Simple mods for earlier breakup- 6g2 Princeton

[BigDaddy23]

I've found a Hammond PT with a 550v C/T tap, the 291AEX. Unfortunately it's not a direct fit for the Mojotone chassis, but I can do a redneck setup with some penny washers.

That's a good choice - I really think the lower voltages are where this amp comes alive. FWIW, I found a good sweet spot in mine running around 317VDC on the plates for 69% max PD with Mullard 6V6's. To be honest, it sounded really good anywhere between 65 and 69% max PD. Any lower and the overdrive was less pleasing to my ear.

 

[D'tar]

mine sounds like that really sweet OD-borderlands spot you can coax out of a 5E3 on a full moon when you finally get the volume knobs set at that magic 35.73 degrees difference in angle

I thought we all agreed to keep this secret well.... secret! Now the real mojo can be had by all

 

[Phrygian77]

I thought we all agreed to keep this secret well.... secret! Now the real mojo can be had by all

Same reason I was reluctant to start my latest build thread.

Well, not really, it just took me forever to get going on it.

 

[King Fan]

I thought we all agreed to keep this secret well.... secret! Now the real mojo can be had by all

Heh, you'll notice I didn't say where either volume knob was set -- and besides, the true angular difference needs to be 91.743°...

 

[schmee]

Why not just bias it less cold?

 

[ruger9]

Why not just bias it less cold?

Or more hot?

 

[King Fan]

Or maybe that depends on how hot/cold it is now?

 

[ruger9]

Or maybe that depends on how hot/cold it is now?

ok ok... let's settle on "warmer"

 

[Badside]

Why not just bias it less cold?

I understand this reduces the tremolo effect though on those amps, it's a balancing act (unless OP doesn't care about tremolo of course)

 

[schmee]

I understand this reduces the tremolo effect though on those amps, it's a balancing act (unless OP doesn't care about tremolo of course)

Yeah it CAN. But it's not a given on any particular amp.

 

[schmee]

Or more hot?

Or maybe that depends on how hot/cold it is now?

ok ok... let's settle on "warmer"

I don't know, I'm kinda hot & cold on this.......

 

[ruger9]

I understand this reduces the tremolo effect though on those amps, it's a balancing act (unless OP doesn't care about tremolo of course)

too cold OR too hot can do this, on amps that use the POWER tubes for the tremolo effect. It doesn't affect amps that use a preamp tube or the opto-coupler for the tremolo.

 

[Badside]

too cold OR too hot can do this, on amps that use the POWER tubes for the tremolo effect. It doesn't affect amps that use a preamp tube or the opto-coupler for the tremolo.

Yes exactly, the 6G2 uses the power tubes for the term effect.

 

[ruger9]

Yes exactly, the 6G2 uses the power tubes for the term effect.

So does the PRRI, which is what I had. I biased it hot (I forget what number), and the tremolo did lose a little depth, but there was still plenty for me.

 

[ElliotKnapp]

As others have noted, the tricky part is that you want more breakup without more volume. The consensus has been fiddling with NFB which will get you more breakup, but in my experience I'd say it also gives you more volume.

I would recommend also trying a clean boost pedal of some kind--you can slam the input but if the volume knob is low the overall amp volume wouldn't go up as much as a cranked volume knob with a different NFB value. You've already built a great circuit--you probably just need a louder signal hitting that 12AX7 to get the effect you want.

And, as others have noted, if you can get a good breakup sound you like but it's at too high a volume, grab an attenuator. IMO everybody who owns a tube amp should own a Weber Mass just to see what kinds of tones you can get out of a cranked amp at more reasonable volumes.