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

  1. #21
    Join Date: Aug 2009

    Location: Staffordshire, England

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    I'm Martin.

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    Maggies all seem to be around 83dB sensitivity, so pretty low. Watts will be needed if you want high SPL in a big room.

    Don't know about maggies in particular but so many speakers are difficult loads, even if it is just over part of the frequency spectrum, I'm sure this, combined with taste in music, is why people have such differing opinions over whether a particular amp is a 'good un' or not.

    In an ideal world all amps would have a very stiff power supply and be able to increase power as impedance drops. But this is the most expensive part of an amplifier to implement so corners get cut. From the manufacturer's point of view what will sell more amps? Good technical spec or a 5mm brushed aluminium fascia? Fact is: it is the fancy fascia.

    Even if a given amp drives the speakers and it sounds fine it isn't necessarily driving them optimally, but you won't notice until you replace it with one that does.
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    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

  2. #22
    Join Date: May 2016

    Location: Notts

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    I'm Geoff.

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    Quote Originally Posted by Macca View Post
    Maggies all seem to be around 83dB sensitivity, so pretty low. Watts will be needed if you want high SPL in a big room.

    Don't know about maggies in particular but so many speakers are difficult loads, even if it is just over part of the frequency spectrum, I'm sure this, combined with taste in music, is why people have such differing opinions over whether a particular amp is a 'good un' or not.

    In an ideal world all amps would have a very stiff power supply and be able to increase power as impedance drops. But this is the most expensive part of an amplifier to implement so corners get cut. From the manufacturer's point of view what will sell more amps? Good technical spec or a 5mm brushed aluminium fascia? Fact is: it is the fancy fascia.

    Even if a given amp drives the speakers and it sounds fine it isn't necessarily driving them optimally, but you won't notice until you replace it with one that does.
    Exactly! Maggies are current "leeches". I can't explain why this is so as although they are relatively inefficient, they are not off the scale.

    They are capable of so much more than many people realise because they hear them with decent amplification not ideal amplification.

    Geoff

  3. #23
    Join Date: Apr 2008

    Location: Warrington

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    I'm Neil.

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    Quote Originally Posted by Sherwood View Post
    Exactly! Maggies are current "leeches". I can't explain why this is so as although they are relatively inefficient, they are not off the scale.

    They are capable of so much more than many people realise because they hear them with decent amplification not ideal amplification.

    Geoff
    Consider that musical peaks can be over 10db from average SPLs, so that 20W or whatever you need for 90db average with Maggies quickly turns into 150W at 100db peaks.
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  4. #24
    Join Date: Nov 2014

    Location: SE London

    Posts: 135
    I'm Oliver.

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    I recall reading somewhere that Glenn Croft uses stacked Quad electrostatics to test his amplifiers, so would assume the Maggies would not pose a problem ?

  5. #25
    Join Date: Apr 2008

    Location: Warrington

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    I'm Neil.

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    Quote Originally Posted by OD1 View Post
    I recall reading somewhere that Glenn Croft uses stacked Quad electrostatics to test his amplifiers, so would assume the Maggies would not pose a problem ?
    Despite both having panels, electrostatics are very different to planar magnetic speakers. Quads don't need a lot of watts, but what they do need is an amp that can handle very high capacitance and a reactive load.
    Mana Acoustics Racks / Bright Star IsoNodes Decoupling >> Allo DigiOne Player >> 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.

  6. #26
    Join Date: Jan 2012

    Location: Norfolk

    Posts: 298
    I'm Chris.

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    As mentioned earlier - I didn't hook up the Croft to these old Maggies knowing that the Croft produces about 45 Watts p/c, so instead tethered the most powerful amp I have at my disposal, a Musical Fidelity MS3i. And from the MF I got some nice sounds so I at least felt that the MF was able to drive some music successfully through these panels whilst I left the Croft sitting disconnected in the corner of a room.

    But it bugged me - shall I try the Croft anyway despite the lowly 45 Watts - and I did! Well by complete surprise it sounded far better than the MF. I was playing music over and over again marveling at the ability of the Crofts having only half the power of the MF, and in turn much lower power than recommended for panels like these! Croft amplification is superb - there's no doubt about it! If you've never owned a Croft - it's about time you did (sorry getting carried away here)...

    This prompted me to email Glenn asking specifics about both driving difficult loudspeakers and what the R upgrade would bring to the party- this is how Glenn replied ...

    The 7 produces 45W into 8 ohms, 50W into 4 ohms and 50W into 2 ohms. It is stable into any load – I have used them into triple stacked Quad 57s which drop to 0.5 ohms at high frequencies.

    The regulation in the 7R is for the driver stage – it does have better output mosfets and a bigger transformer so produces 55W into 8 ohms, 75W into 4 ohms and 90W into 2 ohms.

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