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I bought an inexpensive ($70) JEC phono stage to use while I upgrade/repair my McCormack. The JEC has both MM and MC inputs, and uses a 4558 op amp.I built an outboard regulated power supply using a 317 regulator and a 2 amp transformer to replace the 12 VDC/200 mA wall wart the JEC came with. Since the new supply seemed up to the task, I decided to replace the 4558 with a BB 2604 I had sitting here.
It certainly sounds better now, but when I measured the voltage on pins # 4 and 8, I realized the circuit is only supplying +/- 4.7 volts to these pins, hardly optimal for the 2604.
I could trace the circuit and find out which resistors are dropping the voltage, but I really don't want to spend a lot of time fooling around with this spare unit. I'm wondering if I could simply run two leads from the jack where the 12.3 volts enters the chassis, directly to pins 4 & 8 (there's a 4007 at the DC in jack to reverse bias for the negative voltage).
Assuming that doing this is both possible and wise, would the two pins need to be pulled from the circuit board first, or could I simply parallel the existing supply to pins 4 & 8 of the 2604?
I hope this makes sense (obviously I'm no expert), and thanks in advance.
Edits: 06/09/08 06/09/08Follow Ups:
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