Precision Fidelity C7/A: To modify or leave as is?

Pardon my initial comment that the Precision Fidelity C7/A Revised is "a monument to fine engineering bar none but perhaps few other preamps." Rather, a more appropriate and balanced statement would be that it is "a monument to the finest of engineering bar none given phonocentric systems."

Does anyone know if the C7A "modified" different than the "revised"? and, where the modified and revised versions silkscreened with "C7A Revised" on the back of them or was it just an internal change with the "C7" on the back?

thanks

Just for the record, the original C7 was designed by me when Precision Fidelity had just moved to Santa Rosa, CA in 1977. The company was sold to The Hill Group, a holding company in San Diego in 1978. They eventually sold the designs to Bruce Moore who ran the technical end after that. I went to National Controls to design A/D convertors and exited the audio scene.

I'm delighted that the C7 and the M80 stereo power amp have become such beloved instruments. As an technically inclined artist, it is satisfying to know that my creations have provided so much pleasure for so long.

I never heard an actual C7 but I built one from the schematic a long time ago. As I recall, it sounded very nice, just lacking a bit in dynamics. From looking at your system, I think you would appreciate the improved sound quality that V-Cap coupling caps should provide. Richard is absolutely right that cap upgrades can be risky. They will change the sound, and sometimes a modern cap can be a step backwards. I happen to like the sound of V-Caps very much, both the original Teflon and the newer CuTF series, but that is not a universal reaction. I suspect your C7 uses some mylar film caps from the late 1970s, and V-Caps should be a major improvement in inner detail and (probably but less certainly) tonal balance. If I were you, I would do it. In the unlikely case that you are not happy, you can always put the originals back in.

By the way, if you need a copy of the schematic, send me an email through the Audiogon system. I have one in my files somewhere. As I recall, it shows the original circuit as well as later updates.

Hello,
I must commend your design. I recently purchased a C7 and I love it. For some reason the owner's manual and full schematic are scarer than hens' teeth.
Any chance you have either?
I would gladly pay any costs.
Thank you
Lloyd Foster