This is insane...the Quad ESL

[meistersinger57]

If one considers the excellent stereo amplifier CROFT model 7 R (regulated). It is a hybrid design with valves taking care of the 1st stage amplification and very high quality SS BUZ 900/905DP MAGNATEC Mosfets delivering the output, regulated HT with a 300VA torroidal PSU, with 50/55 watts per channel (input 12AX7 or - in my case - 12AU7), that easily drive my two pairs of stacked quads esl 57s. TUBE CAD Journal on "Hybrid Amplifiers" April/May 2001 :"The common approach is use tubes for voltage gain and MOSFETs or transistors for current gain. This arrangement appeals to our sense of fairness: tubes are happiest with voltage and woefully current limited; solid-state devices are current ebullient but fearful of over voltages. An exaggeration this, but not without a kernel of truth. Which solid-state device should be used in the output stage? The transistor wins in theory, but the MOSFET wins in practice is the quick answer. The transistor has a much greater transconductance which makes for a greater gain, which in turn allows for more feedback, which ultimately lowers more distortion. Yet, the MOSFET is used in most professional, high-power amplifiers because the MOSFET does not blowout as readily as the transistor does. Furthermore, the MOSFET is almost always used in hybrid designs due to its reputation for being more tube like in sonic character and because its gate represents a high impedance that is theoretically easier to drive than the transistor's base." ( http://www.tubecad.com/april_may2001/index.html )

Chris Beeching ( http://www.quadesl.com.articles/quad _stacking.html) says that "Also, by connecting them in parallel the overall impedance curve is considerably flatter, and hovers around 8 to 12 ohms rather than the 15-going-on-30ohm curve for a single panel", so a pair of quads ESL 57 when stacked in parallel, specially when driven by good "hybrid" MOSFETS amplifiers...anyway, MOSFETs being "CURRENT EBULLIENT" are happy with this "high impedance..." speakers...
In the TUBE's simplest configuration, triode amplifier, the plate current is function of grid voltage, as drain current is function of gate voltage in a MOSFET

The MOSFET, on the other hand, is less sensitive to shifts in the bias voltages, as it has a much lower transconductance. Furthermore, MOSFET output stages always require a much higher quiescent idle current, which increases the percentage of Class-A operation in Class-AB mix, which is all for the good, as the first watt of power is sonically the most important watt. Add to these benefits the advantage of virtually no thermal runaway, and the MOSFET appears to be the clear winner/.

MOSFET advantage TUBES in all aspects:
-Very higher transconductance (two magnitude order, typically 3,5 mhos)
-Direct load coupling (transformless) this mean higher bandwidth, less distortion, more damping factor.
-Better gain bandwidth product.
-Power bandwith one magnitude order higher than TUBES.
-Easy paralleling.



Last edited: Nov 24, 2018

 

[meistersinger57]

Amplification for Quads - Fifth Edition
by
Christian Steingruber

"All amplifiers sound the same" - Peter Walker
"Amplifiers DO sound different" - Martin Colloms
​

The question about the ideal amplifier for driving the Quad ESL-57 speaker is not easy to answer. It is well known that the '57 offers a very difficult load, because the load is highly reactive and changes from approximately 60 ohms in the bass to 1.8 ohms in the treble region. The popular stacked pairs of '57 present an even worse load, because when connected in parallel, the impedance at 18 kHz falls to 0.9 ohms which is almost a short wire.
In addition to the problems mentioned above, the original Quad speaker has mediocre efficiency ( approximately 82 db/Watt ) and limited power handling : Original Quads will flash up immediately when the voltage on the input terminal exceeds 33 Volt (peak-peak). From 1990 onwards a protection circuit (a diode rectifier bridge) was suggested by Quad-UK, quite similar to that used in the new ESL-63, though it protects here only the treble unit and not the bass panel. Models which include that protection circuitry can be used safely with powerful valve and solid-state amplifiers although long overdrive is not recommended.
Generally valve amps are not upset by an awkward load as presented by the '57, but many solid-state amplifiers quickly give up in a cloud of smoke. I encountered several "trannies" that immediately blew up - some of these items even damaged the delicate Quad speaker before they died. The biggest crap I ever encountered was the BGW series 200 : I connected it to my Quads as the manufacturer had stated in the manual that model 200 was stable into electrostatic speakers - actually it was not ! Within milliseconds the BGW went into oscillation and killed both treble units. It cost me a fortune to repair both the Quads and the amp. The respected Audio Critic magazine wrote about the BGW : " This one is a disaster...." How true !
On the other hand a Marantz integrated (model 1060), whose manufacturer definitely excluded such a difficult load, worked quite well with the Quads for over a decade. Similar reports can be heard about the original NAD 3020 integrated (designed by Bjorn-Eric Edvardson) which handled the Quads with ease.
The Acoustical Manufacturing Company (better known as QUAD) usually recommended only their own amplifier designs, as they could not guarantee the performance of other brands on their fragile ESL-57. The valved Quad amps of yesteryear were great designs and ideal for driving the ESL, but unfortunately their solid-state successors were not always masterpieces. Many audiophiles have tried other products with the ESL-57 and came to even better results than with Quad's own stuff. The original Quad amps and alternative products are discussed here.
Chapter One : QUAD Amps
QUAD II mono amplifier
Type : Valve ( KT 66)
1949-1970
These ones are real classics. Maybe not the most accurate sound from these mono valve amps, but sweet and euphonic . In one word : MUSICAL ! The II use the legendary KT 66 as power tube, produced by GEC and Mullard. Only 15 watts or so, but this is just right for the ESL57. Used IIs can be found in British magazines for 500 £, modification kits are available from several sources . In 1996 a special 40th Anniversary edition was available , albeit at a price.
A collectors item, like the original Quad ESL. Highly recommended !


BEDINI 25/25
Solid-State ( Class A )
1981 onwards
USA

A class A amplifier with 25 watts, maybe not as stable as the ML-2, but sound wise even better. The Bedini 25/25 was a peach match with the Quads. To quote the Audio Critic : "Nothing makes the Quad electrostatic sound quite as perfect as the Model 25/25". It was difficult to get any Bedini products in former years, because Joe Bedini had closed the manufacturing. But recently he began to design and manufacture amplifiers again.
Graf
EINSTEIN “The Final Cut”
OTL
Germany ( 2001 -)
This is rather a beast and could be the best of all OTL designs that were ever made , because it uses a rather advanced circuit design . Whereas all other designer offer variations of the vintage Cyclotron theme , Mr. Ralf Weiler has developed something new and special - the "Cross Coupled Anodes Circuit". At least the specs are impressive for a valve amplifier :
Power : 55 watt ( 4-8 ohm)
Bandwidth : 3 mega Hertz (!!!)
Distortion : 0.02 %
Output Resistance : 300 milli Ohm
Damping Factor : 70
The only problem with this amp is that probably none has heard it yet on Quads. It could be a perfect match , but only the hearing test can verify if my expectations are true. And as with the Graff one big caveat : The Einstein is ultra expensive !
Postscript :
As so much rubbish has been published on this subject, I was forced to write this article. I recently had to read in an audio magazine that “it was inadvisable to connect any old amplifier to the Quad speaker”. I do not know what “old amplification” the author of these lines had in mind, but it is exactly the old stuff (valve amplification ) which works a treat with the original Quad ESL. { He's right, you know! - Gary Jacobson }

http://www.quadesl.org/index.php/hard-core/amplifiers/christian-steingruber

 

[meistersinger57]

Some british gentleman said this:

• 
  LintoMayor of Simpleton
  Location:South East London, England, Great Britain
  
  I have spent 25 years on this very subject. The very best is the Radford 15 watts or the Quad IIs, but both matching pre amps are poor, so for the best sound a modern valve
  pre like Croft, Copland, or Audio Note.
  
  I could write a book on all the experimenting I have done.
  Above is a very short answer.
  Leaks also do a great job.
  
  The only s/s amp to use in the Nait 2
  Linto, Jan 2, 2017​

• 
  https://forums.stevehoffman.tv/threads/quad-esl-57s-what-amp-makes-them-sing-the-best.635499/
  ​

 

[Audiophile Bill]

Some british gentleman said this:

• 
  LintoMayor of Simpleton
  Location:South East London, England, Great Britain
  
  I have spent 25 years on this very subject. The very best is the Radford 15 watts or the Quad IIs, but both matching pre amps are poor, so for the best sound a modern valve
  pre like Croft, Copland, or Audio Note.
  
  I could write a book on all the experimenting I have done.
  Above is a very short answer.
  Leaks also do a great job.
  
  The only s/s amp to use in the Nait 2
  Linto, Jan 2, 2017​

• 
  https://forums.stevehoffman.tv/threads/quad-esl-57s-what-amp-makes-them-sing-the-best.635499/
  ​

Thanks for this. I always wanted to own a Croft so this is an excuse to buy one.

 

[microstrip]

Amplification for Quads - Fifth Edition
by
Christian Steingruber

"All amplifiers sound the same" - Peter Walker
"Amplifiers DO sound different" - Martin Colloms
​

The question about the ideal amplifier for driving the Quad ESL-57 speaker is not easy to answer. It is well known that the '57 offers a very difficult load, because the load is highly reactive and changes from approximately 60 ohms in the bass to 1.8 ohms in the treble region. The popular stacked pairs of '57 present an even worse load, because when connected in parallel, the impedance at 18 kHz falls to 0.9 ohms which is almost a short wire.
In addition to the problems mentioned above, the original Quad speaker has mediocre efficiency ( approximately 82 db/Watt ) and limited power handling : Original Quads will flash up immediately when the voltage on the input terminal exceeds 33 Volt (peak-peak). From 1990 onwards a protection circuit (a diode rectifier bridge) was suggested by Quad-UK, quite similar to that used in the new ESL-63, though it protects here only the treble unit and not the bass panel. Models which include that protection circuitry can be used safely with powerful valve and solid-state amplifiers although long overdrive is not recommended.
Generally valve amps are not upset by an awkward load as presented by the '57, but many solid-state amplifiers quickly give up in a cloud of smoke. I encountered several "trannies" that immediately blew up - some of these items even damaged the delicate Quad speaker before they died. The biggest crap I ever encountered was the BGW series 200 : I connected it to my Quads as the manufacturer had stated in the manual that model 200 was stable into electrostatic speakers - actually it was not ! Within milliseconds the BGW went into oscillation and killed both treble units. It cost me a fortune to repair both the Quads and the amp. The respected Audio Critic magazine wrote about the BGW : " This one is a disaster...." How true !
On the other hand a Marantz integrated (model 1060), whose manufacturer definitely excluded such a difficult load, worked quite well with the Quads for over a decade. Similar reports can be heard about the original NAD 3020 integrated (designed by Bjorn-Eric Edvardson) which handled the Quads with ease.
The Acoustical Manufacturing Company (better known as QUAD) usually recommended only their own amplifier designs, as they could not guarantee the performance of other brands on their fragile ESL-57. The valved Quad amps of yesteryear were great designs and ideal for driving the ESL, but unfortunately their solid-state successors were not always masterpieces. Many audiophiles have tried other products with the ESL-57 and came to even better results than with Quad's own stuff. The original Quad amps and alternative products are discussed here.
Chapter One : QUAD Amps
QUAD II mono amplifier
Type : Valve ( KT 66)
1949-1970
These ones are real classics. Maybe not the most accurate sound from these mono valve amps, but sweet and euphonic . In one word : MUSICAL ! The II use the legendary KT 66 as power tube, produced by GEC and Mullard. Only 15 watts or so, but this is just right for the ESL57. Used IIs can be found in British magazines for 500 £, modification kits are available from several sources . In 1996 a special 40th Anniversary edition was available , albeit at a price.
A collectors item, like the original Quad ESL. Highly recommended !


BEDINI 25/25
Solid-State ( Class A )
1981 onwards
USA

A class A amplifier with 25 watts, maybe not as stable as the ML-2, but sound wise even better. The Bedini 25/25 was a peach match with the Quads. To quote the Audio Critic : "Nothing makes the Quad electrostatic sound quite as perfect as the Model 25/25". It was difficult to get any Bedini products in former years, because Joe Bedini had closed the manufacturing. But recently he began to design and manufacture amplifiers again.
Graf
EINSTEIN “The Final Cut”
OTL
Germany ( 2001 -)
This is rather a beast and could be the best of all OTL designs that were ever made , because it uses a rather advanced circuit design . Whereas all other designer offer variations of the vintage Cyclotron theme , Mr. Ralf Weiler has developed something new and special - the "Cross Coupled Anodes Circuit". At least the specs are impressive for a valve amplifier :
Power : 55 watt ( 4-8 ohm)
Bandwidth : 3 mega Hertz (!!!)
Distortion : 0.02 %
Output Resistance : 300 milli Ohm
Damping Factor : 70
The only problem with this amp is that probably none has heard it yet on Quads. It could be a perfect match , but only the hearing test can verify if my expectations are true. And as with the Graff one big caveat : The Einstein is ultra expensive !
Postscript :
As so much rubbish has been published on this subject, I was forced to write this article. I recently had to read in an audio magazine that “it was inadvisable to connect any old amplifier to the Quad speaker”. I do not know what “old amplification” the author of these lines had in mind, but it is exactly the old stuff (valve amplification ) which works a treat with the original Quad ESL. { He's right, you know! - Gary Jacobson }

http://www.quadesl.org/index.php/hard-core/amplifiers/christian-steingruber

Just to point that Peter Walker never said that "All amplifiers sound the same" - he denied it several times in interviews and written articles.

I have owned the old Bedini 25/25. Before me it was owned by a friend who used it to power the ESL57 stack in a Mark Levinson HQD system - the other amplifiers were the Mark Levinson ML9 and the original Electrocompaniet, the 100/7000Hz crossover was the LN2. Happy to say that we preferred many amplifiers to the 25/25 when used full range in the ESL57, the Bedini lacked extremes.

The original Bedini 25/25 was a very simple circuit, using 3 pairs of the more vulgar existing power transistor per channel, the slow and often denigrated 2n3055, as driver and output device. No PNP device was used in the output stage. As imitation is the sincerest form of flattery I can remember that many DIY people built excellent copies of it!

 

[Kcin]

I've tried many many amps on the ESLs . Still have most of them. The ESLs don't mind push pull at all.. a nice D70 or D115 from ARC would be good. I also like EL84s like the small Heath UA2.

Any of the Marantz tube amps are excellent I like my Model 2's the best in this series. I have completely rebuilt the QUAD IIs to modern specs as well.

The Music Reference RM9 is very good and a sleeper is the Sherwood Integrated S5000 II . The MC225 is excellent . However, when I play mine its with a Futterman or Wyetech 211c these days. My refurbished Futterman is killer.



Above is a short list of what I have tried

The Bedini has been disparaged above but the amp needs to be serviced and most importantly the ESLs need to be totally refurbished if you are to make a judgement. They need protection as well.

Depending on whether you are in NA or EU will limit your access to some of the above.

 

[BruceD]

I ran Stacked Pairs with the Curl designed ML-2 Monoblocks and /or the original Otala Ampliwire SS tried also the 24" Hartley with the Symmetry X-

over but didn't seem to gel so changed that setup for pair of Sequerra T-1 Ribbons on custom top mounted stand--the treble Air was palpable indeed.

Interestingly 40 years later is there really any "better" transducers out there?

Opinions vary on that score--just our expectations and egos can cloud the judgment on such matters!

BruceD

P:S Yes I've heard the Levinson HQD system --it was a brave attempt /successful?--questionable, I suppose but I still remember the sonics

that fact alone is undeniable.

 

[Big Dog RJ]

That's the main issue with Quads and full range stats for that matter.
They are true classics in every sense of the word but highly flawed. They still remain as my favourite stat, even though I'm absolutely loving the CLX's...

Talk about notorious impedence curve, the CLX's dip to 0.7 in highs and 20 ohms and over in the bass region, and this is not constant, rather variances happen in a blink of an eye at lightening speed. So any so called top amplifier is put to hard task and effort, and if it can't deliver, it will yell out - help!!!

From my first moment I heard the 57's driven by a CJ MV55, partnered with a pv10A pre, it was certainly something extraordinary! Even though I had Maggies at the time, which were far more reliable, were no where close to what the Quads could do. That chap went on to be the Quad guru in cmb, repairing so many models over the years. He then upgraded to the ESL63's stacked up on the Gradient subs, using a pv12, awesome! And that was it! I knew straight away from this point on, where exactly I would be heading...

Going full circle, after too many disasters with Quads, I know that there are people who can refurb these to make them far more reliable than PW would have ever imagined! However, that amplifier matching will always remain a critical factor in order to achieve full stability from these classics.

All the best and I truly hope you find the perfect match, once obtained sit back and enjoy, there's nothing quite like them.
Cheers mate, RJ

 

[Kcin]

I honestly believe they are as near to perfect in the midrange as you can get. I certainly have not heard anything much better. Pure is what I call them.

Of course they are compromised elsewhere: SPL, window on the sound ( very small) and extremes. Even among electrostatics I think they have the best midrange purity. I do think they have very good dynamic contrasts.

Many of their compromises can be ameliorated if they are refurbished- they can't be eliminated. They will become very approachable and they will surprise you.

If you want to keep it simple, this is where 6550's and PP are ok--- will keep you happy.

A really good front end preamp and a decent room... keep them well away from the sides this will pay huge dividends. Nearfield may work extraordinarily well .

Your friends will wonder why they spent the big bucks.

 

[BruceD]

Talk about notorious impedence curve, the CLX's dip to 0.7 in highs and 20 ohms and over in the bass region, and this is not constant, rather variances happen in a blink of an eye at lightening speed. So any so called top amplifier is put to hard task and effort, and if it can't deliver, it will yell out - help!!!
Cheers mate, RJ

Notorious Impedance curves?--indeed my WATT3's dipped to 0.5 Ohm slap bang in the crucial mid range but the Electro A75 handled them with aplomb!-- Hello!-- that little b**ger drove the XG-8 Daytons primary of the Transformer direct--never flinched once!.

Fun times!

BruceD

 

[microstrip]

Notorious Impedance curves?--indeed my WATT3's dipped to 0.5 Ohm slap bang in the crucial mid range but the Electro A75 handled them with aplomb!-- Hello!-- that little b**ger drove the XG-8 Daytons primary of the Transformer direct--never flinched once!.

Fun times!

BruceD

The Watt3 impedance was only 1.75 ohm around 2200 Hz. Because of the Lamm ML3 I did some research in the impedance subject recently ... The friendliest Wilson was the Grand Slamm , 4.6 ohm around 80 Hz.

 

[BruceD]

The Watt3 impedance was only 1.75 ohm around 2200 Hz. Because of the Lamm ML3 I did some research in the impedance subject recently ... The friendliest Wilson was the Grand Slamm , 4.6 ohm around 80 Hz.

Yes Micro--you are correct in the later versions of the Watt 3.

Mine were the first literations I'm told that was mentioned in a conversation with Thierry Budge (who was in the original concept design team)

I would not have mentioned it unless I heard the fact previous .

I've owned and setup Slamms version 1 as well--fine speaker!

Stereophile tested this early version 3's-- clipped from the Jun1991 review ( sorry JA hope this is Ok !)

"Whereas the first WATT plunged down below half an ohm in the low treble"

Read more at https://www.stereophile.com/content...-loudspeaker-measurements#OjvYj4l9I0x3EKMz.99

BruceD

 

[bonzo75]

The grand slamm x1 at @gian60 friend Carlo sounds great with the Riviera hybrids. Much better than his older Levinson. The timing and flow and tone was much improved

 

[Benanton]

The Radford STA25 is a well established partner to Quads. I picked up a new one from Radford Revival, built exactly to spec as the original with some improved parts and materials. https://www.radfordrevival.co.uk/sta-reissue/
I’ve also found success with SS Blue Circle amps as well as an Audiomat integrated. DNM and ASR are other outside the box choices that Quad devotees Robin Wyatt and David Chesky love.

Nothing I’ve tried (including far costlier speakers) has touched the purity of 57’s, particularly in my nearfield listening position. I’ve also subtly supplemented the bottom and top with REL subs and Enigmacoustics super tweeters. Neither were a must, but they do help paint a more complete picture. The tweeters help expand the soundstage to where the “head in a vice” issue is nearly eliminated.

 

[wout31]

The ESL and ESL-63 work great on the modern Schiit Vidar.
The ESL-63 needs two in mono because of the lower efficiency of the speakers
The original ESL can do with 1 in stereo.
Haven't tested the new Aegir yet, but I'm sure they will work even better.

ESL Plus

 

[assessor43]

Is a McIntosh MC 275 too much power for quad ESL 57? Would I be better off with Harbeth monitors? My room is smaller, 12.5 by 14.5 feet

 

[Benanton]

Is a McIntosh MC 275 too much power for quad ESL 57? Would I be better off with Harbeth monitors? My room is smaller, 12.5 by 14.5 feet

Providing the Quads have protection circuitry, not too much power. The length of the room is pushing it unless you don’t mind bringing the speakers way out into the room. Harbeths are very nice (I’ve owned 30.1s and SHL5s) but they really can’t compete with properly functioning Quads in the right room.

 

[assessor43]

I am listening to quad esl 57s with my mc 275 right now. Sound pretty good to me. Quads were made in 1977 so not earlier ones.

 

[wout31]

Schiit Aegir is also a great match with both ESL and ESL-63
ESL has enough with one Aegir in stereo mode, The ESL-63 is more power hungry and needs 2 Aegirs used as mono block.
ESL Plus

 

[Vivianbl]

I came across this thread for the first time a few days and enjoyed the contributions. I have two pairs of 57s- one of which is original and appears from the serial number)to have been produced in the 1980s. I had it serviced about 11years ago. The other one is a fully reconstructed one (2006) with more modern components and small design improvements- the end result being more extension at both ends of the frequency spectrum with wider treble dispersion, can take more powerful amps and play louder! I refer to these as 2057s and are my main listening system speakers.

Over the years I have tried numerous SS and valve amplifiers (vintage and modern) all of which sounded really good. I’m not surprised that so many different amplifiers are recommended by audiophiles for use with 57s.

I found the Leak ST 20 with a dual mono passive pre using Dave Slagle Autoformers, Elna switch and WBT Nextgen sockets gave a superb reproduction. The speakers were very responsive/ sensitive to any changes I made-interconnects, speaker cables, isolation etc.

More recently I had the opportunity to get a used Parallel Singe Ended amplifier. I went against the advice of many HiFi gurus who said SET/PSE and Quad ESLs do not go well together and gave all the technical reason for their views. I took the plunge!

It was an Audion Silver Night Anniversary PSE3 300B (18wpc) Mono blocks. Well it sounded superb with the 2057s -I now had the Quad and SET magic!

I did away with the passive pre as the amplifiers had volume pots and later on upgraded speaker cables and interconnects. The bass is clean and deep and I listen with great joy to the double bass or bass guitar on tracks.
Would be interested to hear if anyone else has tried using SET / PSE with 57s and what your experience was.