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    Dynaco lore - TC-3X - The PAS-3 to PAS-3X tone control modification manual ...

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    Bob Latino
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    Posts: 1883
    Join date: 2008-11-26
    Location: Massachusetts

    Dynaco lore - TC-3X - The PAS-3 to PAS-3X tone control modification manual ...

    Post by Bob Latino on Fri Jan 15, 2010 5:43 pm

    I can still remember buying my Dynaco PAS-3 preamp kit back in the mid '60's at Lafayette Radio in Worcester, MA. The month before I had purchased and built an ST-70 kit. I used them both together for about a year and then learned that all the new Dynaco PAS-3's would now be an upgraded model called the PAS-3X. This new "X" version of the PAS-3 had tone controls with a spot near the middle that effectively removed the tone controls from the circuit. If you rotated the control to that point you truly got your "flat" response from your PAS-3 preamp. A year later I went back to Lafayette radio and bought a TC-3X tone control modification kit that made my PAS-3 into a PAS-3X. I think I paid $16.95 for the TC-3X kit which was a lot of money back then considering also that the whole PAS-3 kit had cost me just $70. The kit consisted of two new bass controls, two new treble controls, two resistors and two capacitors. I installed the kit and low and behold it seemed to work great. I used that PAS-3 (now an "X") and ST-70 for about 10 years until I sold them for a new solid state Pioneer receiver. The cry at the time was "Get rid of your tube stuff now because transistors will make tubes obsolete". Well we know NOW that this just wasn't true but at the time everybody believed it ... Below is the short two page manual that you got with your TC-3X kit ... The same kit also worked for the PAS-2 making it a PAS-2X.

    Bob




    tomlang

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    Join date: 2009-08-12

    Re: Dynaco lore - TC-3X - The PAS-3 to PAS-3X tone control modification manual ...

    Post by tomlang on Sat Jan 16, 2010 11:40 am

    Bob, this is interesting. Was it simply a circuit redesign using different components, that when centered, were more "approximately flat", i.e. flatter than before, in other words not a true "tone bypass" circuit? Or, were they some kind of special pot that electrically and completely removed themselves from the circuit like a modern tone bypass switch? Were they detented at the center?

    Bob Latino
    Admin

    Posts: 1883
    Join date: 2008-11-26
    Location: Massachusetts

    Re: Dynaco lore - TC-3X - The PAS-3 to PAS-3X tone control modification manual ...

    Post by Bob Latino on Sat Jan 16, 2010 4:04 pm

    tomlang wrote:Bob, this is interesting. Was it simply a circuit redesign using different components, that when centered, were more "approximately flat", i.e. flatter than before, in other words not a true "tone bypass" circuit? Or, were they some kind of special pot that electrically and completely removed themselves from the circuit like a modern tone bypass switch? Were they detented at the center?

    Hi Tom,

    The latter is correct. The tone controls were electrically removed from the circuit when centered at the "detent". There was a noticeable detent spot at the center of rotation that you could feel during the rotation of the pot.

    Bob

    GP49

    Posts: 486
    Join date: 2009-04-30

    Re: Dynaco lore - TC-3X - The PAS-3 to PAS-3X tone control modification manual ...

    Post by GP49 on Sun Jan 17, 2010 1:02 am

    The conversion kit made the PAS-3 or PAS-2 the electronic equivalent of the PAS-3x and PAS-2x. Those were special tone controls that provided true out-of circuit operation of the frequency-contouring tone control circuitry (take a look at the schematics of the original PAS vs. the "x" versions to see what Dynaco did).

    Note that Bob states that his kit consisted of several new parts...but no new knobs. The old PAS-3x and PAS-2x had splined shafts on the tone controls, and splined knobs to match. New PAX-3x and PAS-2x had setscrew knobs that went onto plain shafts. So the controls supplied with the TC-3x modification kit must have been different from the ones supplied with new-construction PAS-3x/2x kits, in that the shafts were different though the guts were the same!

    At least that is how I would interpret the data. I worked in the service department of a Dynaco dealer in the early 1970s; the TC-3x kit was available by special order only and I only saw one come through the shop, ordered for a customer; but didn't study it carefully. My own Dyna PAS, which is modified with Van Alstine Super PAS Three circuitry interfaced with tone controls, has the non-splined shafts and knobs and thus was born a new-construction PAS-2x (I have retained the original brass front panel).

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