[sdiy] Request brain dump on balanced lines

[John L Marshall]

Isn't the symmetrical clipping adjustment such that clipping takes place at
the highest possible amplitude? If clipping is not symmetrical then one peak
clips sooner than the other.


Take care,
John
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Pacific Northwest DIY Synthesizer meeting, July 20, 2002
See: www.sound-photo.com
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----- Original Message -----
From: "jhaible" <jhaible at debitel.net>
To: "Don Tillman" <don at till.com>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, October 13, 2002 5:15 PM
Subject: Re: [sdiy] Request brain dump on balanced lines


> > But more practically, most amps work in a balanced configuration that
> > cancels out all odd order distortion products, depending on how well
> > balanced things are.
>
> If the 3rd harmonic would be so much more unpleasant than the 2nd
> harmonic, there would be no such rule as trimming amps for
> symmetrical clipping. (I don't know which is wrong, 3rd harmonic
> being worse than 2nd, or the goal to have symmetrical clipping.
> Just wanted to point out that both can hardly be right at the same time.)
>
> > Further, this explanation assumes that our sense of hearing cares a lot
> > about harmonic distortion, which is not necessarily true.
>
> I fully agree. But maybe the ear cares for a sudden change of harmonics.
> And higher harmonics will come and go much faster than lower harmonics
> when the amount of overdrive changes. I think this is generally so,
because
> the Nth harmonic is created by the x**N term in the Taylor description
> of a transfer courve. So the fundamental is just amplified like it should,
> the 2nd harmonic comes in with input_amplitude**2, which is still rather
> smooth, but a 7th harmonic comes with input_amplitude**7, which is
> almost like a hard switch. Maybe that's the main reason for the "scratchy"
> sound of a distortion that contains a lot of higher harmonics: not the
> harmonic
> content by itself, but the sudden change of harmonic content.
> Does this make sense?
>
> JH.
>
> -----Ursprüngliche Nachricht-----
> Von: Don Tillman <don at till.com>
> An: <madhun2001 at yahoo.com>
> Cc: <debus at cityweb.de>; <synth-diy at dropmix.xs4all.nl>
> Gesendet: Sonntag, 13. Oktober 2002 22:29
> Betreff: Re: [sdiy] Request brain dump on balanced lines
>
>
> >    > Date: Sun, 13 Oct 2002 10:47:05 -0700 (PDT)
> >    > From: Tim Ressel <madhun2001 at yahoo.com>
> >    >
> >    > The best explanation I have heard is this: all semiconductor
> >    > amplifiers add 3rd harmonic distortion, which is unplesant to the
> >    > ear. Transformers tend to add 2nd harmonic distortion (as do tube
> >    > amps), and 2nd harmonic distortion is pleasant to the ear.
> >    >
> >    > There are as many opinions on this as there are people, but this
> >    > explanation makes sense to me.
> >
> > Really?
> >
> > If a tube stage was exactly a square-law device it would only have 2nd
> > harmonic distortion.  But tubes aren't exactly square-law devices,
> > more like 1.5-law, so a single tube stage does contribute third
> > harmonic distortion.  And if there's feedback involved, that will also
> > change the distortion products.  Multiple stages changes the
> > distortion products more.
> >
> > And a single transistor stage has significantly more 2nd harmonic
> > distortion than third.
> >
> > But more practically, most amps work in a balanced configuration that
> > cancels out all odd order distortion products, depending on how well
> > balanced things are.
> >
> > Further, this explanation assumes that our sense of hearing cares a lot
> > about harmonic distortion, which is not necessarily true.
> >
> > So while this explanation is the popular one -- it comes from that
> > engineering math class where you get to derrive the Fourier spectra of
> > exp(sin(wt)) and (sin(wt))^2 -- I think it completely lacks
> > credibility.
> >
> >   -- Don
> >
> > --
> > Don Tillman
> > Palo Alto, California, USA
> > don at till.com
> > http://www.till.com
> >
> >
>
>