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Thread: My New Krell

  1. #41
    Join Date: Jan 2009

    Location: Essex

    Posts: 16,092
    I'm openingabottleofwine.

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    Quote Originally Posted by Arkless Electronics View Post

    There are many more advantages to class A than merely getting rid of crossover distortion BTW! Pretty much everything measurable gets much better when class A is used!! The only down sides are it will be big, it will be heavy, it will be very expensive and it will use loads of electricity... If there is any interest I may come back to these things in more detail.... Technical stuff usually kills a thread though!
    Yep, my 25W Class A monoblocks, dissipate 400W when idling, weigh 30Kg each, are about a cubic foot in volume and run so hot I can't use them in the summer.
    Have you listened to this month's choice in the Album Club?

    Barry

  2. #42
    Join Date: Apr 2015

    Location: Central Virginia

    Posts: 558
    I'm Russell.

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    So I did a bit of reading on the subject. Krell claims that the FPB amps can deliver Class A power to its full rating. Due to a process called Sustained Plateau Bias II it raises and lowers the bias as demand dictates. Of course this is what Krell has to say in the owner's manual.

    In practice, it does an amazing job of performing this function. A Google search on sustained plateau bias 2 brings up much interesting reading. And I found one article where the writer performed some tests on my exact amp, which makes it all the more interesting for me anyway.

    http://audioinvestigations.blogspot....teau-bias.html

    Some mumbo jumbo about what he measured as he pushed the amp. It seems it has about 4 levels of bias it jumps back and forth between as required. Keeping it in Class A at all times. Well all times except if it runs hot. If the amp gets too hot, it will lower the bias level and let it run into A/B to keep the temp within safe parameters. Or if it runs out of current. So, that brings up many variables. Speaker load, current demands, room temp, and the volume you are trying to achieve, and others. But, if your speakers present an easy load, and your room is cool, and you aren't trying to break the windows, it should remain in Class A pretty much all the time.

    If you really want to get into some heady reading, I read most of this:

    https://books.google.com/books?id=7d...s%20II&f=false

    That really takes me back to my college days. Great stuff if you're having trouble sleeping. And there was a whole page on Google on the subject, if anyone was interested enough to read it all. But these modern designs allow us to have large class A amps that would have been cost and weight prohibitive in the past. Not that a $10k amp that weighs 130lbs is practical.


    Sent from my iPad using Tapatalk

  3. #43
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 36,567
    I'm Grant.

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    My MF A1000 was supposedly class A all the way. It certainly got damn hot and had a lot of cooling fins.
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    DENON DV2900 - TWIN PRO MONOBLOCK AMPLIFIERS - XIANG SHENG DAC\PRE\HEADPHONE AMP - AVANTREE OASIS CLASS 1 BLUETOOTH - AUDIO TECHNICA ATH-MSR7 & OPPO PM-3 PLANAR HEADPHONES - WIN10 JRIVER23, SPOTIFY PREMIUM - ECHO DOT - SMSL M6 MINIDAC - FULL RANGE TWIN TELEFUNKEN's - Q ACOUSTIC BT3 actives - CANTON SUB - MAINS REGENERATED AND FILTERED.

  4. #44
    Join Date: Mar 2014

    Location: KY - Scotland

    Posts: 2,356
    I'm Mike.

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    My wife says I'm Class A and I'm definitely hot all the time 😊

    But I might be biased 😂

  5. #45
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 36,567
    I'm Grant.

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    Quote Originally Posted by mikeyb View Post
    My wife says I'm Class A and I'm definitely hot all the time ��

    But I might be biased ��
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    DENON DV2900 - TWIN PRO MONOBLOCK AMPLIFIERS - XIANG SHENG DAC\PRE\HEADPHONE AMP - AVANTREE OASIS CLASS 1 BLUETOOTH - AUDIO TECHNICA ATH-MSR7 & OPPO PM-3 PLANAR HEADPHONES - WIN10 JRIVER23, SPOTIFY PREMIUM - ECHO DOT - SMSL M6 MINIDAC - FULL RANGE TWIN TELEFUNKEN's - Q ACOUSTIC BT3 actives - CANTON SUB - MAINS REGENERATED AND FILTERED.

  6. #46
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,647
    I'm Jez.

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    Quote Originally Posted by struth View Post
    My MF A1000 was supposedly class A all the way. It certainly got damn hot and had a lot of cooling fins.
    I doubt it.... I would expect much bigger heatsinks than that for 50W class A.

  7. #47
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 36,567
    I'm Grant.

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    Quote Originally Posted by Arkless Electronics View Post
    I doubt it.... I would expect much bigger heatsinks than that for 50W class A.
    That was what they said re it... 16 output transistors.. specs were

    Power output : 2x 50W (Class A, 8 Ohm)
    MC input : 600V
    MM input : 8mV
    Line inputs : 350mV
    S/N ratio : > 60dB (MC)
    > 75dB (MM)
    > 85dB (lines)
    RIAA accuracy : 0,7dB
    THD : < 0,5% (20Hz...20Khz)
    Channel separation : > 85dB
    PC : 215W continuous
    Dimensions : 48,3 x 12,2 x 33,5cm (A1000)
    19,4 x 12,2 x 33,5cm (PSU)
    Weight : 11kg (A1000)
    7kg (PSU)
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    DENON DV2900 - TWIN PRO MONOBLOCK AMPLIFIERS - XIANG SHENG DAC\PRE\HEADPHONE AMP - AVANTREE OASIS CLASS 1 BLUETOOTH - AUDIO TECHNICA ATH-MSR7 & OPPO PM-3 PLANAR HEADPHONES - WIN10 JRIVER23, SPOTIFY PREMIUM - ECHO DOT - SMSL M6 MINIDAC - FULL RANGE TWIN TELEFUNKEN's - Q ACOUSTIC BT3 actives - CANTON SUB - MAINS REGENERATED AND FILTERED.

  8. #48
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,647
    I'm Jez.

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    Quote Originally Posted by Barry View Post
    Yep, my 25W Class A monoblocks, dissipate 400W when idling, weigh 30Kg each, are about a cubic foot in volume and run so hot I can't use them in the summer.
    I would expect that these give class A into 4R, 50W, if they dissipate that much! Nice!

    If an amp is specified as say 20W into 8R, class A, then it will only give 10W class A into 4R.... it may well double its power to 40W yes, but only the first 10W will now be in class A. I suspect Barry's amp is biased at probably double the class A current actually needed to give 25W. This is excellent but not cheap!! This means that when the amp is close to voltage clipping into 8R (at 25W) it is still nowhere near to coming out of class A

  9. #49
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,647
    I'm Jez.

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    Quote Originally Posted by struth View Post
    That was what they said re it... 16 output transistors.. specs were

    Power output : 2x 50W (Class A, 8 Ohm)
    MC input : 600V
    MM input : 8mV
    Line inputs : 350mV
    S/N ratio : > 60dB (MC)
    > 75dB (MM)
    > 85dB (lines)
    RIAA accuracy : 0,7dB
    THD : < 0,5% (20Hz...20Khz)
    Channel separation : > 85dB
    PC : 215W continuous
    Dimensions : 48,3 x 12,2 x 33,5cm (A1000)
    19,4 x 12,2 x 33,5cm (PSU)
    Weight : 11kg (A1000)
    7kg (PSU)
    And you believe them? I used to work for them remember

  10. #50
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 36,567
    I'm Grant.

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    Sounded bloody marvellous and I really should have kept it





    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    DENON DV2900 - TWIN PRO MONOBLOCK AMPLIFIERS - XIANG SHENG DAC\PRE\HEADPHONE AMP - AVANTREE OASIS CLASS 1 BLUETOOTH - AUDIO TECHNICA ATH-MSR7 & OPPO PM-3 PLANAR HEADPHONES - WIN10 JRIVER23, SPOTIFY PREMIUM - ECHO DOT - SMSL M6 MINIDAC - FULL RANGE TWIN TELEFUNKEN's - Q ACOUSTIC BT3 actives - CANTON SUB - MAINS REGENERATED AND FILTERED.

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