From: eacj@theory.TC.Cornell.EDU (Julian Vrieslander)
Subject: Re: Eminent Technology Model 8s
Originator: tjk@csd4.csd.uwm.edu
Organization: Cornell Theory Center
Date: Wed, 19 Aug 1992 13:05:12 GMT

In article <1992Aug17.173633.3698@novell.com> bbaker@novell.com (Brad Baker) writes:
>In article <1992Aug14.152825.17274@tc.cornell.edu> eacj@theory.TC.Cornell.EDU (Julian Vrieslander) writes:
>>In article <1992Aug13.212605.3708@novell.com> bbaker@novell.com (Brad Baker) writes:
>>Let's consider the preamp/power amp interface first.  Some passive
>>preamps do not match well with some power amps.  Usually, this is because
>>the power amp has an input impedence that is too low for the preamp, or
>>because the preamp cannot provide enough voltage swing to drive the
>             ^^^^^^
>I think you mean CD player here, right?  Passive preamps do not provide
>voltage swings.  At least the one that I have :> 

Are you saying that the CD player was directly connected to the power amp?
That was not clear to me.   

Regarding voltage swings, virtually all audio signal processing components
(active or passive) communicate with each other via time varying voltage
signals.

>I don't want to get into that "what is a passive preamp" thing.
>I consider passive to mean NO POWER CORD. Simple.

Terms like "passive preamp" can be confusing.  The PS Audio preamps, for
example, can be configured to run with passive high level stages, even though
the component as a whole is powered (and has a power cord). 

>>A badly matched preamp/power amp combination may cause the signal
>>reaching the speaker to be distorted, limited in level, or altered in
>>frequency response.  Depending on the speakers that you use, and your
>>own perceptions, these effects may be (a) inaudible, (b) detrimental,
>>or (c) pleasant.  But it makes no sense to say that a passive preamp
>>(or active preamp) works better or worse with a given speaker, because
>>the preamp does not directly interface with the speaker.
>
>You are correct, but I disagree with your reasoning. 
>It does not make sense, because the rest of the
>components come into play.  Whether or not they interface with
>the speaker is unimportant since everyone knows that changes
>in components in the audio chain "upstream" of the amps can 
>greatly affect the sound.
>
>The point that I was trying to make was that had I listened to the 
>ET's through an active preamp with a "hotter" signal (higher voltage
>swing?), that they would have probably sounded quite different; 
>probably more dynamic with better bass.  You could equally say that
>had I used a more efficient power amp, or a CD player with a "hotter"
>signal, that the same could be true.  However, I believe that the
>VTL's work very well with passive units (does that mean low input 
>impedance?), and that the EAD has a high output voltage when compared
>to most CD players.

Let's say that there *is* an mismatch between preamp and amp.  Perhaps the 
preamp has a relatively low value coupling capacitor on the output, and the
power amp has a relatively low value of input impedence.  In this specific
scenario, the net effect is likely to be heard as weak bass - the extreme
low frequencies are not getting through to the power amp.  That means that
they will not be getting through to the speakers, no matter what speakers
you use.  If you happen to be listening to Acme speakers, it is a bad
generalization to conclude that Acme speakers do not match well with 
passive preamps.  First of all, the missing bass would likely be noticable
on other speakers.  And secondly, substitution of a different passive
preamp (without the impedence mismatch problem) might produce terrific sound.
-- 
Julian Vrieslander 
Neurobiology & Behavior, Mudd Hall, Cornell University, Ithaca NY 14853    
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