[sdiy] Opinions on Switchmode PSUs for analog synths?
ka4hjh at gmail.com
Mon Nov 11 20:38:03 CET 2019
> On Nov 11, 2019, at 4:47 AM, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
> Gas discharge tubes and arcs (arc welder) with negative incrememtal resistance are best suited to being driven with a constant-current power supply, rather than constant voltage. A series "ballast" resistor approximates this, but isn't very efficient!
Exactly. All commercial HeNe supplies are current-limited. Some have a trim pot to adjust the current by ±.5mA or so. The ballast resistor is absolutely necessary because of the parasitic capacitance, something the PS itself can't deal with because it's too high and happening over a considerable length of wire. The "no more than three inches from the anode" rule of thumb is practically dogma.
Terry Bowman, KA4HJH
"The Mac Doctor"
"If only you could see what I've seen with your eyes."—Roy Batty, Blade Runner
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