Audio Note M1 RIAA arrives today... let the SUT wars begin!

Oh yeah... I think you are right! The 103 is one of the oddballs for loading. Hmmm, the A23 is an interesting one. I'm trying my mate's when he's back from holiday so it will be interesting to see if it underwhelms in my set-up too.

 

In my opinion, it is a mistake to even consider a MC cartridge manufacturer's recommendation for load on their cartridge. Technically, it may be reasonable to assume that "they know" what loading will provide optimum frequency response. But there is much more than technically flat high frequency response to integrating your cartridge with your system. And, the manufacturers use factors to determine this recommendation, that do not reflect the best interest of their customers' sound, including the "politics" of what is generally provided in preamps as a default load in MC phono stages: very often 100 Ohms. The cartridge manufacturers also ignore some important factors, such as sample-to-sample variations among their cartridges, users' speaker/room non-linearities, and individuals' sonic preferences.

You may indeed end up with the manufacturer's recommendation. But I think using your own ears and your own audio system is the best way to find your best cartridge loading.

Most importantly, loading a Denon 103 (40 Ohms coil) at only 100 Ohms seriously lowers its effective output level, Signal-to-Noise and compliance. Try somewhere between 400 and 800 Ohms first. If it is too bright then reduce as little as possible, until the tonal balance comes into line with your preference. A higher final choice for loading of any MC cartridge, as high as possible that provides the tonal balance you prefer, will result in improved cartridge performance in dynamic quality, S/N and trackability.

All of items 2 through 5 above indicate to me that the loading on this cartridge was too low, because the transformer had a higher step-up ratio than optimum. Too high a step-up ratio provides an input impedance that is so low compared to the cartridge's output impedance, that too much signal is lost in the impedance of the transformer coil itself. This is the same problem as applying too low a resistor in parallel to the cartridge's coil. Reducing step-up ratio (thus increasing its input impedance) will improve all of these.

 

Thanks Warren. This SUT is designed for a Denon 103 but I was running a Shelter 501 through it (12 ohm internal impedance). Consequently, I was afraid the loading would be too high. The unit gets great reviews in conjunction with a 103, maybe I'll try a nice wood body 103 through it and see how it goes.

 

I wish I could find a spec for the Auditorium 23 for Denon 103. I found the A23 Hommage T1 is about 1:30. Does anyone have any spec for the 103 model: step-up ratio, gain in dB, input and output impedances, or input load into a 47k phono preamp? Just one of these specs will allow calculation of the rest.

Or if someone can actually measure the DC resistance of the input winding and output winding, we can approx calculate its step-up ratio. Just measure DCR across an input RCA (center connection to outside connection) and across an output RCA. The square root of that ratio (output/input) is approx the step-up ratio.

 

I could swear I read somewhere that it was 1:10 but who knows if that's true.

 

According to this, input impedance measures 7.8 ohms and output impedance 505 ohms.

http://www.stereophile.com/content/listening-58-page-2

 

So is it showing the cart 7.8 or 505 Ohms?
505 would be in line with the 10~20x cart impedance (40 Ohms for the 103).

 

Yeah, I don't know why they're so tight with the specs on the thing...

 

Good job finding that spec. With some math, we can now determine the actual step-up ratio, and the load on the cartridge.

Step-up ratio is the square root of turns ratio. We have to guess that the same guage of wire is used in the primary and the secondary, and that no resistor has been added to the input. These are potentially faulty assumptions, that honestly we cannot be sure are true without opening up the A23 to visually confirm.

505/7.8 is 64.7. The square root is about 8. Therefore the step-up ratio is about 1:8.

Now into a 47000 ohm phono preamp, we can calculate the cartridge load by 47000/8/8, or 47000/64.7 = 726 Ohms.

Again assuming that Auditorium 23 uses the same wire in both the primary and secondary, and assuming they don't add a resistor at the input, the cartridge is loaded at 726 Ohms impedance. That falls within the 400 to 800 Ohms that I would expect is best for a 40 Ohm cartridge. But it is way too high for a 12 ohm Shelter.

 

Now that we know this transformer has a step-ratio of only 1:8, which is not much of a boost in gain, I can understand that you didn't hear a big difference in loudness when it was added.

The Shelter should be used with a SUT that has a step-up ratio in the range of 1:14 to 1:20.

 

Thanks so much for doing that Warren, much appreciated for the math.

 

I also want to thank you Warren for your explanations on the SUT math.

 

R,

Congrats on your great sounding phono stage! Indeed, a really nice phono stage can provide a huge upgrade to one's system.

BAM BAM for sure

 

I have to admit that I have very little knowledge of SUT's and my experience with one was so long ago that I honestly have no idea whether I had a good matchup or not (I'd venture a guess that I did but I still don't remember the performance as being earth shattering, especially compared to what I'm running today in active phono preamplification but it could well have been a cartridge that I was not really enamored with) so I've followed this thread with interest. Personally, I don't think that SUT's represent the be-all end all in performance or a panacea; my gut feeling is that SUT vs active is really all about execution/implementation and that there may well be tradeoffs, sacrifices or compromises with either technology. Or, in other words, you can get great results going active or with SUT.

One thing that is at least reinforced to me through this thread, though, is that regardless of which path you take, active or SUT, the interface between the cartridge and the active phono pre or step up is critical particularly with respect to gain and loading. I feel that I have nailed that in my current setup with active phono preamplication and, as a result, am pretty happy with the sound I'm getting. I still find the SUT thing to be somewhat confusing; it would seem to me that a 1:8 step up with a .5 mV cartridge in smctigue's system should be just about dead on in terms of gain, feeding 4 mV into the MM phono preamp but maybe I'm misunderstanding something (wouldn't be the first time haha!). I can understand that a load approaching 800 would not be good for a cartridge with a 12 ohm internal impedance, but I'd expect that to affect tonal balance and screw that up much more than dynamics, speed and bass which I would expect to be not bad (maybe not perfect but not really as described either) if the gain match up is good, which it would appear to be. As I said, maybe I'm just not getting it. And maybe it's not really a 1:8 ratio as that would seem to indicate stepping up the 103 to about 2.4 mV into a MM pre which doesn't seem quite right to me. So more confusion for me.

There's no question that the Auditorium SUT optimized for the 103 is purported to offer great results with the 103 but I've also read that users of the 103R have had good results with it as well and the 103R has a 14 ohm internal impedance and considerably less output voltage than the Shelter smctigue is using. I'd certainly be curious about the Auditorium's performance with a wood bodied 103.

Throw in the general lack of (or at least very difficult to find) published specifications on these SUT's as well as the complication of (sometimes) introducing another interconnect and the essentially fixed load nature of the SUT's and you have an even more complex situation in terms of arriving at/with a great matchup/cartridge-phono preamplification interface as far as I'm concerned. The learning curve looks extremely steep here to me and it looks like a much more hit or miss situation than arriving at good results going active.

So, while I wish everyone well on their audio journey, I'm not so sure I'd want to venture down that path myself. I don't mind living vicariously, however, through threads like this.

 

Once I have my Zu 103 on my Thorens for a while I eventually hope to get the Auditorium SUT. I did inquire about using the 103R with the distributor of the Auditorium SUT and while he said it will mathematically work with the 103R, to really get the magic is to use the 103, as that was the cartridge the SUT was voiced for.

 

I think the turns ratio of the transformer is close to the voltage gain barring losses in the transformer. The impedance is affected by the square of the turns ratio but not not voltage gain per say.

Trying to determine the characteristics of a SUT by the DRC of the coils is a long shot unless you know the wire is the same on both coils. I would say the primary has thicker wire than the secondary in this case to keep the DCR low as it is in series with the reflected impedance.

 

I have compared MANY active MC phono stages and MM stages/transformer step-ups, and spoken with (and read about) other audiophiles who have done the same thing. I came to this conclusion:

The current output of a MC cartridge is high enough that it can be "converted" to higher voltage/lower current by a transformer, very simply and effectively. There is no need to add gain with a complex active head-amp, or an ultra-high-gain phono preamp. All active circuits, that add this much voltage gain, also add much more sonic signature than a "good" step-up transformer. So, step-up transformers just sound better; they provide a more transparent boost to the cartridge's voltage.

The problem is that you cannot just "adjust" a simple transformer like you can a complicated phono circuit. So what about buying a few transformers to compare, or buying one transformer that is a little bit more complicated? EAR made a couple of good ones that offered great flexibility. But Music First Audio is the most flexible of all that I have ever seen.

I sell Music First Audio step-ups. A new one costs $3500 to $7500. (I know that is expensive to most buyers, particularly for somthing I just called simple). From the front panel, it offers a choice of three step-up ratios (1:5, 1:10 & 1:20), with resistors to provide 18 different variations in loading, just by quickly turning two knobs. It also offers a choice of three grounding schemes. This is not an advertisement, I just want you to be aware that there is at least these products out there that make experimenting, to find the perfect match, extremely easy. Just twist the dials until you notice a sonic pattern, and then fine tune using your ears. Reading the resulting dial positions tells you the optimum settings for gain and load you just found by listening.

 

Thanks for the info Warren. Just wondering: do you have any experience with current mode phono preamps like the BMC, Aqvox or ESE Niburu? It seems they would almost be a cross or bridge the gap between a SUT and high gain phono preamp, perhaps offering some of the benefits of a step up and operating in a similar fashion if I'm understanding you?

 

I have read the reviews, by Stereophile and TNT-Audio, of these "current input" designs by Carlos Candeias. I have not heard one yet, but look forward to a chance. My understanding is that the designer recommends very low impedance cartridges, preferably 4 Ohms or less, and balanced (XLR) connections from the cartridge. So these seem to present some limitations. But I do have two 1-Ohm cartridges (an Audio Note Io and a Benz Ebony TR) which might be excellent candidates for this type of phono-preamp. And I am capable of constructing my own fully balanced XLR tonearm cable. This cable must be two twisted pairs in a shield, the cartridge pins must not share ground, and the ground must only connect the cable shield, connector housings, tonearm base and XLR ground pins. These are more tweeky requirements than anything regarding step-up transformers, and this challenge intrigues me.

If anyone has a BMC Phono MCCI to loan to me, I have step-ups and MM phono stages from Music First Audio and Audio Note UK to loan.

 

Another valid approach to choosing the right transformer step-up is considering a cartridge and step-up combination that were truly designed for each other, for example from Dynavector, Audio Note, Denon 103 with its dedicated Auditorium 23, Shelter, Air Tight, Haniwa, My Sonic Labs, an old Fidelity Research, etc. Many of the Denon and Ortofon MC cartridges had dedicated transformer step-ups made to go with them.

 

I drove over to Soundsmith on Wednesday and picked up a stock 103 to run through the Au23. I've never heard a 103 before so I really didn't know what to expect. The cartridge only has 5 or 6 hours on it but I am shocked by what I'm hearing. I'll report back when I feel the 103 has fully broken in.

I also have an EMT TSD15 SFL on the way (the Au23 103 model and the EMT is a very popular combo with the Shindo crowd). We'll see.

 

I find this very interesting as I have a chance to demo the A23 SUT soon..., and the 103 is so affordable, it could be a great option to my Cinemag/DV20x2L.

 

It is so well loved, and there are a bunch of flavors in the 103, and as you say, not that expensive. There are several nude variants as well, so it has been well modified. I have heard one user say they liked the the AT-F7 (baby OC9) more than the 103, and I can vouch for it as a very good match with the Rega arms. I hope they stay cheap for a good long while. A very nimble suspension coupled with the wide/thin eliptical does a really nice job of focusing on the music, IMO. I suspect I would need a much better tone arm to warrant a better cartridge.

 

Have you heard a 103 before?

 

Not yet. Read several reviews... what's your take, can you compare it to the Dv20x2L?