Looking for Opinions on a Modded CJ PV-11 Pre

I'm looking at a modded Conrad Johnson PV-11. It's not close enough for me to audition. Looking for expert opinions on the mods and if I should pull the trigger on this deal. Cost is < $1000.

List of modification as follows:

IEC outlet has been added in lieu of the captivating power cord allowing choice of power cords

Coupling caps have been changed to a custom Cap made by Southern F-Dyne:. Equivalent to the Hovland and MIT in sound quality but more bass

Tube coolers have been added for prolonged tube life. Grounding wires are attached to the coolers in oncrease dynamics and top end ( capacitance between the blackened copper coolers and the tube plates normally rolls off the top end slightly unless the coolers are grounded).

Power supply caps have been augmented in filament supply. This drops filament ripple from 20 mV to 0.2 mV, dropping noise level to that of the Premier series in CJ lineup.. You can see the two large brown electrolytic caps which accomplish this.

Input wiring on CD and Phono input has been changed to Cardas 21.5 gauge internal wiring. Output wiring has also been changed. Not visible since it is under the circuit board, but critical circuit board traces have also been doubled over with the same wiare. In other words CD stage, for example is wired directly to the selector switch then jumpered over to the balance , then jumpered over to the volume control, then over to the input stage of the output tubes. Thus the wiring from input to output on the Phono and CD inputs are completely Cardas wired.

Critical resisters are covered with mumetal to lower inductance of the resisters.(stock dow corning as used by CJ)

Stock tubes have been replaced by GE 5751 and 12AU7's.

four Isosockets (made by PEARL and sold by Parts Connection) have been installed in the output stage and the outputs of the phono stage. These are gold ponned sockets mounted on a PCB and uses sorbothane isolation ring to "shock mount " the tubes. This gives a significant increase on midrange detail and a slight tonal shift towards the warmer side ( hence the GE tubes)

Cover mounting screws have been changed to Staionless socket screws

Circuit topology is unchanged from original CJ design.and power supply regulators are all original CJ design.

With such mods, the PV11 surpasses the performance of the CJ Premier 14, and approaches that of the Premier 17 (not quite. as we have since developed better coupling caps and have better wire installed )
Usually mods degrade the value of the unit, unless the mods are performed and documented by a legitimate, professional mod company like Great Northern Sound Company (out of business), pcX, SMc Audio, etc. If the person who performed the mods is simply a DIY weekend modkateer, it generally damages the value of the unit. I'm not saying that a DIYer can't do good work, but most buyers are very leery of just anyone playing around with expensive gear that they wish to purchase.
If I recall correctly, $1200 is about what I paid for a new CJ PV11 about 15 years ago. A lot of the items you mention would either be 'required' replaced items due to its age or else is nothing more that fluff! Power cord of choice is fluff! The tubes came with tube damper rings installed from CJ. The tubes themselves should have been replaced after all these years so as far as which brand is currently installed, so what! This comment would also apply to the caps. After 15+ years of use, they needed to be replaced. Don't misunderstand. This is a great pre-amp and it had an excellent phono stage. But the seller is selling you what is nothing more that a service and up to date used pre-amp for what it original sold for new!
Interesting list of modifications. Caveat Emptor. This unit could sound very upscale and better than stock as intended. However, IMHO the extensive mods like these require a listen before purchase. Perhaps the seller would allow you to listen before buying at your site. Agree with Jmcgrogan2. Who did the mods? Bill Thalman:


or a ham fisted solder-gun toting hack? Is there any documentation available regarding the mods implemented? Factory CJ technicians will not touch this unit for repair in the future if that makes any difference. With CJ proprietary caps not in the circuit and the exhaustive other mods this really is no longer a CJ unit. Cardas Wire has fans and haters with the solder pot (wire must be dipped before it is soldered) and proprietary eutectic solder. Personally I think it is over-rated. Have a plan for service before you purchase. Preferably the modifier, just in case a mod goes south. Something else to consider, highly modified gear has a shorter shelf life. It's kind of like hot-rodding the Corvette. "speed kills but what a way to go"
Do you know if these mods were done by Bob Backert? How long ago?

If they were done by Bob, the mods would be excellent. CJ sends some of their own repairs to bob because he is considered an expert on CJ electronics.
Mods not done by Bob Backert.