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ccaquest
20-07-2009, 15:08
I noticed MU SUT for quite a few years, but never had the urgent need to get one since I had been happy with my Grado The Reference MM on LP12/Ittok/Lingo. Figured when start using MC then a MU might be good. It's a pity that I realized TX103 based MUs are no longer available a few months ago. I have been hoping the new MU, even spoke to John at Bent Audio a few times during the last few months. Nothing yet.

A few weeks ago, found one listed at Audiogon, grabbed it immediately. And a week later, bought a lightly used Shelter 501MK2 as well. Now the MC episode started.

From searching and reading many writings on the web especially Barry Hunt's writings on this forum, I realized that SUT is hardly a plug-and-play device. Impedance matching seems critial to obtain better sound from MC. The MU I got has a built-in toggle switch so I can play with either 10:1 or 20:1 settings.

Based on MU's specs and TX103 as well, Shelter 501mk2 should be used with 10:1 setting and my brief listening did confirm this.

There are one thing puzzled me is that, Shelter 501MK2 specs recommend load impedance of 10 to 20 ohm when using with SUT. I played with MU with load impedance of 19ohm, sounded so flat. For now, I settled on 319 ohm (No resistor is 470). I will get more resistors so I can fine tune the load impedance. The gentleman I bought MU from, used Shelter 901, and he told me he preferred 20:1 setting on MU, I was wonder whether that's the reason he ended up selling the MU.

I am new to this forum. Any commets welcome especially from Barry Hunt.

Thanks for reading.

Ken

Spectral Morn
20-07-2009, 16:11
I noticed MU SUT for quite a few years, but never had the urgent need to get one since I had been happy with my Grado The Reference MM on LP12/Ittok/Lingo. Figured when start using MC then a MU might be good. It's a pity that I realized TX103 based MUs are no longer available a few months ago. I have been hoping the new MU, even spoke to John at Bent Audio a few times during the last few months. Nothing yet.

A few weeks ago, found one listed at Audiogon, grabbed it immediately. And a week later, bought a lightly used Shelter 501MK2 as well. Now the MC episode started.

From searching and reading many writings on the web especially Barry Hunt's writings on this forum, I realized that SUT is hardly a plug-and-play device. Impedance matching seems critial to obtain better sound from MC. The MU I got has a built-in toggle switch so I can play with either 10:1 or 20:1 settings.

Based on MU's specs and TX103 as well, Shelter 501mk2 should be used with 10:1 setting and my brief listening did confirm this.

There are one thing puzzled me is that, Shelter 501MK2 specs recommend load impedance of 10 to 20 ohm when using with SUT. I played with MU with load impedance of 19ohm, sounded so flat. For now, I settled on 319 ohm (No resistor is 470). I will get more resistors so I can fine tune the load impedance. The gentleman I bought MU from, used Shelter 901, and he told me he preferred 20:1 setting on MU, I was wonder whether that's the reason he ended up selling the MU.

I am new to this forum. Any comments welcome especially from Barry Hunt.

Thanks for reading.

Ken


Hi Ken

Welcome to AOS...all great questions and there are many who can answer them but Barry is probably your man.

Could you pop into the Welcome section of the forum and say hello, give us a description of your system and maybe you might like to post some photos of your set up in the Gallery. Could you also add your first name to your signature and some basic location details...thank you in advance.

Have fun, enjoy the forum and if you need any help with anything just ask a member of the management team.


Regards D S D L

NRG
20-07-2009, 17:46
The shelter has an output impedance of 20 Ohms. Rule of thumb is to load a MC cart with approx 10x the output impedance so you are looking to load it around 200 Ohms not 20 Ohms. 20 Ohms will kill the sound.

A 1:10 step up ratio means to get a 200 Ohm load you will need a 20K Ohm load on the secondary side of the SUT. Times by 100 (10*10) or if 1:20 times by 400 (20*20)

If the Phono Stage is a MM one it will be loaded at 47K Ohm for MM cartridges and at 1:10 the reflected load will be 470 Ohm...too high and at 1:20 117 Ohm maybe too low...

Placing an additional resistor across the secondary of the SUT will change the reflected load the cartridge will see. This resistor will be in parallel with the Phono 47K Ohm load.....so if you place a 33K Ohm resistor across the SUT secondary it and the 47K Ohm phono load, will form a combined parallel load of 19.4K Ohm approx.

The cart will therefore see a load of 194 Ohm....just about right.

You can try other loads as well, I prefer to load my MC cartridges down by 5~7 times the output impedance, it helps tame top end brightness.

The Grand Wazoo
20-07-2009, 18:09
Hi Ken,


Welcome to AoS.

What is your preamp & what load does its phono stage present to the cartridge - do you know?

Don't assume that it's 47k - mine measured at 50k, so I had to do an adjustment calculation to find the recommended loading resistor to go across the terminals on the Mu's.

You should try a wide range around the recommended load (once you've established what it is) & home in by listening tests to find the ideal - I found the differences to be quite distinct. Start with quite big steps, then once you've found an ideal, repeat the process. But this time bracket your ideal with smaller steps.

Once you've found the value that works best, you should try different brands.
The recommended load should just be your starting point.

Presumably, you know that there's a third value tap to the transformers that's not connected to your switch? It's 1:5, giving a 14dB adjustment to gain.

You may find this interesting if you've not seen it yet.
http://www.sixmoons.com/audioreviews/stepup/primer.html

Good luck.

ccaquest
20-07-2009, 23:23
Hi Neal, Sheltor 501MK2 has DC impedance of 12ohm. Based on your 10 times formular, I will definitely try. So far I did 19, 193, 255, 298 and stay on 319.

There are 82, 100, 113 and 140 handy came with the MU.

Hi Chris, I am using CAT Sig. SL1 MK2 before removal of 12AU7 tubes. I believe it has 47K MM, that's what I am using MU with for now.

Thanks,

Ken

The Grand Wazoo
20-07-2009, 23:45
Hi Chris, I am using CAT Sig. SL1 MK2 before removal of 12AU7 tubes. I believe it has 47K MM, that's what I am using MU with for now.

It might just pay you to stick the probes of a meter across the input to see what it is actually reading......

Cheers

NRG
21-07-2009, 07:00
Hi Neal, Sheltor 501MK2 has DC impedance of 12ohm. .......

Thanks,

Ken


Interesting I saw on Daves soundhifi site it's 12 Ohm but went with the 20 Ohm listed on the Cartridgedb.com site :scratch:

Anyhow you now know how to calculate the loading with a parallel resistor, have fun! :)

ccaquest
22-07-2009, 13:18
Hi Chris,

Plugged multi-meter in the phono input of CAT, readings are 47.3K/47.4K, so not too far away from 47K.

I now put in a 113ohm load impedance. Next step, 100ohm start sounding a bit soft on top. I can get more resistors to fine tune loads. What brand of resistors you find sounding better? How to break-in resistors?

Thanks,

Ken

The Grand Wazoo
22-07-2009, 21:26
Ken,
I tried quite a few brands - even the most pricey resistors are not a big outlay if you're only buying 2! And I made sure of the value I wanted before I got all the samples to try.
I can't remember what they all were, but I certainly tried Holco & Shinkoh - the Shinkoh's were the best of all the types I tried. All but 1 of the types I used were as good as or better than the ones John sent me with my Mu's

However, they were still not as good as running with no resistor in my set-up, so that's how I use it now.

It does sound like 100 is too low if you're getting that effect.
Cheers

Mike
22-07-2009, 21:48
There's an easier way to do this, and some prefer it.

Change the 47K resistor to 1 or 1.2meg and load the cartridge on the primary side of the SUT. If you want 100 ohm loading use a 100 ohm resistor on the primary, want 20 ohms? use a 20 ohm resistor... etc, etc. No complicated maths involved!

Simples! <squeak> :)

Mike
22-07-2009, 21:51
the Shinkoh's were the best of all the types I tried.

I like those a lot too! Takman are also worth a try. It's definitely worth using quality resistors for this as they're in a critical part of the signal path.

Mike
22-07-2009, 21:59
There's an easier way to do this, and some prefer it.

Change the 47K resistor to 1 or 1.2meg and load the cartridge on the primary side of the SUT. If you want 100 ohm loading use a 100 ohm resistor on the primary, want 20 ohms? use a 20 ohm resistor... etc, etc. No complicated maths involved!

Simples! <squeak> :)

Have a read through this: http://www.wduk.worldomain.net/forum/showthread.php?t=2442

The Grand Wazoo
22-07-2009, 22:12
I like those a lot too! Takman are also worth a try. It's definitely worth using quality resistors for this as they're in a critical part of the signal path.

Yes!!!!!
I tried the Takmans, also Vishays.
I had to shop around a bit for everything, but most of what I used came from HiFi Collective

Mike
22-07-2009, 22:14
most of what I used came from HiFi Collective

Ditto! :)