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QUAD ESL 57 - which builder, which amp?

Discussion in 'classic' started by goodkeys, Jan 22, 2019.

  1. mandryka

    mandryka pfm Member

    My own feeling about the 520 echoes what Arkless said about the 303

  2. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Lets just say the 520 is easily beaten....
  3. foxwelljsly

    foxwelljsly Keep Music Vile

    What, in your opinion, might be better and worth trying with an active pre and esl 57’s, without breaking the bank?
  4. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    What's your top spend here?
  5. foxwelljsly

    foxwelljsly Keep Music Vile

    Given that it’ll be a year or so before I can afford a well sorted Radford, is there any thing I could get S/H for £500-£600, or less, that would significantly improve on the 520?
  6. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Musical Fidelity P140, P150 or P170... any of those. It will need rebuilding but it could be done within that price.
  7. foxwelljsly

    foxwelljsly Keep Music Vile

    I’m utterly unfamiliar with MF amps. What might ‘rebuilding’ a 140 entail and cost?
  8. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I ended up writing a virtual novel replying to your PM so for the benefit of others (yes and me as I'll no doubt get a good proportion of any rebuild work:)) wondering about these amps I'm posting it here minus the cost estimate but with a few extra points added.

    The same basic design of power amp was used in everything from the B200 integrated to the SA470 beast and basically the more money one spent on this range the more output mosfets were used, the bigger the power supply and the more biased into class A they got... in rough order of expense and "goodness" it went:

    B200 integrated (B200, P140 and P150 basically the same power amp section but you get a pre thrown in with B200)

    P140 (power amp section only of B200)

    P150 (identical to P140 but has "MkII" mod to reduce hiss. I'll come back to this)

    All the above have a rather small mains transformer for the output power but quite a lot of reservoir capacitance so they are a case like the one described by "JimAudiomisc" the other day in that whilst rated at 75WPC they can give more like 200W for very short peaks... this also means that when used as paralleled monoblocks (see below) RMS power goes up to about 110W rather than staying the same (75W). The doubled up mosfets mod adds to this and about 120W then available as paralleled monoblocks.

    P170 older version without a couple of minor "improvements" but bigger power supply and more output devices.

    Studio T Similar to P170 but IIRC even bigger PSU

    P180 A bit of an odd one this... Basically an A370 built down to a budget and without much class A bias (or heatsinking!) but you get the 5 pairs of mosfets per channel. Has a separate power supply and there was an extra "choke regulated PSU" available which if anything held it back a bit. In effect the £3K A370 with much smaller PSU, very little class A bias and vastly under heatsinked but was more like £900 IIRC. Bit of a curates egg... can sound fantastic but if thrashed can have overheating issues....

    P270 An A370 with 3 pairs of mosfets rather than 5 and smaller PSU but still quite a beast.

    A370 5 pairs of mosfets, huge beast of a thing, 2 x 1KW mains transformers,
    big heatsinks 220WPC class A to 18WPC

    SA470 11 pairs of mosfets, two man lift etc....

    There were P140 X and P150 X later on IIRC but I don't know what precisely the differences are to the earlier versions... probably a last run with left over parts and they added the x for marketing reasons! I had left MF when these were around and have never worked on one.

    In original form they share a foible of being a bit hissy. It wouldn't bother me personally as it's not loud and even very quiet listening masks it but with nothing playing it's certainly noticeable. If you have 103dB/W horns I guess it would be a problem! A modification with a couple of transistors solved it and it was gradually incorporated into the range. B200 I don't recall its name changing at all, P140 became P150, P270 and A370 became "MkII" versions. P170 and Studio T are older and had finished production by this time.

    The problem with all of them is they run hot and were built with basic bog stock electrolytics that were only just up to the job....in fact not quite even up to the job as they used 63V rated caps and put 70V across them!!:eek: so even if you find any of the above amps actually still working they will be on their last legs... Don't let this put you off though because....

    A rebuild with 105C rated top quality electrolytics and general service makes them reliable Quad and Naim etc slayers! They really are considerably better sounding than the forum regular fave rave power amps at and around this price bracket:)

    Other mods are available such as doubling up output mosfets. P140/150 also can be used as monoblocks and have a mono button for this. When used as monoblocks they are paralleled, not bridged, so power goes up only a little but real world load driving ability is much increased (doubled). A pair of P140/150's used as monoblocks is quite formidable!
    A mate of mine has been using a pair (with full mods by myself including doubled up mosfets) for about 20 years plus of daily use without any issues and is presently using them to drive his ATC SCM40's.
    jtrade and Copperjacket like this.
  9. Copperjacket

    Copperjacket pfm Member

    ^^^Excellent thank you! Now off to trawl eBay and suspect I won’t be alone.
  10. goodkeys

    goodkeys Member

    Neither. But that's not the end of the story. The Quad Musikwiedergabe pair had a channel imbalance. One speaker played roughly 3db louder than the other. Needless to say they were out. The One Thing pair was more expensive than I would have liked. But the same seller had another pair, also serviced by Quad, which he sold for a great price. Since last week I am a very happy owner of a wonderful pair of ESL 57s I will post my set up when I have the time.
  11. jamesd

    jamesd pfm Member

    can i ask a silly question about 57's? I assume having a cat is a deal breaker with them in the house?
  12. Dowser

    Dowser Learning to bodge again..

    Don’t understand, why?
  13. jamesd

    jamesd pfm Member

    they look like a good scratching post
  14. Dowser

    Dowser Learning to bodge again..

    Ah, OK :) Only the side cheeks are scratchable, doubt they scratch metal grills. I also had mine on long legs 3 foot above the ground...no problem :)
  15. goodkeys

    goodkeys Member

    Not sure, but if a cat jumped on a speaker it might topple. At least with the original feet. Rupert stands are probably more stable. The siderails could suffer scratches. Other than that it's probably fine.

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