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Thread: Upgrading a Croft 7 Power Amp to a 7R - How does this help?

  1. #1
    Join Date: Jan 2012

    Location: Norfolk

    Posts: 206
    I'm Chris.

    Default Upgrading a Croft 7 Power Amp to a 7R - How does this help?

    I am currently enjoying listening to a pair of Magnepan MG-1 loudspeakers - within their limitations in my sitting room. I say within their limitations because I understand that 'Maggies' really need a lot of power and control (similar to Electrostatics) to really make Maggie sing. So I am intrigued at the potential left in this design.

    I really like my current Croft 7 pre/power combo - so my dilemma is that I like the panel sound I am getting from these Magneplanars - but I don't want to ditch the Croft in favour of a more powerful amp with greater drive.

    However, it would seem that by upgrading Croft's power amp to an R - which adds a (valve?) Regulated power supply - this will greatly improve the Croft's ability to deal with the varying impedance fluctuations of panel speakers like these (and Electrostatics if I choose to try those later too).

    If 'R' only adds Regulation and not more power (so 45 Watts now and 45 Watts after upgrading to the 7R) how is this so? And how does that work electrically speaking where Regulation help control difficult loads despite not altering the Wattage of the amp?

    Thanks.

  2. #2
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 3,648
    I'm Alan.

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    Unfortunately it is not the output stage that benefits from the regulation.

    As I understand it the regulation is only to the driver (valve) stage.

  3. #3
    Join Date: Jan 2012

    Location: Norfolk

    Posts: 206
    I'm Chris.

    Default

    Quote Originally Posted by Firebottle View Post
    Unfortunately it is not the output stage that benefits from the regulation.

    As I understand it the regulation is only to the driver (valve) stage.
    Damn - I either give up panels or give up Croft - and I don't want to give up either right now! If keeping the panels I will be in search of a very powerful and stable SS amp that drive low impedances well (powerful SS amps usually sound flat and lifeless and are over complicated designs - but hopefully there are exceptions).

    Perhaps the Cambridge Audio 851W. That's valve designs going up in smoke. I would rather have a minimum of 200 Watts plus if I am going the SS route. For example a Roger Sanders amplifier is 500 Watts - but a tad expensive and not from the UK.

  4. #4
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 3,648
    I'm Alan.

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    Well I make Croft inspired monoblocks that include driver regulation and are rated at 55W.

    They drive Maggies very well, I used to have some 1.6QRs.

  5. #5
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

    Posts: 5,238
    I'm Dave.

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    If you are enjoying the sound of your Maggies with the Croft, then there is nothing wrong with the combination and a 7R will just improve on what you have.

  6. #6
    Join Date: Sep 2014

    Location: Northern Ireland

    Posts: 653
    I'm John.

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    I'm pretty sure there were 100w Croft 7 monoblocks for sale here a while ago. So a "special" could probably be ordered from Mr. C.

  7. #7
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 17,817
    I'm Martin.

    Default

    Quote Originally Posted by loonytunes View Post
    Damn - I either give up panels or give up Croft - and I don't want to give up either right now! If keeping the panels I will be in search of a very powerful and stable SS amp that drive low impedances well (powerful SS amps usually sound flat and lifeless and are over complicated designs - but hopefully there are exceptions).

    Perhaps the Cambridge Audio 851W. That's valve designs going up in smoke. I would rather have a minimum of 200 Watts plus if I am going the SS route. For example a Roger Sanders amplifier is 500 Watts - but a tad expensive and not from the UK.
    The Cambridge certainly has wattage. But is that what you need? If volume is not the issue then you don't. You need power into a low impedance load. Both Rotel and Cyrus do power amps that will double output as impedance halves, Can't recall the models but I think about a grand new. Or consider a second hand Krell. This one I am using right now just cannot be faulted in any respect. Makes a nonsense of all the valve vs solid state business.
    Martin



    Current Lash Up:

    Sony X505ES CD Player * NVA P90SA passive pre / Krell KSA50S Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

  8. #8
    Join Date: Jan 2013

    Location: Birmingham

    Posts: 3,093
    I'm James.

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    If you email Glenn C and tell him what speakers you are using he will upgrade your Series 7 power amp accordingly. The whole point of the 7R was its ability to drive difficult speaker loads but if you tell Glenn exactly what speakers your are using he will also up the wattage if needs be or as in Josie ( Blackadders) speakers he actually reduced the output power.
    VPI Scout 1.1 / JMW 9T Tonearm / 2M Black /Croft 25R+ / Croft 7 / Spendor SP2

  9. #9
    Join Date: May 2016

    Location: Notts

    Posts: 593
    I'm Geoff.

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    Maggies need high current designs. Very few amps work well with Maggies.

  10. #10
    Join Date: Apr 2008

    Location: Warrington

    Posts: 2,471
    I'm Neil.

    Default

    Quote Originally Posted by Firebottle View Post
    Well I make Croft inspired monoblocks that include driver regulation and are rated at 55W.

    They drive Maggies very well, I used to have some 1.6QRs.
    They might drive them 'well', but they won't drive them optimally. Is that 55W into 8 Ohms or 4 Ohms?

    As has been mentioned, what Maggies want (and what Magnepan recommend themselves) is solid state with high current capability (amps that double wattage from 8 Ohms to 4 Ohms as a general identifier). Instantaneous current delivery is also important i.e. the ability for the amplifier to 'dump' huge amounts of current during musical peaks, think 20 amps plus.
    Last edited by Yomanze; 12-10-2017 at 08:18.
    Mana Acoustics Racks >> Custom Silent Media Server >> Halide Bridge USB (with AQVOX USB power) >> Pedja Rogic's Audial Model S DAC + Pioneer PL-71 turntable / Vista Audio phono-1 mk II / Denon PCL-5 headshell / Reson Reca >> LFD DLS >> LFD PA2M (SE) >> Royd RR3s.

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