R. G. Mu doubler: blend question

[tca]

Is there a significant difference in sound in the Mu Doubler if instead of taking the blend from the negative positive part (source of Q1) to take it from negative part (drain of Q1, with the proper changes...) (http://www.geofex.com/Article_Folders/jfetdoub/mudoubler.htm )? For pure sin there is only a difference in phase, but what about a more complex signal?

Cheers.

[Processaurus]

I never got that one to work, anyone else had luck?

[tca]

My question is: is there a difference in sound if the output is

x + |a|*x^2

or

x - |a|*x^2

Thanks.

[Quackzed]

i dont think it would matter, q1 is biased to be in between v+ and ground, and it doesnt  have enough gain to slam either one, so it should be fairly linear for both in and out of phase sides of the splitter...
same for more complex signals as well as pure sine wave signals...

[R.G.]

My understanding is that the audible effects are equal.

I never got that one to work, anyone else had luck?

It took a little tinkering, but I got it to work fine, and I believe at least Mark Hammer did as well.

[Mark Hammer]

Actually no.  I never tried it, and keep meaning to.  But I don't doubt that somebody here got it to work.

[R.G.]

Hmph. Now my memory's failing too.

I thought you were the one who said the thing needed some distortion after it to keep from being a bit too soft.

Oh, well. Mine worked. 

[tca]

My understanding is that the audible effects are equal.

I was not sure about that, thank you for clarifying that. Thanks.

[PRR]

> instead of taking the blend from the negative part (source of Q1) to take it from negative part

Negative or negative??

Whatever. The source impedance is a little lower, which with 100K blend leads to maybe 1% difference in level, which is probably no-difference.

It's all symmetrical. The way it is done, that may not be clear (and there's slight asymmetry due to simple implementation), but it "should" work the "same" either way.

But if you have it built, isn't it quicker to switch the wire than to type-up the question?

One thing about that as-drawn plan catches my eye. No DC blocking cap at the output. This might upset the next input in the chain. In particular it looks like the 100K Blend will raise-up the 330K gate resistor and cause Q4 to hog all the Q3+Q4 current, which probably ruins the effect.

One possible mod:

[tca]

> instead of taking the blend from the negative part (source of Q1) to take it from negative part
Negative or negative??
Whatever.

That is one of my charms, specially specially in written text in a foreign language.

But if you have it built, isn't it quicker to switch the wire than to type-up the question?

I haven't build it, just done the calculations on paper to see if it works... so the question.

I can tell you a bit more about what I was thinking. Any real valued function (sufficiently smooth) has a power expansion, for small x,  of the form (normalized with the first constant)

x+a*x^2

e.g.

sin(x)=x-x^3/6
cos(x)=1-x^2/2
tan(x)=x+x^3/3
sqrt(x+1)=1+x/2-x^2/8

and so I wonder what a truncated power series would make do the guitar signal. Probably adding an extra circuit that cube the input signal would make a difference as a distortion device.

Cheers.

[PRR]

X^2 gives even-order distortion. Distortion products rise as the square of the input signal.

X^3 gives odd-order distortion. Distortion products rise as the cube of the input signal.

Even-order products tend to lie along the harmonic series, and might be called "musical". The fairly slow rise of distortion product level gives a fairly wide range of level with "useful" distortion.

Odd-order products tend to lie *between* the harmonic series, and might be called "un-musical". (But odd-order distortion is a key flavor in electric music.) The faster rise of distortion product level gives more abrupt change from clean to all-dirt.

R.G.'s twin-FET idea gives pure (ideally no fundamental) X^2 at higher level and no output at very small level. Not a perfect Squarer (square of very-tiny signal is difficult and possibly not too useful.)

[~arph]

I never got that one to work, anyone else had luck?

Yes, I tried it, worked like a charm