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Thread: Running an MC cartridge into 47K with no added gain

  1. #1
    Join Date: Apr 2015

    Location: london

    Posts: 162
    I'm martin.

    Default Running an MC cartridge into 47K with no added gain

    Merry Christmas everyone!

    While experimenting with a new step-up transformer - I tried running an Ortofon MC25 FL into the phono stage (Valab LCR) with gain set to 0db and impedence 47K.
    This goes into a stepped ladder type attenuator (I don't use a pre-amp - just an attenuator) and then into a valve power amp. The sound is better than when I was using various step-up transformers and I've got plenty of gain.

    My speakers are Horning Agathon Ultimate, so fairly sensitive and the amp is push-pull EL34.

    The questions is - is it expected that a relatively low output MC cartridge wouldn't need any amplification prior to getting to a power amp?

  2. #2
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    In my limited experience the design of pre stages for MC cartridges has in the past been problematic with regard to S/N ratio.
    MCs generally need a lot of gain, and to achieve this the designs have to be very well done to avoid noise.

    You may have a lucky combination, or the phono stage have an inherently high gain..

  3. #3
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

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    Well, if it works, it works. I've done the same occasionally, but don't need to as I have a fine SUT handy.

    Just don't go switching to other sources while you have the volume up enough the listen to your MC or you could blow your speakers (or ears).
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  4. #4
    Join Date: Apr 2015

    Location: london

    Posts: 162
    I'm martin.

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    Quote Originally Posted by walpurgis View Post
    Well, if it works, it works. I've done the same occasionally, but don't need to as I have a fine SUT handy.

    Just don't go switching to other sources while you have the volume up enough the listen to your MC or you could blow your speakers (or ears).
    I don't have any switching mechanism - it's simply MC into the phono stage into a bare stepped attenuator into the power amp. So, I'm attenuating the already miniscule? signal coming out of the phono stage with no gain applied.

  5. #5
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

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    Ah. Simple but effective.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  6. #6
    Join Date: Apr 2015

    Location: london

    Posts: 162
    I'm martin.

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    If I understand correctly, if you're using a passive amplifier and the signal coming out of the phono stage doesn't need amplifying for your phono stage/power amp/speaker combo - there is no good reason to increase the gain prior to the attenuator.

    I suppose that there are many people running sensitive systems with low output MC who never tried NOT using a step up attenuator or leaving the gain setting as for the MM?

    Also, why 47K sounds better (to my ears and in my system) than say 200Ohms (for this particular cartridge)? Internal impedence is 6 Ohms - so recommended is 60+ ?
    Theoretically, I could be running this into a MM phono stage with fantastic results.

  7. #7
    Join Date: Oct 2009

    Location: Birmingham, UK

    Posts: 394
    I'm Phil.

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    Hi there , is this due to your sensitive speakers that you are getting away without an sut , im using a valab with cadenza bronze 62db and 200 ohms load , great phono
    for the money , also using a tisbury and valve monos , phil.
    Phil.

  8. #8
    Join Date: Apr 2015

    Location: london

    Posts: 162
    I'm martin.

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    Quote Originally Posted by oceanobsession View Post
    Hi there , is this due to your sensitive speakers that you are getting away without an sut , im using a valab with cadenza bronze 62db and 200 ohms load , great phono
    for the money , also using a tisbury and valve monos , phil.
    I suppose it is. Today I've tried 2 other phono stages and they all work with zero gain and output roughly similar levels. How sensitive are your speakers? Have you tried running with no gain? Is your version of Valab the one that goes from 200 ohms straight to 47k?

  9. #9
    Join Date: Jun 2018

    Location: Mildenhall, Suffolk

    Posts: 380
    I'm John.

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    I have three MM Phon's that I can try this with.
    I can try it immediately with a 'rebuilt Ortofon Kb', I can also at a later time do a Ortofon Kb, and a Hana SL if I feel it is worthwhile.
    I have a Slagle AVC Dual Mono Volume Control, as well as two built in Balance Control Pot's on the 845 Monoblocks, that can be used as Volume Controls. Either gives me options to regulate the Volume.

    I like the idea of this method with the MM Input, If it results in my setting the Pot's wide open on the Monoblocks, this setting cancels out any effects of the Pot' on the SQ, and I can eliminate a additional device in the system, hence remove the Slagle AVC.
    If I were to use the built in Pot's only for Volume Control, a quarter turn will offer more than enough volume level.
    If the MM Input works, the possibility is that I then get the opportunity to have the built in Pot's wide open and maintain a acceptable sound level.
    I can then evaluate the effects of both Volume Control methods on the SQ, as the Slagle AVC is usually used with the Monoblocks Pot's wide open, as well as evaluate a Phon's performance with a SUT removed from the set up.

  10. #10
    Join Date: Apr 2015

    Location: london

    Posts: 162
    I'm martin.

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    Quote Originally Posted by JohnG View Post
    I have a Slagle AVC Dual Mono Volume Control, as well as two built in Balance Control Pot's on the 845 Monoblocks, that can be used as Volume Controls. Either gives me options to regulate the Volume.
    I have never heard a TVC but wanted to go that route before scaling down on ambitions and getting a ladder type pot.
    If you can defeat the pots on power amps - maybe it would be better to keep the Slagle as volume control? In my system, I'm roughly half way up the volume scale, so no compromise in terms of loudness range.
    Anyway, please let us know what are your thoughts once you've tried the combo. I've been mercilessly reducing the signal path everywhere - cables from the attenuator to the phono stage (input) and power amp are soldered to the attenuator and only 10cm long.

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