Mark

I can also tell you that A/D/S pretty much made extremely good units except
for a few choice "dogs". I can only currently think of only one. I can't
remember the model, but it had several DSP processors on board. Also had
5, yea 5 separate power supplies. Each one "yanking" the amplifiers ground
all over creation. They also had a rather good Audio Engineer's ( Ed
Meitner ) pre-driver stage that was particularly good at rejecting Power
supply noise or any "common-mode" noise for that matter. It was partly
their saving grace. I think that your P840 shares this pre-driver
technology. If you can get your hands on a schematic of your P840, look
for the pre-driver stage. If you see some OPAMPS whose output pins are
tied to GND and has JFETS between the +/- 15 volt rails and the OPAMPS
input +/- supply pins, then you are indeed fortunate. This type of driver
section is usually only used in audiophile grade home amplifiers. Ed
performed a miracle and got it to work for a car amplifier. Those amps
also typically us Burr-Brown Audio grade OPAMPS as well.

I was working at A/D/S when we made great product, I was there when we
knowingly made crap and I was there when we started to make good product
again. I was there when good Engineers left, I was there when bad
Engineers came in and I was there when these bad Engineers either left or
were fired. Those bad Engineers "talked the talk" but didn't "walk the
walk". FYI, a couple of those bad Engineers were really marketing guys who
were Engineering wannabe's. IMHO, Engineers cogitate and marketing types
scheme. The real downfall of PPI/ADS/ORION was pretty much due to these
guys lack of skill and knowledge when it came to Audio Engineering. On
another side note, these same Engineers had a little something to do with
making bad ORION product as well. Bad PPI products also came about around
this time frame as well due to a person who was in "New Products
Development" ( read Marketing ). It was his scheming and back door dealing
( Engineering was left out of the loop ) that created the first gen of the
PCX amplifier. This line was a year late, poorly thought out and had many
issues. This is what you get when you have Marketing telling offshore
firms how to make an amplifier. This new line of PCX amplifiers was even
approved for production after only visually inspecting the prototype
models. Hell, they "looked" great. The marketing man was pleased. Little
did he know.........

In short, That amp of yours and it's next of kin the P850 are indeed great
amps. Just stay away from Constant Bass. This function was implemented
incorrectly. If it were done right, it would be a blessing. But, it was
implemented wrong and kills your sound stage. Engage this feature and
listen to a "sound staging" test CD. You will indeed hear the loss of your
soundstage.

JA


Mark Zarella wrote:

Mark,

Why the A/D/S amplifiers? It is because they are well made according to
Engineering practices and very high quality parts. I know, some of my
"work" is in that amplifier.

John, I run the a/d/s/ P840 for my front set because it supplies an
adequate power distribution to my a/d/s/ 641is set allowing me to triamp
them and level control the individual drivers, and it has built-in
crossovers that allow me to bandpass the midbass and midrange speakers and
highpass the
tweeters, all with continuously adjustable xover points. Also, its flat
depth means it can be installed up in the rear deck. These features,
along with great support I've had with JD and Directed so far with my
other a/d/s/
equipment, and decent reliability is why I bought this amp. Oh yeah, and
it only cost me $220.