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Millett "Starving Student" hybrid amp

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  1. tomb
    Quote:

    Originally Posted by n_maher /img/forum/go_quote.gif
    Very cool layout! And I'm right there with you on your bang-for-buck analysis, it's very good.



    x2 - that's very cool!
     
  2. trains are bad
    I added a 3.5mm input jack on the back, to allow an ipod or whatever to be plugged in with a mini-to-mini cable. I'm also thinking about gluing a bit of steel plate or something into the box to make it feel heavier, because we all know that heavy things are better! I already taped my spare tubes inside. LOL.

    I'm using this to drive K701s. I'm really impressed with how quiet it is.
     
  3. dgbiker1
    Quote:

    Originally Posted by holland /img/forum/go_quote.gif
    It just makes it easier to stuff parts and not route wires.

    I've decided to build this and I don't think I'm going to air wire all the parts. I'll use breadboard with tacked down bare/unsheathed wire, or an unetched PCB (like pmillett). It's the same idea, except someone does the layout work for you when you buy a PCB.




    Since this isn't a circuit operating in the MHz range I don't know how it applies here, but isn't breadboarding notorious for being noisy?
     
  4. fault151
    [​IMG]

    This thing looks like it is off Doctor Who!

    [​IMG]

    Well done on the build!
     
  5. srserl
    Haven't built an electronics DIY project in over 10 years, so I'm just trying to remember the simple stuff.
    I finished this amp yesterday, but am having a problem with too much volume. I have the pot wired for maximum resistance at counter clockwise of the volume knob. Resistance varies from 54.8kohm at off to 0 at max between the inputs and the tube. I checked all resistor values this morning to make sure I put them in the correct places. Test voltages are correct (19V & 48V) at the points indicated on the schematic. What stupid mistake have I made?
    Sorry for the poor photos...I know you can't see everything.

    Source was CAL IKON MkII cd player and phones were HD555 (50ohm).
    I like this project on the cheap theme, but ptp is a pita...I think I would spring for a pcb to do another.

    Scott
    vbattach4733.jpg
    vbattach4735.jpg
     
  6. n_maher Contributor
    Scott,

    Can you elaborate on "too much volume"? Are you getting a variable signal as you turn the pot? Is it just that you don't get much for a usable range of attenuation before it gets too loud?
     
  7. trains are bad
    Make sure you grounded the other side of the pot. I did that at first. Since the line it's in is so high impedence, you can't just treat it like a resistor; nothing will happen, one side needs to be signal, the other side goes to ground through the whole 50kohm, and the wiper goes to the amp.
     
  8. utilisateur
    I want to incorporate a crossfeed in my MilletSSHybrid , has anyone measured/calculated the Input impedance yet?
     
  9. holland
    .
     
  10. trains are bad
    Quote:

    Routing wires everywhere without some attempt at isolation is just as bad as a breadboard with long wire loops sticking out. Besides, tubes aren't the most distortion free devices, so I'm not sure how important the construction methodology really is. You're not really dealing with devices that have issues with wire capacitance or resistance from traces more than a mm in length between components, or having timing violations due to uneven traces and/or signal degredation, so...YMMV



    I pretty much just routed wires everywhere without any attempt at isolation, I also had to parallel and series a bunch of resistors to get the right values, and my amp looks like a horrible rat's nest. Perhaps I got lucky, but it sounds wonderful. So let's not overthink this too much, this isn't a phased array radar transceiver or anything.

    Quote:

    I want to incorporate a crossfeed in my MilletSSHybrid , has anyone measured/calculated the Input impedance yet?



    What xfeed are you going to use? I built a tangentsoft xfeed kit, and I wasn't happy at all with how it sounded. It affected the sound rather drastically; I'm not sure what I could have done wrong either, what with buying the premade board and parts kit. I had just about given up on analog xfeed, and resigned myself to DSP only.
     
  11. utilisateur
    Quote:

    What xfeed are you going to use? I built a tangentsoft xfeed kit, and I wasn't happy at all with how it sounded. It affected the sound rather drastically; I'm not sure what I could have done wrong either, what with buying the premade board and parts kit. I had just about given up on analog xfeed, and resigned myself to DSP only.



    I'm not realy sure here but i think it's going to be jan Meiers circuit, i'm sure it's not the end of all 3d problems but hopefully an interesting experiment.I'll wire in a bypass switch of course
    I just (ab?)used EloyDarks Thread here to hopefuly get a little discussion going maybe we should discuss it there or even in a new thread ..

    So to avoid the grossest problems with the crossfeed i'd need to aproximate the amps Zin
     
  12. srserl
    Good call Trains. I traced the fault to the solder joint where the pot is grounded to the terminal. I couldn't notice any looseness at the joint, but there was no signal between there and the pot. Works great now...just need some new phones so I can listen to it while building the Millet Max. That makes 2 bad solder joints I had on this small project, but I think it was the cheap 40W iron with a large conical tip that I was using the first night of building. The next day I ordered a soldering station from circuit specialists, and I don't know why I didn't do so before. What a pleasure to use; it heats up in just a few seconds, and keeps up to temp (75 watt model so I can still solder my rc airplane electric motors).

    Scott
     
  13. holland
    .
     
  14. rds
    I'd like to see some actual measurements of this so called significant effect in headphone amplifiers.
     
  15. holland
    .
     
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