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Thread: What an OTL is, and why you should care

  1. #31
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    I have heard ML hybrids with Concert Fidelity (UK Paul's), MSB 200, Gamut monos, also class D Bel Canto. There was no brightness. I will be surprised if Luxman, Pass, and Vitus don't work. I have also heard Soundlabs with Spectral and it was excellent. With Krell sometimes I heard brightness sometimes I did not. I have got thinness in tone relative to valve amps on some but density has been achieved keeping valves upstream in dac, phono, or pre and keeping the SS amp. I once got awfully bright sound using Electrocompaniet on MLs, dunno why.
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  2. #32
    [Industry Expert] Addicted to Best! Atmasphere's Avatar
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    Quote Originally Posted by sbo6 View Post
    There is no issue here, you misread and / or misinterpreted my statement. I never said "any SS amp" I said "most modern SS amps ".

    Also I've owned several and have heard many MLs and they sound fabulous with SS amps, no high end loss. Try them with Pass for example, you'd be surprised.
    I'm OK with 'most modern amps'. The issue is getting too much in the way of highs, rather than too little. Pass Labs are excellent- one of the best SS amps out there IMO. ML speakers, having about 0.5 ohms impedance at 20KHz, represent one solution to getting SS to work with ESLs. Make the impedance super low so most amps won't make power due to a near short, and put a speaker cable in series with that, and you've tamed the top end.

    Quote Originally Posted by bonzo75 View Post
    I have heard ML hybrids with Concert Fidelity (UK Paul's), MSB 200, Gamut monos, also class D Bel Canto. There was no brightness. I will be surprised if Luxman, Pass, and Vitus don't work. I have also heard Soundlabs with Spectral and it was excellent. With Krell sometimes I heard brightness sometimes I did not. I have got thinness in tone relative to valve amps on some but density has been achieved keeping valves upstream in dac, phono, or pre and keeping the SS amp. I once got awfully bright sound using Electrocompaniet on MLs, dunno why.
    Sound Lab solves the problems of ESL drive by installing controls on their speakers- they have a Brilliance control, midrange jumpers and bass jumpers. When auditioning amps on Sound Labs, care has to be taken to know the correct settings for each amp in advance so you are making valid comparisons.
    Atma-Sphere Music Systems, Inc. (http://www.atma-sphere.com)

  3. #33
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    Quote Originally Posted by Atmasphere View Post
    (...) Sound Lab solves the problems of ESL drive by installing controls on their speakers- they have a Brilliance control, midrange jumpers and bass jumpers. When auditioning amps on Sound Labs, care has to be taken to know the correct settings for each amp in advance so you are making valid comparisons.
    One nice aspect of the continuous adjustment of brilliance (treble) is that when you decrease treble (slightly needed most of the time) you increase the treble impedance - this typically raises the horribly low treble impedance a few ohms. For maximum quality, after we find the best sounding position the rheostat should be replaced by quality power resistor of equivalent value. There were several versions of backplates, some with low impedance, but it is very simple to modify any of them to be OTL friendly - it can be done in place, Roger West sends the diagram of the mods and parts if needed.
    Under construction around a pair of Wilson XLF's , the Forsell Air Force One, the ARC Phono 2SE and the DCS Vivaldi 2.0 stack : cj GAT + ARC REF250, TA OPUS MM2 +TA XL digital, TA XL gen V power cables and CenterStage feet ...

  4. #34
    Site Founder And Administrator Ron Resnick's Avatar
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    I personally agree with Ralph. I have never heard electrostatic speakers driven by solid-state amplifiers and liked the sound.
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  5. #35
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    Quote Originally Posted by Ron Resnick View Post
    I personally agree with Ralph. I have never heard electrostatic speakers driven by solid-state amplifiers and liked the sound.
    You should listen to Quad ESL63 or modern versions of them with SS. Or Marting Logan's with Electrocompaniet - your old Prodigy's sounded divine with AW250s or Nemo's.

    Cello electronics sounded fabulous with Quad ESL's. And a little bird told me once Roger West is known to use Soundlabs with SS ...
    Under construction around a pair of Wilson XLF's , the Forsell Air Force One, the ARC Phono 2SE and the DCS Vivaldi 2.0 stack : cj GAT + ARC REF250, TA OPUS MM2 +TA XL digital, TA XL gen V power cables and CenterStage feet ...

  6. #36
    Addicted to Best! Harlequin's Avatar
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    Quote Originally Posted by microstrip View Post
    You should listen to Quad ESL63 or modern versions of them with SS.
    Whilst bearing in mind the Quad 63's were designed in concert with the companies SS amplification!

  7. #37
    [WBF Founding Member] Gregadd's Avatar
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    Once you have heard an OTL paired with electrostatic speakers you'll never go back. Because electrostatics present such a difficult load a lot of people, including manufacturers, believe the answer is to match it with a behemoth solid state amplifer. To my ears, reulting in an unfortunate sound.
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  8. #38
    [Industry Expert] Addicted to Best! Atmasphere's Avatar
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    Quote Originally Posted by microstrip View Post
    One nice aspect of the continuous adjustment of brilliance (treble) is that when you decrease treble (slightly needed most of the time) you increase the treble impedance - this typically raises the horribly low treble impedance a few ohms. For maximum quality, after we find the best sounding position the rheostat should be replaced by quality power resistor of equivalent value. There were several versions of backplates, some with low impedance, but it is very simple to modify any of them to be OTL friendly - it can be done in place, Roger West sends the diagram of the mods and parts if needed.
    Actually Sound Lab discovered an error in their crossover ( the driver is full range; the crossover is for the matching transformers in the backplate) and once that error was corrected, the speaker got a lot easier to drive for any amplifier made, and it sounds better to boot. This backplate is called the 'toroidal II'.


    Quote Originally Posted by Gregadd View Post
    Once you have heard an OTL paired with electrostatic speakers you'll never go back. Because electrostatics present such a difficult load a lot of people, including manufacturers, believe the answer is to match it with a behemoth solid state amplifer. To my ears, reulting in an unfortunate sound.
    Right here we see the problem of driving a full range ESL. The Sound Lab and also the older Quads are moderate impedance. But this means they have a fairly high impedance peak in the bass. In the case of the Sound Labs, about 30 ohms. Now if you have a solid state amp that makes 600 watts into 8 ohms, how much does it make into 32? The answer is 150 watts. This is why a tube amp of moderate power can keep up with a rather powerful solid state amp on many ESLs; in the case of the example I just stated, our MA-1 can do the job that it takes a 600 watt SS amp to do.
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  9. #39
    VIP/Donor [VIP/Donor] microstrip's Avatar
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    Quote Originally Posted by Atmasphere View Post
    Actually Sound Lab discovered an error in their crossover ( the driver is full range; the crossover is for the matching transformers in the backplate) and once that error was corrected, the speaker got a lot easier to drive for any amplifier made, and it sounds better to boot. This backplate is called the 'toroidal II'. (...)
    My Soundlabs have the toroidal II - and long before it had the upgrade for high-impedance, that made it easier to drive - it replaced a resistor with a coil, decreasing the power loss in a part of the crossover connected to the toroidal middle/treble transformer. It was two step process.

    The torroidal II increased the efficiency about 2 dB - not bad at all, but not the enormous value (6-9dB) that was mistakenly referred in audio forums by some owners. Soundlab's are large panels, efficiency measurements can not be directly compared to typical efficiencies of point like box speakers at 1m!
    Under construction around a pair of Wilson XLF's , the Forsell Air Force One, the ARC Phono 2SE and the DCS Vivaldi 2.0 stack : cj GAT + ARC REF250, TA OPUS MM2 +TA XL digital, TA XL gen V power cables and CenterStage feet ...

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