How to Pass a little time ...cont

Discussion in 'DIY' started by dBel84, Oct 22, 2018.

  1. fraggler

    fraggler A Happy & Busy Life

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    Holy cow! I don't think I understood how big those heatsinks were until this picture. Inspiring work.
     
  2. dBel84

    dBel84 Friend

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    if you fancy a drive up to the brew city this weekend I can hook them up and give you a listen - am home alone saturday |\/|
     
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  3. fraggler

    fraggler A Happy & Busy Life

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    Would absolutely love to, but I promised that I would help my girlfriend take her mother car shopping. Already put it off twice...
     
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  4. dBel84

    dBel84 Friend

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    Guilt is a powerful force :)

    I scavanged a pot off another preamp and wired up the NuTube buffer - did not expect that !! It sounds incredible.

    [​IMG]

    (not pretty but functional)

    could be the combo PASS SIT with NuTube but it seems to work well - I wonder if it would be too much of a good thing with decent speakers.

    ..dB
     
    Last edited: Feb 7, 2019
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  5. dBel84

    dBel84 Friend

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    Spent a glorious day in DIY heaven

    My PASS SIT amp closed up but not yet finished - needs finished - initial plan was to paint it but this beast sits at about 50 deg C - most paint will not tolerate that, might explore high temp paints. Anodizing is an option but I am not pulling the whole thing apart - so would have to just be the panels.

    [​IMG]


    The trigger to start the amp - this is Ti Kan's trigger from AMBLABs

    [​IMG]

    Back panel

    [​IMG]

    Internal rail leds for my peace of mind - I hate not knowing that everything is powered as it should be and this way I can chill

    [​IMG]


    and because i had to be around to watch the multimeters while I cooked the amp for a few hours today

    Norwood daughter board for the M2X

    [​IMG]

    Muses volume control for the B1 nutube pre

    [​IMG]

    [​IMG]


    The SIT amp is sounding pretty damned amazing. It ran for about 8 hours straight while I teased the offset into place - finally settled at less than 10mV per channel. Going to run through this exercise with sacrificial speakers for a few more days then plug it into the main rig for a listen.

    ..dB
     
    Last edited: Feb 9, 2019
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  6. LetMeBeFrank

    LetMeBeFrank Won't tell anyone my name is actually Francis

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    Head to an autoparts store and grab some engine enamel. I have had very good luck with Rust-Oleum specifically and it gives a good finish.
     
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  7. dBel84

    dBel84 Friend

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    [​IMG]

    now just to wait for some decent weather - the last time I sprayed down in the basement, I messed with the HEPA filters and was not a popular guy , aside from the fact that new filters cost significantly more than a can of spraypaint ;)

    Hooked it up to the Maggies today - been "working" listening to music - keep getting distracted and finding myself sucked into the music - a very good place to be. This amp reminds me of my original stacker and has the same spatial realization as the stacker power that started me off on this entire adventure.

    [​IMG]

    just scary good, totally not practical though, the amp weighs a ton, doesn't fit into the rack and near boils at 50deg C (too hot to touch for more than a few seconds) , but what sound!!

    ..dB
     
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  8. Zampotech

    Zampotech Facebook Friend

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    don't paint radiators. Only anodizing or natural color. dye strongly affects the cooling.

    The paint layer is equivalent to thermal protection. Paint will add you 10-15 degrees of heat on transistors.
     
    Last edited: Feb 10, 2019
  9. dBel84

    dBel84 Friend

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    I was planning on leaving them alone, mostly because it would be a real pain to disassemble them . thanks for the warning though as it hadn't occurred to me.

    ..dB
     
  10. Zampotech

    Zampotech Facebook Friend

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    Technology of electrochemical dyeing of aluminum simple. But smelly.


    An alternative to electrochemistry. Paints, but the coating is not resistant.

     
    Last edited: Feb 10, 2019
  11. dBel84

    dBel84 Friend

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    that is all I need , add smell to noise and my wife will truly divorce me

    I used to etch my own PCBs and the mess of the ferric chloride used to drive her mad - i see that you have a "mad scientist" lab, very envious :)
     
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  12. Zampotech

    Zampotech Facebook Friend

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    My wife, a former police officer, thinks " a man without a hobby is a potential criminal"
     
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  13. Cspirou

    Cspirou They call me Sparky

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    Congrats on the radiator dBel
     
  14. dBel84

    dBel84 Friend

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    Lucky we were having - 50 deg Temps for a while
     
  15. dBel84

    dBel84 Friend

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    Had been struggling a little to get the amp to bias up appropriately and ( smarter folk than me ) finally figured out that the Vgs of the SIT was too far out of range for the design of this amp. I had measured the Vgs at 19V when I was originally screening components but as the Vgs is dependent on Drain voltage which are higher than anticipated - my amp sits at 25.4 rails - the Avel-Lindberg must have poorly spec'd secondaries so unloaded the AC is closer to 20V and rectified takes it up close to 26VDC unloaded. ( the amp is designed with an anticipated 22.4V on the rails )

    This meant that the SITs were passing close to 3A with the additional voltage and the bias adjustment didn't work as the Vgs of the SITs and FETs were too close .

    Added a patch using a small IRF520 mosfet to drop the voltage to the SIT down to 20V , this drops the Vgs of the SIT and brings the numbers into alignment for the bias circuit to work as designed,

    [​IMG]

    Ran the amp for 5 hours and it is rock solid, still sounding great - finally at a point where I don't need to worry about the amp and can sit back and enjoy

    ..dB
     

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