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Millett "Starving Student" hybrid amp

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  1. the_equalizer


    Cool paint job! Congratulations, I hope you enjoy it!  What tubes did you use?
  2. Darkraver
    thanks, paint job was done by my sis, kinda gave her free reign over what to do.
    As for the tubes, all i know is that they were 12au7's made by Baldwin, found them off of kijiji. No microphonics! Beyond that I have no idea what they are, haha
  3. the_equalizer


    Nice job by both you and your sister!  I hope you find the K701 + SSMH combo as enjoyable as I do :)
  4. nightarya
    Well I just wanted to say thank you to multiple people for your replies to my issue
    I figured out what i did wrong, and the answer is: I screwed up when i first started.
    I bought a METAL case for my build, and used LOTS of parts with open metal connections (doesn't take a genius to figure out there's something that was probably a bad idea) I tried taking off the connections on the terminals touching the case. That didn't work, and that was the only thing i could still do. I assume that was the RCA jacks still hitting the case, because i checked a screw on the case to the positive on the DC in jack. Basically (got 13 ohms resistance, ick!). Tomorrow I'm going to cave in and decide to buy an ABS project box from radio shack (maybe the one thing they still do properly) due to the nonconductance of ABS. So, all in all, it was poor planning that ended up getting me in the end. This wouldn't have happened if i had bought plastic cased jacks, and used a 1/8'' instead of the RCAs. Well, live and learn, it was my first electronics project.
    Then this project should hopefully be done...leaving an opening for the next one...a DIY DAC (SMS Oh jeez)
    But seriously, guys, thanks for your input, it helped me make my realization!
    Lucky the casework should be easier on ABS vs the metal case. I can actually use forstner bits instead of sitting there and trying to circle drill bits haphazardly around the hole to make it 1/2'', that was some serious guesswork.
    I ended up having this epiphany whilst running a show for a dance school. I still have "Wake Me up Before You Go-Go" stuck in my head. It was a mixed victory.
  5. the_equalizer

    A non-metal case is definitely helpful to avoid such shorting issues. Indeed my first SSMH build was done in an ABS enclosure :) .
    If you later feel like it, I'd still recommend you try a build in a metal case. You don't need isolated jacks, just isolating pads for the MOSFETs.  Also, I suggest you follow the path opened by Mr. Millett himself and follow his build layout from this pic. I did and it saved me a lot of work, plus it worked at the first try!
    I hope you're able to get your amp working after you extricate WHAM! from your mind's ear !
  6. Darkraver

    Thanks! Unfortunately there's a buzzing sound whenever I plug it into my laptop, so source will have to be from my sansa clip+ until I build an Alien DAC.
  7. wiisus
    This is my first real electronics project and I'm not really sure how I'm suppose to use the terminal strips.  Can someone take a clear picture of theirs for me, please?  Most of them are kind of hard to see.

    And the the mosfet pins are numbered from left to right, correct?

  8. Ikarios


    I think the terminal blocks are for connecting the output wires to the pot/output jack, but I could be wrong. I was going to ask this question myself at some point.
    You need to be careful about the mosfets - they're deceptive in the way they're wired up.
    Check this post for more info - http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/4320#post_6258684
    read the schematic/pdf for the mosfet, then compare it to the schematic for the SSMH. That should give you a better idea of how they're wired. Go over the last couple pages, too, the_equalizer and ArtemF posted some useful info.
  9. the_equalizer


    Try Mr. Millett's pic (I just posted it a couple of posts up).
  10. wiisus
    yeah, that is a good one.  I was hoping for more of a side view or something.  But I think I got it.

  11. hellomoto
    Wiisus, here are some informations about the Mofsets: http://www.diyforums.org/SSMH/SSMHmosfet.php
    I also have some questions. First, sorry for my bad english, I hope you can understand me! Then, I tried to search the answers to my questions, I wouldn't find anything, maybe I didn't use the apprpriate word, it's hard to speak about technical things in english for me lol
    Si, here are my questions. I'm going to use a blank PCB material for my amp. I received all my stuff, I understand how to mount the major part of the components, but I still have question:
    - About the Power jack: there are three pins on it, I don't know how to connect them to the network, I think there must be two wires coming from it, one from the + pin, and one for the ground right? How can I make a difference between the pins (I use the power jack from the BOM)
    - About the Input: I'd like to use a 1/4" Jack input, but I don't understand how to soldier it: the Jack has 6 pins, but I only have to soldier two wires from the Jack to the pot, right? How should I solder them?
    - About the Output: I also would like to use a 1/4" jack (the same as the input), and I have to soldier three wires to the six pins, which one go where???
    - About the LEDs: I would like to put LEDs in my tubes, one in each, they'll be soldered in the same resistor (the one of the BOM), but where should I put the resistor in the network, and how should I solder the LEDs on the resistor?
    - I also have a question about the terminal strips: where should they be mounted on the shematic?
    That's all... for the moment lol!
    Thank you very much for your help [​IMG]
  12. the_equalizer
  13. ArtemF
    the easiest and safest way to do is to use the multimeter (seriously).
    Take a power jack, plug the power connector, measure the voltages, write them down,
    and so on. I always double-check that even if I know the pinouts.
    Plug the earphones to the output jack and measure the resistance between the contacts.
    The values will be 2R and 2 times R where R is the resistance of one earphone (normally, 32Ohms).
    The points with 2R between them are left and right outputs. The third point will be the ground.
    LEDs and resistors - I would put it off till the circuit starts working.
    Generally, you have to connect them in series with the current limiting resistor. Depending on the
    type of LED this resistor will be in 10-30 KOhm range (if you don't know the specs of your LED
    you can experiment starting with high values like 50KOhms and then go down in 5-10Kohm increments
    till the LED opens and the brightness will be reasonable).
  14. c12mech
    I finally finished my 17EW8 version of this amp last week.  It's been working fine and sounds great.  There is one issue though.  When I turn it on the power supply cycles on and off for several seconds.  It seems to be taking longer and longer each time it is turned on.  The first few times it was turned on only took about 3 or 4 cycles. Last night it took about 30 seconds before the tubes lit up and the PS stopped cycling.  All the voltages are correct according to the schematic.  
    Is this a big problem and if so what do I do to fix it?  I used the equalizers schematic and parts are exactly as listed.  The PS is a Cisco 48V 380ma version that I got from evilbay.  
    It's not in its finished case yet so no pics yet. 
  15. Beftus


    Agreed, first get the amp working then start adding gimmicks.
    LEDs and resistor-wise, use the online LED calculator: http://led.linear1.org/1led.wiz
    For a power status LED 3-5 mA of current is usually enough. For lighting up a tube: 8-10 mA. Don't go up to the maximum current the LED can handle (usually 20mA), it will shorten LED life and it will put a lot strain on the 380mA PSU, assuming you have one like that.
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