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Learning about SUT's

Discussion in 'Turntables' started by Nixxuz, Oct 8, 2018.

  1. Nixxuz

    Nixxuz AK Subscriber Subscriber

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    713
    Location:
    Minnesota
    So a guy on an FB group I'm a part of is looking to run a Yaqin MS23B with an Ortofon Quintet Black. He obviously needs a SUT, but it looks like it'd be cheaper overall to just get an SS pre that supports an MC and be done with it. But it seems as though he really likes the sound of the 23B. I'm seeing wildly differing SUT's on ebay and whatnot, and it seems, from what I'm reading, that you want your output voltage first, and then look at impedance 2nd. I found this guy, but I have no idea if what I am reading corresponds to what he's going to need for a SUT. Moreso, I'm asking because I too would one day like to run an MC, (but probably not $1000 one!), and it would behoove me to know a bit more about what all these numbers mean. I get that you want to match the impedance of the cart, and that you want at least a 1:10 ratio for voltage? Possibly more for the Quintet Black? Any thoughts would be appreciated!

    https://www.ebay.com/itm/4722-Movin...268375?hash=item2cdb16d7d7:g:yLAAAOSwM0FZyXhd

    https://www.ortofon.com/mc-quintet-black-s-p-549
     

     

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  2. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

    Messages:
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    No, matching the impedance is a misunderstood concept which is widely misinterpreted and badly applied to MC cartridges. For example, the Ortofon Quintet Black has a coil resistance of 5 ohms, but that doesn't mean it should see a load impedance of 5 ohms. Ortofon don't even specify an optimum load impedance, just a minimum value of 20 ohms. If you were to "match the impedance" in the conventional sense you would need a transformer with a turns ratio of nearly 1:100, which would be way too high and feed a voltage of 14.5mV into the Yaqin phonostage. As a general rule transformers with high turns ratios don't perform as well as ones with low turns ratios and 1:100 would be an extremely high ratio and I wouldn't expect great performance. I measured a 1:100 "audiophile" step-up transformer once and it was absolutely appalling.
    A turns ratio somewhere between 1:10 and 1:20 will work well with the majority of LOMC cartridges on the market today. Yes, there are exceptions, but I'd say about 80% need something between 1:10 and 1:20. BTW, I'm always suspicious of SUTs which don't even tell you what their turns ratio is.
    The transformers in your link (ratio 1:15) should be fine with the Quintet Black.
    This page might be interesting reading:
    http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html

    There's one other option: get a headamp. A headamp does a similar job to a SUT, ie it raises the output of a LOMC cartridge up to MM level, but it does it with transistors rather than transformers. There aren't many on the market but I supply one called the Headspace.
    http://www.rothwellaudioproducts.co.uk/html/headspace_mc_headamp.html
     
    slimecity, Grbluen, tnsilver and 2 others like this.
  3. Nixxuz

    Nixxuz AK Subscriber Subscriber

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    Minnesota
    Appreciated. I'm just trying to find something for this person that isn't going to cost a heap, and will still let him get the sound he wants from his LesBox. Others have suggested just selling the LesBox and going the route of a solid state phono pre in the $500-$700 range. Perhaps I am just too much of a tube advocate when it comes to vinyl:smoke:
     
  4. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

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    That's one option but many people prefer the sound when using a SUT into an MM phonostage, particularly a valve MM phonostage.
     
    mjw21a likes this.
  5. SB12345

    SB12345 New Member

    Messages:
    41
    Speaking generally, I've found that SUT's sound better than built-in or outboard head amps.

    Some SUT manufacturers build their products specifically for certain MC cartridges and those are the ones to look for if they're available in your "flavor". Just as an example, Auditorium 23 builds their standard model in different varieties. One version works best with the DL-103, Benz, and EMT cartridges, while another version of the otherwise identical SUT is designed for Ortofon cartridges.

    It's this kind of synergy that I would look for first.
     
  6. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

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    The two main variables are the turns ratio and the primary inductance. They are the two parameters which can be altered to suit a particular cartridge, or any other cartridge with the same source impedance and output voltage. Primary inductance is rarely specified but the turns ratio should always be specified in my opinion.

    Auditorium 23 give no specifications whatsoever for their transformers so it's impossible to say how one version suits Benz cartridges etc. and another suits Ortofons.
     

     

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  7. Balifly

    Balifly Listening Subscriber

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    From the end user point of view, it is important to find out what the cartridge out put is.

    Most of the present day production lomc cartridges have out puts in the 0.3 - 0.5 mV range.

    The SUT that can handle that range of output are generally in the $250.00 and above in price.

    Some of the very low out put vintage cartridge with 0.2 and lower may require a SUT that is more efficient and sometimes more costly.

    Most of us would take those factor into consideration before buying the cartridge.

    Some of the build in phono in the integrated amp from the vintage era have exceptional range. :)
    https://www.hifiengine.com/manual_library/luxman/l-435.shtml

    Example of some pretty good and expensive SUT from Japan:

    Denon AU S1

    Audio Technica AT 2000T
     
    Last edited: Oct 9, 2018
  8. hugo454

    hugo454 Gold Member Subscriber

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    Redboy can help,he makes some very nice sut's
     
  9. scoville

    scoville AK Subscriber Subscriber

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    I just purchased a used Denon AU 320 on the auction site for my Supex 900 Super e+ for under 300. It sounds great but when I'm able I'll be going the custom made route. I'll be looking up Redboy for sure.
     
  10. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

    Messages:
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    There's really no connection between turns ratio and quality/price. 1:10 transformers can be quite modestly priced or eye-wateringly expensive.
    At the affordable end of the spectrum I make a transformer called the MC1, available in the USA from Britaudio
    http://www.britaudio.com/

    Used Denon transformers can be found on ebay quite cheaply and they work well with a wide range of cartridges, not just Denons.
     
    mjw21a likes this.
  11. AvFan

    AvFan AK Subscriber Subscriber

    Messages:
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    Location:
    El Cajon, California
    This is a very good thread. I'd like to see the equations that determine the voltage increases of transformers of various ratios and what they do to the impedance seen by the cartridge. Any help with that is appreciated. So does a 1:10 transformer make a 0.3mv into a 3mv signal and a 1:20 transformer turn that signal into 6mv? I thought using a 1:10 transformer resulted in the cartridge being loaded at 470 ohms when using a 47k ohm MM preamp. Similarly a 1:20 transformer would yield a cartridge load of 235 ohms. If that is the case, where in the circuit are resistors applied to adjust the loading to meet a specific cartridge's needs?
     

     

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  12. sqlsavior

    sqlsavior AK Subscriber Subscriber

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    Yes. Multiply the turns ratio by the cartridge output to get the resulting voltage. The result should fall between 2-6 mV, the happy place for most MM phono sections.

    Step-up transformers seem to remove loading fussiness from the picture. Most SUT users do nothing to alter the loading, and report good results nevertheless.
     
  13. mkane

    mkane AK Subscriber Subscriber

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    DSC_0526.JPG Lot's to learn. Hopefully, I get these wire correctly:confused:
     
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  14. Balifly

    Balifly Listening Subscriber

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    The Denon DL-S1 that I am using needs a SUT.

    The SUT that I am using with it at present is on loan to me.

    Been looking for an alternative for some time now.

    The Denon DL-S1 has an output of:

    - Output voltage: 0.15mV
    - Frequency response: 20Hz-70kHz
    - Recommended load impedance: Over 100 ohms
    - Channel balance @ 1kHz: < 1db
    - Channel separation @ 1kHz: > 28dB

    Not many SUT to choose from in today's market. :idea:
     
  15. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

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    Yes, multiplying the signal voltage by the turns ratio gives the output voltage, but only if the cartridge impedance is near zero and the turns ratio quite low. To get an accurate figure for all cases you need to take into consideration the source impedance of the cartridge and the reflected load impedance which become significant when the source impedance is high and/or the turns ratio is high. For example a transformer with a 1:10 turns ratio and a 5 ohm cartridge will output 9.9 times the cartridge voltage, ie very nearly 10 times. On the other hand a transformer with a 1:30 turns ratio and a 40 ohm cartridge will not output 30 times the cartridge voltage. The actual output will be only 17 times the cartridge voltage.
    Yes, a 1:10 transformer will present a 470 ohm load. No, a 1:20 transformer will present a 117 ohm load, not a 235 ohm load. The load seen by the cartridge is the load on the secondary divided by the square of the turns ratio.
    Adding resistors to manipulate the load seen by the cartridge should be done with care because you can't raise the load impedance, only lower it, and you can't lower it without losing some of the signal and affecting the frequency response. The idea that the cartridge must see a specific load impedance isn't correct.
    If you take the recommended load impedance of >100 ohms as gospel you are limited to a maximum turns ratio of 1:20 (or 1:21.7 if you want to be more precise). Unfortunately the DL-S1 has a source impedance of 40 ohms so you won't get 20 times its output from the transformer, only 15 times. That gives you 2.2mV into the MM phonostage. That's just about enough to be ok.
    To get the absolute maximum signal voltage you would require a turns ratio of 1:34. However, that still only gives you 17 times the cartridge voltage, so the signal into the MM phonostage would be 2.55mV, so hardly any more than the 1:20 turns ratio would give you. In addition, the recommended load impedance requirement would not be met because the load seen by the cartridge would be only 40 ohms, not 100 ohms.
    The only alternative would be to use a headamp instead of a transformer. The Headspace would be one possibility:
    http://www.rothwellaudioproducts.co.uk/html/headspace_mc_headamp.html
     
    Last edited: Oct 11, 2018
  16. AvFan

    AvFan AK Subscriber Subscriber

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    Thank you for your thorough reply. I didn't think it would be so easy and I always wondered why my SUT, which has selectable 1:20 and 1:40 ratios, wasn't much louder at the 1:40 ratio. So what equations or method can I use that takes the source impedance and reflected load impedance into account to figure out the cartridge output via a SUT?

    Thank you for noting the equation to find the cartridge load based upon the SUT's turn ratio. Are there any other influences on the amount of load besides the turn ratio and the MM preamps load (typically 47Kohm)? My goal is the load is near but higher than the manufacture's recommended load or 10x the cartridge's internal impedance and then experiment with loads in that vicinity to find what sounds right to me. I must note I generally don't find much difference in sound when at or above the 10x number that I use as a starting point. However, below that load the sound can quickly dull and the soundstage compresses.
     

     

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  17. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

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    The output impedance (aka source impedance) of the cartridge and the reflected load impedance form a potential divider. Use the turns ratio and the load on the secondary of the transformer (usually 47k) to work out the reflected load which the cartridge sees. For example, a 1:25 turns ratio and a 47k load look like a 75 ohm load to the cartridge. If the cartridge has, for example, a 25 ohm source impedance the 75 ohms and 25 ohms form a potential divider just like a volume control and only 3/4 of the signal appears across the primary of the transformer. That 3/4 then gets stepped up by the turns ratio (a factor of 25 in this case) so the output voltage is 18.75 times the cartridge signal voltage. (0.75 x 25 = 18.75)
    In reality there is one further complication. The calculations above assume the transformer windings have zero resistance, but that is impossible. In practice the winding resistance should be low enough to ignore and it shouldn't make a huge difference.
    The load on the secondary side of the transformer is usually 47k - because it's a standard MM phonostage input - but you could put a resistor across the secondary, effectively in parallel with the 47k, and that would be reflected to the primary side and would become the cartridge load. Alternatively, you could put a resistor in parallel with the primary winding and that would load the cartridge directly and appear in parallel to the reflected load.
    However, all these calculations are based on ideal transformers. Real transformers don't behave quite the same and the top-end response can be affected by the load on the secondary - for better or worse. Measurement is the only way to get the best out of real transformers as opposed to text book models of ideal transformers.
     
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  18. mkane

    mkane AK Subscriber Subscriber

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    Is there a way to measure a SUT as a standalone at the output side? In other words, SUT not connected to anything.
     
  19. rothwellaudio

    rothwellaudio Forums Sponsor Sponsor

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    You don't need to connect anything to the output other than test gear. You would need to connect some kind of signal generator to the input.
     
  20. mkane

    mkane AK Subscriber Subscriber

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    DSC_0527.JPG Such as this? Where should it be set?
     

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