A simple guide to MC/SUT impedance matching?

[eddieedwards]

Having bought a Rondo Bronze quite recently, I'm new to the whole world of MC and SUT matching. I've tried reading various guides on vinyl engine, threads on various forums and the articles on Rothwell's website, but I have to admit that I'm struggling. To add to the difficulty, it seems from some comments that it could be a "dark art" and that technical matches don't always translate in to system synergy.

As you can see from my equipment, I'll need a SUT to sit between my Art Audio VPL and the Rondo Bronze. At the most simplistic level, I realise that I need a step up of around 1:10 to get my 0.5mv up to 5mv, but that's as far as I've managed. Not exactly tricky maths!

Something else that confuses me, is that many SUTs are very flexible in loading options, whilst some are fixed. Are the fixed ones aimed at specific cartridge types? E.g. Ortofon has 27db fixed gain as far as I can see, I presume this is made with their cartridges in mind, perhaps as a way of ensuring future sales of their own products?

The obvious option for me is to speak with Mr Willis, but I would like to at least try and understand things for myself if possible. Does anyone know of a link to a relatively simple guide anywhere?!

[walpurgis]

I've had loads of SUTs and don't pay much attention to the specs as I keep a variety of MCs as a rule, they always seem to work for me anyway. The Fidelty Research FRT-3 sounds very nice with the Ortofons I've used with it on its 30 ohm setting. It's a fine SUT.

[eddieedwards]

I've had loads of SUTs and don't pay much attention to the specs as I keep a variety of MCs as a rule, they always seem to work for me anyway. The Fidelty Research FRT-3 sounds very nice with the Ortofons I've used with it on its 30 ohm setting. It's a fine SUT.

Cheers Geoff - I know you have a few SUTs. I very nearly bought one of them until you withdrew it from sale!

Your reply in some ways is part of the confusion i.e. the terminology, not the advice. You say 30 ohm, whilst some have ratios, whilst others state db gain, some just say high and low. It all becomes rather confusing as they obviously all relate to one another, but it's difficult to fathom out how!

[walpurgis]

Cheers Geoff - I know you have a few SUTs. I very nearly bought one of them until you withdrew it from sale!

Your reply in some ways is part of the confusion i.e. the terminology, not the advice. You say 30 ohm, whilst some have ratios, whilst others state db gain, some just say high and low. It all becomes rather confusing as they obviously all relate to one another, but it's difficult to fathom out how!

I'm still deciding whether to keep the FRT-3 or the Art Audio. Something has to go and I'm hanging onto the Luxman and Osawa. Not because they are necessarliy better, but because of their exclusivity, which rather appeals to me. You might be able to twist my arm for one if you're interested.

[struth]

Cheers Geoff - I know you have a few SUTs. I very nearly bought one of them until you withdrew it from sale!

Your reply in some ways is part of the confusion i.e. the terminology, not the advice. You say 30 ohm, whilst some have ratios, whilst others state db gain, some just say high and low. It all becomes rather confusing as they obviously all relate to one another, but it's difficult to fathom out how!

The *30 etc is the gain,ie if cart outputs 0.2 and a 30 gain is used it will multiply the signal by 30 making 6 mv; and the ohms bit is the loading for the cart, often 10 ohm or 30 ohm for example

Dec point in wrong place lol

[eddieedwards]

Geoff and Grant, thank you for your responses.

Geoff, as you can tell, I'm bloody confused with my system and what the hell to do next!

[twotone]

The only thing to do really is buy a couple and see how you get on, I was fortunate in that a fellow AOSer loaned me some SUTs and I bought the Fidelity Research one I've currently got in the classifieds on the back of Geoff's recommendation and as he said, it really is a fine sounding SUT.

I use it with a Denon 103 on the 30ohm setting and it sounds great but it's flexible as it has a by-pass for using a MM cart and also a 10ohm setting which I tried but didn't sound as good as the 30ohm setting with the 103.

Tony

[trio leo]

Hi Mathew,
I quite agree with you, I get totally confused between suts, head amps and phono stages, I'm an electrics numpty, I have a pre-amp with a mm phono stage built into it, I prefer to use MC cartridges so I use a battery powered moving coil amplifier sat between T/T and pre. there are 3 settings with this unit, but I just leave it as it came from the manufacturer, it adds nothing and takes nothing away from the musical performance. does me.

However, I've lent it to a friend at the moment and so I'm playing the Lyra Delos straight into the mm stage of my pre, it sounds pretty good actually, maybe the Delos is a higher output than some low output MCs, I don't know an ohm from a watt.

Hope you find what you need.

Enjoy your music :)

cheers Al

[albertan]

1:5 ratio = 14 dB boost = 1880 ohms load. This would work with a high output moving coil cartridge.
1:10 ratio = 20 dB boost = 470 ohms load.
1:13 ratio = 22.3 dB boost = 278 ohms load. The Denon AU-S1 step up.
1:15 ratio = 23.52 dB boost = 208.9 ohms load
1:16 ratio = 24.08 dB boost = 183.6 ohms load
1:20 ratio = 26 dB boost = 117.5 ohms load. Lyra and Phasemation make dandy step ups here. I use this ratio with my 0.3 mv moving coil cartridge into my 40 dB mm section. 66 dB total gain. I like it.
1:30 ratio = 29.5 dB boost = 52 ohms resistance
1:31.6 ratio = 30 dB boost = 47 ohms load
1:40 ratio = 32.04 dB boost = 29.4 ohms load. These last three ratios are to be used with very low output cartridges with low internal resistance.

There is an obvious mathematical ratio here. Things such as copper plating of the interior of the unit make a huge difference sonically as it cuts down extraneous noise. The quality of the wiring, connections, and soldering all add up. Quality step up transformers (sut) have excellent feet to avoid slippage and to reduce vibration. The coils should be packed in a foam to reduce the vibrations of the coils. The quality of the interconnect cable can make or break the sound of a SUT. Don't go cheap here. I use a Furutech. There are many others.
SUT placement and grounding quality are important to a silent back ground. Hum is avoided by careful placement and assembly, i.e., the connections are clean and tight.

I hope this helps.

[walpurgis]

1:5 ratio = 14 dB boost = 1880 ohms load
1:10 ratio = 20 dB boost = 470 ohms load
1:13 ratio = 22.3 dB boost = 278 ohms load Denon AU-S1
1:15 ratio = 23.52 dB boost = 208.9 ohms load
1:16 ratio = 24.08 dB boost = 183.6 ohms load
1:20 ratio = 26 dB boost = 117.5 ohms load Lyra and Phasemation make dandy step ups here
1:30 ratio = 29.5 dB boost = 52 ohms resistance
1:31.6 ratio = 30 dB boost = 47 ohms load
1:40 ratio = 32.04 dB boost = 29.4 ohms load

There is an obvious mathematical ratio here. Things such as copper plating of the interior of the unit make a huge difference sonically as it cuts down extraneous noise. The quality of the wiring, connections, and soldering all add up. The quality of the interconnect cable can make or break the sound of a SUT. Don't go cheap here.

I hope this helps.

Yes. As with everything on the phono side of things in particular, from the TT to the amp.

[albertan]

A problem with moving coil step ups is that even the least expensive models are still expensive. They are also not universal or accommodating if mismatched.
The British firm of Rothwell Audio make very good quality step ups that should work with your Ortofon. Analogue Seduction sell them in England as does Rothwell themselves. They make a good unit for 280 pounds that has 22 dB of boost and a 100 ohm load. They make an excellent unit for 485 pounds that has a 1:10 ratio and 20 dB of gain. They are worth a look. Their informative website and telephone number are resources as well.

The Ortofon cartridges have very low internal impedance so they can be tricky to match. Older Ortofon step ups come to mind of course, but there will be research required to determine which step up matches with this cartridge. My Sonic Labs make step ups with Ortofon type requirements (lower gains and impedances) but they are expensive. Art Dudley did a review of this cartridge in 2008 and used a K&K Audio step up for the review. The specifications of the transformer were not given.

Good luck.

Walter