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    Best SS Dyna preamp?

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    wildiowa

    Posts : 202
    Join date : 2012-03-19

    Best SS Dyna preamp?

    Post by wildiowa on Thu Aug 30, 2018 11:16 am

    May go shopping today at a place that has several Dyna preamps. Not sure I can afford a tube version plus probable upgrades. What is the better Dyna SS preamp I should be seeking? Thanks...
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    Peter W.

    Posts : 966
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Best SS Dyna preamp?

    Post by Peter W. on Thu Aug 30, 2018 2:29 pm

    wildiowa wrote:May go shopping today at a place that has several Dyna preamps. Not sure I can afford a tube version plus probable upgrades. What is the better Dyna SS preamp I should be seeking? Thanks...

    Multiple schools of thought, so I will write entirely for myself:

    a) Dynaco PAT-4, factory:  Has pretty much everything that the PAS-2/3 has, with the addition of a front-panel microphone input and a small headphone amp on board. It has an NAB head-amp as well. It has sufficient inputs for multiple sources, and the obsolete inputs may be re-purposed as well. And, despite rumors to the contrary, the on-board phono head-amp is not bad, either. Pricing for a clean specimen in working condition should be less than $100, and they sell at Kutztown typically between $40 and $120, entirely based on condition.

    http://home.indy.net/~gregdunn/dynaco/components/PAT4/index.html  

    At this moment, I keep two (2) of them, one being earmarked for one of the grand-kids along with a fully-tweaked ST120. They also have the out-of-circuit-when-centered tone controls, a multi-position filter switch, and an interesting system for A/B/Stereo switching.
    If you get one be prepared to:
    *Rebuild the power-supply. Not always necessary, but often a good idea.
    * Replace the other electrolytic caps.
    * Clean the switches and controls.

    PAT-5 (Not BiFet), Factory: A very mixed bag, here. About 50% sound like glass-in-a-blender if not very carefully tweaked. Apparently the design is very sensitive to channel-to-channel matching, such that if components do not match well, things get ugly. I have seen, but not done, a cure whereby specific transistors (do not ask me which) are matched to cure the problem. May be distinguished from the BiFet by the black buttons vs. silver buttons in the later model. DOES NOT have an on-board headphone amp, nor a NAB head-amp. DOES have two phono inputs, and will accept some MC cartridges. Does allow for capacitance matching for phono cartridges as well. DOES have a speaker A/B switch, but this is done by way of bringing amp outputs to the pre-amp, then out to the speakers. All via 4-way banana jacks. I do not, nor will I ever keep one of these, tweaked or not. Does have an EPL loop switch and a tone-control in/out switch.

    PAT-5 BiFet:  Dynaco got this one right, but, unfortunately did so using the cheapest passive components they could find as they were circling the drain at the time. All, as above, but the Fets solved the ugly sound issues nicely.  I assembled mine from a kit - and I now have to rebuild the power-supply as well as replace the bulk of the electrolytic caps, even though the device has been in nearly continuous use these last 40 years (came in 1974, but the BiFet not until 1977/78). Expect the same. But, well worth it. These are not common units, and a rebuilt 5 will easily fetch $200+. RUN, do NOT walk away from the plain 5.

    Other peculiarities: This amp maintains power to the filters and power-supply even when off (about 3 watts). AND - if you have a power-failure in medias res, there will be multiple loud *THUMPS* when power is restored, if not shut off - which does isolate it.

    Bottom line: If you can find a BiFet, at a reasonable price, get it. Do the power-supply and electrolytics if needed (it may not need it). It handles many types of phono-cartridges that other pre-amps do not, has multiple inputs, an EPL loop, filters and so forth.

    Mine will be pried from my cold, dead fingers as it is one of the first components I ever assembled (from a kit), and one that I have used for thousands of hours over the years.

    http://home.indy.net/~gregdunn/dynaco/components/PAT5/index.html

    wildiowa

    Posts : 202
    Join date : 2012-03-19

    Re: Best SS Dyna preamp?

    Post by wildiowa on Thu Aug 30, 2018 2:45 pm

    I am trying a PAT5, not certain it is the bifet although the push buttons are black. Hopefully this is the better model. Any other way to tell cosmetically, or other indicator? I can also take this back and get the PAT 4 if I would prefer that. Appreciate the help. The one I have only says Dynaco, Blackwood NJ, PAT5 stereo preamplifier.
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    Peter W.

    Posts : 966
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Best SS Dyna preamp?

    Post by Peter W. on Thu Aug 30, 2018 2:54 pm

    wildiowa wrote:I am trying a PAT5, not certain it is the bifet although the push buttons are black. Hopefully this is the better model. Any other way to tell cosmetically, or other indicator? I can also take this back and get the PAT 4 if I would prefer that. Appreciate the help. The one I have only says Dynaco, Blackwood NJ, PAT5 stereo preamplifier.

    Black Buttons = Not BiFet.

    As noted, it is a 50:50 chance with these beasts. I suggest you give it a few days (if you can) and then compare to the PAT4, also for a few days. Do not be fooled by the smaller/simpler PAT4, there is a lot going on in that package. You might not use it, but should you find that old Crown deck with no on-board head-amps, you will be all set.
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    PeterCapo

    Posts : 561
    Join date : 2008-12-05

    Re: Best SS Dyna preamp?

    Post by PeterCapo on Thu Aug 30, 2018 3:04 pm

    Dynaco PAS tube preamp may not need "upgrades" at all, depending on how you plan to use it.  Whether tube or solid state, the Dynaco preamps are all old by now and are likely in need of parts refreshing that is not necessarily costly.  Dropping-in a different circuit design is another matter.

    The BiFet also said "Bi-FET" on the faceplate.

    One other thing... I have a memory of Stereo Cost Cutters selling Bi-FET kits in the early 1980s with black buttons, though my memory is kind of fuzzy.

    Dale Stevens

    Posts : 92
    Join date : 2014-07-06
    Age : 69
    Location : Loris, SC

    Re: Best SS Dyna preamp?

    Post by Dale Stevens on Thu Aug 30, 2018 5:05 pm

    W, the BI-FET is directly under the DYNACO label on the faceplate.
    I am running 2, both with silver knobs. Those also have the EPL loop
    switchable from the front panel. Flawless since the late 70's .
    Be careful not to overload the rear switch/unswitched power outlets as
    the front power switch will burn out. Dale

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