tube noise
 

isw wrote:
In article , BEAR
wrote:

--snippage--


For audio applications though, achieving extrememly low noise levels
isn't really a tremendously important issue, the exception being when
amplifying really low level signals, like condensor mics and phonograph
cartridges... assuming relatively good low noise circuits using tubes
are what we're talking about - there are some very noisy tube units out
there, and that's not a good thing. Usually the inherent noise in a
noisy line stage can be reduced through better design/circuit changes,
or changing out the tube type or selecting for a low noise example of
that given type.


I would argue that even a phono stage isn't all that critical. It's easy
to design a preamp that's better than 10 dB quieter than the noise level
of a stylus in a groove; shoot, that doesn't even take "low noise"
technique. I don't think it matters if the preamp noise is audible when
the stylus is *not* in the groove, BTW; not too many folks spend much
time listening to that.

I don't think you'd want to listen to a phono stage that was only 10dB
quieter than typical stylus noise.

Hum is part of that equation, and getting the hum out is important too.

Solid state is easier than tubes for noise, but still an issue.


More important would be low distortion, and that can be traded off
against lowest possible noise by using, say, a differential input stage.

Actually, "low distortion" is relative.

Differential circuits tend to end up sounding rather more "hard" and
"sterile" than non-differential circuits due to the spectra of
distortion products being mostly odd order, and cancelling strongly the
second harmonic.

It has been shown in peer reviewed Journal publications that merely low
THD does not translate directly to audibility of distortion.

Consider that your signal is *modulated* by all low level artifacts,
noise, hum, distortions etc... so the actual level of the nominal signal
you are listening to being *above* the nominal noise/hum/distortion
floor does not mean that it is unaffected by same.

But as long as one is happy with what one is hearing, then all is well...

As Count Basie said (iirc) "If it sounds good, it is good..." or was
that Duke Ellington??

_-_-bear



Isaac




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