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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 25th September 2017, 04:03 PM   #71
geraldfryjr is offline geraldfryjr  United States
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Join Date: Feb 2008
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Hi there!!

I have been really busy lately, but in the meantime I would like to share my latest DD design I did some time earlier this year in Circuit maker.
Of course like everything else I haven't the time to test it yet.

I do like this design as it features a voltage settable bias current, it is only for a 1kv supply but a pair of them this will provide up to 2kv p-p.
Once I test this I will work on stacking the FET's for a higher supply voltage and swing.

So, I post this here should anyone want to give it a go.
The sim's work Great!!

This version is just a single amp itself without a phase splitter.

The output is taking from the middle of the two FET's.
This is a working simulation rough draft so I don't have any sim data available at this time around.
I will post the CKT file and sim data if I can find it, else I will have to re draw it to produce them.
No biggy really, just extremely busy working on other stuff that must be done First.
It does not require any floating supplies like the Neil S. Mckean ESL amplifier found at TAC or high power resistors the top FET takes care of that..

Cheers !!


jer
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File Type: jpg eslamp.jpg (58.9 KB, 331 views)

Last edited by geraldfryjr; 25th September 2017 at 04:19 PM.
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Old 25th September 2017, 06:58 PM   #72
bentoronto is offline bentoronto  Canada
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Any Direct Drive ESL Amp projects someone could share?
Quote:
Originally Posted by geraldfryjr View Post
I am glad to see some pic's of your ole' DDAmp !!
Thanks, Gerald.

Here's some annotation to give prospective builders some perspective on the pieces needed, apropos post #46.

The amp weighs a lot. I brazed two steel chassis together to form a big one.

The 5 silver boxes in the back are HV oil-fills caps.

The B+ comes from two transformers, I think. There also are transformers for bias voltage, filaments, and transistor power. Hidden inside is a transformer for adjusting the speed/noise of the cooling fan which blows out of the little crack at the top front of the cabinet bottom box.

You can see the red test-lead HV wire. Spark plug wire works too. (For a tweeter with about 1200v bias, I used rather ordinary 15A flexible extension cord to the panels; so long as there's lots of rubber around the wires good for several meters.)

In the foreground, there is a large red resistor grounded at one end that is used for draining HV from any speaker-panel plugs removed from the chassis. Don't build without one.

At least in pre-web days, it was helpful to live in a big city with surplus electronics stores.

Ran this great amp for decades but it has been maybe 15 years since it moved on to other hands. Glad to answer any questions I can.

I remain convinced I never made more perfect ESL sound, luscious and transparent, than with DD.

B.
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Last edited by bentoronto; 25th September 2017 at 07:00 PM.
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Old 27th September 2017, 08:43 PM   #73
esl 63 is offline esl 63
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Old 5th November 2017, 07:56 PM   #74
fsrjd3 is offline fsrjd3  Ireland
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Default DD ESL amp

Here is a direct drive amp I designed. It works perfectly but sounds much more PP than Single Ended. I use it to drive two 3'x2' panels per channel spaced at 1/8" giving 1nF capacitance per channel.

It does not work as a direct drive as the bass volume is too low. I use an active third order crossing over at 200Hz.

It outputs 1040Vrms with a 1kHz sine wave before distortion sets in and the sine wave breaks up.

Playing the Eagles Hotel California and measuring the true rms value of the voltage and current and knowing the capacitance of the panel I was able to calculate an average frequency of 1.8kHZ. Obviously the higher the frequency of the music the more current is drawn
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Old 5th November 2017, 08:50 PM   #75
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by fsrjd3 View Post
It outputs 1040Vrms with a 1kHz sine wave before distortion sets in and the sine wave breaks up.
How is the sound level with this supply voltage? Does it play loud enough for you?

Jan
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Old 8th November 2017, 04:31 PM   #76
Discopete is offline Discopete  Canada
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Any Direct Drive ESL Amp projects someone could share?
Here's an interesting thread I'm waiting on to continue
Build me a ss direct drive ESL amp, please
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Old 9th November 2017, 10:46 PM   #77
esl 63 is offline esl 63
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Why solid state? Tubes and direct drive ESL is a perfect match.
My Beveridge is playing just awsome and you can see the schematics above nr:73
The tubes are dirt cheep and there is a lot of them... so what are you waiting for guys and girls?
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Old 9th November 2017, 11:47 PM   #78
Discopete is offline Discopete  Canada
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Any Direct Drive ESL Amp projects someone could share?
Quote:
Originally Posted by esl 63 View Post
Why solid state? Tubes and direct drive ESL is a perfect match.
My Beveridge is playing just awsome and you can see the schematics above nr:73
The tubes are dirt cheep and there is a lot of them... so what are you waiting for guys and girls?
Sure, but aren't you curious how they would compare? I have Acoustat Monitor 3 with DD OTLs and I also have Model 3 with interfaces coupled to either ss or tube. There is no comparison. The DD OTLs are far superior. I want to hear how DD ss compares to DD OTL. It seems this scenario is the final arbiter in regards to ss vs. tubes. It's the interface that's getting in the way.
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Old 10th November 2017, 09:38 PM   #79
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by esl 63 View Post
Why solid state? Tubes and direct drive ESL is a perfect match.
My Beveridge is playing just awsome and you can see the schematics above nr:73
The tubes are dirt cheep and there is a lot of them... so what are you waiting for guys and girls?
Hear, hear! They are definitely a good match for the output stage, like in your circuit. Beam tetrodes meant for TV line stages biased at a relatively low G2 voltage work fine there. Attached are the schematics of my variant, which was dreadfully inefficient and couldn't play loud enough, but sounded great. In retrospect I think I also should have used an SRPP-like output stage (far more efficient than what I used), and maybe a few transformer secondaries in series instead of the cascade for the high-voltage supply (would allow a much higher supply voltage - with a cascade the output resistance increases rapidly with the number of stages).
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File Type: pdf AMP.pdf (273.8 KB, 60 views)
File Type: pdf AmpSUPP.pdf (252.6 KB, 30 views)
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Old 11th November 2017, 05:32 AM   #80
kazap is offline kazap  Australia
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Quote:
Originally Posted by esl 63 View Post
Why solid state? Tubes and direct drive ESL is a perfect match.
My Beveridge is playing just awsome and you can see the schematics above nr:73
The tubes are dirt cheep and there is a lot of them... so what are you waiting for guys and girls?
Does the Modjeski direct drive amp use that circuit too?

Click the image to open in full size.

Output 4000 volts at 1/3 amps front to back electrode to electrode
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