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


We recently invested in a Precision Fidelity C7/A and I was thinking of upgrading some of the OEM capacitors. The original designer -- Bruce Moore -- apparently built the preamp. to sound as good as could be in stock configuration without having to modify anything, i.e. evincing the philosophy that an intelligent design should be simple and sound excellent as is.

Has anyone upgraded their Precision Fidelity with caps. such as V-Cap teflons or Auricaps and come away with dramatic differences in sonics, either for the better or worse?

Thank you.
Are you planning on keeping it forever? If so mods may be for you. If not, I would rethink modding as it usually does not dramatically improve the resale value against the cost of the mods.

My experience is with a modded Cary pre-amp (cathode follower stage added along with upgraded caps, power supply, & standby switch) that generated only bluebook value on resale and a McCormack DNA-1 deluxe that was modded to the A level by Steve. Again resale value added was about 20% of the mod cost.

If resale does value does not matter to you and it is only about improved performance - mod away. A final note is that some mods may degrade the performance or balance of components chosen by the designer.
Thanks for responding: Yes, we plan on keeping the C7/A for the rest of our lives. At this stage, I simply do not know if $800.00 in V-Cap upgrades -- as excellent as they are supposed to be -- will be a move backward, contravening Mr. Moore's engineering philosophy on the C7/A that an impeccable, scientifically rigorous engineering concept should not need upgrading.
I recall the C7A-Revised being a fantastic sounding preamplifier. If you have merely a C7A, perhaps investigating what exactly the "revised" referred to would be an excellent starting point. Perhaps some generous "revised" owner out there would be willing to take a few detailed internal photographs for you to examine, as well as answer a few questions about the circuit changes in the "revised" version.

Cap upgrades are a crap shoot at best. Often, a designer will use seemingly pedestrian parts that are perfectly voiced into the circuit. Changes will render differences, but only your ears will emphatically tell you whether boutique parts are actually better. In my experience, you have a 50/50 shot of actually improving things without destroying the fundamental characteristics of the unit; presumably, it's these original characteristics which made the unit both worth keeping for an extended period, and worth attempting to improve. You takes your chances.

Thanks for the response Richard. This piece is in fact the "C7/A Revised," as I recall printed on the circuit board. I think it is a monument to fine, fine engineering bar none but the perhaps a handful of other preamps. Thank you.
As I recall, your unit is a couple of decades old.
I had a Precision Fidelity, but a lesser model and it was a very decent sounding unit.
Simple design,dual volume or balance knobs and I think a couple of tubes, but a big open sound.
I should have kept it.
If I would have, considering it's age, I would at least have all the caps and resistors checked out and replace the ones that need to be replaced with better ones.
I would also try to find out where in the circuit that a cap upgrade would yield the best results.
This is where a good tech is invaluable if you can't do it yourself.
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?

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.
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
I remember there was a guy by the name of Joe Bermudez involved in that company. The power supply design reminded me a bit of an Audible Illusions as well as some early C/J product. I fixed one about 10 years ago. Hasn't been back since.
Here's something from High-endaudio:

I sold this model when my store opened back in 1981. This is a "Classic Preamplifier", with a design far ahead of not only its own time, but even up to today. In fact, our current audio market is begging for an updated version of the C-7.

The C-7 was essentially a high quality (tube) phono-stage with two volume controls, a couple of extra (passive) inputs and no line-stage. This is "the dream design" of today's audiophiles who have phono-centric systems, like me. (My own preamplifier, the Jadis JP-80, was heavily modified to copy the basic design of the C-7.)

It's been some time since I heard one of them, but I remember their sheer natural quality and the cleanness and quietness that is consistent with no line-stage. The people who bought them, if they could live with the low-gain, loved them. (I'd love to hear a modified version, with the best caps available today. I would love even more to hear an all-out modern version of this design.)

I remember that the original C-7 had some design problems that translated into sonic problems, so look for the "A" or "Revised" versions. (I can not provide the schematics to make these revisions.) The C-7 should be modified with better capacitors, just like all the other preamplifiers from this era. They also require a high quality step-up device for low-output moving coils.

Recent- One reader just purchased a C-7 based on the above advice. His take:

"...soundwise - Wow! Lumi is taking a long rest. This thing sounds a bit dark (like most passives in my system, probably the amp), but it is so dynamic, immediate, transparent, and not greasy or euphonic or juicy. I'd venture to say it is rather accurate. Of all medium priced preamps that I've tried, and I've had many, including many Bruce Moore designs, this one is by far the best sounding, with great MM phono. It beats Magus by a wide margin and phono is a lot quieter (uses two solid state regulators). Thanks for a great suggestion..."

Bottom Line- If I was on "a strict budget" for a preamplifier, and with the choice of ANY model ever made, the C-7 (modified) would be my first choice.
Hello, My name is Kavi Alexander and I own Water Lily Acoustics, a small record label. In the early 80s your company sold a few of your preamps and hybrid power amps to friends of mine at industry accommodation pricing. You may remember this...
Anyway, I have recently been gifted a Precision Fidelity C7 preamp, which I am enjoying very, very much!!! I must add that it is an outstanding design!
Could you kindly answer the following questions for me?
1) How can I tell if the unit I have has been upgraded to the "A" version?
2) Will the unit fun long interconnect cables, say 15 feet of very low capacitance.
3) Would it be possible to get a circuit diagram?

Please visit my site at:
Should you see any titles you would like, I would be happy to send them your way...
It would be appreciated if you can respond to:

I thank you for your time and wish you the very best.
Kavi Alexander.
Hello, I am Kavi Alexander, an Audiogon member. I recently was given a Precision Fidelity C7 preamp as a gift. A web search for a circuit diagram for this unit lead me here.
May I kindly request a copy of same from you?
If so, please email it to

I would be glad to send you a CD of mine in return, thus please visit my site at: and make your pick and let me know...

Thank you and wish you the very best.
I would like to comment on gsakakeeny's post concerning his claim to have "designed" the Precision Fidelity C7 preamp in 1977 when the company moved to Santa Rosa. I worked for them in San Francisco and Foster City in the late 70's and they didn't move to the business park in Santa Rosa until the Spring of 1980, if I remember correctly. Prior to that I was under the impression that Bruce Moore was the C7 designer, and I had one or more discussions with him that concerned the C7. I was , in fact, the "designer" of the C7a, which was a cluster f___ and turned out to be one of the factors in my exiting the High End Audio business.

Riding on the success of the C7, thanks to glowing reviews which caught our fledgling manufacturing firm quite off guard, Joe Bermudez, who was in charge of Domestic Sales, suggested that we come out with an "upgrade" using polystyrene capacitors instead of polypropylene (or was it the other way around?). We had confirmation of the availability of the new caps and had faceplates made with the new c7a designation, but at the last minute there was some screw up with getting the caps. Joe told me to ship the preamps anyway and we would somehow follow them up with the new caps (when they arrived) with instructions on how to swap them for the old ones. I really don't remember if they ever got to us (it's been almost 40 years...) but we started to get phone calls about how great the "new" modified preamp sounded from our dealers, citing, between gasps, that there was now "depth" and "air" and "transparency" and all the other buzzwords in use at the time. Not a single person complained that the "new" preamp sounded exactly the same as the "old" one, and the accolades about the improved C7 continued to pour in. There were times when Joe, John Fong (the owner and person in charge of International Sales), and I would sit around and read to each other out loud some of the astonishing praises about our C7 being "improved" merely by adding the letter "a" to the faceplate, and laughing hysterically.

Lastly, I hope Mr. Sakakeeny changed the design significantly on the JV1 pre-preamp before he stuck his initials on it - it was my design, as simple as it was...
Just stumbled on this old thread. The Hill Companies did indeed buy Precision Fidelity from John Fong. Since it was my idea the Hill Company's owner handed it to me to manage and grow. I could do neither with it.
Bruce Moore (who I never met) designed the C7 and C7A which were, essentially identical. Gabe Sakakeeny along with Jack Senecal designed the C8 which was a hybrid preamp.
Joe Bermudez was PF's part time sales manager when we bought the company. Joe soon went to work for Mobil Fidelity as PF struggled. John Fong was murdered in Mobile Fidelity's parking lot where he was to meet Joe for lunch as I recall. It was a professional hit--small motor bike and small caliber  hand gun. We handed the company back to Senecal and Sakakeeny and walked away, not so much due to Fong's murder but my inability to make anything viable out of the company.

I purchased a new C-7 and loved it. I sent it in and upgraded to the C-7A.  I liked the original C7A more, especially the variable volume pot as compared to the stepped one on the C-7A   The C-7A then went back to the factory twice under warranty for blown caps. After a third incident, PF offered  me an upgrade to a C-8. I took it.

I preferred the C-7 series to the C8. The remained in service until it smoked many years later. It was brought back to life by Tom Tutay of Transition Audio with an External power supply, great parts and a 12AT7 section.