SynthModules

My reference is the Spectralab software which calulates it from 
the FFT. About.com defines signal to noise ratio this way:

http://stereos.about.com/cs/glossaryandtools/g/sn_ratio.htm

--- In SynthModules@yahoogroups.com, "Scott E." 
<yahudinyhwh@s...> wrote:
> 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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