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Default 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


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Ian Iveson Ian Iveson is offline
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Default 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


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Phil Allison Phil Allison is offline
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Default 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






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Patrick Turner Patrick Turner is offline
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Default Hi Voltage switcher for audio.



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 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.

Phil says follow the lead of what is done in CRO PS but then they are
low power output type supplies where the voltage is more important than
having any current ability.

Halcro of South Australia make fabulous solid state amps capable of
200 watts into 8 ohms and they use SMPS which are well filtered and
shielded or course,
and such techniques have been routine in TV sets and many apps for maybe
20 years,
so much so that the SMPS is a lot cheaper and lighter to carry than a
heavy
linear PS with a massive tranny, even if its a toroidal type.

Perhaps doing a SMPS for +1,100V B+ and -200V for the bias B- for
an SET 845 based amp may present problems, but then problems are there
to be overcome,
and so just why not have SMPS for high powered tube audio??

No need to tell me about filtering and casework; I know that has to be
good,
but what about an actual schematic with full specification of parts
including
recipe for the HF tranny??

I suppose someone is going to say well why use tubes
when solid state and low voltages are so much easier.
My answer in advance is that such recommendations will
never be adopted on a tube discussion group, and we would still want
to know how to do a HV SMPS.

Patrick Turner.
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Ian Iveson Ian Iveson is offline
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Posts: 960
Default 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


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Patrick Turner Patrick Turner is offline
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Posts: 3,964
Default 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.
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[email protected] shoppa@trailing-edge.com is offline
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Posts: 56
Default 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.

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robert casey robert casey is offline
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Posts: 340
Default 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).


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Patrick Patrick is offline
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Posts: 16
Default 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



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[email protected] BobF@nospamno.com is offline
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Posts: 3
Default 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   Report Post  
Posted to rec.audio.tubes
[email protected] BobF@nospamno.com is offline
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Posts: 3
Default 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   Report Post  
Posted to rec.audio.tubes
 
Posts: n/a
Default 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   Report Post  
Posted to rec.audio.tubes
[email protected] BobF@nospamno.com is offline
external usenet poster
 
Posts: 3
Default 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   Report Post  
Posted to rec.audio.tubes
 
Posts: n/a
Default 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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