"Trevor Wilson" wrote in message
...

"andy" wrote in message
oups.com...
As yet another owner of a Pioneer DV-575A I am curious about what the
above modifications will achieve and why?

**Output muting, via the use of BJTs has always been a sonic disaster,
IME. A relay contributes no distortion, whilst in the O/C mode.

A BJT contributes no significant distortion when switched off.

The output
IC used, whilst adequate, is hardly state of the art.

You don't need state of the art ICs for a signal with a guaranteed max
output of a couple of volts, and a guaranteed max bandwidth of 22kHz.
The Pioneer of course has better opamps than this, as it can happily
cope with 100kHz bandwidth for 24/192 - at 0.002% THD - and over six
channels, so plain old CD audio isn't going to be a problem.

Output ICs in 1983
(ie: First generation) CD players were superior.

Utter nonsense!

In Philips derived
machines, that usually meant an NE5532/5534 chip. A fine chip, back then
and still a fine chip today.

Indeed so, as are the perfectly adequate modern chips inside the
Pioneer, which have gain-bandwidth and distortion levels that a 5534
can only dream of!

There are two, 220 Ohm resistors in series
with each O/P IC. These should be shorted (after replacing the ICs with a
more suitable device, of course). A 440 Ohm output impedance is pitifully
high.

No higher than that of many well-regarded ultra-expensive passive
'preamps', and not a problem in most systems anyway. At worst, you
might get a treble rolloff as low as 100kHz in a system with long,
high-capacitance cabling. Hardly a disaster.........................

Additionally, it would be nice to organise a spilt rail power
supply, for the output IC. At present, it is powered by a single rail
supply, thus a large electrolytic coupling cap is required.

So what? Can you hear the difference?

I suggest anyone who is interested, to compare the 575A to a decent,
contemporary CD (only) player, such as a Rotel RCD951 and report on any
differences.

I already compared it to an *excellent* modern CD player, arguably the
very best, and found no audible differences.

Patrick, you're advocating expensive 'audiophile' tweaks of no proven
*audible* worth for a low-cost universal player. That is just plain
*bad* engineering - you should be ashamed of yourself! :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering