You need to know the phono gain of the Shindo preamp and the total gain needed for the Dynavector. The difference between those two numbers (in db) will tell you what you need in terms of the SUT. Then select the best quality SUT that affords you the needed gain when interposed between the Dyna and the preamp. The turns ratio of the SUT will also determine the value of the load resistor needed. |
So you need to step up the voltage by a factor of 10 (from .3mV to 3mV). You can select a SUT with that information. The reflected impedance is related to the square of the turns ratio. With a 10:1 transformer, the impedance seen by the cartridge will be equal to 47K divided by 100, or 470 ohms. Some might say this is a little high for the Dynavector. For best results, you would replace the 47K load resistors with 10K load resistors, so the Dyna would see 100 ohms (10,000 divided by 100). Or,if you don't want to remove the 47Ks, you can calculate the value of the parallel resistance needed to reduce the net resistance to 10K, if you want the Dyna to see 100 ohms. I get 12.7K ohms as the value of that resistance. |
Restock, I take no issue with what you say. I was trying to keep the response as bone simple as possible. Your experience with SUTs is obviously more extensive than mine, especially since my hands-on experience is zero. BTW, I think the OP said that the recommended load is >30 ohms, not 30 ohms. Most would use about 100 ohms, which is why I wrote what I wrote. Carry on. |
Hatari, By all means, if your Shindo already has a built-in MC section utilizing an internal SUT, you should go ahead and use it. The SUT was obviously selected and designed into the circuit for the most seamless possible match. It is unlikely that you can do any better, or even as well, with an external SUT connected thru your MM input. Don't make this stuff harder and more expensive than it already needs to be. Sheesh. |
Hatari, You are hearing the opinions of two very knowledgable persons (Axel and Raul), who have their own private biases based on their own past experiences. There are lots of equally knowledgable vinyl fans who would disagree with Axel on loading with a SUT and with Raul who just does not like SUTs. I tend to agree with Raul, but you should form your own opinion, and one way to start is by listening to the preamp you already own. |
Raul, Have you heard a Masseto or other similar Shindo phono preamp driven by a LOMC? If so, was it on your own system where you are used to the baseline sound? I am asking just out of curiosity, because you are speaking with a great deal of conviction that suggests you have done the homework. |
Dear Raul, If you re-read my previous post, I think you will see where I said that I do agree with you on SUTs. But your remarks about the Shindo preamps were not as diplomatic as is typical of you, so I just thought you might have some direct experience with this unit or similar ones that led you to be so firm in your rather negative statements. If you did have such direct experience, it would lend a great deal of credence to your views, and it would satisfy my own abiding curiosity regarding Shindo et al. Because I have never heard any of that stuff, and I do value your opinion highly, as do others. No offense was intended.
By the way, now that I am beginning to hear what other cartridges have to offer in my own system, I remain a big fan of my Koetsu Urushi. So we will have to agree to disagree on that item. But I have more listening to do of course; I am nowhere near as experienced as you. |
Axel, In order to avoid confusing a novice, I would take issue only with the language you used in the post you referenced above. You wrote:
"Step 2: Find out the 'natural impedance' of the trannie.
Ratio^2 * phono-pre input impedance
e.g. 31.6 * 31.6 * 47k ohm = 47 ohm for a 30dB trannie
(this will be what the cart sees if you do not use secondary or primary loading of the trannie)"
47 ohms (or 47K ohms divided by ~1000, the approx square of the turns ratio of the transformer you described) is about what the cartridge "sees" as a load if there is a 47K ohm resistor across the secondaries of the SUT, i.e., on the preamp input side. A transformer, any transformer, has no "natural impedance" per se. Transformers merely reflect impedances from primary to secondary or vice-versa.
As to the rest of this argument, I would love to hear a very high quality SUT in my own system in order to make up my own mind as to their wonderfulness. I am keeping an open mind, but in principle there are about as many possible problems with a SUT amplifying the voltage output of a very LOMC as there are with an active gain stage. The problems are just different. |
Axel, Sorry for being pedantic. I have to agree that a lot of folks who do use SUTs do not seem to take into account the matching of the SUT to both the cartridge and to the preamp. This is why I urged Hatari to first of all listen to his built-in SUT in his Shindo preamp, because that is undoubtedly set up properly to match the input stage. I dislike comparative testing of SUTs that we see in published articles, where a guy interposes several different SUTs between the cartridge and preamp, without regard for any special measures that might optimize frequency response, etc. The author then makes spurious judgements regarding which SUT sounds best. The Jensen transformer website has a couple of excellent "white papers" (I have no idea why we use that term in the US) on SUT electronics, from which one can learn a lot about this subject. |
Hatari, I had begun to figure out that you have indeed been listening to the Shindo MC input. I did not understand that way back when this thread started. What are you hearing that suggests the MC phono input is not optimally matched to the Dynavector? That cartridge is typical of the whole class of LOMCs in terms of its internal impedance, output voltage, compliance, etc, so it is unlikely to present any special problems to a phono stage, other than its low output. You might also consider the tonearm in this equation. Matching of cartridge to tonearm is a critical factor. |
I just did a little quick research on the Masseto. For $11,500 it ought to have a pretty good SUT inside. But I know it is on the low to middle end of the Shindo line of preamps, in terms of cost. |
Hatari, I think you stimulated an interesting discussion, not an uproar. I learned something from it. There is an interesting piece by Art Dudley that appeared in Stereophile within the past few years, wherein he actually compares the built-in SUT in the Masseto to several other outboard SUTs, in his own system. You might want to Google it. |
