[sdiy] Better testing techiques for audio circuits

[Harry Bissell]

imho, intermodulation distortion is much worse than harmonic distortion.
crossover distortion (which is level independant) might be worst of all...

H^) harry

----- Original Message -----
From: Ingo Debus <igg.debus at t-online.de>
To: synthdiy diy <synth-diy at dropmix.xs4all.nl>
Sent: Wed, 04 Apr 2012 15:31:33 -0400 (EDT)
Subject: Re: [sdiy] Better testing techiques for audio circuits


Am 04.04.2012 um 19:04 schrieb David G Dixon:

>> Then you mention your mixer having <0.0007% THD.  Its 
>> unlikely that you'd be able to simulate to that extreme in 
>> SPICE.  To measure it in the real world needs expensive kit 
>> (Audio Precision 2700 series). 
> 
> I use Multisim, which is a SPICE-based simulator package from NI, and the
> THD tool doesn't even have a fourth decimal point -- it only goes down to
> 0.001%.

Frankly, if audio signals are concerned, I doubt anyone can hear a THD that low. And even if one could, it would be swamped by the distortion of the loudspeakers anyway.

Back in the day, surely a 0.1% THD distortion amp sounded better than a 1% distortion amp (unless a valve amp was compared against a transistor amp...). But 0.001%? It's just the numbers that look nicer. Same as with the megapixel mania of digital cameras.

Another interesting question is: is THD a good criterion for the subjective impression of "distortion" at all?

Ingo
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-- 
Harry Bissell & Nora Abdullah 4eva