To SUT or not to SUT, that is the question

H

He agrees.

 

I have a Balance Audio Technologies VK-P10 phono stage that is very flexible. You can easily switch between low and high gain and engage or disengage the built in SUT. I also have a highly regarded Hagman SUT. You can also adjust load from 100 to 47k ohms. BAT recommends not using the SUT and use the high gain setting for MC carts over .25mV, and mine is .38mV, so I am not using the SUT at the moment. This discussion has me thinking that I should experiment with the low gain setting and the built-in SUT and the outboard SUT, as well as playing with different loads.

I am using a new amp and pre-setup and will be introducing new speakers, so I am going to wait and get used to the new setup before that, however. It is not good to change too many variables at once.

 

What about for low output MCs? How are you going to up the gain without an SUT?

 

If a tube phono preamp has enough gain, it can easily drive a LOMC in the 0.7 mV (or higher) range. I've driven a Clearaudio Concerto (approx 0.8 mV) and VDH Frog (0.65 mV) with outstanding sonic results. Heaps of gain, and absolutely gorgeous sound. Same with a Soundsmith Helios MI cartridge.

 

My all tube Phono stage has 68db of gain. It will handle down to .3mV very well.

I've tried comparing a couple of different SUT's vs going directly into the phono stage and wound up preferring the direct route.

 

Use your imagination

 

So if I'm following this correctly, you just plug an MC cart into a MM phono stage, and maybe turn up the volume more? And the increase in noise floor is worth it?

 

LOL. These forums are a comedy show.

 

MC cart->SUT->MM phono stage

 

Sure, but they explicitly said they weren't using a SUT, and I didn't get the impression they were using MC stages.

 

To be fair "+1" or "+1000" is fairly common internet vernacular, nothing really amiss about it.

 

Sometimes a tragic comedy.

jeff

 

I was referring more to the post he was referencing, that a well-built tube phono stage eliminates the need for a SUT.
Which I don't agree with. To each their own.

 

I'm wondering what it means as well? A tube phono-stage will usually use either a solid state headamp or built in SUT to offer additional first stage gain for a low output MC. There are very few tube phono-stages that are all tube with tube in the very first stage as well. One of the few examples off the top of head is an older Aesthetix model. There are pros and cons to all approaches, the all tube way by far the most difficult since amplifying 0.3 mv (about the average LOMC output voltage) and being quiet is very difficult and this will really be obvious on high efficiency speakers (my definition of high efficiency is greater than 98 db/w sensitive without room gain added).

I'd encourage anyone interested in SUTs to read this page thoroughly: http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html

I used to be a SUT skeptic as well since most of the cheap ones reduce transparency by quite a bit and add too much warmth. But some of the custom bespoke ones are truly amazing once loaded properly. But the downside is they are expensive and often require some DIY'ing. The latter not difficult since there is no hazardous electricity involved. These would be commercial equivalents of ~ $2000-2500, ie what the Music First go for.

 

A .7mV cart is not low output. Generally, .5 mV or less is considered low output.

 

What I meant is that I agree with his opinion or sentiment not 1, but 1000 times. It really isn't a big deal. Let's move on.

 

The best tubed preamps IMHO with phono stages that accomodate both MM and MC (think Shindo in my opinion) use SUTs for the MC stage. Is this what you're agreeing with? Because I have an Audio Note UK tube phono stage that is strictly MM because Audio Note only utilizes SUTs for MC cartridges. They don't manufacture an MM/MC phono stage. An approach many high-end phono and MC cartridge manufactures choose, such as Leben, Shindo and Koetsu, to name a few.

So, you're only talking MM then? As in MM is superior to MC?

 

That's why I qualified my statement by including the output voltages (0.65, 0.7) to vaguely define LOMC. I agree LOMC is even lower.

 

I don't think MM is superior to MC at all. Quite the opposite. I highly prefer MC over MM.

Obviously, MC phono stages/preamps require special consideration to optimize playback of medium output (say .6 mV to 1.8 mV) carts, including having sufficient gain and ideal loading. There are many other factors to getting great sound, of course.

 

It's not quite that easy. MC cartridges, ideally, need to be connected to a phono stage suited for MC. Most MM phono stages load at 47,000 ohms. A MC will work at 47,000, but you won't truly hear the performance of a nice MC cartridge until it is loaded ideally.

For instance, if a person has a nice integrated amp with built in phono stage, and they replace their MM cart with a MC cart, they won't get the full bang for their buck, unless that integrated amp allows for custom loading of the MC cart, as well as increased gain.

 

Agreed.

Sounds like you have a really nice all tube phono stage!

 

It's a Joule Electra OPS2. I'm lucky enough to own an ARC SP10 MKII (all tube) as well. The ARC will comfortably handle down to .5mV via 12 6922's (8 phono - 4 line).

 

I think people either get intimidated by or kind of over think the whole SUT loading issue; and, at the same time in general we audiophiles can sometimes wind up feeling like we've found the one true path -- SUT, or active but only tubes, or active but only JFETs or whatever.

The bottom line is that every audio solution, every circuit design choice, involves compromises and each has pluses and minuses (and furthermore, none delivers perfection). This is especially true in the world of vinyl playback where the whole thing is like a Rube Goldberg contraption -- drag a rock on a needle through a groove to make it wiggle to produce a tiny voltage with magnets and coil, pre-eq the signal going onto the record then re-eq that tiny signal coming off the record; I mean it's so fraught with challenges, it's amazing it sounds as good as it does.

Yeah, there are things you have to be careful about with a SUT -- making sure it's well-shielded, keeping it away from sources of EMF radiation, using short well-shielded interconnects between it and the phono stage -- but if you get a competently designed SUT with the right turns ratio to step the LOMC's voltage up to something like the middle of the phono pre's input range, say up to circa 5 mV, while keeping the reflected impedance loading the cart at 10X the cart's impedance or higher, you'll probably have good sound, low noise, good signal to noise ratio, good dynamics -- in short, it'll work great. If you have an active phono stage with a well-designed amplification stage for a MC that delivers enough gain, low noise, and sufficient headroom, it'll work great. But neither will be perfect.

 

Yes, I'm well aware of all of this, which is why I found your posts saying you preferred to use MC carts with MM phono stages a bit of a head scratcher.

 

You are way too rational- are you sure you're on the right forum?

Everything is a compromise in an audio system- the question is which compromise sounds best to your ears in your system, in your room and there is only one way to find out. But for some of us that is half the fun. Try something and sit back and listen. Try the alternative and sit back and listen. The problem is that method can be somewhat costly. That is why I got such a flexible phono stage. I can try almost all of the phono stage options without switching gear.