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    PAS 3X - loudness and filter switch

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    Feistygoat

    Posts : 15
    Join date : 2012-02-13

    PAS 3X - loudness and filter switch

    Post by Feistygoat on Tue Feb 21, 2012 10:13 pm

    Hey guys, can anyone give me a quick run through on how to bypass the loudness and filter switches on my PAS 3X pre-amp? I want the cleanest passthru possible. I've already had the rectifier and power caps upgraded, as well as all the caps on both the phono and driver boards. Any help would be greatly appreciated
    Thanks

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: PAS 3X - loudness and filter switch

    Post by tubes4hifi on Wed Feb 22, 2012 12:39 am

    fastest way is to cut the wires to the switches, seriously, they are only in circuit when actually used,
    cutting the wires won't change normal operation at all

    GP49

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

    Re: PAS 3X - loudness and filter switch

    Post by GP49 on Wed Feb 22, 2012 12:57 am

    To remove the loudness contour circuitry, remove its connection to the volume control.

    I'd do this along with replacing the stock volume control, which does not sound all that good to begin with
    and which often has balance tracking problems, with a switched type or a higher-quality dual potentiometer.
    When hooking up the new control, leave out the connection to the loudness contour circuitry (it might not
    HAVE such a point for connection anyway).

    As to the filter, remove the 1400pf and .004µF capacitors from the PC-5 board, and replace the 18KΩ
    resistor with a straight wire.

    When the filter and loudness circuits are removed, you can use the switches for other purposes. For instance,
    if you want to remove the mono/stereo/blend switch from the circuit and thus eliminate some more contacts from
    the signal path, you can use one of the switches to blend the two channels for MONO use, such as when listening
    to mono records or noisy FM broadcasts; when switched to STEREO the switch contacts are totally out-of-circuit.


    Feistygoat

    Posts : 15
    Join date : 2012-02-13

    Re: PAS 3X - loudness and filter switch

    Post by Feistygoat on Wed Feb 22, 2012 1:15 am

    Thanks guys, much appreciated. I noticed that my volume knob does have balance tracking problems. - I have to set the volume at a "Sweet" spot otherwise at certain points my right channel will be subdued slightly. Thank you both for the input

    heyraz

    Posts : 58
    Join date : 2011-10-26

    Re: PAS 3X - loudness and filter switch

    Post by heyraz on Wed Feb 22, 2012 1:51 am

    These HTML's concern modification to the PAS pre-amps. I think everyone will find it pertinent.
    http://www.normankoren.com/Audio/Spice_preamp.html
    http://www.normankoren.com/Audio/Spice_preamp_2.html


    Feistygoat

    Posts : 15
    Join date : 2012-02-13

    Re: PAS 3X - loudness and filter switch

    Post by Feistygoat on Sat Feb 25, 2012 12:43 pm

    My god what a difference - I just installed a new volume control knob, and bypassed both the loudness and filter paths - the sound improvement is even more substantial and noticeable than when I switched to telefunken 12ax7's over the Chinese ones. I have to believe that aside from balance tracking issues, my old volume pot was so dirty it was hampering a clean signal transfer. Thanks again for all the help, now I've got to crack open a bottle of 18 year Jameson, and relisten to my entire vinyl collection!
    Good weekend to all

    Feistygoat

    Posts : 15
    Join date : 2012-02-13

    Re: PAS 3X - loudness and filter switch

    Post by Feistygoat on Sat Feb 25, 2012 12:45 pm

    Oops - quick amendment, I didn't mean volume control knob, I meant the entire dual pot.

    gdlen1

    Posts : 17
    Join date : 2012-03-18

    Re: PAS 3X - loudness and filter switch

    Post by gdlen1 on Mon Sep 17, 2012 5:55 am

    hi, apologies if this thread is deemed too old for posting anymore but, with regard to the filter switch, what is the difference between simply cutting the wire to the switch or removing the 1400pf and .004µF capacitors from the PC-5 board, and replacing the 18KΩ resistor with a straight wire? do those caps and resistor even have signal going through them if the wire to the switch is cut?

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: PAS 3X - loudness and filter switch

    Post by tubes4hifi on Mon Sep 17, 2012 1:01 pm

    the two caps won't have any signal going thru them anyway, if the wires to the filter switch are cut.
    I'm not sure I'd use a wire instead of 18K, I'd probably use something like a 1K resistor,
    the signal is passing thru that to the grid of the next tube in the circuit.
    When in doubt, refer to the schematic!

    quadaptor

    Posts : 59
    Join date : 2009-05-04

    Re: PAS 3X - loudness and filter switch

    Post by quadaptor on Thu Sep 27, 2012 4:05 pm

    What make of volume control did you use?

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