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Thread: Utter Confusion - SUT Settings

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  1. #1
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default Utter Confusion - SUT Settings

    I'm sure there is some advice or expert opinions from you Hi-Fi Guru's on the Forum.

    My dilemma, is what settings to use for my current SUT. I have read many articles, and to be honest I'm none the wiser. (Mainly because of lack of knowledge / expertise).

    I have included a few photos / information to assist but personally, I just can't get my head round this one.

    It's not a case of what SUT, as I've tried a few high end examples without success or perceived difference in sound quality.

    Anyway, (and I guess not the populous choice) I have an NJC hand built SUT, purchased on many favourable recommendations.

    The SUT has a multitude of setting options, 1:10 / 1:20 and every conceivable resistance setting (see below). However, I am at a loss of which setting is correct or best for the current cartridge, which is a Benz Wood SL. As there appears to be little difference, apart from volume on any chosen setting.

    Settings: (Benz SL)

    Output Voltage 0.56mV
    Source Impedance 0.12 Ohms
    Recommended Load >100 Ohms


    Amp: McIntosh MA 2275

    Phono Stage Sensitivity: 4.4 mV for 2.5V rated output
    Input impedance: phono - 47K Ohms, 65pf
    High level 22K Ohms

    Maximum Input Signal

    Phono 90mV
    High level, 8V

    The rest of the info is in the form of photos, including my current setup. (See below)







    Sent from my iPad using Tapatalk

  2. #2
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default

    Sorry guys..... failed miserably in getting the photos attached....

    Please ignore the above. Useless without the rest of the info.

    Peter


    Sent from my iPad using Tapatalk

  3. #3
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

    Default

    Hi Peter, with the healthy 0.56mV output of the Benz I would set the SUT for 1:10, that will load it well and should provide the best sound.

    Use for a good while to get the sound quality imprinted on your mind before you think of any changes.
    If you use the 1:20 ratio you will be putting a big signal into the phono stage and losing some of the headroom.

    Cheers,
    Alan
    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  4. #4
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default

    Thanks for that Alan,

    Can I ask a further question regarding the Ratio Setting +20dB (1:10)

    There are also resistance settings as detailed below. Is there a preferred setting to use based on the information already supplied for the Benz, or does it really make no difference.

    Resistance. Ratio Setting.
    10k. 82 ohms
    20k. 140 ohms
    30k. 183 ohms
    50k. 242 ohms
    75k. 289 ohms
    OC. 470 ohms

    Many thanks in advance

    Peter


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  5. #5
    RothwellAudio Guest

    Default

    Quote Originally Posted by Boyse6748 View Post
    Can I ask a further question regarding the Ratio Setting +20dB (1:10)

    There are also resistance settings as detailed below. Is there a preferred setting to use based on the information already supplied for the Benz, or does it really make no difference.

    Resistance. Ratio Setting.
    10k. 82 ohms
    20k. 140 ohms
    30k. 183 ohms
    50k. 242 ohms
    75k. 289 ohms
    OC. 470 ohms
    First off, I think one of the specs you have is incorrect. I doubt very much that the coil resistance of your cartidge is 0.12 ohms. It's more likely 12 ohms.

    Secondly, I agree that a turns ratio of 1:10 is best for your cartridge.

    Thirdly, regarding those figures in the table above (resistance/ratio setting) it looks to me like the "resistance" is the value of a resistive load in parallel with the secondary winding. That resistance will be in parallel with the phonostage's input impedance and will appear to the cartridge as a load with the figure in the second column (bizarrely labelled "ratio setting"). So, given a 1:10 turns ratio, a 47k phonostage and no additional load resistor (ie open circuit, or OC) you get the figures in the last line. If you have a 10k resistor in parallel with the secondary it will also be in parallel with the 47k phonostage and become 8.2k, but will appear as 82 ohms to the cartridge. Those are the figures in the first line.
    However, those additional resistors are mostly a waste of time, or at best a hit-and-miss approach to getting anything right (in my opinion). Yes, they may flatten the frequency response by eliminating ringing or compensating for any deficiency in primary inductance but you have no way of knowing that from the figures given.
    My advice is to use the 1:10 turns ratio and keep the secondary load at OC (open circuit) to start with. Then try some additional resistance and just listen for any beneficial effect.

    BTW, this illustrates how confusing SUTs can be. Say for example you find the 30k resistance setting to sound best, you see that equates to a 183 ohm load on the cartridge and conclude that your cartridge works best into a load of about 180 ohms. No, not necessarily so - the 30k resistance is not acting on the cartridge alone, it's acting on the cartridge and the SUT. It could well be having more effect on the SUT than the cartridge.

  6. #6
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Default

    The Benz ought to work best into the OC setting (470 ohms with 20dB gain), but often things with SUTs aren't as simple as the theory suggests, so that should be your starting point - determine your favourite setting by listening. You won't harm the cartridge at all, but you should find that as you move down the resistance settings the sound will become progressively more rolled off.

  7. #7
    RothwellAudio Guest

    Default

    Quote Originally Posted by Ammonite Acoustics View Post
    The Benz ought to work best into the OC setting (470 ohms with 20dB gain), but often things with SUTs aren't as simple as the theory suggests...
    The implication here seems to be that the theory of step-up transformers is simple and that reality is more complex and into the realms of black art. I beg to differ. The problem is that the theory employed by most audiophiles is an over-simplified one.

  8. #8
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Default

    Actually this is pretty much what I was trying to indicate, although in simpler terms intended to be helpful to the OP. SUTS are far from simple things and sometimes they work beautifully when they should not, in theory, and vice versa. The key is, ultimately, in the listening.

    Quote Originally Posted by RothwellAudio View Post
    The implication here seems to be that the theory of step-up transformers is simple and that reality is more complex and into the realms of black art. I beg to differ. The problem is that the theory employed by most audiophiles is an over-simplified one.

  9. #9
    RothwellAudio Guest

    Default

    Quote Originally Posted by Ammonite Acoustics View Post
    Actually this is pretty much what I was trying to indicate, although in simpler terms intended to be helpful to the OP. SUTS are far from simple things and sometimes they work beautifully when they should not, in theory, and vice versa. The key is, ultimately, in the listening.
    My opinon is that if a SUT works beautifully when in theory it should not, there's something wrong with the theory.

  10. #10
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Default

    Quote Originally Posted by RothwellAudio View Post
    My opinon is that if a SUT works beautifully when in theory it should not, there's something wrong with the theory.
    I can do no better than to quote my friend Dave Cawley, although he refers to the pitfalls of measurements rather than theory, as such:

    "if it measures well and sounds good, then it is good" : "if it measures badly and sounds bad then it is bad" : "if it measures badly and sounds good, then it could be improved" : "if it measures well but sounds bad then it is bad" © Dave Cawley

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