To SUT or not to SUT?

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#1
It seems some like them and some don’t, or just prefer the sound of a more complete phonostage.
I’ve recently purchased a My Sonic Labs Gold cartridge, following Shakti’s interesting journeys through analog.
CBE10594-5A69-4586-A51A-F47FEEBCED19.jpeg

Anyway, I’ve connected it to my XP-25, set the impedance to 500 (in the recommend range) and using the 66dB gain settings.
It sounds really good, and my DS Audio W2 is getting some bench time at the moment.
However, the specs says the Gold outputs a mere 1.4 ohms, this is usually SUT territory, and even though I’m happy with the current end result I’m curious to try a matching SUT and hear what it does.
Immediate suspects are:
1) My Sonic Labs 1030
2) Phasemation T-1000/2000

Thoughts, suggestions and opinions are welcome!
 

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#2
Bump, anyone?
 

213Cobra

Well-Known Member
Aug 27, 2018
253
197
48
66
Los Angeles, CA
#4
Normally I would more than tilt in favor of using an appropriate SUT into the MM inputs of your XP-25, with a MC cartridge. In the specific case of your My Sonic Gold, it's harder to make the case, though that doesn't mean an SUT won't sound different (and better), but the math doesn't lead to the usual conclusions about the differences. The oddity about the MSL Gold is that its internal impedance is a mere 1.4 ohms, but it's output is 0.5mv. Ortofon SPUs vary somewhat in specs but internal impedance of the SPU Wood is just 2.5 ohms with output voltage of a scant 0.18v. In that case, a 40:1 turns ratio SUT yields a cartridge load of ~29 ohms and an output voltage of 6.5mv into a 47kOhms MM load, pretty much perfect. You could even go to a 30:1 xformer and get a 52 ohms load with ~8.5mv output for the MM input of your pre.

But your cartridge combines very low internal impedance (just 1.4 ohms) with fairly strong output (0.5mv) for a low output MC cartridge. It's a lot more like the Ortofon SPU Synergy in that respect (2 ohms internal imp, 0.5mv output). In your case, if you applied a 40:1 ratio xformer for ~29 ohms cartridge loading into 47kOhms, output would climb to ~18mv! That's on the hot side. But your XP-25 is a very robust and flexible phono preamp. As Pass points out in their own manual, MC cartridge loading and gain is not a science, so any settings that work are fair game. So maybe you only need 53db gain with that kind of output. On the other hand, if you go to a 10:1 ratio xformer to get the cartridge load closer to the recommended 500 ohms, you would end up with a 470 ohms load with ~5mv output, spot-on for the 5mv - 10mv range you want to be for most MM inputs. Which approach will sound better, 10:1 ratio, 30:1 ratio or 40:1 ratio xformer into MM, or straight into the XP-25 inputs where you have resistor-based loading in increments beginning at 30 ohms? Hard to predict. But the cartridge sees a resistor and a xformer quite differently, so a 29 or 52 ohms xformer load may well sound much better than a ~500 ohms resistor load. Or maybe only a trifle better. Or not at all.

If you love the direct configuration, then leave it be and listen to music. If you really want to know, you just have to try it. There's no scientific answer. There is math to let you know the electrical context, but as Pass says themselves, MC cartridge loading is a compromise between the cartridge ideal and what satisfies the listener. As you approach a short circuit (low load number) the cartridge will at some point begin to sound muddy and then weaker on dynamics and average level until its unusable. Hence the old rule of thumb that the minimum MC cart load should be at least 10X its internal impedance. As you create more distance from a short circuit, tonal balance can/will shift to treble until you reach a point where no further difference is discernible. Some people like to run some MC cartridges straight into the MM 47kOhms if the preamp has enough MM gain. You never know what people will do!

I use outboard xformers on MC cartridges, or phono preamps with internal MC xformers as 1st gain stage, combined with variable resistance loading. I have not found a case where I prefer an all-active MC gain chain in recent years (circa 1974 the Levinson JC1-DC pre-preamp was a credible exception then), but then there are a lot of phono cartridges & preamps around now and I haven't heard all of them. Just more than a some.

Phil
 
Last edited:
Likes: iaxel

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#5
Thanks Phil!
Indeed it is an art, to match a cartridge to a phono amp.
The My Sonic Lab made SUT has only 1:26 ratio, which, in combination of the 53dB from the Pass low gain setting, may result in relatively ok gain.

But it does require a tryout and the end result is unknown to me. That’s why I asked for the veterans on WBF.
 

howiebrou

Well-Known Member
Jun 29, 2012
1,593
1,356
520
#6
It seems some like them and some don’t, or just prefer the sound of a more complete phonostage.
I’ve recently purchased a My Sonic Labs Gold cartridge, following Shakti’s interesting journeys through analog.
View attachment 67828

Anyway, I’ve connected it to my XP-25, set the impedance to 500 (in the recommend range) and using the 66dB gain settings.
It sounds really good, and my DS Audio W2 is getting some bench time at the moment.
However, the specs says the Gold outputs a mere 1.4 ohms, this is usually SUT territory, and even though I’m happy with the current end result I’m curious to try a matching SUT and hear what it does.
Immediate suspects are:
1) My Sonic Labs 1030
2) Phasemation T-1000/2000

Thoughts, suggestions and opinions are welcome!
I have the MSL 1030 SUT. I quite like it but my phono at the moment has no MM input so it's not being utilised unfortunately.
 
Likes: iaxel

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#7
I have the MSL 1030 SUT. I quite like it but my phono at the moment has no MM input so it's not being utilised unfortunately.
Thanks! To which phono did you connect the 1030?
 

howiebrou

Well-Known Member
Jun 29, 2012
1,593
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#8
Likes: iaxel

213Cobra

Well-Known Member
Aug 27, 2018
253
197
48
66
Los Angeles, CA
#9
Thanks Phil!
Indeed it is an art, to match a cartridge to a phono amp.
The My Sonic Lab made SUT has only 1:26 ratio, which, in combination of the 53dB from the Pass low gain setting, may result in relatively ok gain.

But it does require a tryout and the end result is unknown to me. That’s why I asked for the veterans on WBF.
A 1:26 xformer connected to a 47kOhms input will show the cartridge a load of ~70 ohms. This shows you how even the cartridge maker acknowledges the difference between resistor loading and same by SUT, given that MSL's own resistor loading spec for the cartridge is ~500 ohms. Output from the SUT will be about 13mv, so either or both the 53db or 66db gain settings will likely work.

When people hear meaningful differences between all-active MC preamplification and hybrid (introducing SUT) with a given cartridge, SUT usually wins on overall musicality; active wins on lower noise, deep bass quality, snap and transient definition. But there are certainly instances and combinations that yield completely opposite results. When I first used MC cartridges in the 1970s, a good SUT was always better than all-active MC phono gain, in terms of one sounding more musically convincing than the other. And tubes, noise notwithstanding, were nearly always more musically credible than solid state for the active MM gain stage. Now, as your Pass phono pre shows, a tube isn't mandatory and the burden of proof is on the SUT to justify adding complexity to the gain chain.

Phil
 

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#10
When people hear meaningful differences between all-active MC preamplification and hybrid (introducing SUT) with a given cartridge, SUT usually wins on overall musicality; active wins on lower noise, deep bass quality, snap and transient definition. But there are certainly instances and combinations that yield completely opposite results.

Now, as your Pass phono pre shows, a tube isn't mandatory and the burden of proof is on the SUT to justify adding complexity to the gain chain.
Thanks Phil!
It seems that it boils down to just trying it out on my set up.
 

bazelio

Well-Known Member
Sep 27, 2016
1,446
711
200
California
#11
While I agree with most of Phil's generations, I'd also caution against generalizations. You're in a good position to try SUTs given your low impedance cart. The bass rolloff generalization with SUTs is usually a result of cartridge/SUT electrical mismatches, and usually one that involves carts of higher impedance than yours. But on the other side of the frequency spectrum, you can create a rising response in the high treble region with a low impedance cart, depending on the SUT. So when you try SUTs look for something specified at less than 5 Ohms. But SUT most manufacturers will specify L, M, H. You want L (low). XL (extra low) if that's an option. At that point, you'll know that what you're hearing is not tainted by audible resonances. As for personal preference, I suggest you contact Dave Slagle. The 80% nickel core silver wound SUT is phenomenal, and he'll allow you to demo one that is a good match for your cart and phono. Personally, I doubt you need to go over 1:20 in your system, and 3dB lower is probably still OK. Talk to Dave about it though.
 
Likes: iaxel

213Cobra

Well-Known Member
Aug 27, 2018
253
197
48
66
Los Angeles, CA
#12
While I agree with most of Phil's generations, I'd also caution against generalizations. You're in a good position to try SUTs given your low impedance cart. The bass rolloff generalization with SUTs is usually a result of cartridge/SUT electrical mismatches, and usually one that involves carts of higher impedance than yours. But on the other side of the frequency spectrum, you can create a rising response in the high treble region with a low impedance cart, depending on the SUT. So when you try SUTs look for something specified at less than 5 Ohms. But SUT most manufacturers will specify L, M, H. You want L (low). XL (extra low) if that's an option. At that point, you'll know that what you're hearing is not tainted by audible resonances. As for personal preference, I suggest you contact Dave Slagle. The 80% nickel core silver wound SUT is phenomenal, and he'll allow you to demo one that is a good match for your cart and phono. Personally, I doubt you need to go over 1:20 in your system, and 3dB lower is probably still OK. Talk to Dave about it though.
I was not suggesting that the SUT/MC cart generally delivers bass roll-off compared to all-active gain. I've never found that to be usual. The differences when they appear are more in the realm of bass qualitative character, and even then more a matter of differences where there will be a preference, rather than one being conclusively better or worse, with neither being perfect. The SUT often yields more texture in bass reproduction while all-active gain more slam, for example. But equal response is more common than not, IME.

I agree that the OP probably doesn't need to use more than 1:20 ratio. 1:15 is probably a good match. But it's interesting that the vendor offers one ratio of 1:26, so they think that's ideal for their MC generators. Slagle is definitely good suggestion.

Phil
 

bazelio

Well-Known Member
Sep 27, 2016
1,446
711
200
California
#13
Understood. A lack of slam can be associated with rolloff. And rolloff can be pronounced when there exists a mismatch. I just pointing it out. Otherwise, slam or lack thereof is likely more a function of the phono stage itself than with the use of a SUT.
 

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#14
Thanks! I’ll contact Dave and see what he recommends.
 
Sep 21, 2020
15
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5
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#15
I recently started to use a MSL 1030 SUT to drive the MSL Platinum cart in an MM phono stage and I found it amazingly good. I used to pair MSLP with CH P1+X1 in current mode and/or voltage mode. Also I use Thoress Phonostage. Both gave me a good cart amplification however till I started to use the MSL SUT, I realized that the MSLP has so much more detail and dynamic to be digged out. I heard a much fuller and richer sound from any records that I played, compared to w/o the SUT. It is also quiet in background, though with 26db gain on top of my Thoress and P1 MM at 45db and 55db (on P1).

It is a bit unusual that with 26db, the amplification rate is almost 20x, driving the 0.5mv output up to almost 10mv, out of a normal range. But the sound is good. With a well-paired SUT, I personally believe this is the most efficient way to drive a cart to the best performance it can deliver.
 
Sep 21, 2020
15
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#17
@ShawnZH which MM phono are you using with the SUT that is giving you more detail and dynamics than the P1+X1?
Hi Bazelio,

Actually I used both mm phono of p1 and Thoress, compared to MSL directly into the MC phono input on the same and I got more details and dynamics when feeding MM from the MSL SUT. Though P1 and Thoress carry very different sound signatures, but the improvements made by an MSL SUT are the same.

Interestingly, the improvement made by an EAR MC4 SUT is noticeably less than MSL SUT.
 
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howiebrou

Well-Known Member
Jun 29, 2012
1,593
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520
#18
Hi Bazelio,

Actually I used both mm phono of p1 and Thoress, compared to MSL directly into the MC phono input on the same and I got more details and dynamics when feeding MM from the MSL SUT. Though P1 and Thoress carry very different sound signatures, but the improvements made by an MSL SUT are the same.

Interestingly, the improvement made by an EAR MC4 SUT is noticeably less than MSL SUT.
Would you say that the Thoress with SUT is better than the P1 MC current input?
 

iaxel

Well-Known Member
Oct 25, 2016
178
29
93
#19
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bazelio

Well-Known Member
Sep 27, 2016
1,446
711
200
California
#20
Hi Bazelio,

Actually I used both mm phono of p1 and Thoress, compared to MSL directly into the MC phono input on the same and I got more details and dynamics when feeding MM from the MSL SUT. Though P1 and Thoress carry very different sound signatures, but the improvements made by an MSL SUT are the same.

Interestingly, the improvement made by an EAR MC4 SUT is noticeably less than MSL SUT.
Ok thanks for the clarification. This is definitely useful info. The MSL Platinum is 0.5mV. If you have an even lower output cart, say 0.2mV or less, I'd be curious to find out if the results were the same when comparing the SUT to the P1 current injection input without SUT.
 

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