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Millett "Starving Student" hybrid amp

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  1. Zink
    What are some good recognized tube vendors to check? Is there any way to get a matched pair of tubes for less than $25? Thanks for the help.
     
    Edit: Ok, I found the couple of sites that sell tubes.
     
  2. revolink24
    Does anyone here have any tips for wiring the ground in the SSMH? On a P2P build, do you just wire all the schematic's grounds into a ground plane? Pardon my noobishness but I'm completely new to P2P. Also, can anyone point me to good wire to use for a P2P build?
     
  3. Beftus


    Quote:

    That's exactly what Pete Millett did in his build. You can also star ground it, running the grounds to a single point.
     
  4. kellvyn

     
    Quote:

    I might give the protoboard a shot, just as a learning exercise.  But I know that grounding is an issue.  If you look at a picture of the protoboard I'm considering, you'll see the strips going down the middle (image from Tangent's site):
     
    mini-cmoy--150-board-w-jumpers.jpg
     
    I had thought about using them for the ground bus.  Would that be considered a star ground?  I'm not sure how literally one must understand "tie all ground paths to a single point."  If I use those strips, my ground paths are tied to a line, not a point.  There's also the ground sink issue:
     
    Quote:

    Will those strips be enough of a ground sink if I use a plastic case?  Will it be a non-issue if I use a metal case and non-insulated jacks?
     
  5. Juaquin
    The strips will tie everything together, but I worry that it's not enough metal to act effectively. The PCB/kit from Beezar essentially used the whole case as a ground, with good results for noise rejection. Depending on your application, case, and environment those strips might be ok. In a worse case scenario you could always connect them to your metal case (making sure everything else was isolated, especially the MOSFETs).
     
  6. Trower
    I found just using a bare copper PCB and using it as a ground plane worked well. I will say its a pain to drill, but easy for grounding purposes.
     
  7. Beftus


    Quote:

    Grounding a metal case is a good thing, using the case as a ground conductor isn't because of the unpredictable path the ground would take. I'm sure I have read that somewhere, either here or on diyaudio.com...
     
  8. the_equalizer


    Quote:

    No, you can get a couple of 17EW8 tubes on e-bay for the cost of one 12AU7.
     
    EDIT:  Oh, and let's not forget you can also build the amp with 12SR7 tubes, which are also cheaper than the 12AU7.
     
    cheers!
     
  9. hellomoto
    Hi!
     
    I decided to use a ground plane, that was my very first DIY build, took me a lot of time, but it was pretty easy! With an organized work area, a good soldering iron, and time to spend, everything goes right, just take your time, read and be sure to fully understand the scheme, and use the pics of Pete Millet's website (giant pics, great for details), and P2P will be really easy!
     
    I nerlyh finished my amp, I just have to drill the holes for the tubes, and attach the MOFSETs and heatsinks.
     
    I have two small questions: first, i used the case as ground (Hammond black one, like the PCB build). I removed some black anodiing around the holes of the RCA jacks, to have a better ground, but should I connect the backplate to my ground plane using a wire?
     
    I also noticed a small pin on the pot,, going to the outside, under the axle, and over the 6 pins, you can see it on the picture:
    http://fr.mouser.com/images/alphataiwan/images/inhouse_rv122f2015fa50k_1.jpg

    What the point of that thing? It just make the mounting of the pot harder, I had to use spare spacers I had to have it mounted right, was it the right thing to do?
     
    Thanks for all your help guys!
     
  10. the_equalizer

     
    Quote:

    I completely agree about the pics from Pete Millett's site: they're a great guide for those of you who want to build a P2P version.
     
     
    The 'pin' in the pot goes into an auxiliary hole and helps the pot stay in place under 'heavy torsion'. You could try snipping it of with pliers or a dremel.
     
    cheers!
     
  11. Juaquin


    Quote:

    Yes, I wasn't suggesting using the case as a conductor. The circuit should only contact the case at one point, hence adding a larger mass of conductive metal to ground (but no real current should be flowing through it). The ideal way to build this is to either use a very large ground plane (like Pete's original SSMH) or to use a star ground, where all ground are connected directly to one point which in turn connects to the case.
     
  12. Beftus
    Quote:
    True, 12SR7 tubes can be very cheap ($1 - $2 each) but those metal tubes don't have the appeal of glass tubes IMO. 
     
  13. the_equalizer

     
    Quote:

    You can always get a couple 12SR7GT
     
    cheers!
     
  14. Beftus


    Quote:

    Indeed you can. But those are more expensive IIRC...
     
    When money isn't an issue the 12AU7 is a safe choice. At $10 each for a new production tube I don't think they're expensive at all.
     
  15. c12mech
    I got my 17EW8 tubes from here:
     
    http://www.vacuumtubes.net/
     
    They cost $3 each and shipping was about $6.  I bought a couple other things from them as well.  They had the lowest price that I found for these tubes and were very easy to deal with.  
     
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