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Thread: WTD: MC Phono stage pre-amp.

  1. #1
    Join Date: Jan 2017

    Location: Hampshire

    Posts: 18
    I'm Tony.

    Default WTD: MC Phono stage pre-amp.

    Hi All,
    I am wanting to replace my Cambridge Audio 640P phono pre-amp with something that is a better match to the rest of my system. In particular I have a very low output Dynavector DV-20X2 L which has a maximum output of only about 300 microvolts. The 640P doesn't have enough gain to properly drive my Audiolab 8000Q/8000P combination. Others also observe that, while it is a good entry level phono stage, I need something better than the 640P.

    Any offers?

  2. #2
    Join Date: May 2016

    Location: Notts

    Posts: 2,741
    I'm Geoff.

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    Quote Originally Posted by LateJunction View Post
    Hi All,
    I am wanting to replace my Cambridge Audio 640P phono pre-amp with something that is a better match to the rest of my system. In particular I have a very low output Dynavector DV-20X2 L which has a maximum output of only about 300 microvolts. The 640P doesn't have enough gain to properly drive my Audiolab 8000Q/8000P combination. Others also observe that, while it is a good entry level phono stage, I need something better than the 640P.

    Any offers?
    How about a good step up transformer? https://theartofsound.net/forum/show...ighlight=at630

    Geoff

  3. #3
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

    Posts: 7,087
    I'm Dave.

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    My recommendation would be a Rothwell Rialto or Rega Fono MC. Both very reasonably priced and both excellent.

  4. #4
    Join Date: Jan 2013

    Location: manchester

    Posts: 28
    I'm matt.

    Default

    How about an Arkless Turbo phono stage including special Arkless power supply? Cost me £300 on here including post. Will sell for the same (£300 including post).

  5. #5
    Join Date: Jan 2017

    Location: Hampshire

    Posts: 18
    I'm Tony.

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    Quote Originally Posted by speedboy View Post
    How about an Arkless Turbo phono stage including special Arkless power supply? Cost me £300 on here including post. Will sell for the same (£300 including post).
    Is this 'Turbo' just the re-engineered CA 640P that Arkless Electronics have been offering for some years? I wasn't aware that it has 'special' power supply because the articles about it that I have read state it uses the standard 'wall-wart' supplied with the 640P. The next question in my mind is 'what are the specs?' i.e. how do I know it will deliver the extra gain (up to about 67 dB as suggested by an earlier post) that I require? And how do I know it will sound 'better'. How is that measured?

  6. #6
    Join Date: Jan 2017

    Location: Hampshire

    Posts: 18
    I'm Tony.

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    Quote Originally Posted by RothwellAudio View Post
    If I looked-up the correct specs the 640P has 55dB gain on the MC setting. Yes, that's a bit low for a 0.3mV cartridge. About 64dB, plus or minus 2 or 3dB, would be more like it.
    Alternatively a step-up transformer with a 1:20 turns ratio or a suitable headamp would be a viable option.
    OK, either of these solutions might address the signal level problem, but neither of them will address the 'quality' or 'mis-match' issues that others have mentioned.

  7. #7
    Join Date: Jan 2013

    Location: manchester

    Posts: 28
    I'm matt.

    Default

    I haven't seen it before or since but this example has an upgraded power supply with 12 volt 50VA 'Rcore' transformer in steel case. For technical info pehaps ask Jez Arkless himself as he posts on here. The unit uses loading plugs to supply the exact gain required. If the standard ones are no good, Jez will be able to make up some that are exactly right for you. I'm sorry I don't know what the specs are but I can certainly vouch for the fact that it sounds better than a standard 640P.

  8. #8
    Join Date: May 2016

    Location: Much Wenlock

    Posts: 1,522
    I'm Gary.

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    I though Jez was a bad boy on this forum. Could be wrong though.
    It is easier to seek forgiveness than to ask permission

    Rules are meant for the obedience of fools and the guidance of wise men

  9. #9
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

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    Quote Originally Posted by Stryder5 View Post
    I though Jez was a bad boy on this forum. Could be wrong though.
    He's not on this forum. But folks are free to contact him of course.

  10. #10
    Join Date: Jan 2014

    Location: Northants

    Posts: 276
    I'm Martin.

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    Quote Originally Posted by LateJunction View Post
    OK, either of these solutions might address the signal level problem, but neither of them will address the 'quality' or 'mis-match' issues that others have mentioned.
    What quality and mismatch issues are you referring to? As suggested a 1:20 step up transformer into a 47K ohm MM stage would provide the cartridge with a reflected load of around 117ohms.

    Your Dynavector DV-20X2 L has an internal impedance of 5 ohms and a recommended load of greater than 30 ohms, so the 1:20 step up transformer would be almost perfect.

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