here:

[TurboGuitarMelton]

Thanks guys! The 250k pot really helped! Love it!