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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


    Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center

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    rudes

    Posts : 45
    Join date : 2012-03-07

    Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center Empty Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center

    Post by rudes on Sun May 31, 2020 8:19 pm

    When I turn either treble control from the center by-pass position there is a single slight pop out of the speaker. It only happens ONCE each time after the unit is turned on. You can then turn the treble controls from the center by-pass mode after the initial pop without any more pops. As stated, ONLY does this with the treble controls and only once after each new unit turn on. It's like a capacitor is being charged at turn on and then discharged after the control is turned. All the caps are new. Any clue what could be causing this?
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    rjpjnk

    Posts : 253
    Join date : 2018-07-18

    Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center Empty Re: Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center

    Post by rjpjnk on Fri Jun 12, 2020 12:33 am

    Mine does that too. The treble control on the 3X has a special pot that is actually open circuited at the center. There are two capacitors connected to the ends of this pot, .02 and .002, but unfortunately when the treble pot is in the center these caps are completely out of the circuit and floating. My guess is they discharge internally over time and then when you move the pot away from center, one or the other is suddenly connected causing a surge flow which is heard as a pop.Only way I can think of to fix this would be to use a standard pot instead of the special one, but then you would lose the ability to have the treble control "out of the circuit". Or, just let it pop once and you'll probably be good for hours of playing.
    PeterCapo
    PeterCapo

    Posts : 845
    Join date : 2008-12-05

    Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center Empty Re: Dynaco Pas Makes ONE Pop Sound When Either Treble Control Is Turned From Center

    Post by PeterCapo on Fri Jun 12, 2020 8:21 am

    Do we know for sure that we are talking about Dynaco X pots here?  Please confirm according to the following: http://www.audioregenesis.com/documents/Dynaco%20PAS%203%20or%203X.pdf

    I ask this because I've seen a report where an original non-X pot was failing and caused "pops" or something.

    If X pots are confirmed, then are the 1.0µF capacitors in place, in the associated circuitry?  If so, are they the original, fifty-year-old electrolytic 1.0µF capacitors?  I've always understood that these capacitors, among other things, should prevent any "pops" from reaching the preamp's outputs.  Is this not the case?

    If this PAS has had modifications of one kind or another, then all bets might be off - some photos might help to illuminate the situation.

    Do you have a copy of the manual that corresponds to your version of PAS, including schematic and original pictorial diagrams?

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