Curtis Mathes console

[alchemist]

Just picked up a Cherry French Provincial CM console. Has four original CM 6bq5 (made in Japan) output tubes on a standalone amp. Silver faced preamp/tuner. Has turntable that pulls out on a track and a slot to add a R2R.

Will do the standard work through of replacing electrolytic caps and spec’ing resistors, but consensus, are these nice sounding?

 

[TriodeLuvr]

It will never sound as good as that Dodge.

 

[alchemist]

It will never sound as good as that Dodge.

Correct on that one! I miss it badly. Had to sell it when I had my second child

 

[gizzyman47]

 

[alchemist]

Pics attached now. Note I pulled the amp out of the unit

 

[macyjrm]

Note the heat sinks attached to the power transformer. I don’t see that often.

 

[FlaCharlie]

Here's the schematic. It's in pdf which can be enlarged to view detail.

 

[alchemist]

Here's the schematic. It's in pdf which can be enlarged to view detail.

Thank you!

 

[AlexHempel]

Note the heat sinks attached to the power transformer. I don’t see that often.

Yeah very cool. Curious why they felt it was necessary -- PT looks reasonably sized and not exactly a cheap addition. Wonder if they had big stock of a PT the engineers felt was slightly under-sized

 

[TriodeLuvr]

Yeah very cool. Curious why they felt it was necessary -- PT looks reasonably sized and not exactly a cheap addition. Wonder if they had big stock of a PT the engineers felt was slightly under-sized

Maybe they were also concerned about the lack of sufficient air circulation inside a console. That would sure bother me if I was designing an amplifier for this purpose.

 

[gadget73]

or they were having problems with the transformers overheating and this was a running production change to address it.

 

[TriodeLuvr]

or they were having problems with the transformers overheating and this was a running production change to address it.

That would make sense especially if CM already had a few hundred in stock when the problem was detected. This is such an odd modification, and it looks like the chassis has even been cut away under the heatsinks to promote airflow. Maybe the OP will report back at some point as to whether the transformer runs hot in normal use. I can't tell from the photo - are the heatsinks welded to the lams?

Jack

 

[gadget73]

almost looks like a bolt running across between them, guessing it may have the same below to pinch them in place.

 

[cademan]

That particular power amplifier is missing the gain loop or feedback which is in the tuner preamp in which the tuner preamp will also be needed for it to work as a stand alone amplifier.

If you have a schematic and the knowledge to insert an extra gain tube on the amp, that is what you will need to do if you want to run just the amp without the tuner preamp.

 

[AlexHempel]

Yeah true, only one nine-pin signal tube. Images don’t show it super well but looks like it’s just providing concertina phase inversion to each output tube pair.