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Any Direct Drive ESL Amp projects someone could share?
Any Direct Drive ESL Amp projects someone could share?
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Old 23rd March 2016, 09:36 PM   #1
Penguin87 is offline Penguin87  United States
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Default Any Direct Drive ESL Amp projects someone could share?

There have been a few Direct Drive ESL Amp forays on this forum, but no completed projects posted. I am not interested in headphone ESL Amps.

Has anyone completed Neil S. McKean's ESL Amplifier?

If so, what power supply was used? Or where did you source one?

Were there any boards made for it?

Anyone update it?

Any other designs?

I understand that I am the beggar here, but if someone has made one, or another one, your experience posted here would be very helpful. If this should be in the amplifier section I am happy to move there.

Last edited by Penguin87; 23rd March 2016 at 09:38 PM. Reason: clarification
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Old 23rd March 2016, 10:54 PM   #2
bentoronto is offline bentoronto  Canada
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Any Direct Drive ESL Amp projects someone could share?
I am absolutely sure it provides the best sound you can have. I built a Sanders-like amp maybe 25 years ago and used it very happily for maybe 15 yrs with hardly a hiccough all that time (all rough memories). Drove both Dayton-Wright XG-10s and DIY DW panels with XG8 cells. Sold it when downsizing.

Helps a lot to have a big, dusty, surplus electronics souk in your town.

Dangerous... part of the thrill, eh.

2400v B+ wired direct to panels (and negative voltage bias, of course), inductance filtered and big oil capacitors. 8068 tubes???. Ran a large bank of resistors as the effective load so the panels were hardly noticed by the amp circuit.

Keep the thread here.

Ben
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Last edited by bentoronto; 23rd March 2016 at 10:59 PM.
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Old 24th March 2016, 02:37 AM   #3
Penguin87 is offline Penguin87  United States
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regarding the "danger." I was planning on marrying the amplifier (mono channels) into my Hybrid ESL design in order to prevent some of that danger. Of course that won't prevent any problems during the build (and test) of the amp itself, but at least the hookup from the pre-amp to the amp should be safe (right?).

Are you familiar with McKean's amp?

For as widely a distributed design as it is, I am surprised there hasn't been project to follow on it. I'd put up some money for someone to seriously detail (and maybe improve it some) a build.
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Old 24th March 2016, 05:00 AM   #4
Calvin is offline Calvin  Germany
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Hi,

I assume most have been put off of such a project the moment they figured how much wattage be needed to drive a panel properly.
Also the amplifier would rather be a a specific design for a specific panel.
For non-segmented panels the voltage requirements may be lower while the current requirements are higher than for segmented panels.
If You wanted to design for a full power bandwidth of only 20kHz, a amp for a non-segmented (hybrid) panel would already waste more than 1kW of power.
Reducing the full power bandwidth requirement also reduces the wattage requirement, but shares the risk of current clipping ... the risk of not beeing able to drive the panel under all circumstances.
Segmented panels though requiring more voltage are easier to deal with.
The amp would probabely rather run into voltage clipping, but the lower current requirement and the panel's lower impedance variation let a amp project look more doable.
Still though such an amp would be ridicolously inefficient.

jauu
Calvin
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Old 24th March 2016, 05:07 AM   #5
geraldfryjr is offline geraldfryjr  United States
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I was just cheking out some 500watt 4500v FET's from IXYS last night !!!
They are about $30-$40 at Digikey.

http://www.mouser.com/ProductDetail/...kJ5XxPqQ%3d%3d

IXTH1N450HV
http://www.mouser.com/ds/2/205/Viewer-765421.pdf
ciss=1700pf
coss=80pf

Not bad, I think that they would be workable for audio just fine.

http://www.ixys.com/ProductPortfolio...yInfo.aspx?i=2

Jer

Last edited by geraldfryjr; 24th March 2016 at 05:15 AM.
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Old 24th March 2016, 03:13 PM   #6
alexberg is offline alexberg
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It shows 0 on stock avail...
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Old 24th March 2016, 08:50 PM   #7
geraldfryjr is offline geraldfryjr  United States
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Posted the the Mouser links for the data but Digikey does have them for $37 for one.

FETs - Single | Discrete Semiconductor Products | DigiKey

jer

Last edited by geraldfryjr; 24th March 2016 at 08:53 PM.
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Old 24th March 2016, 10:50 PM   #8
bentoronto is offline bentoronto  Canada
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Any Direct Drive ESL Amp projects someone could share?
I looked for solid state outputs but none available at the time.

With tubes with plate caps on top, the high voltage wires are patently obvious and floating in the air. Also, I suspect tubes have a more benign failure mode than a solid-state device and fairly robust.

Not a lot of extra fuss using tubes (if you know where to buy tube sockets), just heater power and a few little things.

Maybe those are not strong enough reasons to go to old fashioned 8068 tubes, but just saying'.

Ben
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Old 25th March 2016, 03:17 AM   #9
Penguin87 is offline Penguin87  United States
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I am able to understand the value of those FETs, but designing an amp is really beyond my ability.

I noticed that even Nelson Pass has mused on such an idea in the past. I don't know if a donation toward a build could entice him (or someone else).

Even if I never build such an amp (though I really want to), I absolutely love learning about audio. I have enjoyed reading all the content here. It has led to a line array, and two small projects for my teens. An ESL build is in the planning now.

Thanks for the comments. I will just keep watching for a build.
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Old 25th March 2016, 06:56 AM   #10
MyOCD is offline MyOCD
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I'm still in the "considering different approaches" phase of an ESL/Amp design. I've noticed that there are two camps, the most prolific topology uses a standard audio amp driving a 1:50 to 1:100 step up transformer. And then there is the pure direct drive that uses tubes.

Both of those approaches have serious design challenges. I'm concluding that something in between might be the best choice. I think it is possible to design a class d amp using 1200 volt silicon carbide FETs. They are very fast with a low gate charge. Running them at around 900v should provide enough margin. This means that one only needs a 1:3 to 1:6 transformer ratio to reach the same ESL drive levels.

A lower ratio gets the amp "closer" to the ESL load and should facilitate tighter control of the membrane. I'm no transformer design guru, but I'm pretty sure that a 1:6 transformer is a lot easier to design than a 1:100 with equivalent power-bandwidth. Of course, the class d has to be done right with feedback, but D's can be very low noise, low distortion, highly efficient, and they don't mind driving a complex load.

I really hope I follow through on this project and not lose interest once I figure it out. I'll be sure to post some details, but it will be a while. I haven't searched this forum for a similar configuration, so it wouldn't surprise me a bit if someone has already done it.
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