Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Build me a ss direct drive ESL amp, please
Build me a ss direct drive ESL amp, please
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th November 2017, 06:35 AM   #51
kazap is offline kazap  Australia
diyAudio Member
 
kazap's Avatar
 
Join Date: Apr 2011
Location: Brisbane
Quote:
Originally Posted by Nelson Pass View Post
Broskie's second offering points out the crucial thing - you want to make
SS do audio at these voltages, you must cascode the devices.

Been there, and it's the only way.......
Thanks.

I wonder what voltage the MOSFET's were rated for back then?

If the 4,500V IXYS MOSFETs were around back in the day would you have tried them to avoid cascodes?
  Reply With Quote
Old 16th November 2017, 03:03 PM   #52
nauta is offline nauta  Canada
diyAudio Member
 
Join Date: Sep 2017
Hi Guys

I believe the ESLs look much like a 1nF cap, which at 20kHz looks like about 8k-ohm. This might be an acceptable approximation for steady-ish signals, but a fast transient would be more like the charging surge for a power supply cap - essentially unlimited current for a brief instant.

I've seen some ESLs that are unipolar and others bipolar, meaning that there is either one driven plane or two (stators), kind of like a giant ESL head-phone. The bipolar drive is lower distortion and allows the drive signals to be half the amplitude which in turn relaxes some of the requirement. As others have requested, the actual drive voltage needed at the stator(s) would be good information. Otherwise, one is designing blind and possibly going to greater extremes than needed.

So, if you were to use those 4500V mosfets in a totem pole and assume that 2kVp is fine, the 8k-ohm approximation suggests a peak current of 250mA. This does not occur at the voltage peak, rather at zero-cross, so the output devices must be burly and have good heat sinking. Fortunately, the power profile of music falls off towards the 20kHz and the extreme loading on the driver is greatly reduced. It is a POWER amplifier despite driving a nearly pure capacitance.

The SE drivers made for ESL head-phones tend to be majorly compromised THD-wise, with the only benefit being a simple circuit where only the output device sees high voltage.Having true push-pull drive for each stator, as Elvee's circuit does, is a better way to achieve distortion from the amp that is lower than the ESL THD.

Much is said about the EQ of the ESL panels. I think the Quad ESL-63 is still the best-sounding of all ESLs offered and its schematic is not simple. The panel is split into sections with the signal delayed into the sections to create a point-source-like output. The intent was for maximum fidelity at the expense of high loudness - so these sound very good at Human Scale listening levels. The usual single-panel hobbyist units and similar offered by current manufacturers have a critically smaller sweet-spot for the listener, which to me a major flaw with ESLs. EQing cannot "correct" this but can improve the listening experience a small way.

This direct-drive amp absolutely must be built into the case of the speaker itself just for safety purposes already detailed by others.
  Reply With Quote
Old 8th December 2017, 10:02 AM   #53
MrMagic is offline MrMagic  Greece
diyAudio Member
 
MrMagic's Avatar
 
Join Date: Nov 2017
Location: Athens
Quote:
Originally Posted by bentoronto View Post
Juma, post 5, laid out the liability issues for a person to make a black-box for you that could kill you, your dog, or your kids*, whether or not there are cables across your living room floor and/or whether or not they did it turn-key as a single integrated package with the speakers and/or you signed something that provided the false illusion of a legal release.

B.
*I assume you would turn the amp off once it killed your dog or kids and so no need to say "dogs and/or kids...."** Likewise, I assume your estate would likewise protect your dog after your death.

** I am further assuming your kids are not holding your dog at the time of their joint electrocution nor that the dog was holding your kids; please correct me of those are gratuitous assumptions.
Part of the design is and should always be safety measures. All of us are surrounded by dangerous devices -from the microwave oven to a simple floor lamp (that a dog could chew the cable and die instantly), to deadly cars running on the streets (that can also kill a dog or human) and even dangerous helicopters and planes flying on the sky. What keeps as safe is obviously safety measures, and even if we abandon all technology we'll have to face other dangers.

Likewise, you can properly design a DD ESL so that despite the 10KV on the panel, it won't be dangerous at all, to neither kids or dogs.

For maximum safety:
1) Like others have said, completely enclose the amp and cables.
2) Drive the DD panel diferentially so that no DC power supply voltage is applied (the (AC) voltage should only be proportional to the music volume).
3) Put grounded shields on the front and back of the panel, so that (even) touching the shield should be absolutely safe.
4) Put a tough fabric cover (difficult to remove) that will provide an added safe distance from the (shielded) panel.
5) Mount a weight at the base to significantly lower the center of gravity (one or more cheap bodybuilding disks) that along with the extended base design and the addition of soft wheels, will make it impossible to flip over. I personally do that to all my DIY loudspeaker and speaker stands to make them "earthquake-proof".
6) Make the ESL impossible to turn on by anyone else except yourself. There are many easy ways to do that nowadays.

Then you can bet that it will be far more safer and worry-free than your hair dryer.
  Reply With Quote
Old 8th December 2017, 11:35 AM   #54
MrMagic is offline MrMagic  Greece
diyAudio Member
 
MrMagic's Avatar
 
Join Date: Nov 2017
Location: Athens
doublepost(sorry)
  Reply With Quote
Old 8th December 2017, 02:20 PM   #55
bentoronto is offline bentoronto  Canada
diyAudio Member
 
Join Date: Jan 2008
Location: Toronto and Delray Beach, FL
Build me a ss direct drive ESL amp, please
Quote:
Originally Posted by MrMagic View Post
Part of the design is and should always be safety measures.
You seem to require some education in what legal liability entails. And how you protect your back.* Actually, anybody who builds such a device for you needs that education more.

B.
*Forget about it: you can't protect your back apriori. The only place you have wilder wannabee-professional fantasies than law, is DIYaudio with engineering.
__________________
HiFi aspirations since 1957. Currently working on motional feedback again... the final frontier in audio (and just posted data for a folded 17-foot pipe sub)
  Reply With Quote
Old 8th December 2017, 03:53 PM   #56
MrMagic is offline MrMagic  Greece
diyAudio Member
 
MrMagic's Avatar
 
Join Date: Nov 2017
Location: Athens
Quote:
Originally Posted by bentoronto View Post
You seem to require some education in what legal liability entails.
I wouldn't make a high voltage DIY one for anyone if you ask me, no matter how safe -unless I had a company.

I merely stated what measures would make it safe, really safe, implying that DD ESL's can be made completely harmless.
  Reply With Quote
Old 13th December 2017, 10:26 PM   #57
Discopete is offline Discopete  Canada
diyAudio Member
 
Join Date: Nov 2009
Build me a ss direct drive ESL amp, please
BUMP. Okay, so who's gonna step up and give this numpty a price tag? Sheesh!
All things considered, parameters discovered, albeit I want a bandwidth to at least 20khz. Come on, you can't not be interested in this. Seriously
  Reply With Quote
Old 3rd January 2018, 08:52 AM   #58
padamiecki is offline padamiecki  Poland
diyAudio Member
 
Join Date: Mar 2004
Location: Krakow
Hi!
John is the guy: http://www.tubecad.com/2018/01/01/Cl...rs%20Large.png
__________________
regards, Pawel
  Reply With Quote
Old 3rd January 2018, 06:22 PM   #59
Discopete is offline Discopete  Canada
diyAudio Member
 
Join Date: Nov 2009
Build me a ss direct drive ESL amp, please
Thanks. But I want the ss version.
  Reply With Quote
Old 3rd January 2018, 09:31 PM   #60
akimmet is offline akimmet  United States
diyAudio Member
 
Join Date: Jul 2011
Location: NW Ohio
The schematic from tubecad.com is solid state, you must have confused the output MOSFETs for tubes.
Some quick searching shows the full article is at: Digital Electrostatic Loudspeakers & More Direct Drive Amplifiers
  Reply With Quote

Reply


Build me a ss direct drive ESL amp, pleaseHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Direct Drive DSD acko Group Buys 552 10th December 2016 01:18 AM
WTB : Direct Drive Standalone TT Drive Razorblade Swap Meet 0 2nd January 2011 05:22 PM
Direct Drive fun!!! Cobra2 Analogue Source 32 20th January 2007 02:23 AM
Another direct drive thread maudio Planars & Exotics 18 25th June 2006 06:53 PM


New To Site? Need Help?

All times are GMT. The time now is 03:24 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki