I may be talking nonsense, but is there not a dedicated PSU for these speakers? That would seem to be the way to go.
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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.
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!
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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.
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 (:harp::guitar::violin:). 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...
Edit:
If anyone out there believes open baffle speakers don't do deep bass, they owe themselves a listen to these things...
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
HI Chris,
tried to PM you but your inbox is full...