squaring amplifier

[Andy Le Blanc]

I stumbled over this in a tomb in a chapter on analog computing circuits.

it a paraphase invertor and very nearly a push-pull pair, but the way its dressed, unlike P-P which reduces even order harmonic distortion products,
this one reduces odd order harmonics...

Looked pretty neat as part of a distortion circuit, thought I'd pass it along.

[David Root]

Interesting Andy. What's the mechanism? How does it cancel odd order harmonics?

[Phil_S]

Looks very cathodyne to me. What am I missing?

BTW, in my limited experience with a triode power section, the cathodyne is what works best. I built one a few years back and tried the paraphase with poor results, basically no clean headroom at all.

[Andy Le Blanc]

the description is that "as a result of its connection, the even-harmonic terms become the important ones"

this is in compared to a a push-pull, look at how the plates are dressed for a single ended output.

It looks to be like a diff amp with a single ended out, but with a shared anode load.

The "square" is a reference to the output being proportional to the "square" of the input.

I'm intrigued any how, it could be fun to push the even order harmonics.

[johnnyreece]

I'm with Phil...it looks like a cathodyne, with a lot of hardware missing between the PI and power tubes.

[Andy Le Blanc]

it is driven by an inverter... look at the output of the circuit.

Its from a text book, the diagram is to illustrate the mathematical model in the simplest form.


the closest parallel is a P-P, you can see the shared cathode resistor, but the pair also shares a plate resistor and a single ended Vout.

I was thinking of driving it with a variety of invertors, the quality there looks to certainly effect the signal out, might try sub-ing it for a clipper stage in a high gain rig.

I was thinking maybe also rigging it as a "self-split" stage, simple to try...

[teemuk]

Phase inverter feeding two inputs of a shared plate mixer.... I think that's called an "octaver fuzz". It sums the two out-of-phase signals together, creating an octave effect. The effect comes from strongly emphasid 2nd order harmonic, which is caused by such waveform distortion.

This is what Shin-Ei did with bipolar transistors:

[img:945:456]http://www.diystompboxes.com/pedals/Shi ... n_Fuzz.gif[/img]

Note phase inverter feeding two inputs of a shared collector mixer.

[Cameron]

I stumbled over this in a tomb in a chapter on analog computing circuits.

it a paraphase invertor and very nearly a push-pull pair, but the way its dressed, unlike P-P which reduces even order harmonic distortion products,
this one reduces odd order harmonics...

Looked pretty neat as part of a distortion circuit, thought I'd pass it along.

Check out the Laney clip amps....

[johnnyreece]

it is driven by an inverter... look at the output of the circuit.

Sorry, I was just quibbling; I agree it's an inverter, but you said it was paraphase, and I was agreeing with Phil that it looked like a cathodyne instead.

[Phil_S]

I'm easily fooled. I see a cathodyne feeding separate grids so I'm thinking PP, but the plates are wired in parallel. That's just strange and I didn't notice first time around. Plates trump grids? I suppose so and that's what makes it paraphase, I guess. I'm ready to let this one go before my head explodes.

[matt h]

(deleted)

[Andy Le Blanc]

Thank you so much for the octave fuzz scheme,... great to see an application.
That looks like a good candidate to "re-tube". Looks like a practical design for a sand project too.