SynthModules

Grant,

I would respectfully disagree with your definition of signal to noise 
ratio. The inclusion of the second order harmonic is only appropriate 
for determining the THD of the circuit when a signal is applied, whether 
that be steady state or transient. The definition of signal to noise is 
the ratio between the power of of the signal at a certain point in the 
circuit to the power of the noise floor (only) which would exist there 
if the signal were removed. This by definition would exclude any 
harmonic distortion created by the circuit with respect to the input signal.

Regards, Scott E,
===================================================
grantrichter2001 wrote:

>
> > Quality? Let's look at signal-to-noise. According to the
> Synthsizers.com
> > FAQ, the dotcom VCA has "a signal to noise ratio of 82db (CD
> quality is
> > around 96db)." The MOTM-190 has a dynamic range of "better
> than 100dB."
> > That's a very big difference.
>
> It might be useful to note that signal to noise ratio is different
> than the noise floor. The noise floor is the actual hiss (thermal
> noise).
>
> Signal to noise ratio is the ratio between the test sine signal
> peak and the next lowest signal peak. This is usually the second
> harmonic distortion. A second harmonic distortion of -82 dB is
> approx. a THD of 0.005% or as good as virtually all audiophile
> hi-fi gear.
>
> Analog to digital converters have a noise floor fixed by the math
> of 6 dB per bit (hence 96 dB for 16 bit).
>
> Based on my measurements at Wiard, the noise floor of a TL074
> is about equal to the self noise of a 24 bit converter. An LM837 is
> about -15 dB below the same 24 bit converter. But the signal to
> noise ratio is -60 dB or so because the THD is 0.02% (second
> harmonic at -60 dB). This is plenty good enough for prime time!
>
> The major source of hiss noise will come from the A to D inputs
> of the digital compositing system you use, rather than the analog
> equipment.
>
>
>
>
>
>
> Be sure to check out the primary Web site at:
> http://www.SynthModules.com
>
>
>
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