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Stock tubes have been replaced by GE 5751 and 12AU7's.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