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Re: conrad johnson PV2 (early eighties vint.)upgrades ?

You will get the most bang for the buck by tube rolling.

Polypropilene caps last forever (unless there is a leaky/shorted one). Measure DCV AFTER the cap with a DMM (negative probe to ground), it should be zero; then measure ACV after the cap with the phono input shorted, it should also read zero. Any reading above a few mV stray hum means the cap is faulty.

I bet the phono stage uses 12AX7 tubes. The 7025 is a low-noise equivalent tube, worth searching.
Also, if the line stage uses 12ax7, try 5751 as a replacement. The total gain will be slightly lower, however noise will go WAY down.
Do not use 5751s in the phono stage, it will lose lots of gain.

12At7: try 6201
12au7:try 6814 or 5965
Those are the inexpensive options (USA military surplus; IMO RCA, Tung-Sol and Amperex are the best, much better than GE and Phillips-ECG USA).

The expensive route is:
12ax7 > european* gold pin E83cc or ECC803S
12AU7 > european gold pin E82cc or ECC803S
12AT7 > european gold pin E81cc

*=Phillips Holland, Telefunken, Mullard or Siemens
The recommended substitute tubes are 100% pin-compatible.
Good luck
Carlos


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  • Re: conrad johnson PV2 (early eighties vint.)upgrades ? - Carlos 10/30/0423:37:40 10/30/04 (0)


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