You will definitely have to invest in the service manual to start with. As
for doing the proper design, purchasing of the parts, and then building the
proper circuits for this, the end would not justify the cost. If the design
and construction of what is required is done properly, you will have
satisfactory results.

You can buy ready made amplifiers that have a preamp out, and were
originally factory designed that way. This would be the better option than
modifying an older amplifier that was not designed to work with this type of
option.

--

Jerry G.
=====

wrote in message
...

Is this possible with an older amplifier (ca. 1992)?
Classic design, Sony TA-F590ES, with motorized volume control.

I won't be able to do the work myself, but would like to know what's
involved in it, and if the result can be 100% satisfactory?

Is getting the service manual required before starting? (not very
easy, in France)

TIA