From: lstowell@pyrnova.mis.pyramid.com (Lon Stowell)
Newsgroups: rec.audio
Subject: Re: question on pre-amplifiers
Date: 11 Dec 92 18:27:36 GMT
Reply-To: lstowell@pyrnova.pyramid.com (Lon Stowell)
Distribution: usa
Organization: Pyramid Technology Corp., Mountain View, CA

In article <1992Dec10.074303.28850@u.washington.edu> zzjim@stein.u.washington.edu (Zeming Gao) writes:
>
>
>I've got some questions about preamplifiers. Couple of posters on
>this news board suggested that by using a CD player which has
>variable line out, you can go without a pre-amplifier. Does this
>imply that CD players with variable line out have built-in pre-amps?
  
    Actually it depends on your definition of "preamp".  Not wanting
    to start a flame war, I won't bother attempting a definition.

    All CD players with a line out include and output amplifier.
    SOME of these allow you to vary the output level of the line out
    amp.  

    The nominal output for a CD player with a 0 dB (max) signal is
    about 2 volts at the line outs.  This is the same level as the
    typical pre-amp line output to a power amp.  So if you hook ANY
    cd player to your power amp, then you'd have the same condition
    as running it thru a typical "preamp" with the volume full up.

    The volume control on a preamp may ALSO be an attenuator, so
    don't get so hung up on terminology or you'll just confuse
    yourself.  On a passive preamp, obviously the volume control is
    nothing but an attenuator.  Level matching of source to power
    amp, modified by desired volume, is a preamp function.  Whether
    you consider the built-in ability to do this a preamp is a
    religious issue. 


>I thought variable line out was just an attenuator instead of an
>amplifier. But in case that i am wrong, how good are these pre-amps? I
>know it's confusing, but can't resist asking: if such pre-amps, if 
>they are, work fine, why should people buy expensive pre-amps?
>
    If the CD player is your ONLY source, then indeed, why bother?
    But most systems also have other sources, and source selection
    is another function of a preamp.  

    How good the built-in ones are would be highly dependent on the
    brand and model.  But since the intent is to provide high
    quality audio by bypassing a preamp, you'd expect somewhat
    better quality than the typical headphone output.


>How important is the quality of a preamplifier anyway? Can a good
>power amp upgrade the system when you still use the pre-amp out put
>of a low-end receiver?
>
   Darned important.  Remember that signal/noise is usually a
   constant noise floor.  Once you increase the background noise in
   a system, nothing can remove it.  A noisy preamp will hurt your
   quality a lot more than a noisy power amp.

   Whether or not a power amp upgrade helps depends on why you are
   upgrading.  If you mean "budget" receiver rather than low-end,
   yes a power amp upgrade will help.  For example a small NAD
   receiver, which has a pretty clean preamp, would definitely
   benefit from more power.  A junkbrand receiver with a noisy
   preamp will only sound as good...


>Thanks in advance for an explanation.
>
>--- Jim  
Newsgroups: rec.audio