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    PAS 47K resistor

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    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    PAS 47K resistor

    Post by PeterCapo on Tue Dec 08, 2009 6:16 pm

    It looks like the original PAS had a 47K resistor in series between the input and the blend switch (at least with the blend switch set to the normal stereo position).

    Does anyone know why this 47K resistor is there to begin with? Seems to me that the only thing it does is add to the input impedance, but I'd really like to hear what others have to say about it.

    If you eliminate the blend switch and balance pot, I think this 47K can probably be omitted. What do you think?

    Thanks.
    Peter

    GP49

    Posts : 718
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: PAS 47K resistor

    Post by GP49 on Wed Dec 09, 2009 12:39 pm

    If you switch the stock PAS to full blend for mono operation, the inputs to the two-channel linestage are connected together. There is no harm in doing this, but without those 47K resistors in the signal path, you'd also be connecting the outputs of the phono stage together, blending the separate channels' negative feedback in the phono stage. Feedback should be kept separate for each channel (and that's one big reason why paralleling the two channels of the Stereo 70 to get a 70-watt mono amp really doesn't work). If you choose to eliminate the blend switch there should be no harm in eliminating the 47K resistor. I play mono records frequently, and listen to FM in a fringe area where switching to mono reduces the background noise, and have chosen to retain the blend switch; so I have to retain the 47K resistors.

    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    Re: PAS 47K resistor

    Post by PeterCapo on Wed Dec 09, 2009 8:33 pm

    Thank you.

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