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    Have you found poor L-R tracking at low volume a common observation on SCA-35?

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    j beede

    Posts : 316
    Join date : 2011-02-07
    Location : California

    Have you found poor L-R tracking at low volume a common observation on SCA-35?

    Post by j beede on Sat May 14, 2016 3:04 pm

    Low level stereo tracking seems to be a common issue with PAS and SCA-35. I have yet to dig into my "barn find" SCA-35 but it sure has poor L v R tracking between 7 o'clock and 12 on the volume control. Tracks great anywhere past 12 o'clock.

    I will replace the filtering caps before, and the coupling caps after the volume control. I'd like to swap out the volume pot too. If I recall correctly the SCA-35 volume pot taper is not particularly standard... Do you have a favorite (and available) substitute for that 250K dual volume pot? Preferably one that preserves the stock pots taper.
    ...j

    GP49

    Posts : 717
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Have you found poor L-R tracking at low volume a common observation on SCA-35?

    Post by GP49 on Sat May 14, 2016 8:01 pm

    http://www.ebay.com/itm/DACT-Type-21-Stepped-Attenuator-Pot-250K-for-Tube-Amp-/200929768726?hash=item2ec858f516:m:mdJKC5hB5hMtparRbKUJgUQ\

    $12.00 plus $6.00 shipping from Hong Kong.  Delivery to me was quick and trouble-free.  The Ebay
    listing says there are two available.  I don't know if the seller actually has more and will relist once those two are gone.

    Prior post about this item including the revelation that it has been standard equipment in the SP12 & SP14
    preamps for the past two years:

    DACT Type* 21 Stepped Attenuator 250K for Tube Amp

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Have you found poor L-R tracking at low volume a common observation on SCA-35?

    Post by tubes4hifi on Wed May 18, 2016 5:48 pm

    yes, these 23 step attenuators use 1% metal film resistors and are super accurate and sound excellent.
    Even the famous blue ALPs volume controls are lucky to have better than 6-8% tracking accuracy, I've meaured alot of them.
    Cheap common carbon pots are even worse.

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    Re: Have you found poor L-R tracking at low volume a common observation on SCA-35?

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