SUT Interconnects

I use a very short 0.4m Van Damme XKE cable terminated with ETI connectors, made by Aurealis Audio, between my EAR MC4 SUT and Nagra VPS phono stage: www.aurealisaudio.com.au/phono-cables/

This is very low capacitance at less than 50pf per metre, is inexpensive and sounds very good. It is also the same as the captive cable of my Audio Origami PU7 arm.

Shielding adds capacitance. Cable geometry also affects capacitance. The 12AX7 tube, often used as the input voltage amplifier in tube MM stages has a high Miller capacitance that adds to cable capacitance. Transistors also add capacitance at the input.

20pf/foot is a practical value for a cable. Mogami makes a console cable that specs in this area. Since transformers can receive either a single-ended signal or balanced, you could run a balanced connection from your arm to the SUT and thus obviate the sonic attributes (or artifacts, however you want to look at it) of the cable.

@atmasphere 

Very interesting! Your vast and deep expertise is always appreciated. 

Considering that SUT box users like me are, for practical reasons, usually limited to a 0.5m minimum cable length on either side (and usually RCA) - what are some good "audiophile" cables with the smallest possible capacitance per foot? Capacitance specs aren't always listed. From the specs I have seen, Cardas interconnects seem to consistently show an impressively low capacitance - much lower even than my AudioQuest phono / LP cables (AQ's normal interconnects are WAY too high). Is there anything likely to be better than Cardas for this role?

I know that besides a spec, there are some clues you can use - like avoid large gauge wires (keep it smaller than 23 AWG) and avoid braided geometries. The Stax headphone cables uses a ribbon layout (with large spacing gaps) to minimize capacitance. 

Could you please explain why it is important to have low capacitance cable before the transformer. how does that affect the transformer ?

The inductance of the cartridge and transformer in parallel with the capacitance of the tonearm cable causes an electrical resonance. Best to keep that resonance as high as possible. Depending on the transformer design you may well have to load the transformer in a certain way to deal with this resonance. So its best to minimize variables by minimizing the capacitive aspects since there is little you can do about the inductances involved.

This is one reason why I prefer to run direct if I can.

@mulveling I have tried numerous interconnects within my system and have had a very tight focus on the Vinyl Chain from Cart' Tag Wire through to Phon'.

After trying  many Cables and then commencing in a investigation of Wire Types.

I urge you to look into a Cable that has a PC Triple C Wire or a D.U.C.C Wire. 

With your willingness to trial and compare, I think this will be a great addition and very very worthwhile to add to your trials.

At first I thought I was over rating the positive influence I was being met with, but after loaning the Cables in both PC, 5 Pin DIN Phono and RCA Phono, the responses from others has pretty much proven to myself, these cables are adding extra in a very attractive way.

I am now working with a few friends to produce and Internal Tonearm Wire in both Wire Types, as well as the RCA and Later on XLR Cables in PC Triple C to be used upstream of the Phonostage.     

@lewm 

The Rothwell MCX uses both primary and secondary internal loading to achieve a 100 ohm load for the cartridge from a 1:10 transformer and minimise ringing etc.

I would have assumed you want low capacitance all the way from the cartridge to the phono inputs. Now you’ve got me thinking.

audioguy85, can you say more about your 1:10 SUT that results in the cartridge seeing 100 ohms? Insofar as transformers have no intrinsic impedance (ideally) you would have to place a 10K resistance across the secondaries of a 1:10 SUT to achieve a 100 ohm load. Maybe that’s what you do. Just curious.

@atmasphere 

Could you please explain why it is important to have low capacitance cable before the transformer. how does that affect the transformer ?

I understand the need for low capacitance after the transformer, but not before.

I always though it was more critical to keep capacitance low AFTER the SUT, rather than BEFORE the SUT, becasue of the after-SUT’s capacitative load supposedly "reflecting back times the sqaure of the turns ratio" (i.e. the opposite of what happens to load resistance)?

@mulveling Its critical to keep the capacitance down on either side of the transformer. Ultimately you'll want to load the transformer correctly for the cartridge you have and the input impedance of the phono section (typically 47KOhms). Some SUTs are designed for a specific cartridge and assume a 47KOhm load so these are less worries. Something like a Jensen which is designed to work with a wide variety of cartridges will need very specific loading to work right. The interconnects are part of that loading and very simply have to be low capacitance.

DNM Reson for unique coherency and overall sound and cost effectiveness but these are not shielded. Shielded ICs are safer in general between SUT and phone. I added custom mu metal foil shielding to my SUT section to facilitate using unshielded ICs with the SUT. See my system pics. I use DNM Reson ICs whenever possible. Cheers!

@mulveling , The advantage of making your own cables is being able to keep them as short as possible. If you use a high bandwidth balanced cable like Canare Da206, use the two inner connectors for signal wires and connect the shield only at one end ( I usually use the load end), you will have a better cable than you can possibly purchase. You will also save a pile of money which you can spend on music.  

I try to use a short length of whatever I'm using as a tonearm cable.

@lewm

The "flying leads" makes sense, thanks. But as far as optimizing total run length to a phono 47K input - I always though it was more critical to keep capacitance low AFTER the SUT, rather than BEFORE the SUT, becasue of the after-SUT’s capacitative load supposedly "reflecting back times the sqaure of the turns ratio" (i.e. the opposite of what happens to load resistance)? I don’t pretend to understand the electrical theory behind this. What’s the theory behind prioritizing the tonearm to be as short as possible? My tonearm cables are all the "standard" 1.2m, but I definitely don’t need all of that length.

Captive, low capacitance, short length leads are best, sometimes known as "flying leads", because the leads are directly soldered to the transformer secondaries inside the chassis of the SUT, at that one end. That way you at least eliminate an RCA jack and plug in the signal path and effectively minimize capacitance. But if you must traverse a distance of 3 ft or greater from cartridge to phono inputs, it would be preferable to have shortest possible (flying) leads on the cartridge to SUT side and make up the remaining distance on the SUT to phono inputs side.

My Fidelity Research FRT-4 has a captive cable, with verry common rca connectors and a ground wire.

I sometimes think of changing it, but it sounds great, gives me no trouble, doesn't lose contact or give intermittant balance issues like some flexible jacks like these do.

Entre ET-100 lets you use your own cable.

What ever Denon used in the AU-320 SUT for the output cables seems to work really well.

BillWojo

I had also used the Bobs silver plated copper but switched to the 

top line Anti-Cable and or top line Morrow silver, 

all .5 M.

Auditorium23, also used as a tonearm cable. 

.5 meter atlas element integra tonearm cables, low capacitance. Also, rothwell the river .5 meter interconnects...these sound a bit brighter than the atlas to my ears. They are silver plated copper. A well shielded cable is a must to reduce noise and hum. The same cable should be used from TT to SUT. You can use whatever interconnect you want from the phono preamp to your integrated/preamp. For that, I use an Atlas elements integra conventional interconnect. My goal is to keep the sound Signature consistent from TT to the integrated line input. My preference is the Atlas cables, they seem to be neutral. I use two different SUT’S, the Jensen mc-2rr-l (made in USA, 1:10 ratio, 430 ohm input impedance) and the Rothwell mcx (UK, 1:10 ratio, 100 ohm input impedance). My cartridge of choice is the Hana EL (.5 mv, >400 ohm) and Goldring Eroica LX (.5 mv, 100ohm) They are a good match to both SUT’s, impedance loading wise, as well as step up ratio requirements. Yes, my set up is low budget in relative terms, however, the cables and SUT’s are of high quality. If I were using a cartridge worth thousands, and a turntable like Mike Fremer’s, then maybe I’d spend more...what I got is fine to my ears.

The lenght of the Verion cable off the SUT was about 12 inches. I still have six pairs of the one-meter Verion RCA cable pairs! Alas, they remain buried in storage!

My Verion - aka Cotter - Type P SUT came with a captive lenght of Verion Tri Axial cable for its outputs. IMO still one of the best SUT’s ever! I paid $375 for mine in 1978! Used with the GAS Sleeping Beauty (Coral 777) mc cartridge. Word to the wise: keep any cable from the SUT output jacks short to avoid capacitive roll-off of highs!