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Old 19th January 2016, 06:04 AM   #1
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Default Economic driving of an ESL?

Hey guys,
I have been navigating around for minimal methods for driving Electrostatic Panels. Minimal as in minimal parts count, not so much cost.

I have been toying between direct drive methods and transformer methods.
Also toying with what is the 'safer' of the two operations.

I have the assumption that kv power supplies are more dangerous than output transformer trickery. The downside with output transformers is possible capacitance and frequency response issues.

I was kind of envisioning using around a 500v supply and some KT88's in a push pull configuration with some transformers to make an easier design.

A major question I had was;
Is it reasonable to do a step up 1:4 or so? (being that I can get a transformer custom wound) to take 500v swings to 2000v swings? Without suffering too much performance.

I don't plan on cranking the volume very high, and figured a 50W design with a 1:1 transformer would suffice for most of my regular listening at 10 feet away...

or am I wasting my time with iron?

Click the image to open in full size.

Last edited by woodrough; 19th January 2016 at 06:09 AM.
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Old 19th January 2016, 06:34 AM   #2
WrineX is offline WrineX  Netherlands
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if you can get an amplifier to output 500 volt a 1:4 will work like a charm. direct drive esl's are still far far away. unless you talk about using tubes


still not seen any direct drive class D for instance

Last edited by WrineX; 19th January 2016 at 06:37 AM.
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Old 27th January 2016, 10:40 PM   #3
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Ok cool thanks for the thought.
I thought about transformers and electrostatics and constrained myself to the economic off the shelf Antek toroidal transformers. I wanted to maintain the UL taps in a typical output transformer by using the "distributed network" approach to iron.

I compromised lightly by making the taps 50% to break up a single channels output to two series transformers. The overall ratio linked together is about 1:3

Using the Monobill design, with a 1:3 step-up to drive Electrostatic panels.

Using the graphic I uploaded bellow;
-does this approach look feasible for ESL's?
-Does this high value loading resistor mean anything concerning for me?
-Also what is the purpose of a shunt capacitor (as seen in other designs)


Click the image to open in full size.
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Old 29th January 2016, 09:51 PM   #4
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Maybe this diagram will be clarifying for what crazy thing im planning on:

Click the image to open in full size.

two in one transformer! Has anyone done this before?
what about loading resistor values?

I have a similar transformer from Antek on my desk and I measured one of the 115V windings and it read about 10Hy.
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Old 31st January 2016, 02:14 AM   #5
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This was the amp with the double transformer set up
Click the image to open in full size.

And a weird thought I had was what if I were to take advantage of the 6.3V windings to run regular speakers as well.
An all purpose PushPull amplifier set up using economic power supply transformers?
That could drive ESL's or 8ohm speaker cones?
Click the image to open in full size.
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Old 31st January 2016, 08:57 AM   #6
Calvin is offline Calvin  Germany
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Hi,

Quote:
if you can get an amplifier to output 500 volt a 1:4 will work like a charm.
This only holds true, if the amps output impedance is low, like with solidstate emitter-follower output stages.
Itīs not the case when the transformer sees a source impedance of several hundreds or thousands of Ohm.
Itīd require a special winding of the transformer with loads of turns.
Then Youīre getting probs with capacitances etc etc.
Many thought of that idea before, but I donīt know of one single successfull implementation (especially not for fullrange useage).
But then .. what do I know? ... maybe someone comes up with the ultimate catch22

jauu
Calvin
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Old 31st January 2016, 10:51 AM   #7
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Designing high voltage high bandwidth high quality x-former is not that easy. I wish arranging low cost halogen lamp x-formers would be the way to go. Pentode output stage behaves like a current source requiring huge primary inductance at lower frequencies.

Last edited by alexberg; 31st January 2016 at 10:56 AM.
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Old 31st January 2016, 07:03 PM   #8
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ohh dang, I forgot about that part.

My assumption was that the backwards output transformer to simulate a step up worked with solid state AND tube amplifiers.

and my belief was that 'if so', then why not eliminate the extra parts (with a tube design)

[being that with tube amps, the step up transformer ultimately turns the set up into a 1:1]

Click the image to open in full size.

So that means if anyone is using the step up transformer approach With vacuum tubes WITH loudspeakers (Not headphones), they are inherently limiting high freq response because vacuum tubes (as a source) has way higher impedance than the output. right?

or is that negligible when not blasting... Im curious about this threshold of ESL capable and not capable.

Last edited by woodrough; 31st January 2016 at 07:10 PM.
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Old 31st January 2016, 10:35 PM   #9
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Also extra thought: since I'm not necessarily married to tubes either,
what is stopping people from using D-class amplifier that can efficiently dump hundreds of watts? Ive heard debates about it but never had a clear answer on why.

but dang they are cheap! (for 100W per channel)

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Old 31st January 2016, 10:49 PM   #10
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Quote:
Originally Posted by woodrough View Post
...
what is stopping people from using D-class amplifier that can efficiently dump hundreds of watts?
One of the biggest issues is that many(most?) class-D amps have a frequency response that is highly dependent on the load they are driving.
For example, I posted some measurements here:
Behringer iNuke NU3000 Measurements

That being said, my current favorite amplifier for driving ESLs uses Hypex modules which don't have the issue mentioned above.
In fact, they are less affected by load impedance than most analog amplifiers.
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