If you’re happy with 10 watts now, and then you replaced the step-down/step-up pair with one step-up transformer with the same equivalent turns ratio, you’d still be happy with 10watts. In general, most ESLs with their step-up transformers have about the same *sensitivity* as cone speakers. (ESLs are usually way more *efficient* watt for watt, but that’s not counting reactive VA, another story.) My Quads make around 86dB SPL at 1kHz at one meter at 2.83 V rms (equivalent to 1 watt into 8 ohms). This is average for cone speakers.
To “Hermanv”, if you drive a capacitor with a current source you get an integrator, which has a 6 dB per octave downward slope from very low frequencies all the way to the highest frequencies. Maybe not what you want, but your point of voicing an ESL with a series R is potentially useful to counteract directivity gains.
To “Hermanv”, if you drive a capacitor with a current source you get an integrator, which has a 6 dB per octave downward slope from very low frequencies all the way to the highest frequencies. Maybe not what you want, but your point of voicing an ESL with a series R is potentially useful to counteract directivity gains.
That was exactly my intent.
As I proposed, the accoustic power ouput, all else being equal, should rise 6 db per octave if driven with a voltage source, if the integrator drops 6 dB per octave you end up with a flat response
I know its not that simple. ESL panels have resonances resulting in peaks and valleys. Some are a series of different size panels in parallel partially to spread out those resonances. Film tension and total area enter the equation. As must conductivity of the conductive coating and the holes, slits or vents needed in the stators
At some point the wavelength exceeds the membrane width so you get roll-off at low frequencies etc..
Just musing out loud.
As I proposed, the accoustic power ouput, all else being equal, should rise 6 db per octave if driven with a voltage source, if the integrator drops 6 dB per octave you end up with a flat response
I know its not that simple. ESL panels have resonances resulting in peaks and valleys. Some are a series of different size panels in parallel partially to spread out those resonances. Film tension and total area enter the equation. As must conductivity of the conductive coating and the holes, slits or vents needed in the stators
At some point the wavelength exceeds the membrane width so you get roll-off at low frequencies etc..
Just musing out loud.
AudioExclusiv
Hi,
The AE´s come in passive and active versions.
The active version utilzes an amplifier that is nearly an exact copy of the Strickland amp. Using the same design, same transistors and Tubes (6HB5, to my knowledge a relatively unstable guy in this application, running on app. 2.5kV continous plate voltage while rated for just a couple of hundred continous volts. Think the PL/EL509 should be a bit better). Both designs feature a SRPP similar structure and rely on heavy compensation and feedback to get things linear)
yeah
Clvin
Hi,
The AE´s come in passive and active versions.
The active version utilzes an amplifier that is nearly an exact copy of the Strickland amp. Using the same design, same transistors and Tubes (6HB5, to my knowledge a relatively unstable guy in this application, running on app. 2.5kV continous plate voltage while rated for just a couple of hundred continous volts. Think the PL/EL509 should be a bit better). Both designs feature a SRPP similar structure and rely on heavy compensation and feedback to get things linear)
yeah
Clvin
Some HV amps in here
Here some more ESL sites.
http://www.earthcurrents.com/london-live/systems/LD_system.htm
http://www.earthcurrents.com/london-live/systems/LD_system.htm
http://www.earthcurrents.com/london-live/systems/LD_system.htm
http://www.buenzow.de/english/mystat.htm
http://www.ossaudio.com/cadencemain.htm
http://www-personal.engin.umich.edu/~jglettle/section/rapture/esltheory.html
http://ccrma.stanford.edu/~byoink/220c/est.htm
http://www.dayton-wright.com/index.shtml
http://www.dayton-wright.com/XG-8-Mk3.html
http://www.onethingaudio.com/
http://pkant.htmlplanet.com/elstatr.htm
http://www.sowter.co.uk/2esl.htm
http://www.audio4.nl/enproducts.htm
http://werple.net.au/~kiewavly/esl.html
http://www.justrealmusic.com/
http://www.eraudio.com.au/
http://www.sacdmods.com/ESL/
http://www.quadesl.org.uk/
Here some more ESL sites.
http://www.earthcurrents.com/london-live/systems/LD_system.htm
http://www.earthcurrents.com/london-live/systems/LD_system.htm
http://www.earthcurrents.com/london-live/systems/LD_system.htm
http://www.buenzow.de/english/mystat.htm
http://www.ossaudio.com/cadencemain.htm
http://www-personal.engin.umich.edu/~jglettle/section/rapture/esltheory.html
http://ccrma.stanford.edu/~byoink/220c/est.htm
http://www.dayton-wright.com/index.shtml
http://www.dayton-wright.com/XG-8-Mk3.html
http://www.onethingaudio.com/
http://pkant.htmlplanet.com/elstatr.htm
http://www.sowter.co.uk/2esl.htm
http://www.audio4.nl/enproducts.htm
http://werple.net.au/~kiewavly/esl.html
http://www.justrealmusic.com/
http://www.eraudio.com.au/
http://www.sacdmods.com/ESL/
http://www.quadesl.org.uk/
DD amp
Hello guys,
Let me jump inn.
I am sorry to tell you that you need about 10KV pp for full output to your ESL.
Math is simple: 100W amp vill produce 28V RMS. 28x1.414=39.5V p
and double that = 79Vpp. If you use 1: 100 step-up you have close to
8000Vpp. With little head-room close to 10KVpp.
Accoustat uses 5KV B+ in bridged config. = 10KV ideally but in practice
maybe 8KVpp.
I was thinking to build AB push-pull tube amp in bridged mode with
5KV B+ using 4(one channel) 6HV5 tubes good for 5.5KV plate voltage.
This will give me 8KVpp with not much plate dissipation, meaning
500W or so power supply.
Another solution is solid state DD amp. Yes, it is possible.
You can use cheap horizontal output transistors used in tv's and
with 1200 B+. This in AB class will give 1000Vpp and two amps bridged
2000Vpp. Now you just take as many of the bridged amps as you need connected in series and you can get as much swing as you need.
The trick to do this is that every amp (block) has it's own independent power supply and than you can connect output of one block to ground
(floating) of next block and output of that block to ground of next block and so on. Good thing about bridging the amps is no matter
how big ripple is in your power supply it will be canceled on the
output because it is in phase. For power supply You can use 12V / 50W transformer put backwards and you can usually increase 12V
to 16-17V without overheating to get more voltage on the other end. I was able to get over 800V DC from one 12V/110-220V (dual primary) with 12V increased to 17V and with use of voltage doubler.
Capacitors used 4 33mf/400V ripple 2%. You can use 7 transformers
with 12V primaries connected in series to 110V main. Well, you got
the picture. Main thing is to have individual power supplies for every
amp block. My amp block design was very simple.
Two high voltage NPN transistors working in push-pull AB class
biased to couple of mA and for drive I used two small signal
transformers connected out of phase to transistor base.
Primaries in parallel in phase. Use of transformers is needed to
insulate low voltage input side from multi KV output side.
This transformer is not critical just be sure it has good bandwidth
and good insulation between primary and secondary (more than 10KV). This can be 1:1 ratio and also if you cant find such transformer it can be built easy. 50 turns or less on each side and
that is it. You gonna need two transformers for each amp.
So if you use 7 cascaded and bridged amps you need 28 transformers for one final mono block. Also to get higher impedance
on main input you can connect transformer primaries in series
and say drive it with gianclone. Amp is without neg feedback so distortion will be high but no more than 1% in total. Use of emitter
resistor is necessary and it is 220 Ohm with 0.2 mfd capacitor across to bust voltage on output on high freq. Well, emitter resistor is kinda
neg. feedback.
Why use this design and not tubes? It is simple, proven to work
cheap parts are available and it will be in the future, stable, no
maintenance, and after all it is another way of doing DD amp.
Regards.
Hello guys,
Let me jump inn.
I am sorry to tell you that you need about 10KV pp for full output to your ESL.
Math is simple: 100W amp vill produce 28V RMS. 28x1.414=39.5V p
and double that = 79Vpp. If you use 1: 100 step-up you have close to
8000Vpp. With little head-room close to 10KVpp.
Accoustat uses 5KV B+ in bridged config. = 10KV ideally but in practice
maybe 8KVpp.
I was thinking to build AB push-pull tube amp in bridged mode with
5KV B+ using 4(one channel) 6HV5 tubes good for 5.5KV plate voltage.
This will give me 8KVpp with not much plate dissipation, meaning
500W or so power supply.
Another solution is solid state DD amp. Yes, it is possible.
You can use cheap horizontal output transistors used in tv's and
with 1200 B+. This in AB class will give 1000Vpp and two amps bridged
2000Vpp. Now you just take as many of the bridged amps as you need connected in series and you can get as much swing as you need.
The trick to do this is that every amp (block) has it's own independent power supply and than you can connect output of one block to ground
(floating) of next block and output of that block to ground of next block and so on. Good thing about bridging the amps is no matter
how big ripple is in your power supply it will be canceled on the
output because it is in phase. For power supply You can use 12V / 50W transformer put backwards and you can usually increase 12V
to 16-17V without overheating to get more voltage on the other end. I was able to get over 800V DC from one 12V/110-220V (dual primary) with 12V increased to 17V and with use of voltage doubler.
Capacitors used 4 33mf/400V ripple 2%. You can use 7 transformers
with 12V primaries connected in series to 110V main. Well, you got
the picture. Main thing is to have individual power supplies for every
amp block. My amp block design was very simple.
Two high voltage NPN transistors working in push-pull AB class
biased to couple of mA and for drive I used two small signal
transformers connected out of phase to transistor base.
Primaries in parallel in phase. Use of transformers is needed to
insulate low voltage input side from multi KV output side.
This transformer is not critical just be sure it has good bandwidth
and good insulation between primary and secondary (more than 10KV). This can be 1:1 ratio and also if you cant find such transformer it can be built easy. 50 turns or less on each side and
that is it. You gonna need two transformers for each amp.
So if you use 7 cascaded and bridged amps you need 28 transformers for one final mono block. Also to get higher impedance
on main input you can connect transformer primaries in series
and say drive it with gianclone. Amp is without neg feedback so distortion will be high but no more than 1% in total. Use of emitter
resistor is necessary and it is 220 Ohm with 0.2 mfd capacitor across to bust voltage on output on high freq. Well, emitter resistor is kinda
neg. feedback.
Why use this design and not tubes? It is simple, proven to work
cheap parts are available and it will be in the future, stable, no
maintenance, and after all it is another way of doing DD amp.
Regards.
Yes, for full-range use with Acoustat-type panels, you do need that kind of swing. Or swing less and accept a loss in attainable SPL. The beauty of the autoformer and direct-drive-with-dummy-load shown in the earthcurrents link is that the amp can be configured to run class AB or B. This makes the output tube choice much easier.
BTW, you really don't want to use 6HV5s, unless you love oscillation and smoke. They were the weak point in Acoustat's d-d amps.
BTW, you really don't want to use 6HV5s, unless you love oscillation and smoke. They were the weak point in Acoustat's d-d amps.
Sasha,
Good plan. I’m not a solid state fan, but your design makes good sense. I have also floated supplies before for various applications. In addition to being concerned about the insulation rating of the power transformers, you must be concerned with primary-secondary capacitance and perhaps secondary-to-frame (usually grounded) capacitance. The preceding amp stage has to drive not only the bases/gates/grids, but also these capacitances all added together. I chose split-bobbin transformers in such applications to minimize capacitance between primary and secondary. I measure transformer capacitance by shorting the primary leads to each other, and also shorting the secondary leads to each other, and then connecting a cap meter across these two nodes.
Your point on high drive voltage requirements is well taken. An output stage in a bridge configuration is almost essential since you get double the drive voltage for a given power supply configuration compared to a single ended drive. And the balanced nature of the ESL almost demands it anyway. In my wacko transmitting tube design, I used bipolar supplies at +4000 and – 4000 volts (it’s all DC coupled with level shifters and a pentode servo amp). Ideally this would give 16KV peak-peak output which is about 5.6KVrms drive. In practice the outputs won’t quite reach the rails, but I do achieve my design goal of 4800 Vrms (13.5V peak-to-peak). This is all my Quad ESL-63s can/should handle anyway.
I made my own high voltage scope probe which is capacitively compensated for flat response. It’s impressive to watch music waveforms dancing on the scope at thousands of volts while listening at normal levels.
My friend refers to all this as “Lethal Fidelity”.
Good plan. I’m not a solid state fan, but your design makes good sense. I have also floated supplies before for various applications. In addition to being concerned about the insulation rating of the power transformers, you must be concerned with primary-secondary capacitance and perhaps secondary-to-frame (usually grounded) capacitance. The preceding amp stage has to drive not only the bases/gates/grids, but also these capacitances all added together. I chose split-bobbin transformers in such applications to minimize capacitance between primary and secondary. I measure transformer capacitance by shorting the primary leads to each other, and also shorting the secondary leads to each other, and then connecting a cap meter across these two nodes.
Your point on high drive voltage requirements is well taken. An output stage in a bridge configuration is almost essential since you get double the drive voltage for a given power supply configuration compared to a single ended drive. And the balanced nature of the ESL almost demands it anyway. In my wacko transmitting tube design, I used bipolar supplies at +4000 and – 4000 volts (it’s all DC coupled with level shifters and a pentode servo amp). Ideally this would give 16KV peak-peak output which is about 5.6KVrms drive. In practice the outputs won’t quite reach the rails, but I do achieve my design goal of 4800 Vrms (13.5V peak-to-peak). This is all my Quad ESL-63s can/should handle anyway.
I made my own high voltage scope probe which is capacitively compensated for flat response. It’s impressive to watch music waveforms dancing on the scope at thousands of volts while listening at normal levels.
My friend refers to all this as “Lethal Fidelity”.
Brian,
Capacitance of primary/secondary in my driver transformers is not an issue because it is only small transformer used to insulate input and output and each amp block has it's own driver transformer.
True primaries are connected together but still this is only little transformer easy to drive. Maximum of 7 transformer primaries is connected together in series probably better than in parallel to reduce capacitance or maybe some combo parallel/series.
Capacitance of primary/secondary in my driver transformers is not an issue because it is only small transformer used to insulate input and output and each amp block has it's own driver transformer.
True primaries are connected together but still this is only little transformer easy to drive. Maximum of 7 transformer primaries is connected together in series probably better than in parallel to reduce capacitance or maybe some combo parallel/series.
ESL direct amp
Hi guys, look what I found
http://users.forthnet.gr/ath/sifakhs/amp838.htm
An ESL direct drive amp
(or if your not careful a direct drive barbeque party !)
Hi guys, look what I found
http://users.forthnet.gr/ath/sifakhs/amp838.htm
An ESL direct drive amp
(or if your not careful a direct drive barbeque party !)
http://users.forthnet.gr/ath/sifakhs/images/the_amp.jpg
This looks so much like my test bench, it's frightening.
This looks so much like my test bench, it's frightening.
Hi. Jumping in a bit late i the discussion. Couldn't a Class D amp be used ?
The output stage of a digital amp is (basically) a pair of transistors generating a square wave of (say) +/- 50V. To make this more "analog" the square wave is put through a choke and then loaded by a capacitor, before being sent to the speaker.
If we could use (some sort of) transformer instead of the choke, we could produce a high voltage squarewave loaded by the ESL panel (being a capacitor in itself).
As the transformer would work at the sampling frequency (I suppose) say 96kHz, all the problems that are frequency related, as the transformer having to cope spanning from 20Hz to 20kHz, would be gone. Also, the efficiency would be much higher, i.e. it could be made smaller and cheaper.
Still haven't built those panels...
/Urban
The output stage of a digital amp is (basically) a pair of transistors generating a square wave of (say) +/- 50V. To make this more "analog" the square wave is put through a choke and then loaded by a capacitor, before being sent to the speaker.
If we could use (some sort of) transformer instead of the choke, we could produce a high voltage squarewave loaded by the ESL panel (being a capacitor in itself).
As the transformer would work at the sampling frequency (I suppose) say 96kHz, all the problems that are frequency related, as the transformer having to cope spanning from 20Hz to 20kHz, would be gone. Also, the efficiency would be much higher, i.e. it could be made smaller and cheaper.
Still haven't built those panels...
/Urban
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