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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all products

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    quad esl 57


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    quad esl 57 Empty quad esl 57

    Post by kost Wed Nov 02, 2011 7:50 am


    Iam running a pair of esl 57 with a dynaco VTA.
    The sound is ok, very transparent in the middles but the bass is boomy and heavy.
    Any advise?


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    quad esl 57 Empty Re: quad esl 57

    Post by GP49 Wed Nov 02, 2011 12:17 pm

    Compared to what other amplifier?

    The Dynaco Stereo 70 has always been considered an ideal amp for the Quad ESL-57. The Quad actually can do with a bit less power (15 watts to a recommended 25 watts maximum, particularly if the treble section hasn't been retrofitted with the protection circuitry based on that of the ESL-63), so some prefer the Stereo 35 for the sound from its EL84 tubes.

    Have your Quads been checked over thoroughly? I don't have much experience with them but do remember that low polarizing voltage will cause loss of efficiency and bass control. I once heard a pair that sounded loose and flabby but they needed rebuild; new diaphragms.

    The Quad ESL-57 has a very strange impedance curve. It is lowest at 10KHz and up: 2Ω and lower. It is highest at around 100Hz: over 30Ω. The impedance is almost pure capacitive, which will blow up a lot of transistor amplifiers by sending them into fatal oscillation (probably burning out the treble panels in the ESL-57 as they do so). So, as you compare with other amplifiers, be very, VERY careful! A properly functioning stock Stereo 70 is unconditionally stable into the Quad ESL-57. So are the AVA-modified Stereo 70 and the reissue from Sound Valves. I don't know about the VTA circuit since it is, after all, a totally different driver. Maybe Bob can tell us, have the VTA amps been tested with the Quad ESL-57?
    Bob Latino
    Bob Latino

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    Post by Bob Latino Sun Nov 06, 2011 6:27 pm

    Hi Kost,

    I have a few ST-120 customers driving Quad speakers - I don't know if they are the ESL 37? I also have ST-120 customers driving hard to drive Magneplanar planar magnetic and Martin Logan full range ESL speakers. No one has ever mentioned that the bass is "boomy or heavy" with the ST-120? You may want to move your speakers out away from the walls both rear and side walls (if you can). The correct speaker location for one amp may not be the correct location for another amp ?


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    quad esl 57 Empty Re: quad esl 57

    Post by StevieRay Mon Nov 14, 2011 3:52 pm

    The first question is: Do they sound boomy with other tubed/and or SS amps? And that word of caution is justified: unless you know a particular amp is stable with the ESL-57, don't take it for granted. The amp and or ESL's may go up in smoke.

    Second, the HV power supply must be in good shape.

    Third, if the bass panels are old and haven't been rebuilt, they will be boomy, because the bass film is not at the proper tension -- this ages/stretches or perhaps even gets tighter over the years. This is not a jab at VTA's tube kit or a Dynaco 70 or anything else here -- but on these older ESL panels, a SS amp will usually control the bass panels better and help with the boomy bass.

    If on the original legs, which placed the speakers only a few inches off the floor, they could also sound boomy, especially if near a back wall. Side walls are probably OK, but keep them out of corners.

    As far as the VTA board working with Quad ESL-57's: I don't know. I've asked this before on this forum and no-one chimes in except Bob, and he says he has some customers using Quad Electrostats, but doesn't say which. Magneplanars don't count either, as they are a (pretty much) 4 ohm resistive load -- easy load, but they like lots of current (I also have MMG's). Martin Logans don't count either, as their load is much more easy than an ESL-57. In fact, I know of nothing else quite like the Quad ESL-57 that is as difficult a load -- and Quad's ESL-63, 988, 989, 2905 or 2905 aren't as bad. So until I know of someone using the VTA board with the ESL-57, I'm not jumping on board....

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