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Millett "Starving Student" hybrid amp

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  1. nullstring
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    So whats the next step, bigger resistors? I'm at 100k for R16/R17 and 1k for R14/R15. My next step up is 330K for what I got laying around.



    The 100k resistors helped, right? You can get farther in the pot before you get to this point?
    If so, you could try the 330k resistors..

    However, I have 50k resistors and a 50k pot and line out from my ipod (which I can't turn down either), and it works.. alright for 32ohm cans..
    It's possible that our compass is louder than the ipod.. /me shrugs?
     
  2. ezzieyguywuf
    Could be. I probably should have mentioned that I've build a 12AU7 version. And come to think of it, I don't think I can turn the pot much further than before. I could be wrong though, I've been doing this over the course of a few days. Where else can I get a line-out signal to test this? I have a cowon D2, and thats the DAP I mentioned before, but nothing else. I guess for now I'll just run it throught the Compass' amp and attentuate the signal before it gets to the SSMH. Not really optimal though...
     
  3. Juaquin
    Not many people have had to use more than 100k, but it can't hurt much to go higher if you need to.
     
  4. ezzieyguywuf
    Could it be something else that is causing this? Maybe my gain is too high for some reason?
     
  5. netsky3
    Quote:

    Originally Posted by tomb /img/forum/go_quote.gif
    Do some reading in this thread and on the SSMH website - Starving Student Millett Hybrid

    I keep getting inquiries, but the PCB's are gone. If someone tells me where I can buy a hundred or more 19J6's, we'll do another PCB production run - but other than that, no.




    Is this the PCB for the "basic" version of the millett?

    Beezar.com

    [​IMG]
     
  6. the_equalizer
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    Could it be something else that is causing this? Maybe my gain is too high for some reason?



    I've already posted in the previous page that your 'off off off ON' problem is most surely caused by an incorrectly wired volume pot. Check that it's the pot's wipers that are connected to the tubes.

    The fact that it's a 12AU7 does not make much difference as the 12AU7 and 19J6 versions have more or less the same gain.

    cheers!
     
  7. the_equalizer
    Quote:

    Originally Posted by netsky3 /img/forum/go_quote.gif
    Is this the PCB for the "basic" version of the millett?

    Beezar.com

    [​IMG]




    That's it. But as TomB mentioned, there are no more PCB's and unless someone uncovers a stash of a hundred 19J6 no more of that PCB shall be produced.

    cheers!
     
  8. revolink24
    Actually, that's the Millett Max, which doesn't use the 19J6 tubes, and isn't nearly as basic as the SSMH, if I'm not mistaken.
     
  9. netsky3
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    That's it. But as TomB mentioned, there are no more PCB's and unless someone uncovers a stash of a hundred 19J6 no more of that PCB shall be produced.

    cheers!




    Quote:

    Originally Posted by revolink24 /img/forum/go_quote.gif
    Actually, that's the Millett Max, which doesn't use the 19J6 tubes, and isn't nearly as basic as the SSMH, if I'm not mistaken.



    Thanks =)
     
  10. tomb
    No offense netsky3, but if you looked at the Starving Student Millett Hybrid PCB website, you would have seen this:
    [​IMG]

    So, I'm not quite sure how you would mistake it for this:
    [​IMG]

    [​IMG][​IMG][​IMG]
     
  11. netsky3
  12. Sganzerla
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    Well, after reviewing your pics, I just can't find any obvious mistake.

    On other things... the components you used look all so very familiar, I'm betting you bought them as a kit on ebay; my first SSHM I built from that very same kit [​IMG]




    Thanks for your suggestion! I'll remade those "strange" solders you pointed when I got back home, and hope solves the problems.

    This kit I bought from Alphaphoenix here at HeadFi.
     
  13. m11a1
    Quote:

    Originally Posted by tomb /img/forum/go_quote.gif
    Sorry about that. I didn't think the MOSFETs could cause a channel imbalance, but it was easier to send them to you rather than argue the point.[​IMG]

    There are potentially three things that can cause the channel imbalance:
    1. Mis-matched tubes,
    2. imprecise volume pot tracking, or
    3. mis-matched resistors somewhere in the signal path.

    Of those three, the tubes and pot have the greatest chance of causing the imbalance (unless you mistakenly used different-sized input resistors, as in one at 100K and the other at 200K). If the volume difference is consistent across the range of volume travel, then most likely it's the tubes. Swapping the tubes is an easy check. If the volume difference is inconsistent and changes with the volume travel, then it's the pot. What you can do there is adjust the input resistors to get the volume range you like within the most consistent portion of the volume pot travel.

    As for the resistors, it would take a huge difference to cause a volume mis-match between channels - something like the example given above - as in incorrect values, period, in one channel.

    Hope that helps.[​IMG]




    I'll start working on it. Thanks for all the help!

    Cheers!
     
  14. timmyGCSE
    I've bought all the parts for SSMH mk2 [​IMG]
    This time, still using the 12AU7 version but with Dsavitsk's mods, plus I've designed my own PCB that I think is correct lol, I've got the copper board and echant and stuff. I've also bought a nice MB plastic box for it:
    MB Plastic Boxes : Plastic Enclosures : Maplin

    plus the heatsinks are much beefier than the last ones I used.

    Hopefully will make the PCB and solder the PCB components this weekend then do the casework next weekend
     
  15. ezzieyguywuf
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    I've already posted in the previous page that your 'off off off ON' problem is most surely caused by an incorrectly wired volume pot. Check that it's the pot's wipers that are connected to the tubes.

    The fact that it's a 12AU7 does not make much difference as the 12AU7 and 19J6 versions have more or less the same gain.

    cheers!




    Oh, sorry. I did see your previous post but disregarded it as I've rewired my pot once already, and triple checked against the datasheet to make sure I wired it correctly. Here is the datasheet I'm talking about. Excuse my screenshot, I couldn't be bothered to GIMP out the image from the pdf. As per that image, I've got pins I2 and II2 going to the pot "grids" (I'm unfamiliar with that term), I got I3 and II3 going to the RCA jacks, and I1 and II1 are my ground. Is this not correct? Looking at my pot from the back, the six pins are wired as follows:

    RCA L, RCA R, GROUND, GROUND (I jumped the two), GRID L, GRID R

    This corresponds to the image I posted, which shows the pins with a "view from mounted part side". My extreme zoom on there blocked out that foot note.

    Please, tell me if I'm wrong as I'd love to get this thing up to 100%.

    My power switch has a LED, and this thing pulses two or three times when I first power it up. I guess this is normal?
     
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