Learning about SUT's

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

Thank you very much for the comprehensive reply! :thumbsup:

A different approach may be the beginning of a winter research and acquisition fun project.

Separate pre-amp and power amp .......:idea:
 
Couldn't wait for the rest of the parts to arrive Background noise almost non-existent without shielding. Wired 1:20 for the 501mkIIIDSC_0529.JPG
 
@mkane: So how does the Shelter sound with these? 117 ohm load is right where you thought the Shelter sounded best as I recall. What MM phono preamp are you using?
 
Sounds sweet. Beyond the speaker imaging, tight, detailed and focused. Using the Ph3d and I just stuck some Burson OPA's in place of the 637's. Another rabbit hole to contend with. So easy to put together.
 
Love to try those transformers some day. Glad to hear they are working out for you. Not cheap compared to some others... no? I like the current spartan look by the way. Something cool about being able to see the handiwork. What wire did you use or plan to use in the final build? Ever do something like this before? Was it pretty straight forward? Thanks.
 
A mix of 23g & 28g cotton wrapped silver wire. GoIng to use the same wire in the final build with Vampire RCA'S. I've built a few amps, reworked a pair of monoblocks and DIY OB speakers. Putting together this was a snap after a bit of research. I tried to get Nate to put this in a box for me but he said I could do it. transformers were $500.
 
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.

View attachment 1302584 Such as this? Where should it be set?

Here's a relatively easy way I tried (thanks to Rothwell when I was testing some SUTs a while back). Using 1kHz test tone, a 5mV input voltage, and 47kOhm resistor soldered to an RCA connected on secondary side. Measured output voltage was 72.72mV, which is close to as expected (e.g., 5mV x 15 = 75mV).
 
Ok Jumping into this thread.

I have an Entre' MC20 that I re-tipped and need an SUT .
I am looking at a fairly priced Entre ET-15 , A more expensive ET 100 which has three inputs and three load settings .
Now some non Entre SUT's I saw a Fidelity Research FRt-3 with a 10 ohm and 30 ohm load setting priced close tot he Entre ET 15 ,
And a Denon AU-320 with a 3 and 40 ohm setting with a dual input. So Which would fit my cart best? The ET 100 is more than I'd like
to spend right now but in the long term If i get more MC's, might be the best option?


44672290484_7d3e5eeb6f_b.jpg



Athanasios
 
IMO you only need I input and 15:1 might be a good middle of the road setting. 208 ohms
 
I am looking at a fairly priced Entre ET-15 , A more expensive ET 100 which has three inputs and three load settings .
Now some non Entre SUT's I saw a Fidelity Research FRt-3 with a 10 ohm and 30 ohm load setting priced close tot he Entre ET 15 ,
And a Denon AU-320 with a 3 and 40 ohm setting with a dual input. So Which would fit my cart best?
Glad to see you have Rothwell SUTs on your shortlist :dunno:

Anyway, this is a perfect illustration of how people get confused - all this stuff about ohms and load impedances :idea:
What you're trying to achieve is an output from the SUT which is at about the same level as a typical mm cartridge, ie about 5mV. The source impedance of a cartridge (as alluded to in the Denon's "3 and 40 ohm settings") in itself tells you nothing about the level of signal you will get, so what's that all about? It's actually about the frequency response, particularly the low frequency response, you can get with a particular cartridge source impedance and a particular transformer. A 3 ohm cartridge with a "3 ohm" transformer will give you a particular low frequency response, whereas a 40 ohm cartridge with the same "3 ohm" transformer will give you a higher LF cut-off, ie less bass. The problem is that the frequency response is hardly ever specified and without that specification a label such as "3 ohms" is meaningless. From one manufacturer a transformer labelled "3 ohms" might mean a 3 ohm source will go down to 20Hz, whereas a different manufacturer might label a transformer "3 ohms" but with a 3 ohm source it will go down to 5Hz. Who knows if the frequency limits aren't specified? What would be more useful is the turns ratio, but that is often not specified either. None of the transformers on your shortlist specify their turns ratios so no wonder you're confused.

For the Entre cartridge you have in mind you need a transformer with a turns ratio between 1:10 and 1:20, preferably at the 1:20 end of the spectrum. The cartridge's source impedance is only 3 ohms so it will drive practically any transformer with no worries about the bass response.
From my own range I would recommend the MCL or if you're looking for something cheaper the MC1. They're available in the USA from Brit Audio http://www.britaudio.com/
 
There is a MC1 that i was looking at and couldn't find what model number it was so didn't add it to the list, your mentioning it jarred
my memory.

Thanks for the info.

EDIT: But I do prefer to have two inputs as I have Three TT's near my set up and this would allow all three to be connected. And then I could Swap the Entre cart between two on the TT's connected to the SUT.

Nashou
 
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But I do prefer to have two inputs as I have Three TT's near my set up and this would allow all three to be connected. And then I could Swap the Entre cart between two on the TT's connected to the SUT.
Yes, a SUT with multiple inputs and a switching system to select the input you want might be very convenient - but it might also compromise quality or even cause problems with earth loops between turntables. Personally I would prefer to sacrifice convenience to maximise sound quality and minimise the possibility of problems. Threads on the forum about hum problems with turntables are a common occurrence and connecting multiple turntables to one SUT could be great recipe for hum. It wouldn't be impossible to do it hum-free but it would require very careful wiring and switching.
 
So the Entre Et-15 is the way I should go?

Nashou
Don't take what I say as gospel. I'm also quite new with SUT. Shelter 501 is .5mv and to my ears I like 1:20. Denon DL-301mkII is .4mv and it seems to like 1:15.
 
Don't take what I say as gospel. I'm also quite new with SUT. Shelter 501 is .5mv and to my ears I like 1:20. Denon DL-301mkII is .4mv and it seems to like 1:15.
Your advice (1:15) made sense and your choices for the Shelter and Denon cartridges make sense too. It's really the primary inductance of a transformer that determines the LF cut-off but primary inductance is a parameter you will hardly ever see specified. You need more primary inductance for higher source impedance cartridges, but since it is rarely specified, how do you make choices? My advice is that a lower turns ratio is more likely to have a high primary inductance then a high turns ratio. Why? Because for a given size of transformer core/bobbin there's a limit to how much wire you can wind on it. If you want a higher turns ratio the obvious way to do it is to have more turns on the secondary and fewer turns on the primary, resulting in less primary inductance. Less primary inductance makes the transformer less suitable for higher impedance cartridges.
The Shelter 501 has a source impedance of 14 ohms whereas the Denon DL-301mkII has a source impedance of 33 ohms. All else being equal, the Denon needs more primary inductance than the Shelter to get the same LF cut-off. Maybe the lower turns ratio transformer gives you that. Of course, that's only speculation because transformers from different manufacturers could vary wildly, despite having the same turns ratio.
 
Thanks @rothwellaudio for returning to this thread. Your comments are insightful but what I glean from the info in this thread is that 1) transformer performance can vary between different manufacturers, 2) the output of the transformer is not a straight multiplier of the turns ratio times the MC cartridge output but is less as the SUT turns ratio increases and 3) the cartridge load with a SUT is the MM preamp's load (typically 47k ohm) divided by the square of the turns ratio.

I'm trying to narrow down the variables to the few that are typically listed for SUTs. Final cartridge load and output seem to be, at least to me along my ongoing learning curve, the two parameters I can reasonably determine. I'm sure @mkane won't mind if I use his examples.

Don't take what I say as gospel. I'm also quite new with SUT. Shelter 501 is .5mv and to my ears I like 1:20. Denon DL-301mkII is .4mv and it seems to like 1:15.

So the Shelter cartridge/1:20 SUT is not delivering 10mv to the MM preamp but something less. Can the actual output to the MM be calculated or is there a guideline I can use? Say 1:10 is 90%, 1:20 is 65%, etc.? The Shelter is loaded at 118 ohms (assuming he is using a 47kohm MM preamp) and pretty close to the guideline of 10x the cartridge impedance of 140ohms. I suspect that may be a major reason it sounds good with the 1:20 transformer.

The Denon/SUT is probably not yielding 6.0mv but something less but probably around 5mv? The Denon load would be 208 ohms, not quite the 330 (10x source impedance of 33ohms) but high enough to sound better than using a 1:20 SUT. Of course it could be that 208ohms in @mkane's system is just right. Am I correct that a 1:10 SUT might be a better choice to yield a load above 330 ohms? A 1:12 transformer might be optimal and would have a 326 ohm load plus enough output to the MM preamp.

Lastly, in cases where the cartridge impedance is high but the output is low a head amp might be a better choice since it may not be possible to get a high enough output along with a high enough load using a SUT.

Thanks!
 
1: 10 is 470ohm using the Lundahl. The 103r sounds ok here but I think it sounds better @ 168 0hm. The thread is very useful and thanks to everyone for chiming in.
 
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.

Have you ever tried LTspice or something similar? You can simulate the cartridge/load using a SUT and get frequency responses etc. that are pretty close to reality. It takes a bit of work, but it is successful. I was able to get a surprisingly accurate result for a Miyajima Madake cartridge.
 
...what I glean from the info in this thread is that 1) transformer performance can vary between different manufacturers, 2) the output of the transformer is not a straight multiplier of the turns ratio times the MC cartridge output but is less as the SUT turns ratio increases and 3) the cartridge load with a SUT is the MM preamp's load (typically 47k ohm) divided by the square of the turns ratio.
Yes, that is correct.
I'm trying to narrow down the variables to the few that are typically listed for SUTs. Final cartridge load and output seem to be, at least to me along my ongoing learning curve, the two parameters I can reasonably determine.
Those are two parameters which you can determine if you know the turns ratio. Unfortunately the turns ratio is often not specified. Even worse, a manufacturer may label a transformer as, for example, "3 ohms". You might reasonably think that that means the cartridge sees a load impedance of 3 ohms, but in reality that's probably not the case. All too often things are left very vague in the world of step-up transformers. Maybe the manufacturer is trying not to confuse the customer or maybe they're trying to maintain some mystic around their product - who knows?
So the Shelter cartridge/1:20 SUT is not delivering 10mv to the MM preamp but something less. Can the actual output to the MM be calculated or is there a guideline I can use? Say 1:10 is 90%, 1:20 is 65%, etc.? The Shelter is loaded at 118 ohms (assuming he is using a 47kohm MM preamp) and pretty close to the guideline of 10x the cartridge impedance of 140ohms.
Yes, you can calculate it if you know the cartridge's source impedance. First you work out the reflected load impedance (47k divided by the square of the turns ratio). The cartridge's source impedance and the reflected load impedance form a potential divider, and you work out the voltage dropped across the load impedance. Then multiply that by the turns ratio. (see post #17) No, there is no "guideline" for any particular step-up ratio because it will depend on the cartridge's source impedance. If the cartridge had a source impedance of zero the output voltage from the transformer would always be the cartridge output times the turns ratio.
Maybe it's best not to get too hung-up on the maths because for low source impedances (< 12 ohms?) and low turns ratios (1:10?) you can simply multiply the cartridge's output voltage by the turns ratio and you'll be pretty damned close - within 1dB. Of course, the output voltage varies according to how loud the music on the record is, and a cartridge's output voltage may not be what the manufacturer's specs say anyway, and bear in mind that the output is sometimes specified at 3.54cm/sec and sometimes specified at 5cm/sec.
The Denon/SUT is probably not yielding 6.0mv but something less but probably around 5mv? The Denon load would be 208 ohms, not quite the 330 (10x source impedance of 33ohms) but high enough to sound better than using a 1:20 SUT. Of course it could be that 208ohms in @mkane's system is just right. Am I correct that a 1:10 SUT might be a better choice to yield a load above 330 ohms? A 1:12 transformer might be optimal and would have a 326 ohm load plus enough output to the MM preamp.
Yes, the Denon/SUT is yielding 5.2mV, not 6mV. Bear in mind that 5.2mV is only 1.2dB lower than 6mV, so the difference isn't very much at all.
Is the load impedance critical to getting a good sound? I think it's a lot less important than many people assume it is.
Lastly, in cases where the cartridge impedance is high but the output is low a head amp might be a better choice since it may not be possible to get a high enough output along with a high enough load using a SUT.
Yes, I agree. A headamp with a variable load impedance (aka input impedance) would also allow you to test the theory that the load impedance is critical because it's possible to alter the load impedance and maintain the same gain, unlike a transformer. The Headspace lets you do that:
http://www.rothwellaudioproducts.co.uk/html/headspace_mc_headamp.html
I said I agree that a headamp might be best when the cartridge's source impedance is high and its output voltage low but there is a caveat - the headamp has to be a low noise design. When the cartridge's output voltage is low you need a lot of gain and it's difficult to maintain a good signal-to-noise ratio, ie hiss might be audible. Hiss is unlikely to be a problem with a step-up transformer. On the other hand, hum is more likely to be a problem with a transformer.
Personally, I would avoid cartridges with high source impedances and low output voltages - why bother with the hassle when there are so many other cartridges to choose from? :dunno:
 
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