"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.

Musta never seen it done right.

A relay contributes no distortion,

As long as the contacts are good.

whilst in the O/C mode.

In which case there is no signal at all.

The output IC used, whilst adequate, is hardly state of the
art. Output ICs in 1983 (ie: First generation) CD players were
superior. In Philips derived machines, that usually meant an
NE5532/5534 chip. A fine chip, back then and still a fine chip
today.

Right, but just because it aint' a 5532 doesn't mean it sounds bad or
contributes any audible flaws at all.

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).

Why? Aren't building-out resistors good practice?

A 440 Ohm output impedance is pitifully high.

Isn't 600 ohms the standard source impedance for audio production?

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.

What's wrong with a well-biased electrolytic?

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 suggest that Trevor quit pontificating and do some bias-controlled
listening tests of his own.