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    Dynaco Preamp PAS-2

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    specsvc2

    Posts : 1
    Join date : 2016-02-22

    Dynaco Preamp PAS-2

    Post by specsvc2 on Fri Feb 26, 2016 7:49 am

    I have a PAS-2 I purchased in Germany . I have not been using it for some time and recently woke it up. As I was working on it I noticed that the previous owner wired one of the plates on the 12X4 to pin 5 instead of pin 6. Although the unit seems to be working fine I am concerned as to why this was so and if I change it back the way the book says what will be the affect. To me it is running as a half wave rectifier instead of full wave . I do not hear any ac hum but still think it would be better wired the right way. Any help out there? Don

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Dynaco Preamp PAS-2

    Post by Bob Latino on Wed Mar 02, 2016 10:59 pm

    Hi Don,

    You had originally posted this in the wrong area of the forum about a week ago.. Now that we have the post in the correct (basket) area of the forum, I am sure that someone familiar with the PAS preamps will give you an answer about the wiring of your preamp.

    Bob

    GP49

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

    Re: Dynaco Preamp PAS-2

    Post by GP49 on Wed Mar 02, 2016 11:44 pm

    There are some who claim that the fundamental ripple frequency of a half wave rectifier (in the USA, 60Hz) is less audible than the fundamental of a full wave rectifier (120Hz). However both are within the audible frequency range, the current capability of the full wave rectifier is higher, and a well-designed power supply will be well-filtered anyway so as to reduce ripple to virtually nothing. I'd put it back as Dynaco designed it.

    Incidentally, if it hasn't been done already, you should add a fuse to the primary circuit of the power supply. Dynaco didn't include one, the result being that the primary of the power transformer serves as an overcurrent protection device. Something wrong happens, you buy a new transformer instead of a 30 cent fuse.

    peterh

    Posts : 641
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Dynaco Preamp PAS-2

    Post by peterh on Thu Mar 03, 2016 3:18 am

    specsvc2 wrote:I have a PAS-2 I purchased in Germany .  I have not been using it for some time and recently woke it up. As I was working on it I noticed that the previous owner wired one of the plates on the 12X4 to pin 5 instead of pin 6. Although the unit seems to be working fine I am concerned as to why this was so and if I change it back the way the book says what will be the affect. To me it is running as a half wave rectifier instead of full wave . I do not hear any ac hum but still think it would be better wired the right way.  Any help out there?     Don
    Yes, it has used as half-way rectifier.
    The reason noone has noticed could be that it draws very little current. But by all means
    reconnect to pin 6.


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