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Thread: Field coil DC power supply help

  1. #21
    Join Date: Apr 2012

    Location: Southall, West London

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    I'm Geoff.

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    I may be talking nonsense, but is there not a dedicated PSU for these speakers? That would seem to be the way to go.
    "when common sense, logic and plausibility are excluded. All that remain are foolishness and lies"

  2. #22
    Join Date: Apr 2012

    Location: London

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    I'm James.

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    Seems not, the manufacturer is a little eccentric and does things his own way, didn't even come with an upper voltage limit.

    I measured coil temperature and worked accordingly to keep it under 60C. With Paul's speakers that's South of 90V, I run them at about 70V. TBH the voltage is subjectively to me about a quarter as significant to the sound as the impedance and I keep the volts down as they aren't mine!

    Sent from my BLA-L09 using Tapatalk

  3. #23
    Join Date: Apr 2016

    Location: Bishops Stortford

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    I'm Chris.

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    Quote Originally Posted by Jazid View Post
    The PSU is a doddle, hum is not a major issue in anything working adequately on PSUdesigner.
    Just a word of caution for those listening near field. Hum can be very pervasive and annoying.
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  4. #24
    Join Date: Jan 2009

    Location: Essex

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    I'm openingabottleofwine.

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    Quote Originally Posted by bumpy View Post
    Just a word of caution for those listening near field. Hum can be very pervasive and annoying.
    Then a pretty lousy power supply is being used. A half decent power supply ought to have a minimal and inaudible hum level.
    Barry

  5. #25
    Join Date: Apr 2012

    Location: London

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    I'm James.

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    Quote Originally Posted by bumpy View Post
    Just a word of caution for those listening near field. Hum can be very pervasive and annoying.
    I work at approx 5cm with ears to the coils. No hum at all. Approx 5uV on the analyser. Thanks for the advice.

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  6. #26
    Join Date: Apr 2016

    Location: Bishops Stortford

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    I'm Chris.

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    Field coil driver power supplies are rarely debated or reviewed.

    You will obviously rail against this, but the consensus from things I have read and listened to is that valve power supplies sound better than transistor and that hum can be eradicated easily at the expense of sitting on sound quality. Perhaps when you have tried both you can help us out with your opinions.
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" Supravox 215 RTF64 vintage midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  7. #27
    Join Date: Apr 2012

    Location: London

    Posts: 651
    I'm James.

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    Quote Originally Posted by bumpy View Post
    Field coil driver power supplies are rarely debated or reviewed.

    You will obviously rail against this, but the consensus from things I have read and listened to is that valve power supplies sound better than transistor and that hum can be eradicated easily at the expense of sitting on sound quality. Perhaps when you have tried both you can help us out with your opinions.
    Hi Chris,

    I have tried both. I've tried a regualted valve PSU, a regulated transistor PSU, the one I am making for Paul, and a couple of similar variants. I cannot see the need for a valve rectified stage or those super old school selenium rectifiers. I also abhore hum but see no need for it, as Barry pointed out - it's just a badly designed supply if there's any hum. The current drawn by the field coils barely varies when playing music, far far less than in any SET for instance let alone a class B amp. Back EMF is lost in the final capacitor, so I can't see how a valve two capacitors and resistors further back in the supply would change the sound since its characteristic differences from silicon just aren't being exposed? And it's not that I like silicon, anyone who knows me knows that I'm a died in the wool valve guy.

    The PSU I have made has had the trafo snubbered and optimally damped so there is diddly squat ringing from the diodes, and nothing that is getting through for sure. What does make a difference is the resistance of the final stage, howsoever achieved. As a result I imagine that the smoothing caps chosen in a valve reg PSU would likely make a significant difference: NOS or old electrolytics for example usually have far more ESR than the modern equivalents which I have used. That's why I went down the impedance rabbit hole to see if that made a discernable difference, and it seems that it does. Since capacitor ESR is a function of frequency there may be more to experiment with for sure, but for me the journey is done. The PSU is finished and encased, and being soak tested this weekend (). Paul's speakers are playing very nicely with 81V on the coils and 1 ohm impedance in series with the each side's final reservoir caps, and presently to migrate to their rightful owner sadly...
    Last edited by Jazid; 03-07-2020 at 17:35. Reason: Adding summat

  8. #28
    Join Date: Apr 2012

    Location: London

    Posts: 651
    I'm James.

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    Edit:
    If anyone out there believes open baffle speakers don't do deep bass, they owe themselves a listen to these things...

  9. #29
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 922
    I'm Chris.

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    Quote Originally Posted by Jazid View Post
    Hi Chris,

    I have tried both. I've tried a regualted valve PSU, a regulated transistor PSU, the one I am making for Paul, and a couple of similar variants. I cannot see the need for a valve rectified stage or those super old school selenium rectifiers. I also abhore hum but see no need for it, as Barry pointed out - it's just a badly designed supply if there's any hum. The current drawn by the field coils barely varies when playing music, far far less than in any SET for instance let alone a class B amp. Back EMF is lost in the final capacitor, so I can't see how a valve two capacitors and resistors further back in the supply would change the sound since its characteristic differences from silicon just aren't being exposed? And it's not that I like silicon, anyone who knows me knows that I'm a died in the wool valve guy.

    The PSU I have made has had the trafo snubbered and optimally damped so there is diddly squat ringing from the diodes, and nothing that is getting through for sure. What does make a difference is the resistance of the final stage, howsoever achieved. As a result I imagine that the smoothing caps chosen in a valve reg PSU would likely make a significant difference: NOS or old electrolytics for example usually have far more ESR than the modern equivalents which I have used. That's why I went down the impedance rabbit hole to see if that made a discernable difference, and it seems that it does. Since capacitor ESR is a function of frequency there may be more to experiment with for sure, but for me the journey is done. The PSU is finished and encased, and being soak tested this weekend (). Paul's speakers are playing very nicely with 81V on the coils and 1 ohm impedance in series with the each side's final reservoir caps, and presently to migrate to their rightful owner sadly...
    James, you seem to have cracked it, well done. Although I love the sound quality and the ability tweak them, I have always steered clear because of hum. I listen near field which compounds the problem. Can you offer some ballpark figure for build and supply of a pair. Thanks Chris
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" Supravox 215 RTF64 vintage midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  10. #30
    Join Date: Apr 2012

    Location: London

    Posts: 651
    I'm James.

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    HI Chris,
    tried to PM you but your inbox is full...

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