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 Post subject: Anybody know this SUT?
PostPosted: Fri Aug 25, 2017 11:22 pm 
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I’ve had this Grace GS-10 MC step up transformer for quite a while but up until this afternoon have never tried it out. A very pleasant surprise it was. Researching the unit on the internet I hit a lot of dead ends. There is some information about Shinagawa Musen, but very little about the GS-10.

Does anyone know anything about these? Here’s some information I found on an old Australian eBay listing:

Input impedance: 3, 25, 40 ohms
Output impedance 4k, 25k, 50k, 100k
Gain 1:10

Using data for specific MC cartridges I own (found in vinylengine’s cartridge data base), the input impedance figures kind of make sense to me, but I don’t understand the output impedance figures. All of my cartridges’ output impedance values are much lower. Besides, the figures printed on the faceplate under “LOAD” don’t jibe with the figures given by the aforementioned eBay seller. Those on the faceplate read: 4K/T, 25K, D/50K, 100K. Don’t get it…

And what does “PASS” mean?

If someone can explain to me how to decipher the settings on this SUT, I would be VERY appreciative. Thanks in advance!


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PostPosted: Sat Aug 26, 2017 4:37 am 
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Output impedance is what the MM phono preamp sees. 47K Ohms is the output impedance loading of the average magnetic cartridge, so the 50K setting is what you would likely use. I have an Audio Technica quad cartridge that is 100K, so you would probably use that setting for a CD-4 demodulator input. PASS is what you would use if you were playing a magnetic cartridge, if you had a turntable with interchangeable headshells and a variety of cartridges ... so you wouldn't have to swap cables around to bypass the step-up. This is an interesting piece. I have a Grace F10L moving coil cartridge on my Linn Sondek/Ittock, and I love it. For me, transformers are the way to go if you need a step-up device, although I prefer a dedicated MC phono preamp.

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PostPosted: Sat Aug 26, 2017 7:07 am 
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Nice piece! I'd keep and use this device.

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PostPosted: Sat Aug 26, 2017 8:44 am 
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Quadzilla, thanks for your reply. (I should have stated in my original post that I'm trying this SUT out with a number of MC cartridges I own e.g. Koetsu, Benz, Kiseki, Linn, Miyajima etc.)

Do you know what the T and D stand for in 4K/T and D/50K?

Also, as I turn the dial between 3, 25 and 40, the volume is affected. It makes sense what you said about PASS because when a MC is in the circuit, turning the dial to PASS the volume is diminished significantly (all of which—in my muddled mind—made me think that somehow 3, 25 and 40 had something to do with db boost).

As far as the numbers 3, 25 and 40 are concerned, am I correct in thinking that these are indeed Load Impedance figures? In other words, we're talking 3 ohms, 25 ohms and 40 ohms—and not db boosts?

Sorry for the confusion. I've used SUTS before but none with choices like this one offers...

Below is load/output data from cartridigedb.com for a couple of my MC cartridges. Would you be able give me a couple of suggestions of settings I would use for them? Do the Output Impedance numbers even apply to this SUT?

Kiseki
LI: >60 ohms, OI: 6 ohms

Benz Micro
LI: 1k - 47k, OI: 41 ohms

Koetsu
LI: 5-100k, OI: 5 ohms


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PostPosted: Sat Aug 26, 2017 10:02 am 
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The output setting will depend on your phono preamp. I expect that it would be 50k Ohms if it is a standard moving magnet preamp. As for the input setting, just use the numbers that apply to your cartridges ... e.g. 5, 6 or 41 (or close to those settings). Those "3, 25 and 40" numbers are not dB, they are Ohms. I am sorry, but I don't know what the 'T' or 'D' means.

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PostPosted: Sat Aug 26, 2017 10:25 am 
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I think the T is for transformer, as 4k is, I think, the output of the transformer itself. The D might stand for direct, as this would be the load if using bypass for MM. Not sure though, and I'm not sure how the 25k and 100k loads are obtained. They could be series resistances tacked on to the end of the transformer, or they could be parallel and series resistances (respectively) added to modify the D/50k load.

A good person to ask would be Rothwell Audio over at Audio Karma. His specialty is transformers, and has an informative web page dedicated to how they work, including load modification and its effects.

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PostPosted: Sat Aug 26, 2017 1:24 pm 
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I think it's time to pop it open to see if it has a tapped primary and any loading resistors on the secondary.
Maybe sketch up a wiring diagram.Only way to know for sure.
I'd be curious to see the innards.

Gary


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PostPosted: Sat Aug 26, 2017 2:32 pm 
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Ok, Gary, good idea...

I'll have photos posted tomorrow of the inside.


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