Princeton Non Reverb to TR JM thoughts.

[Zorojuro]

I have a Princeton non reverb and tremolo amp (Rob Robinette). I'm thinking to modify it's preamp to a JM two rock. I need your thoughts about this. Thank you.

[ijedouglas]

Is this a Dumble circuit?

Mods, can we please keep this forum on point to discuss Dumble and his circuits.

[Zorojuro]

Is this a Dumble circuit?

Mods, can we please keep this forum on point to discuss Dumble and his circuits.

It's a Princeton circuit. I'm planning to modify its preamp to a John Mayer two rock/wonderland. I just want to hear some thoughts on this or if this modification is a waste of time.

Or should i post it in the fender discussion board?

[erwin_ve]

Is this a Dumble circuit?

Mods, can we please keep this forum on point to discuss Dumble and his circuits.

It's a Princeton circuit. I'm planning to modify its preamp to a John Mayer two rock/wonderland. I just want to hear some thoughts on this or if this modification is a waste of time.

Or should i post it in the fender discussion board?

You could post a schematic of the JM amp and then compare:
-the amount of pre tubes with the Princeton.
-Is the current draw of the PT sufficient icw with the tube rectifier?
-Is there enough room for the change. (debatable?) In other words what are the dimensions of the chassis for both amps?

Doing this kind of homework has more potential for a serious response.



Erwin

[10thTx]

I just want to hear some thoughts on this or if this modification is a waste of time.

If your expectation is that "the conversion" will sound anywhere close to a John Mayer Two Rock amp, then I think you are likely to be very disappointed?

You might do a search on the "Small Special" with the idea of using 6V6's instead & see if that is something you're interested in?

With respect, 10thtx

[Zorojuro]

Thanks for your responses Erwin and 10thx. I think it is not worth the time and effort to make some mods with my amp. I really appreciate your thoughts about it.

[martin manning]

It's a Princeton circuit. I'm planning to modify its preamp to a John Mayer two rock/wonderland. I just want to hear some thoughts on this or if this modification is a waste of time.

You could certainly modify the preamp stages to the JM sig. The first stage would be the same, but then you'd have the Dumble tone stack (same controls, different circuit), and the second stage in the JM has R//C input, a smaller Ck, and local negative feedback. Nothing wrong with trying that as an experiment. It will sound different from the Princeton.

[Zorojuro]

It's a Princeton circuit. I'm planning to modify its preamp to a John Mayer two rock/wonderland. I just want to hear some thoughts on this or if this modification is a waste of time.

You could certainly modify the preamp stages to the JM sig. The first stage would be the same, but then you'd have the Dumble tone stack (same controls, different circuit), and the second stage in the JM has R//C input, a smaller Ck, and local negative feedback. Nothing wrong with trying that as an experiment. It will sound different from the Princeton.

Thanks martin. This is much more encouraging to widen the perspective of modification. I know it will not sound exactly like JM but I just want to try if some of it's vibe will also be available to this amp. Especially it has a different phase inverter, different power tubes, transformers, speakers and voltages. Thank you for your kind response.

[10thTx]

It may or may not be a good sounding amp? This is a DRAFT unproven idea only for discussion and edits. It allows for a psuedo pretend active FX where you can place reverb and/or delay to fake some of the JM aspects.

I am NOT advocating building this. I would anticipate if this idea works that it would sound nothing like a JM Two Rock.

My advice is if you're not a reasonably advanced seasoned amp builder then I would NOT attempt this.

With respect, 10thtx

[Zorojuro]

It may or may not be a good sounding amp? This is a DRAFT unproven idea only for discussion and edits. It allows for a psuedo pretend active FX where you can place reverb and/or delay to fake some of the JM aspects.

I am NOT advocating building this. I would anticipate if this idea works that it would sound nothing like a JM Two Rock.

My advice is if you're not a reasonably advanced seasoned amp builder then I would NOT attempt this.

With respect, 10thtx

I like the idea. Thanks for your suggestions.

I've already built some amps and preamps in the past 4 years or so.

Really appreciate your efforts in drafting schematics.

[10thTx]

Another one to consider given two 12A_7's. Obviously you'd need to make some changes for 6V6's.

With respect, 10thtx

[WhopperPlate]

Really appreciate your efforts in drafting schematics.

I second that , very considerate and caring of you 10thTx, appreciate the extra effort to help each other

[pompeiisneaks]

Is this a Dumble circuit?

Mods, can we please keep this forum on point to discuss Dumble and his circuits.

Two things:

1. I can't be expected to mod every post within 1 hour - If you can, I'd be happy to add you as a mod, but don't miss that 1 hour deadline.
2. It sounds to me that a john mayer Two rock is basically a dumble amp clone if I recall no?

~Phil

[ijedouglas]

Two things:

1. I can't be expected to mod every post within 1 hour - If you can, I'd be happy to add you as a mod, but don't miss that 1 hour deadline.
2. It sounds to me that a john mayer Two rock is basically a dumble amp clone if I recall no?

~Phil

Hey Phil, I appreciate all you do for the forum. Not sure where the 1 hour expectation came from though.
I was just trying to make the point that this forum was supposed to be about discussing Dumble and his circuits but often devolves into clones and in this case a circuit with distant Dumble DNA (ie not a clone). I am all for discussing new circuits and evolving the design but maybe a different forum may suit this discussion better.
I may be totally off base here and I apologize if so,

[Zorojuro]

Another one to consider given two 12A_7's. Obviously you'd need to make some changes for 6V6's.

With respect, 10thtx

Thank you 10thx. I have a board for fender vibrolux (non reverb) in my stash. Maybe this is more easy to build than to modify my current princeton.