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Millett "Starving Student" hybrid amp

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  1. tomb
    Everybody - please, I beg your patience. I've had some inquiries about shipping time which is not unexpected, I guess. As with last time, the most I can ship during the week is about 4-5 a day. Because of the tube sockets, I actually didn't start shipping until Tuesday. So far, more than a dozen kits have shipped, but I'm still behind. I'm usually able to catch up on the weekends, so please bear with me awhile longer.

    Thanks![​IMG]
     
  2. simwells
    This should actually be the final question now!

    For the pot and switch I am using the alps RK0971221Z05, but I am not entirely sure on wiring it, the back pins are obviously the switch and I'm presuming non directional but I am unsure of the direction of the pot pins, though I guess it's one row per channel.

    Data sheet is here if needed

    RK097/RK098 Series|Basic information
     
  3. Juaquin
    Yep, one row per channel, middle pin should be wiper.
     
  4. simwells
    Does it matter whether I go from left to right or vice versa?
     
  5. Dunceiam
    Not getting any resistance between the metal tab and the case, I take it that's a good thing? [​IMG]

    Quote:

    Originally Posted by tomb /img/forum/go_quote.gif
    If the Gorilla glue is not conductive, then maybe you'll be OK. Use your DMM to measure the resistance between the metal tab of the MOSFET and the case - see if you get near infinite resistance or near zero (very bad).

    The caps look OK as you have them arranged in that list.




     
  6. Juaquin
    NO. That is BAD. There should be a lot of resistance (infinite, or close to it) between the MOSFET tab (which carries voltage) and the case (which should be at ground). Hopefully you mean that you are not getting any conductance between the two? There should be no electrical connection between them. From what you've described earlier I don't think you are isolated properly. Use a Berquist pad, mica, something that's purpose-built for isolation.
     
  7. Juaquin
    Quote:

    Originally Posted by simwells /img/forum/go_quote.gif
    Does it matter whether I go from left to right or vice versa?



    Not terribly, but you probably want to set it up so that when the switch is off, you're at very high resistance (so that when the switch gets turned on, it doesn't start at the highest volume).
     
  8. simwells
    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    Not terribly, but you probably want to set it up so that when the switch is off, you're at very high resistance (so that when the switch gets turned on, it doesn't start at the highest volume).



    Hopefully I've got it the right way round then!

    It's all finished just waiting on the tubes arriving! LED's are working at least!
     
  9. Dunceiam
    By, 'no resistance' I meant the meter was not picking up any signal whatsoever between the two prongs of the meter. By this, I'm led to believe there is no electrical connection between the two, therefore a good thing. (Right?)

    I probably meant the wrong thing when I said, 'not getting any resistance'. When the meter's prongs are not touching (while measuring ohms), I get a flashing '0.00' to indicate no continuity, when I put one prong on the MOSFET's metal, and one on the case, the meter continues to read out the flashing '0.00' without any change. Sorry for any confusion.

    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    NO. That is BAD. There should be a lot of resistance (infinite, or close to it) between the MOSFET tab (which carries voltage) and the case (which should be at ground). Hopefully you mean that you are not getting any conductance between the two? There should be no electrical connection between them. From what you've described earlier I don't think you are isolated properly. Use a Berquist pad, mica, something that's purpose-built for isolation.



     
  10. UKToecutter
    I'm not sure what your meter is saying or how it works, but......

    If you just short the two meter probes together and you get the same flashing 0.00, then this is bad !!!!!

    It means the tabs of the mosfets are directly shorted to the case.
     
  11. UKToecutter
    bah.

    Scrub that. I just re-read Dunceiam's last message properly......

    :)
     
  12. Lil' Knight
    Ordered the kit 2 days ago. So excited because it'll be my first project ever.

    What's the recommended headphones' impedance for the SSMH? I'm thinking of using it with the AD2000 which is only 40ohm.
     
  13. the_equalizer
    Quote:

    Originally Posted by Lil' Knight /img/forum/go_quote.gif
    Ordered the kit 2 days ago. So excited because it'll be my first project ever.

    What's the recommended headphones' impedance for the SSMH? I'm thinking of using it with the AD2000 which is only 40ohm.




    In my experience the amp handles both low and high impedance with aplomb. It has both voltage gain (for high impedance 'phones) due to the tube's high gain; and current gain (for low impedance 'phones) due to the power MOSFET output stage.

    Also, according to Pete Millett's page on the amp it's output impedance is around 3 ohms, confirming it's quite adecuate for both kinds.

    cheers!
     
  14. kevenigma
    got my kit from Beezar today!

    too bad my right hand is in a cast for the next 8 weeks... won't be building it for a while... [​IMG]
     
  15. tomb
    Quote:

    Originally Posted by kevenigma /img/forum/go_quote.gif
    got my kit from Beezar today!

    too bad my right hand is in a cast for the next 8 weeks... won't be building it for a while... [​IMG]




    It's nice to hear that the kit arrived! I was hoping some people would've received theirs by now.

    Sorry to hear about the cast, though - that's a bummer.
     
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