Newsgroups: rec.audio

>Now that we have CD, MD, DCC, DAT, and even Laser Disc players with digital
>outputs, and pre-amps that will accept and convert them to analog, the
>next logical step is digital amps, and obviously, speakers. Is this type
>of technology possible? Does it even exist? Assuming these are true, what
>advanatages/disadvantages would this provide? I think a discussion on this
>subject would be both interesting and educational.
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>Dave Hukill <dhukill@esprit.prime.com>
----------
If not, it will at least be amusing! 8-)
Digiatal preamps exist and sound pretty good (Sony TAES2000 @$1200).  They
take either a digital signal, process it (DSP) and convert it to analog
with D/As or take an analog signal, digitize it, process it and D/A it.

For the "best" sound, you want the preamp seperate from the power amp so
the large signals generated by the poweramp don't get back and mix into the
low level signals of the preamp.  Ideally, you want all low-level processing
in one box and high-power processing done in another - hence seperates.

Quality power amps typically have SNRs (A weighted and converted to 1V ref)
of 100 db or more while line preamps do well to get 90-95db.  Acurus, for
example is 110 and 95dB (not sure if this is referenced to 1V).  DSP units
are in the mid 80s under $1000 and reach the 90dbA range for $3000 
(Lexicon CP-3).  My GUESS is that DSP lowers SNR because all the digital
switches (or gates) pump transient current into the ground as well as radiate
off the power supply bondwires.  Both sources can find their way back into
the analog section unless you spend alot of money to isolate and shield
them.

For a mixture of decent sound with low cost and lots of "features", it might
make sense to have powered speakers with D/As in them.  They would be fed
with Plastic Optical Fiber (hopefully HP) links from the console that had
DAT, CD, DSP, etc.  The cost savings comes from only needing one pair of
D/As with this method as well as not needing alot of expensive cables.
We aren't talking "audiophyle sound" with this sort of system, but I bet
you could easily get mid 80 dbA SNRs which would satisfy 99% of the
market.  I believe SONY has gone half way to this with some of their
"100 WPC rack systems" at the $1000-$1500 range with speakers.  SInce
these SONY systems are 4 channel for surround-sound, I think it is 
cheaper to have one set of D/As in the preamp box and drive the speakers
(four) with cheap speaker wire.

Kirk out
=> "We are what we pretend to be."  -  Kurt Vonnegut Jr.
+---------------------------------------------------------------------+
| Kirk Lindstrom - OCD Product R & D | Hewlett-Packard Co.  M/S: 91UA |
|   Engineer/Scientist, Hardware     |                                |
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From: kirk@hpcc01.corp.hp.com (Kirk Lindstrom)
Date: Sun, 22 Nov 1992 14:45:21 GMT
Subject: Re: Problems with my system ...
Organization: Shredding the water of SF Bay, HP-OCD