Can anybody give me some info on voltage doubler power supplies? I thumbed through a bunch of amp schematics, and I don't think I saw any that used a voltage doubler.
Reason I ask is I have an old junked Drake power supply (ham radio type of thing - model AC-4), and the transformer is still good. But it has no center taps on the windings, so I would be forced to use either a half wave rectifier or a voltage doubler. The original AC-4 schematic shows it used as a voltage doubler to give about 600 VDC for radio transmitter tubes.
It's a nice transformer. It has 2 separate B+ windings, plus a separate winding for a bias supply and a 12 V filament winding (Drake used an artificial CT to get 6.3 volts, apparently). I was thinking of building it into a general purpose power supply for testing tubes, etc. It would proabably also be fine for a guitar amp. Not sure how well suited a half wave rectifier would be for an audio amp where we want to avoid hum - maybe that is why I don't see any guitar amp schematics with them.
I'm guessing that doubling the voltage comes at the expense of halving the current?
Voltage Doublers
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Voltage Doublers
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Re: Voltage Doublers
boots wrote:Can anybody give me some info on voltage doubler power supplies? I thumbed through a bunch of amp schematics, and I don't think I saw any that used a voltage doubler.
Reason I ask is I have an old junked Drake power supply (ham radio type of thing - model AC-4), and the transformer is still good. But it has no center taps on the windings, so I would be forced to use either a half wave rectifier or a voltage doubler. The original AC-4 schematic shows it used as a voltage doubler to give about 600 VDC for radio transmitter tubes.
It's a nice transformer. It has 2 separate B+ windings, plus a separate winding for a bias supply and a 12 V filament winding (Drake used an artificial CT to get 6.3 volts, apparently). I was thinking of building it into a general purpose power supply for testing tubes, etc. It would proabably also be fine for a guitar amp. Not sure how well suited a half wave rectifier would be for an audio amp where we want to avoid hum - maybe that is why I don't see any guitar amp schematics with them.
I'm guessing that doubling the voltage comes at the expense of halving the current?
MusicMan high plate voltage amps used a doubler supply and yes they require a winding with a higher HT rating. For example, the MM PT is anywhere from around 700mA to 1A depending upon the model.
TM
Re: Voltage Doublers
Even the 50W MusicMan with 'only' 585V on the plates is a doubler supply.
I think there was a Silvertone that used a quadrupler, maybe the 1484 ?
The doubler supply can give a bit more sag than a full wave or full wave bridge solid-state diode design.
rd
I think there was a Silvertone that used a quadrupler, maybe the 1484 ?
The doubler supply can give a bit more sag than a full wave or full wave bridge solid-state diode design.
rd
Re: Voltage Doublers
That is a serious hunk of iron! The manual says it does 650VDC @ 300mA from one winding, 250VDC @ 175mA from the other (both with doublers) and it has a separate bias winding, plus the 12.6VAC 5.5A heater winding. You don't necessarily have to double the output. A straight full-wave bridge off the big winding should give you 325VDC @ 600mA; you can use the doubled 250VDC as a screen supply. If you wanted to use conventional tubes, you could run 12A?7 types in parallel off the 12.6VAC heater winding and run a couple of 6V output tubes in series.
Re: Voltage Doublers
IIRC, the lower high voltage scheme uses the PT thats 680mA.rdjones wrote:Even the 50W MusicMan with 'only' 585V on the plates is a doubler supply.
rd
TM
Re: Voltage Doublers
Drake equipment is fairly well regarded is ham radio circles (or at least it was back in the day).
I wonder if it might be better to salvage it back into ham use than to re-purpose it.
It would make a killer bass amp if done right with a proper OT.
rd
I wonder if it might be better to salvage it back into ham use than to re-purpose it.
It would make a killer bass amp if done right with a proper OT.
rd
Re: Voltage Doublers
Only half wave? No CT works fine in a full wave bridge. With cap input, you will get 1.4x and sacrifice some current. www.hammondmfg.com/pdf/5c007.pdf
With a Greinacher doubler you will get 2.8x
http://www.kronjaeger.com/hv/hv/src/mul/
With a Greinacher doubler you will get 2.8x
http://www.kronjaeger.com/hv/hv/src/mul/
Re: Voltage Doublers
Phil, I thought you had to have a CT in order to do a full-wave bridge? Maybe I better review the books tonight....
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Re: Voltage Doublers
Well, I guess not, according to that Hammond link!
Somewhere along the line I picked up the notion that doublers were a hokey thing. I will probably see what I can do with a full wave bridge.
Somewhere along the line I picked up the notion that doublers were a hokey thing. I will probably see what I can do with a full wave bridge.
Don't you boys know any NICE songs?
Re: Voltage Doublers
Doublers, quaduplers and even hextuplers work really well if they're done right. Valve recto sag without the valve recto. But in your case it should be good with just a SS bridge.
Re: Voltage Doublers
LOL! I don't need a CT, maybe you do? Jokes aside, it won't work with a CT. If your PT has one, you don't use it with a FWB. Look at the diagram. The FWB makes it's own faux CT that is grounded.boots wrote:Phil, I thought you had to have a CT in order to do a full-wave bridge? Maybe I better review the books tonight....
Re: Voltage Doublers
Schematic in (new) attachment in next postboots wrote:Can anybody give me some info on voltage doubler power supplies? I thumbed through a bunch of amp schematics, and I don't think I saw any that used a voltage doubler.
Last edited by tubeswell on Thu Feb 28, 2013 11:25 am, edited 1 time in total.
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Re: Voltage Doublers
Tubeswell, in you tripler supply the diodes are reversed. Also note that there are half-wave (as shown), and full-wave doublers.
Re: Voltage Doublers
I know peavey used some PT's In FWB Configuration that had Centre taps (not coneccted obviously).
I know if You use a tradtional full wave rectifier with the CT it will be aprox half the voltage.But will the amount of current the PT is able to supply stay the same?
I know if You use a tradtional full wave rectifier with the CT it will be aprox half the voltage.But will the amount of current the PT is able to supply stay the same?
Re: Voltage Doublers
I'm an extra class Ham since 1983. Drake stuff from that era was pretty well built and used good components. Their iron was generally made by Cin-Tran, who is also a Dr. Z supplier. I love to see old Ham gear restored and used, but re-purposing an AC-4 really doesn't give me much pause.
As far as voltage doublers go, see the ARRL handbook or Merlin's power supply book for more information. They work OK, but the load regulation isn't as good as a normal full-wave power supply (as others mentioned, they can sag a bit). Good low-ESR caps are essential. That said, one of my favorite HiFi amps, the Fisher 500c, uses a doubler and sounds fantastic (it has been re-capped). The bass is surprisngly solid; much better than my Dyna ST-70.
As far as voltage doublers go, see the ARRL handbook or Merlin's power supply book for more information. They work OK, but the load regulation isn't as good as a normal full-wave power supply (as others mentioned, they can sag a bit). Good low-ESR caps are essential. That said, one of my favorite HiFi amps, the Fisher 500c, uses a doubler and sounds fantastic (it has been re-capped). The bass is surprisngly solid; much better than my Dyna ST-70.