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All-Purpose Stereo 5-20 front-end PCB

Discussion in 'Tube Audio' started by thorpej, Dec 23, 2017.

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  1. thorpej

    thorpej AK Subscriber Subscriber

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    Happy New Year, AK peeps! So, I did a trial run of these boards, and of course upon inspection I found a mistake that I made -- oops! Luckily, it's just a silk screen mistake that I can document as errata in the instructions; the orientation indicator (where the outside foil end of the capacitor should be connected) is backwards for the output coupling caps -- the outside foil end should be connected to the long tail pair tube plates. I'll correct that for the next run! In the mean time, I'm hoping to build one up before the end of the month. Teaser photo attached.
     

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    prelius and drtool like this.

     

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  2. thorpej

    thorpej AK Subscriber Subscriber

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    Decided to populate one of these boards today... this one is destined for an EL84 amp that uses Heathkit AA-100 iron. Flying leads for connections to external constant current sink board (for long tail pairs) and feedback loop. I put TE screw terminals on the other connections, but I may simply end up using flying leads soldered onto those pads all the time, going forward.
     

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    Retrovert and Dandy like this.
  3. PakProtector

    PakProtector AK member

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    If you ever decide to make a run of an amplifier front end that does not depend on loop NFB, I am in...:) Say a LTP of EL84's for instance...as well as a battery biased DN3545N3/10M45 current reg. Run it in 4 oz Cu, and stick in some solder posts for the connections. There is no need to put traces closer together than what 4 Oz will stand...and the stuff is durable for when things need to get replaced and tuned.
    cheers,
    Douglas
     
  4. thorpej

    thorpej AK Subscriber Subscriber

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    Of course, nothing is forcing you to use NFB with this one. All this board does is enforce the "gain stage DC-coupled to LTP inverter / driver stage".

    (Yes, I use the 10M45s in the tails of my LTPs.)
     
  5. PakProtector

    PakProtector AK member

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    3,672
    Location:
    Ann Arbor, MI
    In cascode I hope. I built a lot of them with two depletion-mode MOSFET's, and using the 10M45 on top leaves more room for the FET on the bottom to work in, and with the higher drain-source voltage its gate capacitance is reduced.
    cheers,
    Douglas
     

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