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    PAT-4 >> to ULTIMATE tube preamp

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    tubes4hifi
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    Join date : 2008-11-30

    PAT-4 >> to ULTIMATE tube preamp

    Post by tubes4hifi on Sat Apr 06, 2013 10:09 pm

    OK, next project, hopefully done in a week or so if not too busy.
    I'll be converting a stock Dynaco PAT-4 solid state preamp into the ULTIMATE mod for the PAS-4 - an SP12 tube preamp.
    I've done several of these using my PAS3 mods, but wanted to do something nicer and better with this chassis. Cost was $60.
    Add an SP12 board, throw in a couple of leftover power transformers from other projects, about $300 worth of parts total,
    and a budget SP12 in a vintage style chassis . . .
    OR, you could do the exact same thing but using an SP9 board if you want tone controls, the PCB is the same size and price.




    peterh

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

    Re: PAT-4 >> to ULTIMATE tube preamp

    Post by peterh on Sun Apr 07, 2013 3:10 am

    This is an infinitesmal better idea then to destroy an existing PAS2/3 !
    Well written!

    tubes4hifi
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    Re: PAT-4 >> to ULTIMATE tube preamp

    Post by tubes4hifi on Mon Apr 08, 2013 11:12 pm

    OK, it's about 3/4 done now, about an hour left to wire up the selector, volume, balance, power switch,
    and connections to the PCB.
    So we've got the SP12 PCB kit ($179), the PAT4 I-O board with all new RCA jacks ($70), ALPs volume & balance ($50), selector $8,
    and two DPDT switches $10, one for SOURCE-TAPE and one for POWER On-Off. All that's left is a tube set $70, so $387 in parts,
    plus the cost of the PAT4 (which I got for $60, now they go for $80-100). It will be done in just under 4 hours.
    That beats paying $990 for a new assembled/tested SP12 preamp.
    Also BTW, available with the stock PAT4 front panel as shown in the first post, or with a brand new custom machined/engraved front panel.


    Last edited by tubes4hifi on Sun Apr 21, 2013 2:00 pm; edited 1 time in total

    peterh

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

    Re: PAT-4 >> to ULTIMATE tube preamp

    Post by peterh on Tue Apr 09, 2013 2:06 am

    How is the PSU designed ? Is it the 2 transformers to the right ?

    tubes4hifi
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    Join date : 2008-11-30

    Re: PAT-4 >> to ULTIMATE tube preamp

    Post by tubes4hifi on Tue Apr 09, 2013 10:09 pm

    it's a stock SP12 board, just using some leftover transformers that had the right voltages.
    If I was building this with new transformers, I'd use a single toroid or a couple of flatpaks like the ones I use for the PAS3 PS upgrade.

    OK, so all done wiring, here are the finished photos, and the very bottom photo is a "mock-up" of the custom panel I ordered to use,
    or I can finish it off with the original PAT4 faceplate, as shown on the first photo at the top of the orignal post.
    4 inputs on the selector plus a tape in (or any other source), a tape out, and two preamp outputs (use one for a sub if you want).
    No phono board, sorry. Now posting for sale in the FOR SALE section of the forum.



    Very Happy





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