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Millett "Starving Student" hybrid amp

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  1. ezzieyguywuf
    P2Y7503-ND I orderered this pot off of digikey, but realize now that the shaft doesn't have any threads. Anyone know of a good way of mounting this to my enclosure? I was thinking of making a square hole that fits the flats, and then just putting a piece of tape behind it to hold it in place. Theres gotta be a more elegant way though. Also, CP-009BH-ND that is the connector I got for the power supply. I'm guessing that for this I make a square hole in my case and just shove it in? The material really doesn't seem like it'll give enough to allow that to happen.

    Thanks for your help guys!

    Ah yes, I also got HS374-ND those as heat sinks. I know some people pull the pin out and tap some threads in it, so that they don't have to solder it down. Now that I got them, though, I see that the hole the pins go in aren't really holes. They're more like a C slot, i.e. one side has no material. Is that what you guys are tapping? I'd think that gap would pose some problems, but maybe I'm wrong.
     
  2. Sganzerla
    I need some help from you guys. [​IMG]

    Today I build my first amp, this one, with some help from a friend that was guiding me trough MSN (mic + webcam), he got the picture of the layout I was using, and the circuit from official website.

    Everything was installed and then when I got to use this amp, I have some strange behaviour occuring:

    - First when I turn it ON I hear a loud pop and then 5 pop sound (I think it is the power supply causing this). Is everything ok? My worry is about this very loud pop...

    - After turning volume on, I hear more sound on the right side, and after 10 seconds or so, sound begin to turn down and it keeps going until it has almost none. While this occur, the sound imbalance goes from right side to the left. I'm pretty sure something wrong is happening here... [​IMG]

    - I think my tubes are a little oxized, is there any easy way of cleaning this and my tube socket? I live in a country where some speciality things aren't easy or cheap to get.

    Here is a picture of my build, I think will try to desolder and solder everything back tomorrow, if someone can instruct me on what look/is wrong and/or how to solve this problem, I'd be very thankfull:

    LINK TO BIG IMAGE

    While the sound lasts 10 seconds or so, it sounds like it will kill my Compass amp on quality (timbre is different, bass and highs too), hopefully it will begin to work as desired.
     
  3. n_maher Contributor
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    Is that what you guys are tapping? I'd think that gap would pose some problems, but maybe I'm wrong.



    Yup. There's no issue taping that section of the heat sink.

    As for you other parts problem I don't have much for advice other than to say I don't think either was a good choice and I'd get the "right" parts rather than kludge together the bits that don't want to work.
     
  4. the_equalizer
    Quote:

    Originally Posted by Sganzerla /img/forum/go_quote.gif
    I need some help from you guys. [​IMG]

    Today I build my first amp, this one, with some help from a friend that was guiding me trough MSN (mic + webcam), he got the picture of the layout I was using, and the circuit from official website.

    Everything was installed and then when I got to use this amp, I have some strange behaviour occuring:

    - First when I turn it ON I hear a loud pop and then 5 pop sound (I think it is the power supply causing this). Is everything ok? My worry is about this very loud pop...

    - After turning volume on, I hear more sound on the right side, and after 10 seconds or so, sound begin to turn down and it keeps going until it has almost none. While this occur, the sound imbalance goes from right side to the left. I'm pretty sure something wrong is happening here... [​IMG]

    - I think my tubes are a little oxized, is there any easy way of cleaning this and my tube socket? I live in a country where some speciality things aren't easy or cheap to get.

    Here is a picture of my build, I think will try to desolder and solder everything back tomorrow, if someone can instruct me on what look/is wrong and/or how to solve this problem, I'd be very thankfull:

    LINK TO BIG IMAGE

    While the sound lasts 10 seconds or so, it sounds like it will kill my Compass amp on quality (timbre is different, bass and highs too), hopefully it will begin to work as desired.




    Your wiring looks OK. I'd need to see some other angles of your build, for instance, to have a side look at those terminal strips, and more detail on the volume pot.

    Also, when this 10 second fade-out happens.... do the tubes remain lit up? I'm betting they don't.

    cheers!
     
  5. Juaquin
    Taking stabs in the dark here, but it sounds like a capacitor is draining (given the slow fading over ~10 seconds). Perhaps one of the output caps is shorting?

    [EDIT] If the LEDs fade through, that indicates the power supply (likely the power caps are draining somehow).
     
  6. ezzieyguywuf
    So I got my build laid out on the table, with a bunch of alligator clips connecting stuff (just to test it). I noticed that when I power it on, nothing happens. After a bit of troubleshooting, I find that when I make the very first connection after the switch in the schematic, I get a spark. More specifically, when I hook up the resiston/capacitor, which I've got hooked up on a breadboard. I used the breadboard due to all the common nodes at the "48V" on the schematic. Any guess as to why this connection would result in a spark? I've double (though not quite triple, it's getting late) checked all the capacitors to make sure they're lined up right, and I've also checked all the connections on my breadboard, but to no avail. I can post pics tomorrow morning, but just thought I'd go ahead and post this to see if anyone with more experience with this schematic than me might offer a suggestion as to what is causing this spark.

    <edit> couldn't wait . You'll notice that I joined the ground for C6, R4 and R10. Also, the "48V" is that one node in the schematic that is marked as such. The 48V to the top right connects directly to my power supply, and this is what causes the sparks. If I connect just the mosfets, pin 2, I do not get any sparks. I should also note that I'm not getting the "~12V" that is listed in the schematic, though I am getting the "48V".....

    <double edit> Got this far in my post and decided to actually try measuring the "48V" on my breadboard, as I had only been measuring it at the Pin2/Pin2/48V--> . Hooked it up and my tubes are a glowin! I'm getting ~32V where I'm supposed to be getting ~12V though, coming out of pin4 and into the + of C3 and C5. Is this gonna blow up?

    <triple edit> Turns out I had forgotten to connect the "Pin 1/6" L and R as I have it annotated. I now get the appropriate voltages AND sound! Only problem is the right channel is significantly lower volume than the left, and it hummmms. I haven't started troubleshooting it yet, but heck I got sound! time for bed cheers!

    <I really should be in bed right now> Omg... http://tangentsoft.net/audio/bitmaps/annotated-evj.jpg I used that image to wire my pot and just realized I did it looking at it from the front, not the back. Man this sucks. I spent soooo much timing doing a "good" job wiring that thing too. at least I know where the problem is. I'm surprised I got any sound out of it at all......
     
  7. Sganzerla
    Well, let me first thank you both for your time and attention.
    Here are the links for the 4 images I made:

    LINK1
    LINK2
    LINK3
    LINK4

    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    Your wiring looks OK. I'd need to see some other angles of your build, for instance, to have a side look at those terminal strips, and more detail on the volume pot.

    Also, when this 10 second fade-out happens.... do the tubes remain lit up? I'm betting they don't.




    Yes, they do. Looks like they fade a little from the intensity they are at start, but they continue lit up.

    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    Taking stabs in the dark here, but it sounds like a capacitor is draining (given the slow fading over ~10 seconds). Perhaps one of the output caps is shorting?

    [EDIT] If the LEDs fade through, that indicates the power supply (likely the power caps are draining somehow).




    I have problems with terminology of these components, could you point wich value (or the color) are the power caps and the output caps? It is easier for me to understand.

    Thanks again!
     
  8. the_equalizer
    Quote:

    Originally Posted by Sganzerla /img/forum/go_quote.gif
    Well, let me first thank you both for your time and attention.
    Here are the links for the 4 images I made:

    LINK1
    LINK2
    LINK3
    LINK4



    Yes, they do. Looks like they fade a little from the intensity they are at start, but they continue lit up.





    Thanks for the pics! I'll review them carefully and comment on them later (gotta go to the office now!). If the tubes remain lit up then it's stranger than I thought; I was aiming at the same thing Juaquin mentioned: power supply shut off and power caps draining causing that slow fade out. The issue still probably has to do with caps slowly discharging but if the tubes remain lit up, the power supply is working.

    I do have a question already, on the first pic, the terminal strip on the right side, immediately to the right of the solder point connecting the terminal's middle pin to ground there's a small solder blob... is anything connected to it? From the pic it seems as though one teflon cable is connected to it.

    Oh, forgot to mention, those loud thumps at turn on are normal: those are the sound of the output caps charging up through the parallel combination of your 'phones and R6, R12. That's why you do not want to turn the amp on or off with your cans plugged in.

    Quote:

    Originally Posted by Sganzerla /img/forum/go_quote.gif
    I have problems with terminology of these components, could you point wich value (or the color) are the power caps and the output caps? It is easier for me to understand.

    Thanks again!




    Refering to the schematic, power caps are C1 and C6; output caps are C3 and C5.

    cheers!
     
  9. Sganzerla
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    I do have a question already, on the first pic, the terminal strip on the right side, immediately to the right of the solder point connecting the terminal's middle pin to ground there's a small solder blob... is anything connected to it? From the pic it seems as though one teflon cable is connected to it.



    Thanks again, no, there is nothing connected to that blob, it is there alone - I almost soldered the terminal there, but later moved more to the center.
     
  10. Juaquin
    I had trouble following your description - which channel is getting quieter and fading away? I would check the output capacitor in that channel for shorts or damage.

    Also, until you nail down the problem, don't plug any good headphones into the amp. It's possible that you're passing DC voltage through the to headphones, which could fry them.
     
  11. ezzieyguywuf
    alright, "finished"! The only thing I use the alligator clips for now are the ground connections, which I'm running to a huge copper thing I bought at Lowe's. I got everything laid out on the table, and seeing as to how I went over budget, might have to resort to poking some holes in a cardboard box as an enclosure. The problem is, though, that I have humming! When I have the pot really really low, first of all, I only get sound in the right ear. As I turn the pot higher, I eventually get sound in both ears. It doesn't sound uneven though, same volume in both ears. Also, with no source connected, I can adjust the pot until I find a "sweet spot" where there is no hum.

    Finally, with my source set at 0dB volume, I can barely touch the pot on the amp before it is too loud to do anything with. Its like off-off-offf-off-SUPER LOUD. The only reason I mention this is that on my CMOY, I can use the same source at the same volume and have a fair bit of play with the volume knob.

    Any help with any of these issues guys? I realize after searching that ground seems to be the issue for humming, but I wonder if this "sweet spot" business I described might now point to something else?
     
  12. nullstring
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    The problem is, though, that I have humming!



    This could very well be caused by the alligator clips
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    When I have the pot really really low, first of all, I only get sound in the right ear. As I turn the pot higher, I eventually get sound in both ears. It doesn't sound uneven though, same volume in both ears.



    pots that are mismatched at low volumes are very common.

    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    Finally, with my source set at 0dB volume, I can barely touch the pot on the amp before it is too loud to do anything with. Its like off-off-offf-off-SUPER LOUD.



    You don't have any high impedance cans...
    What did you use for your R16/R17? you may need to increase them.
    When you fix this issue, the mismatched pot won't matter.

    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    but I wonder if this "sweet spot" business I described might now point to something else?



    Might be oscillations in that case. I don't know enough about the circuit to tell you where the problem parts are.
     
  13. ezzieyguywuf
    Thanks for the response nullstring. I'll try removing the alligator clips and see what happens.

    Quote:

    What did you use for your R16/R17



    I did not use an R16/R17 as they are marked "optional". Decided to go with the simplest build possible. (already over budget ya know). I do have some spare resistors though, so what would you suggest?

    FYI I used none of the highlighted parts shown here

    Quote:

    When you fix this issue, the mismatched pot won't matter.



    You mean the resistors? I see, so the higher resistance means that a lower sweep of the pot will fix the mismatch. Gotcha.
     
  14. nullstring
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    I did not use an R16/R17 as they are marked "optional". Decided to go with the simplest build possible. (already over budget ya know). I do have some spare resistors though, so what would you suggest?



    lol, you shoulda done a bit more research.
    Anything from 33k to 150k or so should work fine... just make sure they match.
    [EDIT: you should probably add R14/R15 as well if you have any spare resistors in the 1K area.]

    What pot do you have?

    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    You mean the resistors? I see, so the higher resistance means that a lower sweep of the pot will fix the mismatch. Gotcha.



    It won't actually fix the mismatch.. you just won't be using the pot at the very low end anymore.
     
  15. Sganzerla
    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    I had trouble following your description - which channel is getting quieter and fading away? I would check the output capacitor in that channel for shorts or damage.

    Also, until you nail down the problem, don't plug any good headphones into the amp. It's possible that you're passing DC voltage through the to headphones, which could fry them.




    Juaquin,

    First it was the right channel playing stronger, but I noticed I may had made a mistake, so I changed the L/R wire in the phone jack, and now it is stronger on left side. To say the truth I still don't know if these cables are right, here is a link to the image showing how it is wired:

    LINK
    (Hope it is not wrong...)

    It plays this way now: I turn on, plug my headphones, level up volume and sound is good, but imbalanced towards left speaker. When the sound begin to fade away, after 10/15 seconds, it happens to both channels, but at the same time sound begin to imbalance toward the right side.
     
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