Advice on SUT for Koetsu Rosewood - EAR MC-4, Slagle/EMIA, other

Hang on guys, some transformers have multiple taps and others do not. You have to check on the wires coming out of the transformer. Most are color coded. While having multiple taps gives you flexibility. I think but I am not entirely sure that a single ratio transformer is theoretically better. Ralph may be able to comment on this. Sowter has multiple tap transformers but I have always avoided them. May be just a knee jerk assumption. My brain hates unused wires.  

Over a decade ago I made the below linked post and still stand by it 100% today.

https://forum.audiogon.com/discussions/thoughts-on-cartridge-loading-with-a-sut?highlight=intractaudiohttp://

Some basic takeaways I have found.
-Loading the secondary is the worst thing you can do to a transformer. With a known source  / load combo an optimal transformer can be designed.  
-47K is a silly value for the input of a phono stage when considering a SUT.  Selecting a turns ratio on the reflected load of that 47K is misguided.
-Turns ratio and cartridge load should have zero connection to each other when selecting a SUT.  Turns ratio should be set for appropriate gain (with careful attention to possible overload). Load resistor should be also as high as possible.  Any needed cartridge load should be placed directly at the cartridge.
-Zobel Networks are a Band-Aid for a source to load mismatch of a transformer.  They will make the test equipment happy but always leave the music feeling something is amiss.  
-high Q resonant behavior of a SUT at 30Khz is audible and objectionable yet Low Q resonant behavior above 100Khz seems audibly benign.

dave
 

Dave
Complete novice here on SUT so bear with me please.
"47k is a silly value for an input of a phono stage"
Bearing in mind that is the figure majority of MM phono stages come with and the likely application what figure do you suggest is NOT silly and how to go about making it so?

Hope that makes sense as genuinely intrigued as yep I am running a SUT through a 47k phono stage right now...….

Indeed the 47K is there for MM inputs to properly load a MM cartridge. The 47K value is not a liability for an active MC stage but when the turns ratio of a SUT is considered things change. The 47K value reflects to the Cartridge as 47K/Turns ratio squared. The perfect example of where this becomes an issue is with the Altec 4722. This is a 30/200:40K mic transformer that found a cult-like following because it is a great match wired 1:18 (120:40K) for a denon 103. The interesting thing with this combo is you get essentially the same gain out of a 103 in both the 1:18 hookup and the 1:36 hookup. This happens because assuming 47K, the reflected load of the 1:18 is 145Ω which is fine for a 103 but moving to 1:36 nets a 36Ω load which is less than the 40Ω internal impedance of the 103 which results in a 6dB loss which roughly offsets the 6dB gain from doubling the turns ratio. If the 47K resistor were increased to say 200K suddenly the increase of gain by doubling the turns ratio would be returned however the transformer behavior would also change which may be better or worse. It is interesting to note that some people do prefer the sound of the 1:36 connection with the 103 which has two possible expanations. 1) the transformer has no ringing and is critically damped. 2) loading a cartridge with its internal impedance reduces IM distortion and increases high frequency tracking (Peter Moncrief IAR #5)

Since with the SUT connected the secondary of the transformer serves the purpose of the grid resistor, it can in theory be removed completely. The problem with this is if the SUT is external and the interconnect gets unplugged or has a fault the phono stage can immediately become unstable and wreak havoc with a system with the tweeters usually becoming a casualty. The better solution is to increase the 47K value to the largest value that still keeps the phono stage stable with an open input. This becomes a situation where it is wise to open a dialog with the manufacturer and then have a competent tech change the value retaining the original part to replace if the unit is to ever be resold. I should also point out that increasing the value from 47K serves no purpose if the SUT is relying on that value (and possibly an additional Zobel) for controlled response.

I install a 300K at the input of my LR phono and I believe shindo used 100K so no everyone adheres to that antiquated 47K value.

dave

Dave
Thank you very much indeed, something even my poor simple head can grasp and comprehend!
Dialog with Manley will commence!

Ralph, I will ask Dave Slagle what he thinks about my setup and loading. The original sound tradition Hashimoto hm-7 I tried had an even higher winding ratio such as 1:30 I think. It sounded pretty amazing with 29dB gain. But it was a little too big and "in my face." This will be 26 dB on top of 46 dB of my linestage, which seems reasonable.

Dave didn't believe me when I commented on AudioAsylum some years back that interwinding capacitive coupling is affected by loading, and thus to get flat frequency response loading is a pretty important aspect of transformer use. He's a believer now. BTW his updates on the H/K Citation 2 are excellent.

Hang on guys, some transformers have multiple taps and others do not. You have to check on the wires coming out of the transformer. Most are color coded. While having multiple taps gives you flexibility. I think but I am not entirely sure that a single ratio transformer is theoretically better. Ralph may be able to comment on this. Sowter has multiple tap transformers but I have always avoided them. May be just a knee jerk assumption. My brain hates unused wires.  

Multiple taps don't do anything to degrade performance, but they do allow you to use the transformer in a more flexible manner. The Jensen transformers in the OP's preamp have as commented earlier three different setups that can be used. The wires don't hang unused- they have to be connected together to form either parallel or series arrangements. This affect they way they respond to inter-winding capacitance so the loading requirements change as well.


A nice little side note: All phono cartridges are balanced sources and most of the time are run as if they are single-ended. But when you do this you wind up with that odd 'ground wire' that other single-ended sources don't seem to need. That ground wire is pin 1 of the XLR if you were running balanced. All transformers are capable or running balanced or single-ended input or output, so if you have an SUT you can run balanced from the tone arm to the transformer and single-ended from the transformer output if your phono section is single-ended. The advantage here is that the tone arm interconnect cable ceases to be as critical in the overall system sound; if you had to audition this cable to find the right one for your system you know exactly what I mean.  So you can take another step closer to neutrality by doing this, although you will have to find a place to install the XLR connections to the transformers... again, a fun little fact :)

I think I was better off when I knew nothing at all.... At least I was blissful in my ignorance!

My largest concern here is that it sounds like it is the optimal to build the sut to suit one cartridge so when/ if you do the cartridge square dance ideally you would need change sut too?
Ming boggling.....

Dave didn't believe me when I commented on AudioAsylum some years back that interwinding capacitive coupling is affected by loading, and thus to get flat frequency response loading is a pretty important aspect of transformer use.

I still don't believe you :-)

I think this was in reference to a transformer inside an ampex deck that showed different behavior than I had seen from other line level transformers.  This particular transformer showed a critically damped but rolled off top end and when loaded the midband gain was reduced without effecting the high frequency corner which in "extended" its bandwidth.   I still believe that designing for the specific situation is the best approach and only rely on the load to control things if it is the main purpose of the transformer.  Power delivery to a speaker necessitates a load, working in a 600Ω professional environment also necessitates a load.  A SUT or line level transformer driving a gate/grid of an active device is a different situation where any load or network required is a function of a compromised transformer design and not part of the transformers "job description"

I have seen the age old 'all cartridges are balanced' along with the 'all cartridges are current generators' and rather than bicker about a technical definition, I look at the primary as a two terminal generating device that inherits its mode of behavior from whatever you hook it up to.  I have found that when operating as balanced care must be taken with the cable layout to adhere to the balanced standard and simply attaching an XLR connector to an existing tonearm wire is hit or miss when it comes to hum pickup.  

dave

My largest concern here is that it sounds like it is the optimal to build the sut to suit one cartridge so when/ if you do the cartridge square dance ideally you would need change sut too?

No. You simply have to load it correctly for that cartridge.

I still don't believe you :-)

That's a bit of a surprise- your response on AudioAsylum lead me to believe otherwise. I can point you to a number of other examples should you need more proof.

A SUT or line level transformer driving a gate/grid of an active device is a different situation where any load or network required is a function of a compromised transformer design and not part of the transformers "job description"

SUT's typically drive the input of a phono section, where the input standard is 47Kohms. In this situation, the inductance of the cartridge and the capacitance of the interconnect cable form a resonant circuit. This resonance might have to be snubbed else it can cause troubles for the preamp, if the preamp has poor RFI immunity. That's what the loading resistor is for. However, driving a SUT with its additional inductance this peak is a bit different.  If you don't deal with it it might cause the transformer's response to not be flat- depends on if the transformer is designed specifically for a certain cartridge, but if the transformer is mounted in the preamp as is the case with this thread where the transformer is expected to work with *any* cartridge then loading should be set up. 

  I have found that when operating as balanced care must be taken with the cable layout to adhere to the balanced standard and simply attaching an XLR connector to an existing tonearm wire is hit or miss when it comes to hum pickup.  

Actually you treat it like any other balanced source. The '+' and '-' outputs of the cartridge travel in a shielded twisted pair, the shield is the tone arm ground (pin 3 on DIN connections, pin 1 on XLR connections). If you set it up this way (assuming that the arm itself is actually connected to the ground) there will be no hum whatsoever. 

@intactaudio 

 47K is a silly value for the input of a phono stage when considering a SUT. Selecting a turns ratio on the reflected load of that 47K is misguided.

I install a 300K at the input of my LR phono and I believe shindo used 100K so no everyone adheres to that antiquated 47K value.

Very Interesting.
I can confirm that higher load resistor value in MM input for SUT is harmless, at least to for my ears. I was concerned about it simply because most of my MM phono stages already upgraded with 100k Ohm Vishay instead of some cheap stock 47k Ohm resistors manufacturers installed by default in MM input. But i was a bit afraid to use SUT since 47k Ohm recommended, not 100k Ohm. However, i tried and it was OK. 

Actually it's a good news. 
Luckily my favorite JLTi phono stage was upgraded by the manufacturer upon my request too (internal resistors is 500k Ohm), so i can use parallel RCA plug resistors of 47k Ohm (or 100k Ohm), i can go even higher if needed. The only problem is that i don't have higher than 100k at the moment, but i could buy to try. The reason why i like this JLTi phono stage so much is the flexibility and convenience.

That's a bit of a surprise- your response on AudioAsylum lead me to believe otherwise. I can point you to a number of other examples should you need more proof.

I think we are missing each other on a few of these things.  I have no doubt that assuming enough inductance and a reasonably competent transformer design that for a given cartridge an acceptable network can be found to give flat response.  My contention is those networks put in place to account for a mismatch also do some sincere damage to the sound quality.

We agree that SUT's can never be "universal plug and play" and while you say issues can be fixed by loading, I contend while that is technically true, this imparts a rather large sonic compromise.  

While on this topic I will add that in a perfect world I would install the "ideally matched" SUT into the front end of the phono stage but then what happens when you want to compare a Lyra Atlas to a Van Den Hul Colibri?  In my world you would need a new SUT and in Ralph's world you would need to hope that there is enough inductance to support the VDH and then adjust the load accordingly. In either case with an internal SUT this becomes a difficult task which is why i advocate for using external devices as the best option for this situation.

Which the above answers my thoughts that in the ideal world the SUT would be built and tailored exactly to the cartridge in question.
Makes it a bit of a pain if you swap carts a lot though......

Which the above answers my thoughts that in the ideal world the SUT would be built and tailored exactly to the cartridge in question.
Makes it a bit of a pain if you swap carts a lot though......

I can just swap SUTs for almost any LOMC because smart manufacturers like Luxman made at least 3 different toroidal silver plug-in SUTs for one base connected to the arm and phono stage, very easy to swap in 5 seconds. On that page you see 2 of them, but there was actually one more in the middle (8025 for 3-40 Ohm). There is a SUT for any situation, for carts under 3 Ohm, for carts over 3 Ohm til 40 Ohm, for carts over 40 Ohm. But most of my favorite LOMC are all low impedance, anything from 0.17 mV works fine. 

Any modern manufacturer can offer something like that ?

Not really Uberwaltz, most of the best cartridges now a days are very low impedance. I would just get  transformers for low impedance cartridges.
IMHO an internal transformer is always better. I guess some people are not so hot with a soldering Iron.

Chakster, The Sowter trandformer for low impedance cartridges is good for 1-15 ohms. 1:10 or 1:20. 

Mike

@mijostyn i think we have many good SUTs available today, but the prices are sick for many of them. An old japanese SUTs are great and very cheap compared to modern SUTs, so i’m happy with my Luxman 3 in one.

More like some people do not want to modify the inside of a phono there by ruining potential resale value......

However it should be fairly easy to build a stout SUT as very simple device after all.

Ortofon also made a nice looking SUT in the t-30 that has multiple options although $600 plus used right now.
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F163831234051

Uberwaltz it is very easy to put a transformer in in such a way that the phono amp can be returned to stock and nobody would ever know it had been modified.
chakster, Sowter transformers are British and are made like SME stuff. They cost about $100 per transformer which relative to transformers with a shiny face plate and chassis is CHEAP. Uberwaltz just mentioned a used Ortofon for $600! 

Exactly Mike which I think is pretty Spendy, actually that one was $700 and there are even more Spendy examples on ebay.

And yep I will be first to admit my welding and soldering skills are woefully lacking.
Monkey 💩 springs to mind when viewing the results....

I tried to modify my WLM Phonata Reference phono stage by replacing the built-in SUTs. I gave up, because they are smaller than usual, maybe i will do that when i will find a better SUTs of the same size to fit in, the closest are 1:10 Lundahl SUTs that can be ordered directly from Sweden. This brand is one of the oldest SUTs manufacturer.

The Ortofon T30 had been praised by Jean Hiraga on a phone call we had together many years ago.
I have one.

The HM7 is a bit better sounding for me but twice the price.

If you have several carts the T30 is a top choice as can be a Air Tight ATH2 A with connections for 3 arms an different loadings.

chakster, you can always out board them.

Montaldo, read this.
http://www.kandkaudio.com/applications-guide/
It will back up what Atmasphere has discussed and give you the math to properly load your cartridge.

Mike

Regarding the reviews for various SUTs you will find a lot on Arthur Salvatore's site, he praise ZYX CPP-1 headamp and prefers it over many SUTs. 

The K&K link does not "back" what Ralph says.  Ralph states (correctly) that for any given source there is one load that will make the transformer act in the manner for which it was designed.  The K&K link assumes the transformer to be a perfect device that simply reflects an impedance and has no other impact on the sound.  It is my belief that SUT's should be designed to work optimally in an unloaded situation with 47K input resistor and ~100pf of cable capacitance being the worst case situation.  If the cartridge needs additional loading that should be placed at the primary of the SUT to load the cartridge directly.  I find secondary loading to make a cartridge behave under various situations to be a sonic band-aid.

Years ago I found it interesting that people who use active gain stages tend to find their MC cartridges insensitive to loading and those who use SUT's can get fanatical about it.  I then went through the process of playing with loads on both the primary and the secondary of various SUT's and found that loading the secondary had a much more profound effect on the sonics.  If the transformer were ideal then a 100Ω load should be a 100Ω load independent of whether it is at the cartridge directly or reflected through the transformer.  Since the differences were not subtle I came to the conclusion that the load on the secondary was altering the sound of the transformer as much or more than  it was the cartridge.  This goes a long way to explain the "black art" label attached to loading SUT's since loading the secondary changes both the sound of the SUT and the sound of the cartridge at the same time.  

dave

Dave I am confused on the second variable.  Or what you can do to the transformer to make the cartridge  not need loading.

Let's say you have 5 ohm cart.  We use the 10x rule so 50 ohms is a ballpark load.  We have no input resistor on the phono amp.  Can you build a transformer say 1 to 20 to meet that 50 ohm need.

Or to put it another way on a 1 to 20 step up,  what is the load  variance window you can get by material and or winding?

Thanks Tom

Hey Tom,

Transformer "misbehavior" (ringing etc) is a function of source and load values.  With a known source (cartridge impedance) and load (47K+||100pf) the transformer can be wound such that it gives the desired behavior.  This is a completely different concept than loading the cartridge and much of the confusion in the topic comes from lumping everything together into an "ideal black box"

For your 5 ohm cartridge and a need for 20X gain, a 1:20 can be done to have a low Q resonance of 3-5dB above 100Khz loaded only by the test rig.  Adding the actual input impedance of 47K+ and 100pf for cable capacitance will damp this behavior down to an extended well behaved top end.    Lets assume you want the cart to se 50Ω and the input resistor is 300KΩ.  The turns ratio of 20 will give an impedance ratio of 400 so that 300K becomes 750Ω.  Placing a 54Ω resistor at the cartridge in parallel with the reflected 750Ω will net a 50Ω load with minimal effect on the transformer behavior.  From the transformer primary viewpoint, the 54Ω resistor will lower the 5Ω source impedance to 4.6Ω.   The change in source impedance from 4.6 to 5Ω  is well within the range of source impedances that will work for a given design.  It is when you start changing the source or load impedances by a factor of 2 or more from the "design center" that transformer behavior starts to dominate the sonic signature.  Take the peerless 4722 that works nicely with a denon 103 and drive it with a 2Ω SPU and that controlled top end suddenly turns into a 10+dB peak @ 22Khz.  Fix that 10dB peak with a 10K secondary load and you end up with syrup.

The important thing to understand here is that the load the cartridge sees and the turns ratio of the SUT do not need to have any relationship to each other and simply mathematically attaching them to each other as a ROT generally leads to inconsistent sonic results.  

Reporting back on the effect of adding Dave slagle's 1:20 Copper SUT to my Berning pre and Koetsu Rosewood Signature. In short, everything is back. The gorgeous tonal balance and graceful top end of the Bernng remain,  but now all the Dynamics have been restored and the engagement and involvement is stunning.  the difference is not subtle.  it's as if every component of system were upgraded.

 am I am I right that this huge difference can be attributed to some sort of better loading match between the Transformer and the cartridge?  and maybe it is aided by the additional gain but not primarily driven by that?

Thanks Dave

It is one more variable in the 100's so we can black art our way to audio nirvana.  If you are out at a west coast event let the forum's know.  To hear your modified stacked 57's would be a delight!!!

Enjoy the ride 
Tom

Montaldo it is great to hear your happy.  Dave knows his stuff and can obviously hear music.  He can do all the math and graphs, but when he is done he listens.

Part of the sound difference is in the materials and the build.  Loading and step up are also in the equation.  You changed multiple variables at the same time.  Dave may jump in with some more thoughts.  You may have got lucky and the ballpark is as goods as it gets.  Regardless you seem to be excited about the results so enjoy.

Enjoy the ride
Tom

There was definitely some luck involved but it offsets all the times I have been unlucky with equipment failures, red herring issues, ghosts, phantoms, and just pure stupidity! All the fun of music and audiophilia.
I would like to understand why this sounds so good, but I can live with not knowing in this case and just enjoy the music. It is a real luxury to have all you guys willing to share knowledge. Thanks to all.
Stu

If the cartridge needs additional loading that should be placed at the primary of the SUT to load the cartridge directly. I find secondary loading to make a cartridge behave under various situations to be a sonic band-aid.

Years ago I found it interesting that people who use active gain stages tend to find their MC cartridges insensitive to loading and those who use SUT's can get fanatical about it.

FWIW the loading doesn't do anything for the cartridge at audio frequencies except reduce its output. The loading is audible though, but that is because it detunes the RF resonance caused by the cartridge inductance and the tone arm cable capacitance.
If the preamp is insensitive to RFI the loading doesn't do anything. 47K is therefore an effective load. I've heard loading make a difference but when you get the RFI problems sorted at the phono input, that difference goes away.

While the Jensen is one of the best SUTs available, being best isn't the same as being right for all cartridges for the reasons Dave mentions above. Quality and application are two different things!
But in Stu's system, the problem he described sounded very much like any phono section that isn't getting enough signal. Dynamics wake up, the sound is more vivacious when that is rectified. So comparing the Jensen which is set up for a low boost to a transformer set up for a lot more may not be about the transformers so much as it is the amount of signal presented to the input of the phono section. For that you would have to have both set up as much as possible the same way.