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Millett "Starving Student" hybrid amp

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  1. intlplby Contributor
    I was thinking of building Pete's ECC99 SRPP Headphone Amp to drive my K-1000 but the BOM is outside my current budget. I saw that Pete said that this amp was able to drive the K-1000s. I have two questions:
    1) Is it worth building this to drive K-1000? It doesn't have to drive the K-1000s perfectly. It just has to drive them well enough to be delightful
    2) What modifications are suggested to the original design to make this amp more appropriate for the K-1000?
  2. Uncle Erik Contributor

    I haven't built this one yet, but I have the parts for it. The biggest problem is getting the output transformers from Sowter in the UK. Sowter is great, but it took something like four to six weeks to get them over here.

    You shouldn't need to mod the design to work better with the K-1000. Millett designed it specifically for the K-1000. You might want to pick around with the out resistors to make it work better with other headphones, though,
  3. the_equalizer

    Uncle Erik, I believe when intlbpy said the above he was referring to the "Starving Student"  [​IMG].
    Unfortunately I've never even listened to the K-1000s, much less tried them with my SSMH so... someone else would need to chime in here.
  4. intlplby Contributor
    Yeah, I was referring to mods to the Starving Student. Sorry for not being clear. Those transformers are like ~130 each and you need more than one of them so that makes the SRPP much more expensive. 
    I saw that Pete said that he tried driving the K-1000 with the Starving Student and that it performed very well. I wanted to see if it is a worthwhile build for the K-1000. 
    I currently run my K-1000 off my Consonance Cyber-800 Power Amps, but it's a huge pain to disconnect the speakers to then connect the K-1000s and vice versa. Because of this I use the K-1000s a lot less. I would like a dedicated amp for the K-1000, but I am cash poor right now as I am currently funding my own startup and need to watch my burn rate.
  5. Secretninja
    Well, I just got done redoing my internal wiring, and have the same problem of a dead left channel.  Pretty sure it is the mosfet, so I'm going to buy another one next time I'm near radioshack.  Here are some pics in the meantime.
  6. th3bl0b
    Thanks for helping me out guys and in particular the_equilizer! I checked the RCA jacks and it was fine. Turns out one of the resistors wasn't completely soldered... I don't know how that happened. I probably overlooked it when I was double checking the board before putting the FETS in. At any rate, a little soldering did the trick and it works now!
    I'm now enjoying my amp... and looking for another one to build [​IMG]
  7. the_equalizer

    Great news, glad you squashed that bug !  Good luck with the next build and, if it's another SSMH, post some pics here.

  8. hellomoto
    So, I finally managed to find some time to debug my MSSH. (Again, sorry for my bad English!)
    Here it was, one month ago
    - When I first tried to plug it in, the tube glowed nicely and equally, but suddenly it began to sparkle, and the tubes shut down.
    - I then checked the circuit, there was conductivity between the Mofset tab and the case/ground, even when not mounted on the case. I used heatshrink and shoulder washer to assure there was no conductivity between the tab and the case, I'm sure the tab and the screw and washers were not in contact with the case, but still, there was conductivity. I was quite busy then, and I didn't find enough time to take more time to debug, and I let it like this.
    - I verified the circuit, and all seems ok.
    - I put some heatshrink on some opened connections that may short
    - There is no more conductivity between the mofset tab and the case and the ground
    - I tried to plug it in, but the tubes didn't start to glow.
    Does that mean that the Mofsets are dead?
    Here are some pictures I took of my wiring, not very clear, I can take other pictures of certain spots if necessary!
  9. electrovice
    Hello, I am a new poster on this forum.
    I had  seen a Starving Student amp at a recent Headphone meet here in Seattle. I researched the amp and thought it would make an interesting project but I was also quite became quite concerned about the lack of 19J6 tubes. Fortunately I was able to find enough cheap tubes at a radio swap meet and that auction place to try the amp.
    I used a small stainless steel tray from Goodwill for my amp's chassis. I wired  the amp "point to point" using the standard inexpensive parts from Mouser and salvaged tube sockets. I shamelessly copied Pete Millett's original layout and used the 4 by 6 inch copper ground plane.  The base is made from some scraps of maple that I have had for years.
    The amp worked perfectly when I fired it up. It sounds great without a trace of hum. I have only listened to it using a portable Sony CD player for my source and  Sennheiser  HD 414 headphones.  I am very pleased with this amp even with the modest source and old school headphones. I will try the amp soon with better sources and upgraded cans when I get some.
    This was a fun build. I will probably try a 17EW8 version of this amp too. I have a nice stash of those tubes. I also have a huge stash of 12AU7 tubes.
    A few questions:
    What sort of life can one expect with these tubes? I have two spare pairs, will that keep me going for a while?
    Is this a final amp or is this a gateway to better amps?
    What headphones should I ....? Just kidding
  10. Beftus
    Nice build!
  11. akgfan
    Is there any hiss or hum on this amp? It is something that bothers me because I always wanted to build headamp with tubes. And this headamp looks good and simple that I am "DIY horny". [​IMG] I want it to be deadly quiet. There is probably no high gain but are tubes quiet in this application?
  12. tomb

    Built correctly, there is no hum ... period.  The key phrase in that sentence, though, is "built correctly."  Those who have had problems with hum have tried to shortcut things by leaving out a decent ground plane (as in, copper plate).  If you case the amp up without enough metal to provide a decent ground sink, or you snake wires that are so long that the signal is exposed to every interference that exists, then you may have an issue.

  13. akgfan
    OK. And what about hiss? Is there any?
    Edit: I'm on page 69 and it looks like there is no hiss if everything is OK. So my only problem would be 19J6 tubes but I could use other and do some modification if it would be posible.
  14. Secretninja
    Well, I finally got around to replacing the mosfet I thought was bad.  Turned out to be the case, as both tubes fired up.  I set it down to go get an rca cable and test for audio, and when I got back everything had gone dark.  I opened up the case and a wire to ground had snapped.  Resoldering the wire, everything was still dead.  I had one spare tube, and tried it out.  It lights up and produces sound.  I guess both tubes that were in got blown by whatever the ground hit as it broke.  I don't mind buying another couple tubes, but I am having the same problem of a very quiet amp.  Will removing the resistors that are right before the pot help with the volume issue?  If not, I may as well save my money on the tubes, because the amp is unusable with the volume it currently produces.
  15. wiisus
    How bright were the tubes?  I had a quiet issue when I first built mine, and the tubes were super bright.  I had resistors mixed up. 
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