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Millett "Starving Student" hybrid amp

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  1. Juaquin
    You can definitely do it cheaper yourself if you're ok with making your own enclosure without a PCB. It is called the Starving Student after all. That also gives you the option of using the 12AU7 (and similar) tubes - while they might be a little more expensive now, they'll still be available in ten years.

    Equalizer, thanks for clarifying, I was a little confused. I didn't think that the 19J6-12AU7 conversion was all that easy (as it turns out it isn't) but it makes sense that you can roll the 12_7 series fairly easily.
     
  2. timmyGCSE
    ah great that looks awsome, I'll end up most likely building the 12AU7 version since I can get the tubes for £5-£10 each on ebay, I will build p2p so don't have to worry about the PCB and I'll be extra creative over an enclosure [​IMG] I will probably cut my teeth (done electronics but not audio electronics) on mini3 to start with then have this as my second project probably in a couple of months time. One of the cisco power supplys for this project finished on ebay UK for £3 with no bidders the other day [​IMG]
     
  3. loki993
    So here's another thing that confuses me. Like I said I'm basically a total noob. The BOM for the amp says the caps can be anything 150uF and up. So the first thing I think is bigger is better, but to what extent. Thats what I think, but I don't really know what going with a bigger cap does. Also the BOM that TomB put up has 2 different sizes. I'm assuming that 2 are for input and 2 output. What does putting larger ones in one spot or another accomplish?

    Boutique caps. Ive read a bit about them, They're supposed to sound better ok. What are the boutique caps though? I know about the Blackgates, but Ive seen them at $20 a pop so that's out of the questions. Also there's gotta be a point of diminishing returns with this thing right?

    Sorry for all the questions. Feel free to answer or if you want point me somehow where I can read up and learn about all this stuff without having to dig through tons of threads. I search the board a lot trying to find out, but it can be hard getting info that way.
     
  4. the_equalizer
    Quote:

    Originally Posted by loki993 /img/forum/go_quote.gif
    So here's another thing that confuses me. Like I said I'm basically a total noob. The BOM for the amp says the caps can be anything 150uF and up. So the first thing I think is bigger is better, but to what extent. Thats what I think, but I don't really know what going with a bigger cap does. Also the BOM that TomB put up has 2 different sizes. I'm assuming that 2 are for input and 2 output. What does putting larger ones in one spot or another accomplish?
    <snip>




    Two electrolytic caps are for the output stage, the other two are for power supply decoupling. Power supply decoupling is an important topic, but the explanation is a bit long and you'd do better to google it and read up [​IMG].

    In general, the answer to what extent bigger is better with these caps can be answered by:

    a) the size of your chosen enclosure.- Capacitor size increases rapidly with increasing capacitance value.
    b) the size of your budget.- Capacitor prices increase rapidly with increasing capacitance value.

    Within these two constraints you want to get the highest value capacitors that you can, so that the bass frequency response doesn't suffer (this is also dependent on the impedance of the phones you're planning to use with the amp, lower impedance 'phones require higher valued output caps to preserve bass frequency response)

    As to 'boutique' caps, these are manufactured with higher quality raw materials and techniques to offer reduced distortion figures for signals crossing them. Read up on 'reactance' and 'phase distortion' to get the details of why/how caps distort.

    cheers!
     
  5. simwells
    I'm about to build a P2P SSMH, but am wondering if you guys think it'd be worth trying out one of the PCB based ones too or whether thart'd be a bit of a waste and I should think about a larger scale project next? (only audio exp is building a mini^3 if that effects things)
     
  6. UKToecutter
    I'm going to build a PC based one.
    I don't want any hassle with stray emf (I like to play safe !!)

    If you want to do a more elaborate project you could try the beta 22....

    That'll keep you quiet for about 3 months
     
  7. FallenAngel Contributor
  8. UKToecutter
    yeah, I know.

    I might have a go at a P2P one as well, but only after I've done a PCB version.

    I'll give the PCB one to my son.
     
  9. Juaquin
    P2P is probably more of a learning experience because you'll probably end up with some issues (oftentimes, hum from a ground loop or insufficient grounding). With the PCB version you're virtually guaranteed to get an awesome working amp as long as your soldering skills are good.
     
  10. simwells
    Hmm, guess I'm unlikely to have time to wait to see how mine sounds before they'll sell out. I wonder if I could get a partial kit so as not to be buying the parts I already have.
     
  11. tomb
    Quote:

    Originally Posted by simwells /img/forum/go_quote.gif
    Hmm, guess I'm unlikely to have time to wait to see how mine sounds before they'll sell out. I wonder if I could get a partial kit so as not to be buying the parts I already have.



    No.
     
  12. revolink24
    Quote:

    Originally Posted by simwells /img/forum/go_quote.gif
    Hmm, guess I'm unlikely to have time to wait to see how mine sounds before they'll sell out. I wonder if I could get a partial kit so as not to be buying the parts I already have.



    Why not just order from Mouser or digikey? The BOM on the site is useful enough, thats how I built mine.
     
  13. loki993
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    Two electrolytic caps are for the output stage, the other two are for power supply decoupling. Power supply decoupling is an important topic, but the explanation is a bit long and you'd do better to google it and read up [​IMG].

    In general, the answer to what extent bigger is better with these caps can be answered by:

    a) the size of your chosen enclosure.- Capacitor size increases rapidly with increasing capacitance value.
    b) the size of your budget.- Capacitor prices increase rapidly with increasing capacitance value.

    Within these two constraints you want to get the highest value capacitors that you can, so that the bass frequency response doesn't suffer (this is also dependent on the impedance of the phones you're planning to use with the amp, lower impedance 'phones require higher valued output caps to preserve bass frequency response)

    As to 'boutique' caps, these are manufactured with higher quality raw materials and techniques to offer reduced distortion figures for signals crossing them. Read up on 'reactance' and 'phase distortion' to get the details of why/how caps distort.

    cheers!




    Thanks.

    So bigger is better than and bigger caps help bass response?

    Ill be running AD700s, not sure what impedance they are, 32 maybe? Also, and honestly what the amp will be for mainly, will be my dt770 pro 80s. Id love to clean up the highs on those. Giving the AD700s a bit more punch in the bass department wouldn't be bad either [​IMG], I have no complaints about the AD700s except the weak bass.
     
  14. the_equalizer
    Quote:

    Originally Posted by loki993 /img/forum/go_quote.gif
    Thanks.

    So bigger is better than and bigger caps help bass response?

    <snip>




    In general, yes, higher capacitance value is better for the supply decoupling and output caps. And for the output positions in the SSMH, it helps bass response.

    As mentioned, there are other factors and you don't want to end up with a cap so big that it becomes unwieldy.

    You do want to get good quality caps too. A bad quality part will distort your signal in many ways, so it doesn't matter that it's a zillion microfarads and get's you a theoretical bass response down to 2Hz...

    So, short story, order the parts specified in the BOM.

    A good place to get them is Beezar.com, for example these look great for the output caps of a "Starving Student".

    cheers!
     
  15. tomb
    I can only see this on my BBerry right now, but if that Beezar link goes to the Muse ES 1000uf 16V - remember that we want a 63V rating for the power and output caps in the SSMH. [​IMG][​IMG]

    There is a very nice cap that's newly available at Handmade Electronics that would be interesting to try at the output - a Muse Fine Gold (FG) at 470uf, 63V - only 25mm high, too.

    We're still using the Nichicon KW's in the kit, but it might be a decent option if someone is interested. Remember though, that bypassing with the Wima's tends to level things out with many electrolytics. The improvement would be very subtle, if at all noticeable.
     
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