Sanders ESL Amplifiers

[Big Dog RJ]

I think way back... when Arnie Nudell was finalising his radical Servo Static One speaker system, one of his engineers tried the direct drive concept. That system was so complicated, that it took several attempts just to get the servo units stable and finalise on viable production. However, I don't know how many were produced, and if so the long term reliability factor. I guess his Infinity IRS systems proved to be more reliable.

 

[Robert D]

Attn: Rob D

Yes, when I first read those comments/ specs on Sanders ESL's, I thought to myself that these must be the ultimate! However, after subsequent discussions and my disastrous experience with Quad ESL's... only did I realise the true benefits of Sanders ESL's. So unlike Quads, Sanders ESL's don't arc, they are built on high standards to tolerate very high dynamic peaks, and they're not as susceptible to environmental issues, such as dust, humidity and tropical climes... which the Quads were always prone to!

So, it's pretty much a slight marketing spin- won't arc, impervious to dust & etc , and can play at ear bleeding levels... basically the very same standards as ML! Absolutely no difference. The only major difference being ML has curved panels and some with a fix tilt angle backwards... their dispersion pattern is slightly different.

Anyway, after our last chat, I gathered who would ever want to listen to music at ear bleeding levels? You'd go deaf! As humans, our natural hearing abilities have fairly high tolerances but pushing those levels to extremes constantly will render us deaf! So there's no way we can listen to music at high levels at length without ending up with ear pain... eventually ending up deaf.

In fact I ordered and sold one of his ESL's to a customer, that was the Model 10 series I think. We also set his system up with the Magtec monoblocks and his preamp was a tube version from Sonic Frontiers. A marvellous combination! I think that customer still has this system, never really wanted to upgrade it to anything, happy as!

Whether they're related or not... I was under the impression they were but I don't think so.
Speaking of unusual panels, there's another chap who makes an interesting ribbon panel hybrid with dynamic drivers, called GT Audio. Based in the US, he goes as George Takesh and claims that his panel hybrids are superior in terms of dynamics and large scale music reproduction. I have heard his models on several occasions and they did impress but I just prefer full range stats.

All three of these chaps know each other and have been involved in technical discussions sharing expert knowledge but none of them cross each other's paths... that's respect! True gentleman and pure engineers!

Cheers, RJ

Nice information! That's about what I figured regarding the durability of the panels. You're right about volume too. I've been to some very loud concerts and lost so.e of my hearing because of it. I have tinnitus from listening to music too loud. The folly of youth! My Alpine car stereo in the 80s did some serious damage.

When I go to concerts now, I bring a special set of audiophile ear plugs. I wish I had them for the Slayer concert. The plugs are supposed to protect your hearing but not ruin the sound so much.They do muffle a lot, but suppose they work somewhat.

 

[Robert D]

I guess this is GT Audio?

https://gtaudioworks.com/Speakers

 

[Robert D]

No, I think it is just a coincidence.

One of the things I really like about Roger is he has been pursuing the ideal ESL amplification goal for a long, long time. Decades ago, he created an ESL direct-drive amp that had amazing performance, but was a bust in terms of a possible product due to cost, complexity, and most importantly, danger. Direct-drive means it is powering the stators directly, and at very high voltages (~5Kv ). No step-up transformer is needed here, just very careful connectivity to keep people from frying themselves. The beast was all tubes (IIRC, some were from radio stations that use high-power/voltage tubes for transmission ) and it was effectively a whole-home heater as well.

In the Monoray brochure, I describe a modern interpretation of the direct-drive concept using modern high-voltage FETs and leveraging the DDFA architecture (which I called Dynamic Direct Panel Drive (DDPD) ) for implementing feedback-driven closed-loop amplification that should handle the complexities of an ESL quite well.
My solution to the 'danger' part is to specify a custom umbilical cord with locking (and safe) connectors between the amp and speaker units.

Re-reading my posts and docs on the Monoray, I sure wish someone would produce that, it would be killer.

High current/voltage definitely scares me now, since I have an implanted defibrillator. It's has shocked the hell out of me probably 20 times, I lost count. I also fear getting shocked externally because I'm not sure what it might do to my defibrillator. Would it get "fried", ruined? Being in V fib sucks!


https://www.scienceabc.com/humans/how-many-volts-amps-kill-you-human.html

 

[Robert D]

No, I think it is just a coincidence.

One of the things I really like about Roger is he has been pursuing the ideal ESL amplification goal for a long, long time. Decades ago, he created an ESL direct-drive amp that had amazing performance, but was a bust in terms of a possible product due to cost, complexity, and most importantly, danger. Direct-drive means it is powering the stators directly, and at very high voltages (~5Kv ). No step-up transformer is needed here, just very careful connectivity to keep people from frying themselves. The beast was all tubes (IIRC, some were from radio stations that use high-power/voltage tubes for transmission ) and it was effectively a whole-home heater as well.

In the Monoray brochure, I describe a modern interpretation of the direct-drive concept using modern high-voltage FETs and leveraging the DDFA architecture (which I called Dynamic Direct Panel Drive (DDPD) ) for implementing feedback-driven closed-loop amplification that should handle the complexities of an ESL quite well.
My solution to the 'danger' part is to specify a custom umbilical cord with locking (and safe) connectors between the amp and speaker units.

Re-reading my posts and docs on the Monoray, I sure wish someone would produce that, it would be killer.

In comparison, how many volts do most audiophile quality amps produce?

 

[john65b]

As far as Sanders panel being indestructible and arc proof, remember that Roger's ESL is only driving high frequency, so without the high amplitude Bass on the panels, they last a hell of a lot longer and much more durable. The Sanders 10C HF crossover is (I think) is 175hz and up...

Now as far as panels that are full range and indestructible, one only has to look at Acoustat Panels... don't know how, but Jim Strickland nailed it.

Not to take anything away from Roger...as far as I am concerned, Roger Sanders and Jim Strickland are The "Real Deals" in the ESL world.......

 

[john65b]

In comparison, how many volts do most audiophile quality amps produce?

Ohms Law V=IR
Power =VI
Power = Voltage Squared/Resistance

So 100 watts @ 8 ohm speaker is 28.3 volts at speaker terminals.

 

[Robert D]

As far as Sanders panel being indestructible and arc proof, remember that Roger's ESL is only driving high frequency, so without the high amplitude Bass on the panels, they last a hell of a lot longer and much more durable. The Sanders 10C HF crossover is (I think) is 175hz and up...

Now as far as panels that are full range and indestructible, one only has to look at Acoustat Panels... don't know how, but Jim Strickland nailed it.

Not to take anything away from Roger...as far as I am concerned, Roger Sanders and Jim Strickland are The "Real Deals" in the ESL world.......

Man, yet another company to consider! Never heard of Accoustat.

 

[Big Dog RJ]

Yes, Acoustat was another fantastic ESL. They were really big and tall and could reproduce full range. Needed hefty amps to drive them well though.

It's a shame the company is no more... nor did any others want to continue the ESL brand of Acoustat, so if you do ever come across one, it's as rare as the saber tooth tiger!

Cheers, RJ

 

[john65b]

Not as rare as one may think - I see the 2+2 (four panels each channel, over 8 feet tall and around 2 feet wide) often on Craigslist and ebay...I have a pair myself, along with a pair of 1+1. The Medallion interfaces are a bit rare, bust standard interfaces are somewhat easy to find. Acoustat does also have an all Tube Driven interface that is rare...

I played around with a set of Acoustat Medallion Interface on a pair of ML CLS panels...sounded interesting....promising...

The Sanders ESL / Magtec is perfect amp for these speakers.

 

[Big Dog RJ]

Attn: Rob D,

As mentioned above, based on Ohms law... that's correct. Also, based on the parts used in the amplifier's output stage, there are lethal voltages running around... this could be anything from 600v to 1.5kv. Tube amplifiers are high voltage devices with low current. So, they get the required current from their trannies. Whereas SS amplifiers are high current devices with low voltage, so as long as the voltages are stable, the amp can drive effectively. Since SS amps are high current devices, they're ideal for driving ESL's, since half the job is already done!

With tube amps driving ESL's, you have to get the high powered ones, with stable current capacity and well designed power supplies. This type of combination will have no issues handling full range stats.
Each of my CJ monoblocks has 1.5amp 600v fuses to protect the Output trannies. So, this is serious lethal voltage and high current.

Other tube amps that have double the power output, have very high voltages floating around, with even greater amperage, 2 - 4amps and above on the AC mains fuse alone. B+ fuses are usually the output stage fuses protecting the output trannies. Tube amplifiers being very high voltage devices are lethal! SS amplifiers being high current devices are just as lethal, some producing more than 40amps of current. Yep! So you don't want to go poking around when it's powered up...poof!!! There goes my five fingers!

 

[Big Dog RJ]

Not as rare as one may think - I see the 2+2 (four panels each channel, over 8 feet tall and around 2 feet wide) often on Craigslist and ebay...I have a pair myself, along with a pair of 1+1. The Medallion interfaces are a bit rare, bust standard interfaces are somewhat easy to find. Acoustat does also have an all Tube Driven interface that is rare...

I played around with a set of Acoustat Medallion Interface on a pair of ML CLS panels...sounded interesting....promising...

The Sanders ESL / Magtec is perfect amp for these speakers.

Nice one john65b!

Those Acoustats are something else... real top notch stuff during their hay day. BTW, what kind of power amplifiers do you use to drive them? Any tube amps in there...

I also remember the huge Sound Lab ESL stats. Those were so massive that sometimes they would nearly touch the ceilings... mighty presentation though, the last time I heard one of these were driven by the VTL Wotans (1000w of tube finesse).

Cheers, RJ

 

[john65b]

The Acoustats really came alive with the higher power amps - Krell KSA amps, the Sanders ESL amps, an ICEPower 500 watt ASP amp..etc.

They did OK with my tube amps...but didn't quite do it. The tube amps work much better on Quad ESL as they are more of a delicate speaker than the Acoustats and ML CLS...

 

[Robert D]

Attn: Rob D,

As mentioned above, based on Ohms law... that's correct. Also, based on the parts used in the amplifier's output stage, there are lethal voltages running around... this could be anything from 600v to 1.5kv. Tube amplifiers are high voltage devices with low current. So, they get the required current from their trannies. Whereas SS amplifiers are high current devices with low voltage, so as long as the voltages are stable, the amp can drive effectively. Since SS amps are high current devices, they're ideal for driving ESL's, since half the job is already done!

With tube amps driving ESL's, you have to get the high powered ones, with stable current capacity and well designed power supplies. This type of combination will have no issues handling full range stats.
Each of my CJ monoblocks has 1.5amp 600v fuses to protect the Output trannies. So, this is serious lethal voltage and high current.

Other tube amps that have double the power output, have very high voltages floating around, with even greater amperage, 2 - 4amps and above on the AC mains fuse alone. B+ fuses are usually the output stage fuses protecting the output trannies. Tube amplifiers being very high voltage devices are lethal! SS amplifiers being high current devices are just as lethal, some producing more than 40amps of current. Yep! So you don't want to go poking around when it's powered up...poof!!! There goes my five fingers!

My father was an electrical engineer for the local power company. He would tell me stories about lineman that would get fried, and how it cooks you on the inside. Scary stuff what those guys have to do. He never had to work on the lines, I think he was at his desk most of the time.

 

[JonFo]

I also remember the huge Sound Lab ESL stats. Those were so massive that sometimes they would nearly touch the ceilings... mighty presentation though, the last time I heard one of these were driven by the VTL Wotans (1000w of tube finesse).

He, they are large and Impressive, we discussed these before in this thread, which has a cool picture of them Soundlabs vs. Logans

 

[JonFo]

SS amplifiers being high current devices are just as lethal, some producing more than 40amps of current. Yep!

One of the reasons the Sanders ESL amp is such a great match for ESL, it has crazy high amperage:

The Sanders Sound Systems Electrostatic Amplifier ("ESL amp") solves this problem by using a massive output stage. Each output transistor is capable of delivering 250 watts -- and there are eighteen of these per channel. As a result, it can deliver a staggering 135 amps of current with a combined power rating of 4500 watts per channel!

pulled from Sanders Sound Systems - ESL Amp White Paper

 

[john65b]

I like Roger, but that is a bit of a silly claim...any amp on a 15 Amp circuit @120 VAC cannot deliver over 1800 watts per channel, 2400 watts per channel on a 20 amp circuit...

But Hey, what do I know!

 

[JonFo]

I like Roger, but that is a bit of a silly claim...any amp on a 15 Amp circuit @120 VAC cannot deliver over 1800 watts per channel, 2400 watts per channel on a 20 amp circuit...

But Hey, what do I know!

Well, it is an audio amplifier, not a welder, so I think the claimed output amperage is there only for short periods and comes largely from the reserves in the transformer and capacitors, not just the wall. But a design still needs sufficient transistors of good enough specs to flow the amperage/wattage.
For audio signals, it's plenty.

 

[ttocs]

Well, it is an audio amplifier, not a welder, so I think the claimed output amperage is there only for short periods and comes largely from the reserves in the transformer and capacitors, not just the wall. But a design still needs sufficient transistors of good enough specs to flow the amperage/wattage.
For audio signals, it's plenty.

That Amperage rating is at a lower Voltage. It's a very high Voltage for an amplifier, but lower than house Voltage.

The claimed output is 92V. Now, using the Volts and Watts claimed, the math is a bit off but it's close enough to work with to get near the claimed 4500 Watts. I just don't know what they are using for Impedance. So if we want to be exact it'll look like this:
(92V x 92V) ÷ 1.88Ω = 4502W

A 120 Volt, 20 Amp house circuit in the USA will provide 2400 Watts.
Change the Voltage to 92V and the Amperage goes up to 26 Amps to get the same 2400 Watts. Sanders states the amp is capable of 135 Amp output, which again, is a lot! But I'm not sure how they arrive at that 135A number, unless they're mixing some specs, like one spec is rated at 1.88Ω and the other is 0.7Ω, which is the only way I can make the math work.

Either way, the amp is capable of LOTS of Amps and LOTS of Volts!

Also keep in mind that a 20A breaker has an instantaneous limit much higher than 20 Amps, it's more like 35 Amps for a period of a few seconds (depends on the breaker), which is more than enough for brief periods of loud transients. So 35A will get the wattage of a 120V circuit up to 4200 Watts. We're getting closer without using reserve power, assuming an awful lot here, like going over the mandated 80% rule which states that each electric circuit in a house will only be loaded up to 80% of its capacity. But I'm just having fun here playing with some numbers so it's ok to max out.

This is just to give a sense of what is gotten from each amount of Voltage. I'm sure the amplifier uses the incoming Voltage/Amperage such that the reserves don't deplete below a given threshold and eventually run out completely.

 

[wink]

One of the reasons the Sanders ESL amp is such a great match for ESL, it has crazy high amperage:


pulled from Sanders Sound Systems - ESL Amp White Paper

Current! Stats love current! One of the reasons I felt my Coda Continuum #8 had better control over my Prodigy than the Krell FPB600 it replaced. The Coda outputs 150 amperes of current. Double the current output of the mighty Krell. (And it’s much lighter)