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

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.