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    Questions about upgrading to the Z mod boards for the PAS...

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    rerunmedia

    Posts : 1
    Join date : 2011-10-29

    Questions about upgrading to the Z mod boards for the PAS...

    Post by rerunmedia on Sat Oct 29, 2011 8:34 pm

    New to the Forum, and I have a couple of questions about the Z mod boards for the PAS:

    1. With regard to the Z mod phono board, is the RIAA curve on the board more accurate than the Dynaco originals? If so, is it still compatible for use with the stock Dynaco selector switch (which I believe in the original design, has some EQ correction mounted on it that is used for the Tape Head and Special inputs)? I'd like to retain the use of those inputs as originally designed, if possible, yet still get the upgraded phono circuitry of the Z mod board...

    2. With regard to the TCLA board, I know it is also available with an outboard circuit board that can be used with the original "dual mono" Dynaco bass & treble controls (rather than the modern stereo controls that it's usually pictured with), but will it work with the original PAS-3X bass & treble controls, that have the "drop-out" feature built in to them? And if so, is there still a need to attach an extra capacitor from the main board to the bass controls, as is done in the original PAS-3X build?

    3. Is it possible to buy **only** the boards, with a parts list that contains the necessary values to stuff it with different caps & resistors? (I'm thinking that some upscale carbon comp resistors might be nice, if they'll fit in the space provided on the boards). If so, what are the prices for the "bare boards + parts list"?

    Thanks for any assistance... I did searches of the forum, but I couldn't seem to find any definitive answers to these questions.

    - Kevin

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: Questions about upgrading to the Z mod boards for the PAS...

    Post by tubes4hifi on Sun Oct 30, 2011 11:28 pm

    Hi Kevin,
    The Zmod phono board is FAR superior to the original PAS3 circuit, which had limited low frequency response and used alot of active feedback to provide the RIAA EQ, which was only fairly accurate from around 50Hz to 20KHz.
    The Zmod circuit uses passive EQ which is far more accurate and extends the bandwidth over the entire 10Hz to 50KHz range. It can be used with the original selector switch.
    The board can be bought without parts, it includes schematic, parts list, circuit diagram, and connection instructions.
    The TCLA board comes with your choice of 2 stereo or 4 mono tone controls, it can't be used with the original controls (wrong resistance and non-linear). At center position the tone EQ is perfectly flat.
    See attached photo, the purple line is center position, and flat from 10Hz to 50KHz.
    All parts are mounted on the boards, the original controls and extra parts and caps are removed.
    The bare board set of 3 (PC6 phono, PC5 line, power supply) are $95.
    The PC6-Z phono only is $50. The TCLA boards without any parts are $80.
    Roy www.tubes4hifi.com/PAS3.htm


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