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Millett "Starving Student" hybrid amp

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  1. the_equalizer
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    Oh, sorry. I did see your previous post but disregarded it as I've rewired my pot once already, and triple checked against the datasheet to make sure I wired it correctly. Here is the datasheet I'm talking about. Excuse my screenshot, I couldn't be bothered to GIMP out the image from the pdf. As per that image, I've got pins I2 and II2 going to the pot "grids" (I'm unfamiliar with that term), I got I3 and II3 going to the RCA jacks, and I1 and II1 are my ground. Is this not correct? Looking at my pot from the back, the six pins are wired as follows:

    RCA L, RCA R, GROUND, GROUND (I jumped the two), GRID L, GRID R

    This corresponds to the image I posted, which shows the pins with a "view from mounted part side". My extreme zoom on there blocked out that foot note.

    Please, tell me if I'm wrong as I'd love to get this thing up to 100%.

    My power switch has a LED, and this thing pulses two or three times when I first power it up. I guess this is normal?




    You almost got it right. It seems only one of your channels is wired in reverse [​IMG]

    According to the datasheet pinout here's how it should go:

    RCAL - RCAR - GRIDR - GROUND - GROUND - GRIDL

    I3 - II3 - II2 - II1 - I1 - I2


    Just to clarify it a bit, label "II" corresponds to one 'pot' (for the right channel in your build) and label "I" corresponds to the other pot. Pin 2 on both sections corresponds to the wipers, pin 1 goes to ground, pin 3 to the inputs.

    Also, I couldn't find in the datasheet something that told me if the pinout was looking from the front of the pot or from the back... but I only skimmed over the datasheet

    The pulsing at startup is normal. When cold, the tube heaters (filaments) draw much more current, so much so that they look like a short circuit to the power supply which starts up, shuts down due to the "short", comes up again, etc.. after some such cycles, the heaters have warmed up a bit, and their current demand lowers to the point where the power supply can cope with it. Then the supply stays on (no more pulsing) and the heaters start glowing.

    BTW, nice Linux desktop [​IMG] I'm also a *IX user.

    cheers!
     
  2. ezzieyguywuf
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    </snip>

    BTW, nice Linux desktop [​IMG] I'm also a *IX user.

    cheers!




    Lol thanks. Its my first gentoo box, and I love it! I used 'buntu for the longest time, but was ready to have greater control over my linux desktop.

    I'm playing FFXII right now, so I'll get around to fixing the pot tomorrow. Thank you so much for your help, and for your modified schematic for the 12AU7!
     
  3. nullstring
    lol, ubuntu has just as much control as gentoo..
    It's just not as required >_>.

    But, anything that you can do in gentoo, you can do in ubuntu minus seemlessly compiling your packages with your own optimization options (but who really wants to do that >_>)

    figures ezzieguywuf would be a ricer =p.
     
  4. Volkum
    Quote:

    Originally Posted by nullstring /img/forum/go_quote.gif
    lol, ubuntu has just as much control as gentoo..
    It's just not as required >_>.

    But, anything that you can do in gentoo, you can do in ubuntu minus seemlessly compiling your packages with your own optimization options (but who really wants to do that >_>)

    figures ezzieguywuf would be a ricer =p.




    I much prefer compiling my own stuff so that I can have more control over my dependencies rather than having to pull in a bajillion packages (bloat) I don't need just because someone thought compile a package their way with all possible options. I've also yet to come across a package manager as robust as Portage.

    Not a diss to Ubuntu, but just my preference. I run a Proxmox server and Proxmox is using Debian.
     
  5. ezzieyguywuf
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    You almost got it right. It seems only one of your channels is wired in reverse [​IMG]

    According to the datasheet pinout here's how it should go:

    RCAL - RCAR - GRIDR - GROUND - GROUND - GRIDL

    I3 - II3 - II2 - II1 - I1 - I2


    Just to clarify it a bit, label "II" corresponds to one 'pot' (for the right channel in your build) and label "I" corresponds to the other pot. Pin 2 on both sections corresponds to the wipers, pin 1 goes to ground, pin 3 to the inputs.

    Also, I couldn't find in the datasheet something that told me if the pinout was looking from the front of the pot or from the back... but I only skimmed over the datasheet

    The pulsing at startup is normal. When cold, the tube heaters (filaments) draw much more current, so much so that they look like a short circuit to the power supply which starts up, shuts down due to the "short", comes up again, etc.. after some such cycles, the heaters have warmed up a bit, and their current demand lowers to the point where the power supply can cope with it. Then the supply stays on (no more pulsing) and the heaters start glowing.

    BTW, nice Linux desktop [​IMG] I'm also a *IX user.

    cheers!





    Ok. Here is my pot.

    [​IMG]

    I was mistaken the first time I posted my pinout. I believe that the way I have it is just as you described it. To explain my wiring, red is one channel, black is the other, and green is ground. That green wire is jumping the 4th and 5th pins. The red/black pair on the left go to RCA jacks, and the pair on the right (separated by ground) goes to the tubes. Sooo, whats the next step in shooting this trouble?

    Quote:

    ol, ubuntu has just as much control as gentoo..



    I suppose you could make that arguement. I just got tired of having to use packages the way someone else decided to compile it.

    Really, my evolution to gentoo stemmed from my winter break, in which I built an LFS box. It was a lot of fun, and very enlightening. I learned that I could have so much more control over my linux box than I actually had. When I saw how gentoo worked, I realized that, "Hey, this gives me about as much control as an LFS box, but with a super awesome package management system".

    Ubuntu is great. It was my first distro and I used it for a long time. I really see it as an intro-to-linux distro though. They do everything for you and keep it all hidden behind-the-scenes. Yea, you could theoretically change whatever you want, but it becomes a chore sometimes, especially when you update and something breaks due to your custom configs. On gentoo, you have a make.conf and package.use that specifies your customizations, so that when you emerge --update world, portage takes care of making sure that everything agrees with each other.
     
  6. the_equalizer
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    Ok. Here is my pot.

    </snip>

    I was mistaken the first time I posted my pinout. I believe that the way I have it is just as you described it. To explain my wiring, red is one channel, black is the other, and green is ground. That green wire is jumping the 4th and 5th pins. The red/black pair on the left go to RCA jacks, and the pair on the right (separated by ground) goes to the tubes. Sooo, whats the next step in shooting this trouble?

    </snip>




    It's difficult to tell from the pic if the wiring is alright. I would just make sure if the pinout from the datasheet is from the front or the back of the pot, this is important because if you follow the pinout from the 'wrong' side then both your channels end up wired in reverse.

    The practical way would be to get a multimeter and determine which pins are the wipers.

    Oh, and BTW I'm actually a FreeBSD user [​IMG] it wasn't my intention to open that Linux distro can of worms (not in this thread, at least)

    cheers!
     
  7. ezzieyguywuf
    Quote:

    It's difficult to tell from the pic if the wiring is alright. I would just make sure if the pinout from the datasheet is from the front or the back of the pot, this is important because if you follow the pinout from the 'wrong' side then both your channels end up wired in reverse.



    Hm, I thought it was a pretty good picture :frowning2:. Either way, I know that the datasheet says the pinout I posted is from the pront. As a matter of fact, here is the datasheet, so you con see for yourself. Page 5.

    What else could be causing my problems?
     
  8. timmyGCSE
    now..
    *sigh*
    I've just finished my second SSMH, used the 12AU7 version (as before), but this time I completely designed the PCB from the schematic myself, and used the extra Dsavitsk mods.
    it works, it looks the dogs (pictures will follow I promise), but....

    ...same problem as before on my p2p first attempt - left ear plays louder (this shouldn't happen). When I remove the right RCA I still get sound from both channels (this also shouldn't happen). When I remove the left RCA I only get sound from the right channel (this should happen).

    I've tried multiple headphones, multiple sources, multiple connection cables.
    And sorry but to have exactly the same issue on two builds, especially this one where there is a very slim chance of a wire being accidently grounded, I think it highly unlikely..
    plus I don't believe I am interpreting the schematic wrong...

    so this leads me to the conclusion that I'm either wiring the pot wrong (I really don't think I am, this has been checked so many times), or..I'm wiring my TRS jack wrong.
    This is the jack I have used:
    Rapid Electronics - Cables & Connectors
    and this is its datasheet:
    http://www.neutrik.com/Secure30/getM...pplication/pdf

    I've used only 3 of the 6 pins on the jack...should I be using all 6? :-/

    the jack is definately wired correctly as in ground at the rear, right in the 'middle' and left at the tip.

    Just can't figure this one out..arggh

    then again.....lets relook at the pot for a second....

    edit...ermm...hold on..

    edit2: idiot!! idiot idiot idiot

    I just said
    Quote:

    the jack is definately wired correctly as in ground at the rear, right in the 'middle' and left at the tip.



    no it friggin well was not! in a state of sheer stupidity, I wired the ground to the tip and the left to the sleeve..on both!?! hahahaha. So I now have two working SSMH's, and one working tried and tested 12AU7 PCB design (albeit very messy and scrappy design and its very amatuerish and looks awful tbh but het it works!!) [​IMG]

    I will upload pictures and stuff tomorrow
     
  9. timmyGCSE
    right so as I said its all done, I still have a little issue in that the right side is a bit crackly sometimes so I obv have a cold joint somewhere but it works now as to be expected.
    Making a PCB and stuff was, imo, a lot less laborious than P2P, and it was enjoyable to make the PCB too. My PCB design leaves a lot to be desired, but this is my first design since I was studying electronics at school 9 years ago (I made a random number selector..I still have it in the cupboard [​IMG]) and it works at the end of the day. But more about that later.

    So here is some pictures for you:

    [​IMG]
    soaking the PCB to remove the glossy paper

    [​IMG]
    PCB all done and drilled, the hardest part was removing the toner after! see the design..poor eh [​IMG]

    [​IMG]
    all my bits, ready to start work....and inexplicably a comic with some fishes on it :-/

    [​IMG]
    all the board components soldered. Notice the wires? yea thats coz I can't design PCBs so I cheat when I can't figure out a way to 'escape' a track. At least there is only 2..my original design had about 5 [​IMG]

    [​IMG]
    casework done with a pillar drill

    [​IMG]
    tube sockets wired, note the use of ribbon cable, I though this would be easy because the cables are stuck together making them easier to manage, and it was a good choice (albeit not audio grade stuff but meh)
    Ginger Beer is the best drink going btw [​IMG]

    [​IMG]
    tube sockets wired to the PCB

    [​IMG]
    everything wired in place, of course..the TRS jack at this point was wrong [​IMG] messy? thats my middle name didn't you know? haha

    [​IMG]
    oh hello there..a finished SSMH 12AU7 [​IMG]

    [​IMG]
    looking laaavly darling, just laavly

    [​IMG]
    oo looking sexy, give me fierce, I wanna see some attitude..ooh laavly, you're doing great

    [​IMG]
    now twirl, show us some of that gorgeous backside, oh you're giving me the chills

    [​IMG]
    and relax..natural pose. beautiful.

    so ahem..anyway..yes, this is loud..much more than my previous one, because I've used the mods on this one. I left out R14/15 too (by accident I admit). But it sounds great, I haven't had a proper listen because I finished it at 5am and like I say I have a slight crackling issue.

    The PCB design - I will upload it a bit later if anyone is interested, but you have to promise not to laugh.
    - Its big, I designed it around the case I bought for it to go in.
    - The pad sizes are wrong in some cases (all the component spacing is right though, designed for the components I had in front of me)
    - the layout is poor, I had to use two wires to join tracks

    blah blah it could be a hellavalot better I know but I'm learning and it works so that's whats important. enjoy [​IMG]
     
  10. the_equalizer
    Fantastic timmyGCSE, simply fantastic! Your PCB looks nice and clean as does your casework. I really like it! Congratulations, I hope you get some time to enjoy it today!
     
  11. the_equalizer
    Quote:

    Originally Posted by ezzieyguywuf /img/forum/go_quote.gif
    Hm, I thought it was a pretty good picture :frowning2:. Either way, I know that the datasheet says the pinout I posted is from the pront. As a matter of fact, here is the datasheet, so you con see for yourself. Page 5.

    What else could be causing my problems?




    I didn't mean the pic was bad, it's just that you're familiar with your build while I'm obviously not, so the pic makes perfect sense to you while looking unclear to me [​IMG]

    Ok, I can see the little note in page 5:
    "3. View from mounted part side"

    I assume that means from the back of the pot, doesn't it? [​IMG] Man that is one confusing datasheet to me...

    EDIT: Oh! I think I understood it: it means from the component side of the PCB; so neither from the front or the back of the pot, rather from the top of the pot.
     
  12. Yaka
    very nnice work mate
     
  13. timmyGCSE
    Quote:

    Originally Posted by the_equalizer /img/forum/go_quote.gif
    Fantastic timmyGCSE, simply fantastic! Your PCB looks nice and clean as does your casework. I really like it! Congratulations, I hope you get some time to enjoy it today!



    thank you [​IMG]

    I was pretty proud of my casework but I still think I could have done better on the PCB

    anyway as promised:
    4shared.com - online file sharing and storage - download SSMH v3.pcb

    be gentle [​IMG]
     
  14. ezzieyguywuf
    I think I'll have to attribute my channel imbalance to a bad pot. I've checked the resistances manually and they are never equal, throughout the whole sweep of the wipers. I mean, I payed $2.53 for it. I dunno if that's a lot for a pot or not, but I was seriously trying to keep this thing cheap. And (as I've mentioned twice) I'm already over budget, so I new pot will have to wait. Probably for a while... *sigh*.

    the_equalizer, thanks for all your help. I'm rather certain that its wired up properly. I did all the checks that dsavitsk talks about in post #3861 on page 258 and everything actually measures pretty good. The thing is, though, that my AC Voltmeter doesn't have super high resolution, so even with the pot maxed and the input maxed, the voltages at grid and output are still in the 0.0 to 0.3 range. And I noly get the one decimal, so yea on that. Oh, and I had to use a 70Hz tone, though I'm sure that made no difference...oh gawd, did my headphones just blow up? :p

    Anywho, I had lots of fun building this thing, but can't really listen to it as it stands now. I'll have to wait till later in the summer, or maybe closer to august to give a new pot a shot.

    It does sound good though :-D
     
  15. nullstring
    did you add the 330k resistors?

    if the pot balances out as it gets louder, then this would be a quick fix..
    It wouldn't be able to get as loud.. but at least it'd be usable right?
     
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