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Quad ESL 57+A&R Cambridge A60 amp?

Discussion in 'classic' started by Radfordman, Aug 19, 2009.

  1. Radfordman

    Radfordman pfm Member

    Does anyone know if this is safe? Will the A60 be able to handle the very low impedance at high frequency that the Quad ESL 57 presents?
  2. Analog addict

    Analog addict pfm Member

    My experience of A60s coping with loads below 8 ohms was not a happy one. The fuses blew at modest volume levels when demonstrating a pair of JBL Radiance speakers, rated I think at 6 ohms.

    Hope this helps.
  3. Radfordman

    Radfordman pfm Member

    Thanks for the reply, I can imagine that happening with those speakers. But its only at high frequencies that the 57 is wicked! Powers will be lower at those frequencies. It is just possible that the A60 will do OK, the impedance of the 57 is fine lower down the scale.

    I have A60's and ESL57 and many other amps, but it is is a friend that is interested in the A60/ ESL57 combination.
  4. DSJR

    DSJR Between us and them

    The A60 is no longer a new amp and hasn't been since the mid eighties. As said above, it was always happy to blow fuses, often for no reason and some unlucky owners had full scale blowups too if "prog" was played too loudly through them.

    For not much more, why not invest in a Quad 33/303, have the preamp Net-Audio'd when funds permit (or Google up the simple layout to the spare disc adaptor input allowing overload-free CD replay) and have the 303 re-capped with beefier supply and output caps, along with modern ones on the amp board (again, net Audio and Dada Electronics do bits and bobs for this purpose). Not only will you get a better sound out of the ESL 57's, you'll stand far less chance of a terminal blowup.
  5. Radfordman

    Radfordman pfm Member

    Well, there is a reason the friend has had a lot of amps, he's very fussy, and likes the A60 into his Spendor BC1's better than any other amps that he's tried (including some of Quads integrated offerings). He is now talking about getting ESL57's.

    I have 57's and well sorted Quad 303's, 405-2, Radford STA25 II, Quad II, etc. etc.

    Comparing the amps through moving coil speakers, I can understand that he wants to stay with the A60. To me it's not as good as the Radford, certainly better than the 405-2 though.
  6. Robert

    Robert Tapehead

    RM, I'll try my 57s with the A60 tomorrow and report back.

    If I go AWOL you'll know it exploded! ;)

    Should work..... although the 57 dips to just over an ohm at 20k there is very little power required up that high.

    I recall many years ago having to use an A60 to drive a big pair of Apogee ribbons with a horrid load. Didn't play very loud but it was useable, sounded ok and didn't go into meltdown.

  7. Radfordman

    Radfordman pfm Member

    Hi Robert, Thanks, but I hope that you are happy to do that. I remember in the 70's connecting a cheap Teleton SAQ206B to ESL57s, it worked and they both survived, though there was a not a lot of power. The same cheap amp into Tannoy 12" Silver DC's was very good, plenty of volume and good sound.
  8. Robert

    Robert Tapehead

    I'm sure it will be fine.

    Teleton - that's a blast form the past.
    Fake wood enclosures, black facia and silver sliders :)
  9. Radfordman

    Radfordman pfm Member

    Yes the B was for black facia, the only slider on the SAQ206B was the balance slider, the slightly later SAQ307 had more sliders (I think!). Actually they were very good little amps, think they were made by Mitsubishi.

    I still have one and it works fine.

    Think it was plywood (only thin) with quite a dark finish, I though it looked quite attractive, but then I drive a very old Volvo!
  10. Robert

    Robert Tapehead

    Didn't know they were built by Mitsubishi.
    I can't recall the model number now, but it had silver sliders and was rated at 20wpc.
    You could switch between magnetic/ceramic cartridges on the back.
    I think we had old Goodmans RB20 speakers at the time and those belonged to my Grandfather. All came from Laskys on the Tottenham Court Rd - happy days :)
  11. Radfordman

    Radfordman pfm Member

    Think that may have been the GA202, the 206B was less than 10W per channel and a very slim cabinet a bit like the A60.
    GA202 was chunkier, think it was about 20 W per channel and did have sliders, think the knobs were silver as you say.

    yes, just seen a pic of GA202, all sliders for the pots and an imitation wood finish on the top. The 206B was better finished. The GA202 was a good performer though. Info I saw says 15W/ channel, but I seem to remember that when tested by a magazine, it did better than that.
  12. Dowser

    Dowser Learning to bodge again..

    Robert - interested to hear the results of your A60/ESL57 pairing. It is exactly what I was intending to use to drive my recently acquired 57's :)

  13. Tony L

    Tony L Administrator

    I didn't know that! I thought the 57 was right at the other end, i.e. nominally 16 Ohm, hence the 303 and 405 being at their happiest at 8 Ohm or above. The 405 in particular is utterly hopeless below 4 Ohms as I recall.

  14. martin clark

    martin clark pinko bodger

    Yes, 405/405-2s have aggressive limiters which hold things down to 50W into 4R and only 17W into 2ohms. But that's OK, 15W is the limit for 57s :)
  15. Robert

    Robert Tapehead

    In addition to Martin's post, if you look at the response of the original Quad treble panel it starts to rise above about 12khz on axis, which is exactly where the impedance is falling.
    Combine that with a typical PP valve amp, eq a Quad II and the amplifier output impedance flattens the top end. The 303 also does this to a more limited extent. Most modern SS amps do not due to very low output impedance, often expressed as high damping factor.

    Thankfully, treble from clingfilm sound wonderfully sweet and clean, so a bit of lift is not a problem - quite a nice effect in fact.

    The poor old 405 gets a bad press but only becasue of incorrect matching IMO.
    Again as Martin says, while 17w into 2 ohms sounds pathetic, it is ample at 20khz for most users :)
    The real reasons for the current limiting on the 405 were cost and size considerations.
    Quad wanted a reasonably priced and compact amplifier that would drive most speakers around at the time.
    The sinking would need to be far larger if more power into low loads was allowed.
    If you disable the 405 protection it will happily give you plenty of power into 4 ohms - until it goes into thermal runaway!
    Its a pragmatic design and to get the best form it requires looking beneath the headline spec figures.
  16. Robert

    Robert Tapehead


    Been running the ESLs from the A60 for a couple of hours and all is well.

    Runs cool, no odd noises, goes plenty loud, no blown fuses and sounds great.
  17. Radfordman

    Radfordman pfm Member

    Hi Robert, that's very good of you to try the test. My friend will be pleased that this combination works.

    I guessed it would be OK for several reasons, an almost silly one is that A&R Cambridge is near the Quad factory, It would seem strange to make a new amp that was not compatible with the ESL.

    Thanks once again.

    I have three A60's earliest one has the discrete phono stage, later one, IC's but still all Din inputs and just recently got a late one which has phono sockets for the disc input and CD input.
  18. Dowser

    Dowser Learning to bodge again..

    Thanks Robert!

  19. davewells

    davewells Member

    Guys. Just had to add that my A60 has been happily powering ESL57's for over 25 years. Not a single problem with either.
  20. Radfordman

    Radfordman pfm Member

    Errmm, do you think you can do an extended test for us?

    Just joking.

    Useful to know, Thanks.

    That is a good record of service and I suspect that it sounds good, otherwise you would have changed something.

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