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Thread: Utter Confusion - SUT Settings

  1. #1
    Join Date: Feb 2016

    Location: WIltshire

    Posts: 65
    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)







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  2. #2
    Join Date: Feb 2016

    Location: WIltshire

    Posts: 65
    I'm Peter.

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

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

    Peter


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  3. #3
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 3,299
    I'm Alan.

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    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
    Firebottle - for the no bottleneck approach.

    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: WIltshire

    Posts: 65
    I'm Peter.

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    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
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,123
    I'm Hugo.

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    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.

  6. #6
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 387
    I'm Andrew.

    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.

  7. #7
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 387
    I'm Andrew.

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    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: Feb 2016

    Location: WIltshire

    Posts: 65
    I'm Peter.

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    Andrew,

    Many thanks for that, it's clarified a few confusions on my part.

    You are quite correct, internal impedance is 12 ohms not 0.12 ohms.

    I've now found the very posh box the Benz was supplied in and the documents for this particular cartridge and there are a few differences to my original supplied figures.

    They should have been as detailed below..... and I'm not sure if it will make any difference to your assessment.

    Output Voltage: 0.4 mV at 3.54 cm/s
    Internal impedance 12 ohms
    Recommended loading 100 - 47000 ohm
    Optimum tracking force 1.7 - 2.0 grams

    Sorry if I caused confusion, but I do really appreciate your response.

    BTW! I'm currently trying 1:10 OC at present..... and sounds pretty good.

    My confusion in sound quality (perhaps in my head) is the swop from the Whest Two (line stage) phono preamp to the SUT. I assumed the MM phono stage on the McIntosh was the business, but it is a softer sound as you might expect with a valve amp.

    I've tried a couple of other SUT's without success, I.e Stevens & Billington and the Audio Note.

    Perhaps, it's back to a good phono stage Preamp, unless I can get used to this sound.

    Regards

    Peter


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  9. #9
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,123
    I'm Hugo.

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    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.

  10. #10
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 387
    I'm Andrew.

    Default

    Cartridge outputs are sometimes specified at 3.54 cm/s, sometimes specified at 5 cm/s and sometimes "specified" at some unspecified velocity
    Anyway, even at 0.4mV I would say 1:10 is the best ratio.

    I'm a bit confused by the rest of the info you give though. Whest Two line stage ? I though Whest only made phonostages. And where does McIntosh fit in? Stevens and Billington transformers are very good in my experience, though I still wouldn't recommend a turns ratio much more than 1:10 if possible. Not sure what ratio you had with your S&B transformer.
    My only experience with Audio Note transformers has left me unimpressed.

    The best SUT/non-SUT comparison you could try is to use the cartridge straight into the Whest Two phonostage set to MC operation (about 60dB and 100 ohms(ish)) and compare it to the cartridge into the SUT into the Whest set to MM operation (about 40dB and 47k). I'm assuming the Whest can be set for MM and MC but the manual is rather vague. I note with interest however that Whest claim that "during the design stages of the whestTWO we made a crazy decision to incorporate some of the MC REF V ideas, namely its hybrid active/passive RIAA filter stage. Unlike other units at this price point that use the standard ‘input stage-Passive RIAA filter-output stage’ configuration, the whestTWO uses an identical configuration which was borrowed from the MC REF V Mk4 and this can also be found in the PS.30R. This new RIAA configuration...".
    New configuration? I was using an active/passive approach to RIAA eq about 20 years ago and it was an idea I nicked from somebody else!

    Anyway, when you say you have used other SUTs "without success", could you define success? What is it that you're not getting? And how come you haven't given up on SUTs by now if you had no success with S&B etc.?

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