Tube preamp with phase inverter

Hello—wanting some input for an idea I had, making a tube preamp, with a phase inverter incorporated to get the desired tone for guitar/bass.

Has this been done before?

I was thinking of just having a standard circuit with a transformer for balanced out after the P.I., as well as an attenuators for course to back the swing down some. what type of transformer would you suggest??

Thanks,
Eric

Back in the 80's I included a switch in a phono preamp to invert the polarity, back then recordings were not standardized for absolute polarity (than most listeners cannot hear anyhow).

Easy enough with op amps. 

If you have a balanced or differential input you can just reverse the wiring.

JR

I don't see how an Inverter and Tone are related.

I don't know why a preamp needs a PI.

Or why that wants a transformer (which can do its own inversion, IF that really affects Tone).

It is true that a few musical instrument amps in some situations are better with a phase flip. Harmonica amps are prone to feed-back, and frequently a phase-flip changes that (50:50 better or worse). That case is best done with a DPDT switch to the speaker.

I wonder if the OP actually meant a "phase splitter" such as found before the PP outputs of a guitar amp.....

Bri

> actually meant a "phase splitter"

I took the broad view, and I still don't understand how this goes with "tone".

In the tube guitar amps we know and love the tone comes from mainly the output stage ,transformer and speaker in combination .
The distortions produced by the final stages of a guitar amp isnt really reproducable by preamp stages alone from my experience
Maybe a push pull line output stage might get some of what your after ,but doing that might end up costing more than a really good guitar amp in the first place . 2 EL84's or two 6v6's is generally good for almost any recording situation , you can drive it into crunch without lifting the roof off , but you still get that wonderfull dynamic  we associate with tube amps . By the time your guitar  gets eq'd to tape and mixed down its all but impossible to tell what kind of wattage was used to get the sound ,that being said different output tubes can have their own unique effect on the tone thats unmistakable.
Vox EL84 and GZ34
Marshall  EL34
Fender 6L6

Hopefully your on the mend PRR , I see you were out of sorts the last few weeks .

PRR said:

I don't see how an Inverter and Tone are related.

Click to expand...

not

I don't know why a preamp needs a PI.

Click to expand...

if it is used as an instrument preamp for a lead guitar, that will intentionally make acoustic feedback by standing in front of the speaker, polarity inversion could make it easier (or harder) to feedback. 

Or why that wants a transformer (which can do its own inversion, IF that really affects Tone).

It is true that a few musical instrument amps in some situations are better with a phase flip. Harmonica amps are prone to feed-back, and frequently a phase-flip changes that (50:50 better or worse). That case is best done with a DPDT switch to the speaker.

Click to expand...

yup, but incorporating it inside an instrument preamp is cleaner than reversing speakers in a guitar amp, etc.  Adding a transformer is the hard/expensive way to accomplish polarity reversal (IMO).

JR