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#1
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Hi group:
Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. RonL |
#2
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Yep:
That's where I'm kinda leaning toward a linear. No more power than I need (14VA) a conventional supply will be cheaper and a lot less headache. "Bret Ludwig" wrote in message ps.com... wrote: Hi group: Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. Commercial brick supplies can be used for tube HT and filament power but considerable attention has to be paid to shielding and filtering. The entire unit would need to be in a well secured shielded can and power brought out through feedthru caps. Even at today's low prices, a conventional power transformer and rectifiers and filter caps are cheaper. |
#4
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Ron wrote
Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. 12V at several amps shouldn't be a problem. You could then use an inverter and an LC filter for the HT. A long way round, but available. A purpose built, dual voltage, isolating switcher would take a bit of development to get quiet, safe and reliable, and through a heap of statutory approval procedures. Not a good bet for a market, either, considering a valve amp is never going to be very efficient. It's not surprising if you can't find one. I imagined rewinding computer PS transformers might be a popular entertainment, like hot-rodding microwaves or making jet engines from turbochargers. Can't find any aficionados though. cheers, Ian |
#5
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. ** Take a look at some schematics for 'scope power supplies - they have the ideas you need. Typically, the EHT and supply voltages for the deflection electronics are derived from a very simple, self oscillating * square wave inverter * running from a regulated 12 or 15 volt DC supply. Such an inverter uses a small ferrite transformer, two switching transistors, some fast rectifier diodes and low value filter caps - because a rectified square wave is nearly pure DC very little filtering is needed. Output voltage regulation is good because the DC input voltage is stiffly regulated. You can buy a low cost, consumer style SMPS that delivers regulated 12 volts DC at say 1.5 or 2 amps and use that as the basis of a fully switching PSU for your tube audio device. ........ Phil |
#6
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
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#7
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Patrick Turner wrote
I have been on the lookout for a SMPS for a tube amp capable of +500Vdc at 1 amp dc for larger style tubed power amps. I've never seen or heard of anyone doing a SMPS with that specification, and not seen any schematic for one that I could for build myself. I think you are the perfect candidate for the job. You have pretty much all the skills and instrumentation required. As with valve amps, the transformer is the crux of the matter. All the usual considerations apply, in order to ensure stability and avoid saturation. I got a book from Newnes called "Demystifying Switching Power Supplies", which probably contains all you need although the author isn't very good at writing books. Seems to me you could quite easily adapt a design for a forward converter. Just a matter of working out how to use more turns on a secondary for the HT, finding suitable output-side diodes and cap, scaling the voltage feedback, and reworking the feedback compensation circuit to suit. I gave up because simulation in this case takes much longer than making a real circuit, and isn't reliable anyway because the devils are in the small details of switching behaviour and parasitics. I don't have fast enough instrumentation to prototype for real and am too scared to attempt progress by successive approximation, given that every error is likely to lead to total carnage. cheers, Ian |
#8
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Ian Iveson wrote: Patrick Turner wrote I have been on the lookout for a SMPS for a tube amp capable of +500Vdc at 1 amp dc for larger style tubed power amps. I've never seen or heard of anyone doing a SMPS with that specification, and not seen any schematic for one that I could for build myself. I think you are the perfect candidate for the job. You have pretty much all the skills and instrumentation required. As with valve amps, the transformer is the crux of the matter. All the usual considerations apply, in order to ensure stability and avoid saturation. I got a book from Newnes called "Demystifying Switching Power Supplies", which probably contains all you need although the author isn't very good at writing books. Seems to me you could quite easily adapt a design for a forward converter. Just a matter of working out how to use more turns on a secondary for the HT, finding suitable output-side diodes and cap, scaling the voltage feedback, and reworking the feedback compensation circuit to suit. I gave up because simulation in this case takes much longer than making a real circuit, and isn't reliable anyway because the devils are in the small details of switching behaviour and parasitics. I don't have fast enough instrumentation to prototype for real and am too scared to attempt progress by successive approximation, given that every error is likely to lead to total carnage. cheers, Ian One would have thought someone somewhere would have tried to make a business making SMPS capable of HV or at least 500V, which is only 1/2 a thousand volts. But it doesn't look like it has happened so far, but nobody has ever addressed the design issues AND gone public about it all it seems, AND got public and hi-fi cognescenti acceptance for such a radical PS solution to make a PS for 600VA at about 6Kg instead of 26Kg. I might be able to do something like this but I always have so much to do I don't have a great deal of time to R&D from the ground up. One would think making a tranny that copes with switching a chopped +350V supply but gives a peak output voltage of 500Vdc instead of the usual 5 or 12V found in a PC would be doable, except that its all got to happen fast, so capacitance becomes a bother with such a wide V swing; However they used to use oscillating transistor PS in auto apps to get from +12V to about +350V for mobile radios. The switch speed has to be quick enough to get efficiency.... The old oscillators used for radios were not that efficient, but at least they were less likely to wear out like a vibrator supply. Patrick Turner. |
#9
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Patrick Turner wrote:
One would have thought someone somewhere would have tried to make a business making SMPS capable of HV or at least 500V, which is only 1/2 a thousand volts. In fact there are lots of businesses doing this, but they are making complexly synthesized voltages for large traction motors. Voltages are in the range you are talking about, but currents in the thousands of amps. Decades ago in fact they used tubes (thyristors, ignitrons). At the very low currents the OP was asking about, it is hard to justify a switcher when a small very-low-dollar 60Hz transformer does the job (e.g. the AES P-T442 sounds like a perfect match.) Tim. |
#10
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
If your input voltage is a car battery, like 13VDC, look at some of
those "inverter" AC supplies. Though they normally produce 120V AC square wave outputs, internally many are just really low DC to high DC converters that feed a set of switching fets or transistors to create the AC waveform. Remove these, and you would have 170VDC (if the inverter says it produces a "modified sine wave", which is just +- 170V with some dead time in between to make it the RMS equivalent of a real sine wave). |
#11
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Vicor has nice and small dc/dc converters 12V in to 95V out (adjustable).
http://www.vicr.com/documents/datasheets/ds_vi-j00.pdf. If you're lucky you can find these in machines at the scrap-metal yard. You could use 2 in series fed by the same 12V SMPS you use for the heaters. I plan a headphone amplifier with one or 2 of these modules. I tought 6N6 tubes might be OK. Some industrial laser printers use multi-output SMPS with e.g. 300V 0.3A output in addition to 12 and 24V and 5V adjustable as well, ideal for a tube amplifier. Internally 2 rectified secundaries are placed in series to make the 300V. I think finding efficiënt high speed HV diodes are the problem. The new SiC diodes might bring relief to that problem soon. Patrick schreef in bericht . .. Hi group: Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. RonL |
#12
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
On Thu, 30 Nov 2006 18:24:05 -0600, wrote:
Hi group: Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. RonL I once made a 2 transistor power oscillator, and wound the ferrite pot transformer myself. The collectors of the transistors feed an 8 turn CT winding, there is another "tickler" winding of maybe 12 turns, that feeds the bases... and a few bias resistors, and that's it. The secondary is a few hundred turns, with a small cap across it ( .01 or something) it created a "sine wave" output due to the resonance of the output "tank", and was around 250 volts if I remember correctly. The supply was 12vdc. It ran at 65KHz, and produced about 12 watts, enough for a portable amp. It didn't create any noise at all due to the "soft" wave output. (And it was in a VERY high gain circuit, 5mv input) There are DOZENS of variations around of this circuit. I can get you a schemo if it interests you. I'm going by memory of this circuit since I built it around 1985... The transistors were "junk" in TO3 cases. If you can build the tranny, you can build this circuit. |
#13
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
On Fri, 01 Dec 2006 15:18:55 GMT, Patrick Turner
wrote: Ian Iveson wrote: Patrick Turner wrote I have been on the lookout for a SMPS for a tube amp capable of +500Vdc at 1 amp dc for larger style tubed power amps. I've never seen or heard of anyone doing a SMPS with that specification, and not seen any schematic for one that I could for build myself. I think you are the perfect candidate for the job. You have pretty much all the skills and instrumentation required. As with valve amps, the transformer is the crux of the matter. All the usual considerations apply, in order to ensure stability and avoid saturation. I got a book from Newnes called "Demystifying Switching Power Supplies", which probably contains all you need although the author isn't very good at writing books. Seems to me you could quite easily adapt a design for a forward converter. Just a matter of working out how to use more turns on a secondary for the HT, finding suitable output-side diodes and cap, scaling the voltage feedback, and reworking the feedback compensation circuit to suit. I gave up because simulation in this case takes much longer than making a real circuit, and isn't reliable anyway because the devils are in the small details of switching behaviour and parasitics. I don't have fast enough instrumentation to prototype for real and am too scared to attempt progress by successive approximation, given that every error is likely to lead to total carnage. cheers, Ian One would have thought someone somewhere would have tried to make a business making SMPS capable of HV or at least 500V, which is only 1/2 a thousand volts. But it doesn't look like it has happened so far, but nobody has ever addressed the design issues AND gone public about it all it seems, AND got public and hi-fi cognescenti acceptance for such a radical PS solution to make a PS for 600VA at about 6Kg instead of 26Kg. I might be able to do something like this but I always have so much to do I don't have a great deal of time to R&D from the ground up. One would think making a tranny that copes with switching a chopped +350V supply but gives a peak output voltage of 500Vdc instead of the usual 5 or 12V found in a PC would be doable, except that its all got to happen fast, so capacitance becomes a bother with such a wide V swing; However they used to use oscillating transistor PS in auto apps to get from +12V to about +350V for mobile radios. The switch speed has to be quick enough to get efficiency.... The old oscillators used for radios were not that efficient, but at least they were less likely to wear out like a vibrator supply. Patrick Turner. There is a new type of supply on the market, and we have some of them to power our fiber equipment. The supply is feeding a bank of battery's, not sure of the voltage now but it's 48 or less, but the thing is, the voltage in the supply is around 450VDC! So why turn 120vac into 400vdc and then cut it to 36vdc? Its because of the fact that most power supply's take power from the AC only during the peak. The diodes in your supply only conduct when the voltage is higher at the input, right? This causes a flattening of the AC wave in large industrial areas. These new supply's are designed to take power from the leading and trailing edges of the incoming sine wave, and are actually shut down during the peak. So the 36 or 48 volts is obtained as the supply ramps up or down to the 400 volts, so the middle of the wave isn't flattened. There are some complicated switching chips and scr circuits in there - lots of custom chips. There is talk of these types of supply's being required in the future to protect the AC supply in the country. The power company may discount prices if you use this "non demand time" supply. As for me - I've got my eye on those 10,000uf 450vdc caps! Hey boss, I think we need some spare caps here... |
#14
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Hey
I would be interested in looking at that if you have it handy. RonL wrote in message ... On Thu, 30 Nov 2006 18:24:05 -0600, wrote: Hi group: Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. RonL I once made a 2 transistor power oscillator, and wound the ferrite pot transformer myself. The collectors of the transistors feed an 8 turn CT winding, there is another "tickler" winding of maybe 12 turns, that feeds the bases... and a few bias resistors, and that's it. The secondary is a few hundred turns, with a small cap across it ( .01 or something) it created a "sine wave" output due to the resonance of the output "tank", and was around 250 volts if I remember correctly. The supply was 12vdc. It ran at 65KHz, and produced about 12 watts, enough for a portable amp. It didn't create any noise at all due to the "soft" wave output. (And it was in a VERY high gain circuit, 5mv input) There are DOZENS of variations around of this circuit. I can get you a schemo if it interests you. I'm going by memory of this circuit since I built it around 1985... The transistors were "junk" in TO3 cases. If you can build the tranny, you can build this circuit. |
#16
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
On Sat, 2 Dec 2006 00:23:26 -0600, wrote:
Hey I would be interested in looking at that if you have it handy. RonL OK I dug up my circuit - it's pretty simple, I should be able to describe it to you... The transformer is one of those little ferrite jobs, with a small bobbin enclosed in 2 ferrite shells. It's about 1" round and 1" high. There are 3 windings in it, all are center tapped. The 2 transistors are NPN, I have no part numbers but you want something rated for higher frequencies than just audio. The emitters go through 3 ohm resistors to ground. The collectors go through a CT winding of 40 turns (so much for my memory!) and the CT goes to 12v+. There is a .047 cap across this winding. The bases connect to an 8 turn winding, whose CT goes to a 100k pot... this pot is across 12v+ and ground, and was used to set the bias for proper operation. Once you get it working you can measure the pot and use fixed resistors. The output winding will be as many turns as you need voltage, mine was a few hundred, and it had a .001 cap across it. I found the schemagic of the circuit I used for the design, I'll post it on one of the electronic binary groups... look for me! You can use this circuit for lots of things... the original was 100 watts! Note the original was 3.5khz, I changed it to 65k so you can't hear it... wrote in message .. . On Thu, 30 Nov 2006 18:24:05 -0600, wrote: Hi group: Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. RonL I once made a 2 transistor power oscillator, and wound the ferrite pot transformer myself. The collectors of the transistors feed an 8 turn CT winding, there is another "tickler" winding of maybe 12 turns, that feeds the bases... and a few bias resistors, and that's it. The secondary is a few hundred turns, with a small cap across it ( .01 or something) it created a "sine wave" output due to the resonance of the output "tank", and was around 250 volts if I remember correctly. The supply was 12vdc. It ran at 65KHz, and produced about 12 watts, enough for a portable amp. It didn't create any noise at all due to the "soft" wave output. (And it was in a VERY high gain circuit, 5mv input) There are DOZENS of variations around of this circuit. I can get you a schemo if it interests you. I'm going by memory of this circuit since I built it around 1985... The transistors were "junk" in TO3 cases. If you can build the tranny, you can build this circuit. |
#17
Posted to rec.audio.tubes
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Hi Voltage switcher for audio.
Hey Thanks Bob!
I got it. I'll build this up and play around with it. wrote in message ... On Sat, 2 Dec 2006 00:23:26 -0600, wrote: Hey I would be interested in looking at that if you have it handy. RonL OK I dug up my circuit - it's pretty simple, I should be able to describe it to you... The transformer is one of those little ferrite jobs, with a small bobbin enclosed in 2 ferrite shells. It's about 1" round and 1" high. There are 3 windings in it, all are center tapped. The 2 transistors are NPN, I have no part numbers but you want something rated for higher frequencies than just audio. The emitters go through 3 ohm resistors to ground. The collectors go through a CT winding of 40 turns (so much for my memory!) and the CT goes to 12v+. There is a .047 cap across this winding. The bases connect to an 8 turn winding, whose CT goes to a 100k pot... this pot is across 12v+ and ground, and was used to set the bias for proper operation. Once you get it working you can measure the pot and use fixed resistors. The output winding will be as many turns as you need voltage, mine was a few hundred, and it had a .001 cap across it. I found the schemagic of the circuit I used for the design, I'll post it on one of the electronic binary groups... look for me! You can use this circuit for lots of things... the original was 100 watts! Note the original was 3.5khz, I changed it to 65k so you can't hear it... wrote in message . .. On Thu, 30 Nov 2006 18:24:05 -0600, wrote: Hi group: Has anyone in the group found a switcher good enough for high voltage (180 VDC), low current (.010 amps) audio use. When I say good enough, I'm referring to noise and EMI. I've been looking at LT, National and power integrations but haven't found anything yet. I also need 12V @1.0 amp for filaments. Any ideas appreciated. RonL I once made a 2 transistor power oscillator, and wound the ferrite pot transformer myself. The collectors of the transistors feed an 8 turn CT winding, there is another "tickler" winding of maybe 12 turns, that feeds the bases... and a few bias resistors, and that's it. The secondary is a few hundred turns, with a small cap across it ( .01 or something) it created a "sine wave" output due to the resonance of the output "tank", and was around 250 volts if I remember correctly. The supply was 12vdc. It ran at 65KHz, and produced about 12 watts, enough for a portable amp. It didn't create any noise at all due to the "soft" wave output. (And it was in a VERY high gain circuit, 5mv input) There are DOZENS of variations around of this circuit. I can get you a schemo if it interests you. I'm going by memory of this circuit since I built it around 1985... The transistors were "junk" in TO3 cases. If you can build the tranny, you can build this circuit. |
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