Philbrick opamps P25a, P65a, P85a for preamp, etc?
« on: April 03, 2008, 03:02:33 PM »
Gents,

Has anyone tried these in any projects?  Found a local source for these 3 models for $5ea.  Looked at the Philbrick archive and the AD book on them and they seemed interesting.  Just curious.

Thanks, Nathan


Samuel Groner

    Z├╝rich, Switzerland
  • Posts: 2935
Philbrick opamps P25a, P65a, P85a for preamp, etc?
« Reply #1 on: April 03, 2008, 03:42:24 PM »
Forget it--these are precision opamps, way to low slew-rate and GBW for audio. Noise is high as well.

Samuel

Philbrick opamps P25a, P65a, P85a for preamp, etc?
« Reply #2 on: April 03, 2008, 04:13:48 PM »
The guts contain AF transistors and/or FET's and found these very basic schemos and thought I'd consult this forum.




PRR

Philbrick opamps P25a, P65a, P85a for preamp, etc?
« Reply #3 on: April 03, 2008, 10:34:27 PM »
> Looked at the Philbrick archive and the AD book on them and they seemed interesting.

Of course. The unwarranted popularity of "Opamps everywhere" is due to those very-very-very good papers.

The op-amps are comparable to LM741, only not as good.

Sure, we did a LOT of listening through 741s.

There was always something "off", a smeared sound.

OTOH, compared to starved 12AX7 or roll-yer-own 2-transistor preamps, a Philbrick or a 741 gives a predictable response and no more noise. In those days, a 6dB noise figure was not embarrassing.

Just do it. Except haggle down to $2 each.

clintrubber

Philbrick opamps P25a, P65a, P85a for preamp, etc?
« Reply #4 on: April 04, 2008, 05:32:21 AM »
For either of the mentioned prices you could at least get a few to serve as reference, as in: how much a fresher opamp can improve things.

Maybe it has a use for 'shaping' sound, like people use the Melcor 1731 etc (which could be miles better though as I understand from the words above).
And maybe it's of use for another not-critical appliction, since it will look pretty on a PCB.


 

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