Solid State Amps for Quad ESL 57?

George,

Interesting you should point out that Pass design. About 20 or so years ago N.E.W. loosely based their DCA-33 amp off the A-40. It was about 25 watts Class A and used a separate battery (lead acid) power supply. I owned this amp along with their P-3 preamp which was built for them by Cary and essentially an SLP-50. I still scour the ads for a DCA-33. Nice little amp.

Chris,

The crossover is 100 Hz. The ESL-57s have a 90 Hz bump so you want to crossover above that. The 8" woofers Roger selected can be built in a small sealed enclosure which allows them to have a resonance frequency above 100 Hz that compliments the crossover setting.

There is no significant difference in the RM-3 settings with either the amps. Sometimes I trim the high end a couple dB when running the RM-10 depending on the music. I run the M-60s with 4 tubes each channel so probably about 20 watts. I do use Speltz autoformers with them at 3x setting so that bumps up their power at some frequencies.

Hi Clio09 - the bass impedance hump at 100 hz can be managed by modified placement in the room, especially when it is a fairly large room. See pic 41 on my virtual system. It is roughly 20 x 24 with stairs going up at the back end.
I could never go back to running the speakers in stock mode on the 3 wooden legs. This setup with mid panel at approximately 44 inches, fills the room with sound. and also pretty much eliminates the head vice characteristic of the stock mode.
The preamp has two direct outputs. I am running the Quads full out on the RM10. 
My subs receive a separate direct signal from the preamp and are crossed over at 60 hz. The subs each have Class A/B amps with Linkwitz-Riley crossovers. So with the RM10, three amps are being used in the setup.

Chris,

Sounds like a nice set-up. What subs are you using? My room is 12' w x 18' d and there is a lot of stuff taking up space. So I am pretty limited in placement. I have them about 4' out from the front wall and they are on wood spider legs so they are lifted off the floor. This does make a difference versus the original feet in my opinion, although I'm sure Peter Walker had a good reason for having the speakers so close to the floor.

Clio09
The subs are Dynaudio Acoustics BM12s . In the search to replace the previous sub they were a kind of dark horse for me. Not really known in the consumer area in North America, but well known and used in the recordings studios. For serious listening it’s just me really, so my setup with two works really well with me sitting in the area of the couch position. If I was to extend the seating "around" the room, and needed good sound all around the room, one could just add one or two more in master slave fashion. Each sub has its own 250 Watt Class a/b amplifier. I was given the ability to trial them first.
The subwoofer category in the audiophile world has to be at the top when it comes to # of choices these days ? So many choices. I find the companies like to call the way they control their woofer by a special code name. Dynaudio’s special woofer control is called CEC (Cone Excursion Control) :^)

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Your comments re; RM3 settings on the OTL versus Push Pull amp were very interesting - thanks for that.

There is no significant difference in the RM-3 settings with either the amps. Sometimes I trim the high end a couple dB when running the RM-10 depending on the music. I run the M-60s with 4 tubes each channel so probably about 20 watts. I do use Speltz autoformers with them at 3x setting so that bumps up their power at some frequencies.

My Quad room has an adjacent music room which is really my main room - defined by (where do I go if I need a quick fix) Fwiw the Quad room can not be called my main room because the right sub is placed in very close proximity to where my wife sits upstairs ......anyway.

So I was running 200 wpc OTL’s on the matrix 800 in that room. It was sweet and very nice. Then one day when they were being serviced, I subbed in my modded RM9. It outperformed the OTL’s in the bass department with half the power. That was sort of the beginning of the end for them.

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sorry to digress back to the Quad 57.

The three wood legs allow the speaker to be planted well. This is important. When raised it is important to affix them in a way to allow for the same thing to happen. Stock presentation is like viewing an orchestra from a balcony. I have spent time in the balconies, but it is more the norm to be in a room with multiple tables, and the band/group of musicians on an elevated stage. So the first mod was a 2x4 piece of wood under the rear leg - lowering - the projection angle of the speaker - but - raising - the soundstage. This is one example for me of "Audio Magic" happening in this Audio Hobby. When you experience this the first time, it goes against the way we think. IMO, we don’t generally think about the back wave on an ESL.

From there the speakers were raised onto Arcici stands and moved 7 feet out into the room. This provided the best bass in the space, but I needed better sound dispersion. Raising another foot did it. If you click on the runner and see pic 41 - the last one shows current setup from the last year. The subs are positioned with the woofer cone slightly forward of the speakers with 0 Phase.

That is an interesting set up for the ESL-57s. The Dynaudio subs sound interesting as well. I may look into them a bit more.

The spider legs I have do use a three leg approach like the original. The back leg is affixed in the exact position as the original. The difference is the bottom of the panel is now raised about 14" off the floor and the and panel is no longer tilted back. I am going to try and push them out into the room a bit more. I probably have another foot to play with.

I can say these speakers were a game changer for me in a lot of ways. Even in stock form. I'm regret it took me so long to get there.