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    Dynaco PAM Project

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    denny9167

    Posts : 152
    Join date : 2011-05-09
    Age : 49
    Location : Texas

    Dynaco PAM Project

    Post by denny9167 on Mon Jul 01, 2013 7:59 am

    Howdy all! out of all the products that Dynaco put out the one that hasn't got as much attention, is the lowly Dynaco PAM-1, I have always been intrigued by it's design, as far as I know it was one of the first of it's kind, setup to be a truly dual mono design. I must say preamps with external power supplies is a plus, especially one that contains an RIAA stage, with most of the power supply contained outside the chassis, one could put an extreme interest on the tubes heater supplies, where it seems that noise tends to be an issue particularly in the higher gain stages. I'm doing research right now on circuit topologies, would love suggestions and input. Layout and design would stay very close to the PAM-1,most of the chassis work I would be able to do myself, it is essentially a wood chassis with a metal top and bottom, and working on a front faceplate and rear backplates , using Front Panel Express. I'm looking forward to this build, let me know what you think. Will try and post some concept drawings in the near future.

    GP49

    Posts : 718
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Dynaco PAM Project

    Post by GP49 on Mon Jul 01, 2013 12:03 pm

    The pair of PAM-1 that my brother used (mismatched in color, one with tan cover and one brown, and without the Dynaco stereo adapter) with two Mark II in the early 70s, before we got used PAS-2 preamps from Pacific Stereo for $10 apiece, had to be carefully set up and a specific ground scheme used, to eliminate ground loop hum.  Take that into account in your plans.

    I still have them in a box in the garage...I have plans to rebuild them and fine-tune the multiple phono equalization curves for use in playing 78s. In mono, there should be less ground loop trouble.

    denny9167

    Posts : 152
    Join date : 2011-05-09
    Age : 49
    Location : Texas

    Re: Dynaco PAM Project

    Post by denny9167 on Mon Jul 01, 2013 3:18 pm

    GP49 wrote:The pair of PAM-1 that my brother used (mismatched in color, one with tan cover and one brown, and without the Dynaco stereo adapter) with two Mark II in the early 70s, before we got used PAS-2 preamps from Pacific Stereo for $10 apiece, had to be carefully set up and a specific ground scheme used, to eliminate ground loop hum.  Take that into account in your plans.

    I still have them in a box in the garage...I have plans to rebuild them and fine-tune the multiple phono equalization curves for use in playing 78s.  In mono, there should be less ground loop trouble.


    You are spot on, the grounding scheme can be very tricky, I've built preamps in the past with external power supplies. Thanks for reminding me.

    denny9167

    Posts : 152
    Join date : 2011-05-09
    Age : 49
    Location : Texas

    Re: Dynaco PAM Project

    Post by denny9167 on Tue Jul 02, 2013 5:05 pm

    Here is a concept photo, it's not quite to scale, but you will get the idea.

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    I'm still debating on a dual mono, or stereo. the upside would all be in one chassis.

    denny9167

    Posts : 152
    Join date : 2011-05-09
    Age : 49
    Location : Texas

    Re: Dynaco PAM Project

    Post by denny9167 on Wed Jul 03, 2013 3:56 pm

    I have decided on the topologies for both the line and phono stages. I will retain the use of the PAS phono section, modified, and I will use a single 6922,with the last stage in a cathode follower arrangement. I will use both channels in one chassis for now, with possibly a mono version in the future. No tone controls. The power supply is a custom design using a 320V single secondary through a SS bridge w/ DC heaters. Will update on project. Any input is appreciated.

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