[John Stone]

On 6/15/10 9:06 PM, in article
, "Bret L"
wrote:
*I would build a modern and better power supply, for starters. *In
fact in a commercial product I'd build a chassis like the many
communications equipment mainframes where the PS would be unitized and
either physically bolt to the back of the chassis or could be run
remotely via an umbilical. This beats the CE regulations because the
set is one piece in those markets.

*All components would be modern and of good quality.

*A stereo stepped attenuator would replace the volume control pots .

Residual line noise would be lower with a better power supply and with
fewer noisy components of course.

*An article on this was put forth in Audio Amateur magazine in the
mid-1980s. That was actually the start of American, versus mainly
Oriental, interest in the Marantz 7 (and its impossibly close copy the
McIntosh C22) : people realized how well the old beast worked when
updated.

*As far as high output impedance, it's fine with most all tube
amplifiers. If lower output impedance is needed, one refinement would
be to provide for transformers to be added via sockets as was done in
so much commercial gear. This would provide for true balanced 600 ohm
output so it could fit in tho the Real World of pro audio if needed
whilst not inflicting the considerable cost of the transformers on
users not needing them.

Why would you go to all of this bother when there are better products
available for far cheaper without butchering up an expensive old
Marantz?


I wouldn't. I would build a new unit from scratch with the features I
wanted. A good DIYer could do it for maybe three hundred bucks in
parts, if he made his own step attenuator from switches and boards,
with a little scrounging.

The Audio Research SP3a would be a much better preamp to clone than the 7.
(There's actually no such thing as a 7C The C part is the wood case. )
ARC based their preamp on the Marantz 7, but with numerous enhancements like
regulated power supply for B+ and heaters, better parts, etc. It also
sounded far better than the Marantz, but mechanical design left a lot to be
desired. It was a spaghetti factory inside. But given you would start from
scratch, you could easily improve the mechanical quality. The basic design
was very stable. I had both the 7 and SP3 in my audio systems, and compared
the two extensively. It was no contest. The ARC won hands down.
The Marantz 7 was really nothing special. Just a well executed, basic
preamp. In fact, it really wasn't that much different from the Dyna PAS
series, except that Marantz added a set of cathode followers for the phono
and line stages, and of course used higher quality parts. But even Dyna had
DC heaters and unlike Marantz used a full wave B+ supply.