What type of phase inversion is this

[Stuff4bikes]

This.....

[pdf64]

Basic paraphase.
http://www.valvewizard.co.uk/paraphase.html

[Stuff4bikes]

Is there an advantage to that version over the cathodyne version?

[tubeswell]

Is there an advantage to that version over the cathodyne version?

Not really any gain advantage. However, Paraphase output from each side is more asymmetrical/unbalanced when the PI is being overdriven (to do with non-linearity of attenuation going to the 2nd inverting stage’s grid as the signal gets bigger). Results in some degree* of distortion.


(*But cathodyne PIs can also become distorted when overdriven, but IMHO, the Paraphase has nicer sounding overdriven distortion).

[shooter]

pretty good write up on the different types here;


How to design valve guitar amplifiers (valvewizard.co.uk)

[Stuff4bikes]

I am pretty much just an amauter hobbyist at this point. I have built 6 or 8 amps all but two have been done with turret boards.
Two point to point 5F2A's one with a 7868 and the other was a 6F6.
The amp with this particular circuit I showed above has been upgraded to a 6SQ7 6SN7 and 6L6GC's with rubber stamped tube indicators next to each. Infact I have identical amps with one running 6L6GB's both factory magnavox pulls.

This amp in present form including the FC speaker sounds very good with tight bass and I would like to use the entire system sans the non guitar amp circuitry. With the exception of the RCA metal 6SQ7 the rest of the tubes are all tung-sol including the 5U4GB rectifier...

Just trying wrap my head around the PI circuitry....

Thanks for all your help...

[PRR]

Is there an advantage to that version over the cathodyne version?

It happens naturally if you have a one-6V6 radio and extend it to two 6V6. Replace the single triode driver with a twin triode bottle. Each triode has gain and inverts. The second triode, clobber the gain down to unity.

Assume each triode has gain of -16. The "-" means inverting. The plus/minus of phase works through the gain equations just like gain does. The top triode is gain of -16. The 220k:15k divider is +1/16 of gain. the bottom triode is -16 of gain. The two outputs end up at -16 and -(-16) or +16. Gain of 16 but + and - phase.

It makes no special demands on the triode cathodes. Early cathodes were shared-battery filaments; later ones did not like to be raised far above common. The Paraphase cathode is a calm place. So calm it may not need a bypass cap (a trouble-part in early electrolytics).

[HotBluePlates]

Basic paraphase.
http://www.valvewizard.co.uk/paraphase.html

Is there an advantage to that version over the cathodyne version?

If you needed it, the paraphase can develop a larger output from the same supply voltage.  That's because each triode develops a single output signal, not two output signals.

Some builders favor paraphrase because it is "less perfect" than cathodyne, and develops a little more distortion.