Driving Quad 57s with First Watt J2 amp?

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For the few here who are not familiar with the Quad ESLs https://en.wikipedia.org/wiki/Quad_Electrostatic_Loudspeaker
and the ESL 57 in particular QUAD ESL-57 ONE THING

The 57s were intended to be driven at about 15 wpc. They are somewhat fragile, not so easy to repair and cannot be driven beyond 100db SPL without risk of damage from arcing. But ~ 83.5db SPL at 11 ft is probably a bit loud for me in my room anyway. One 57 owner gets very good results by raising them ~ 18” above the floor and using them with a pair of Dynaudio subs. Mine are Rythmik 12" sealed subs.


However, while I’m no kind of expert, success driving the Quads with the J2 seems mostly dependent on two things:

1.) Damping Factor: One Quad 57 owner I know told another one that he tried the Atmasphere S30 OTL tube amp but said it “sounded terrible” with the 57s; “…..nonexistent bass”. The S30 might be an otherwise excellent balanced input, very low feedback Class A amp. But notice that there’s no spec for damping factor or output resistance. Atma-Sphere Earlier when discussing this, Ralph Karsten made the invaluable point that high efficiency speakers-like my 97db, 7 to 8 ohms two way mains-don’t like amps with high damping factor. The midbass will likely sound lean!

So amps with damping factors over 20 are off my short list to drive my hybrid horns.

Conversely, ESLs in general are at least 10db less sensitive than my hybrid horns. For example, Soundlab recommends a 100 wpc amp for their smallest full range ESL model. The more powerful amps tend to have lower output impedance and thus higher damping factors, like the Pass Labs XA series, with typical DFs of 150. https://en.wikipedia.org/wiki/Damping_factor OTOH, the Quad 57s, though even less sensitive that the Soundlabs, probably can’t take much over 50 watts without risk of damage. But, like the Soundlabs, they apparently need an amp with a much higher DF-perhaps at least 20, which is likely at least 5 times higher than the Atmasphere S30.

No wonder that Quad owner go no bass from the S30 driving his 57s.

2.) Stable Output Impedance: The Quad 57’s, like ESLs in general, have wild impedance curves that can play havoc with a lot of amplifiers, regardless of type or output power. Quad ESL & ESL63 Information And so another important point that Ralph made is that “Bass is hard to get with transistors and Quads because many transistor amps will double power as you cut the load impedance in half. The Quad has high impedances in the bass region and low impedances in the treble/HF region. Most transistor amps would likely play the Quad 57s with weak bass and too much highs."

So it looks like the Quads need an amp having both ample damping factor and a high impedance output; not so easy to find in most solid-state amps

But the solid-state J2 has a damping factor of 20. http://www.firstwatt.com/pdf/prod_j2_man.pdf
And according to John Atkinson’s measurements, the J2 not only prefers high impedance loads, but when the 57’s impedance drops to about 3 ohms at ~ 18kHz the J2’s output power drops to perhaps less than half what it is at 8 ohms. Thus, wouldn’t that keep the 57s from sounding bright? Check out this report. First Watt J2 power amplifier Measurements | Stereophile.com

Obviously, the big questions are what is the J2’s watts/channel at 30 ohms?

And what are its overall frequency response, distortion and noise with that load?

Has anyone done or may care to make those J2 measurements or estimations at 30 ohms?

If yes, on a scale of 1 to 10, with 10 being best, how might the J2 amp and the Quad 57s sound together?

Would bass response extend down to its 45Hz spec?

And would treble reach up to its usable 18kHz? And sounding sweet-and hopefully airy-but never bright?
 
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I don't know about the J2, but I built a pass Zen when the design first came out and it worked remarkably well with my original quads at the time (that was really surprising to me). I haven't had luck with single ended tubes and any electrostat, but single ended transistors in the case of the zen worked pretty well. That said, I prefer EL84 based amps with the original quads. But I also often use the Quad II's or a ST-70 variant on them.

I generally listen to my 63's these days with either a quad 99 , or a classe 70, or a citation II.

Also if you are going to be trying higher powered amps, you might want to install a set of the treble panel clamp boards just in case.

Sheldon
 
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I haven't had luck with single ended tubes and any electrostat, but single ended transistors in the case of the zen worked pretty well.
What's so strange is how some Quad 57 owners risk dancing around the 57's wild impedance curve. Friday I'll be attending my VERY first Quad 57 session with at the home of long time owner on Long Island. He's actually driving them with a Wavelength Duetto 300B SET amp. He's also got a Wavelength Crimson DAC. Wavelength Audio Duetto Stereo Amplifier by Ian White It only does 8 wpc. But its switchable down to a 4 ohm output. Presumably, that allows the output voltage to be a lot more constant with frequency, compared to the transformer's 8 ohm tap, yes?


But I suppose that my solid-state J2 amp's output couldn't do this? First Watt J2 power amplifier Measurements | Stereophile.com

Also, if you are going to be trying higher powered amps, you might want to install a set of the treble panel clamp boards just in case. Sheldon
I hadn’t planned on buying higher wpc amps. If I was I would probably pass on getting the Quads and go for this kit.

Acorn Electrostatic Loudspeaker Kit

But Toppsey here said that he actually drove his Acorns with a Yarland 845SE 16 wpc amp! ER audio’s US rep said, that amp must have less than 1 ohm output impedance and the highs would be rolled off as the ESLs’ impedance drops so low up there. But who wants and amp that draws >600w!?

Meanwhile, the J2 is only 13 wpc into 4 ohms, so forget about that option. I just wish I could find a great sounding Class A transistor amp that wasn’t so big and didn’t get so hot and that could drive the Acorns to an average of ~ 84db SPL at ~ 11 ft in my 14 ft x 19 room. If not, then maybe a tube amp-IF it didn’t get so hot.
 
Currently driving my ESL 57's (rebuilt by Wayne Piquet) with a First Watt M2. Very sweet and detailed, but not as punchy as with my diytube st35, an el-84 amp. Try to hear them with Rodger Modjeski's RM-10, which was designed using them. They don't tend to like single-ended triodes.
 
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First Watt F7, Cascode and/or 300B P-P Amps for Quads?

Thanks to Sheldon for the feedback about the First Watt F4 p-p amp and SET amps, if only to rule them out for the Quads. Indeed, the only First Watt that seems to be a really safe bet is the F7, at least according to the ears of this reviewer. https://www.cnet.com/news/first-watt-f7-very-special-amplifier-dazzled-the-audiophiliac/

The F7 is a p-p Class A amp, 20 wpc, damping factor 100. Nelson Pass discusses the design and what he tried to achieve in the manual FIRST WATT F5 Again, like many p-p amps the F7 doubles its power into 4 ohms to 40 wpc, so I’d have to be sure that the Quads have the voltage clamping to protect the tweeters.

The “ideal” amp for the Quads seems to be the same as for probably most speakers: low output impedance and low and local (not global) negative feedback? But what about damping factor? More about this later.

Is anyone familiar with a rather strange high performance animal called a cascode amp? https://en.wikipedia.org/wiki/Cascode Gary Dahl built this ~ 20 wpc amp to drive his two way mains, which are 97db and 7 to 8 ohms. It’s a balanced input, direct coupled, local feedback, two stage cascode amp. It uses with Bud Purvine’s O-Netics Level 3 output transformers, presumably to reduce the amp’s high output impedance.

Gary says the sound is “fantastic”, though his speakers are very different from the Quads; Azura 425 horns/Radian 745 Neo Beryllium drivers atop sealed Altec 416 midwoofers, plus powered Acoustic Elegance subs with passive radiators.

In lieu of schematics, Gary said that this cascode amp uses local feedback. But what might this cascode amp’s output impedance be measured at its output transformers to thereby compute damping factor? https://en.wikipedia.org/wiki/Damping_factor

As for tube amps, I am aware that many find the Quads and 6BQ5/EL84 amps to be among the very best sounding combinations. But would most 300B p-p amps be a good or not so good choice for the Quads?

Before building the cascode amp, Gary’s built Lynn Olson’s Amity 300B p-p mono blocks. http://www.nutshellhifi.com/IT-Triode-Amp.gif However, Gary found that the Lundahl transformer interstage coupling was far less able to get his Azura/Radian beryllium diaphragms to produce highs and upper midrange as cleanly and strongly as does his solid-state cascode amp’s input stage-also a 20 wpc amp.

Again, his main speakers’ system sensitivity and impedance are 97db and 7 to 8 ohms; much different than the Quad 63s, and the 57s even more so. When last we chatted Gary was indeed upgrading his 300B p-ps. I hope to soon learn about those mods. Perhaps he removed the Lundahls and used some very high quality film or oil caps to couple the two stages.

But would 20 wpc 300B p-p mono blocks typically be a good or not so good choice to drive Quads, regardless of input stage design?

Would these amps’ 4 or 8 ohm output taps have low enough impedance and high enough damping factor to get the Quad 57s to deliver all of their bass, and robustly, down to 45Hz or so.

And without rolling off the highs or making them sound bright?

If yes or no, please explain why. Or would 6bq5/EL84 still be a better sounding choice for the Quads in every way?
 
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Proper WPC and Damping Factor for Quad 57/63s?

Currently driving my ESL 57's (rebuilt by Wayne Piquet) with a First Watt M2. Very sweet and detailed, but not as punchy as with my diytube st35, an el-84 amp. Try to hear them with Rodger Modjeski's RM-10, which was designed using them. They don't tend to like single-ended triodes.
Regarding the seemingly mysterious damping factor, OTL amp designers David Berning and Atmasphere’s Ralph Karsten caution that amps with relatively high damping factor tend to sound less than pleasing with high sensitivity speakers like Gary’s >96 db 7 to 8 ohm impedance system. Says Berning at his website “Higher damping is likely to give a tighter, dryer and more analytical sound, and low damping is likely to give a more open and resonant sound. The sonic attributes of damping show up most dramatically in the bass.”

I doubt that Gary’s build of Lynn Olson’s Amity 300B P-Ps have high damping, but one thing that I just found is that relatively high amplifier damping factor is apparently not essential to make the Quads sing. Indeed, lafish recommends the RM10MK2, which Roger Mojeski had voiced with the Quads. It too is an EL84 amp but its damping factor is only 12.5! Music Reference RM-10 Vacuum Tube Amplifer

How can that be? Isn’t it all but physically impossible to have low output impedance without getting high damping factor, at least with 300B or EL84 push-pull amps, compared to their SET counterparts?

So unless the Mojeski’s transformers and/or the EL84 p-ps tubes are as “magical” as the 300B p-ps-or more so when paired with the Quads-then provided the amp has low output impedance is damping factor irreverent?

But what about output power? What is the comfortable amount that the Quads need for best sounding full range response, regardless of average listening levels?

For solid-state, I googled Sheldon’s Classe 70 amp; 70 wpc 8 ohms/ 140 wpc 4 ohms. His Quad 99 amp delivers at least as much power Quad 99 stereo power amplifier Hifi Gear And his Quad 303 does ~ 45 wpc. https://www.hifiengine.com/manual_library/quad/303.shtml

For tubes, Art Dudley’s review has the Quad II’s push-pull paraphrase mono blocks driving his Quad 989s. Apparently he found everything wonderful except that Steeley Dan’s “Reelin in the Years” bass seemed noticeably slow (??). Quad II Classic monoblock power amplifier Page 2 | Stereophile.com Why might this be? The paraphrase circuitry? The selected tubes, none of which are EL84s? And/or that the Quad II mono blocks are only 15 wpc? Quad II Classic monoblock power amplifier Specifications | Stereophile.com

Or do the 989s need more power than the Quad 57s? But again note that while the Quad II monos have half the power of the RM10MK2, they both have the same very
low damping factor, ~ 12.
 
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EL84 P-Ps Still Kings for the Quads?

Conclusions:

Even if a 300B p-p tube amp or solid-state cascode amp has suitably low output impedance, if they have more than 15 but less than 25 wpc, bass response to 45Hz or so may not happen with the Quad 57s?

EL84 p-p amps, which deliver at least 30 wpc are a much safer bet for all around performance than are 20 wpc 300B p-p amps for Quads?

And would the Quad 57s deliver better full range response with 30 wpc than 20 wpc, regardless of average listening levels and room size?

My room is 14 ft x 19 and average listening levels ~ 50 phons or ~ 80db at 70Hz (perhaps +/- 5 phons?), as per the revised 2003 curve shown here. https://en.wikipedia.org/wiki/Equal-loudness_contour

The RM10MK2 might well be a very cost-effective amp for the Quads. It would have been interesting if Srajan Ebaen, Art Dudley or Dick Olsher heard and wrote about such a listening session. 6moons audio reviews: Music Reference RM-10 MkII

As would have been a shoot out like this.
PrimaLuna DiaLogue Seven Monoblock Amplifiers (TAS 199) | The Absolute Sound

But I know that ct0517 was very happy with the RM10MK2. And I suppose that my pair of Rythmik 12" sealed servo subs would blend with the Quad 57s at least as well as his Dynaudio BM12s. https://forum.audiogon.com/discussions/review-quad-57
 
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Have a look to the tube designs of the Quad II amps, for a stable design driving ESL57. The RM10 is an excellent choice, if you can find one. They're rare, second hand.
While I am certainly tied to a budget, the latest RM10MK2 is under $2K.

But as there are clear advantages to OTL amps, are there any such models that you would especially recommend?
 
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