Preamp mixer vs. HiFi preamp - what parameters determine sound quality:

[Martin Fuchs]

Hi, this is a follow-up to my question about a comparison between HiFi
preamps and mixers; I consider buying a mixer/poweramp combo for my HiFi
system at home instead of a full HiFi amp:

I've gone through some technical specs of mixers that were recommended
and looked for parameters that I sort of understand, such as Signal to
noise (S/N) and crosstalk between channels.

Allen&Heath, Rane and Numark mixers looked pretty good there, for
example (S/N -90 dB or better). Denon, OTOH, had S/N specified as better
-80 dB only.

So is this as important as I think it is?

What other parms determine "sound quality" on paper? I know that numbers
on paper are not everything but they certainly help to rule out some
mixers for what I want to use them. Are the THD (total harmonic
distortions) important there?

In the end I will listen to a few models, but I'd like to know how far
off (if at all) mixers are from HiFi preamps.

Price range should be 500-1000$.

Thanks for all input, cheers, Martin

[P Stamler]

Unfortunately, the published specs on mixers typically correlate not at all
with perceived sound quality. Most mixers have specs that are adequate, as
quoted, but some sound decent (= sound like they're not there) and some don't
(= add stuff). As a general rule, in mixers, the more you spend, the less
impact it will have, which is good.

BUT -- most hi-fi preamps have much less circuitry in them than a typical
mixer. A line-level preamp (really a misnomer, but let it pass) usually has
only one amplifier in it, following the level control, with perhaps a buffer
for the REC OUT jack. If there are tone controls (increasingly rare in hi-fi
preamps) there'll be an amplifier for that.

In a typical mixer, however, the signal will pass through a minimum of about
half a dozen amplifier stages. Now, an amplifier stage, unless it's perfect
(and there aren't any) must add some degradation to the signal. So you're
guaranteed that, all other things being equal, half-a-dozen amplifiers will
usually sound worse than one. Obviously there are exceptions (compare and
contrast a high-quality professional console with a Radio Shack hi-fi preamp,
for example), but as a general rule less stuff means better sound.

This also applies to consoles, of course, which is one reason a lot of people
track through stand-alone preamps instead of consoles, or at least take a
direct out from the channel strip rather than go through all the mixing
circuitry unnecessarily.

Peace,
Paul

[Mike Rivers]

In article <bj2c7n$ep2ap$1@uni-berlin.de> REMOVEMEmartinDOTfuchs@physik.fu-berlin.de writes:

> Hi, this is a follow-up to my question about a comparison between HiFi
> preamps and mixers; I consider buying a mixer/poweramp combo for my HiFi
> system at home instead of a full HiFi amp:

They're two very different things. A HiFi preamp has two functions.
First (and why it's called a preamp) is to amplifiy and equalize the
low level signal from a phono pickup. Second, it's to provide a
control center for selecting one of various sources to be amplified
and fed to speakers or headphones. There are often tone controls and
sometimes other routing, for instance to and from a recorder.

A mixer is designed to combine several sound sources so that, rather
than listening to one or another, you hear a mix of them. Nothing's to
say that you can't make a mix consisting of just one source, but
that's really not what it's for.

> Allen&Heath, Rane and Numark mixers looked pretty good there, for
> example (S/N -90 dB or better). Denon, OTOH, had S/N specified as better
> -80 dB only.
>
> So is this as important as I think it is?

Sounds like you're talking about DJ mixers here, not general purpose
mixers. They're designed mostly to switch between two sources
(turntables), but they're mixers in the sense that instead of using a
selector switch, they crossfade between sources. Using this
cross-fader effectively is part of the DJ's craft.

As far as the difference between 80 and 90 dB s/n ratio, whether it
makes a difference depends on how you're using it and how the
manufactuer has measured it.

> What other parms determine "sound quality" on paper? I know that numbers
> on paper are not everything but they certainly help to rule out some
> mixers for what I want to use them. Are the THD (total harmonic
> distortions) important there?

Sure, THD is important. But the best way to determine sound quality
for your personal application is to listen for yourself. When it
comes to DJ mixers, quality of mechanical components (like the all
important cross-fader) and construction are often more important than
some tweak parameters on paper, particularly since often measurements
of the same parameter can't be directly compared unless you measure
them yourself.



--
I'm really Mike Rivers - (mrivers@d-and-d.com)