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  #1  
Old 14th August 2019, 02:41 PM
goomer goomer is offline
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Default WD MCT SUT question

Firstly, apologies if this is in the wrong forum, I hope I picked the correct section.

I have been lucky enough to purchase a pair of World Designs MCT moving coil transformers, from an unfinished project with case, transformer clamps, earthing post and phono sockets. None of the wiring from the transformers has ever been connected, though the case has been drilled and the clamps, sockets and earthing post already fitted to it. These are older versions of the MCT, I think, different to the rectangular block ones shown on the WD shop page, and are circular 'can' type ones.

I got some hand written notes with the unfinished project but this doesn't give me enough detail to enable to work out which cables connect where, the original builder is unfortunately no longer around to ask for advice. I am able to solder but am a total novice regarding circuits and reading circuit diagrams.

My question is, does anyone have any simple 'how to' guides on how to wire the transformers I have up correctly? I understand that the transformers have two output ratios of 1:10 and 1:20, am I correct in thinking these could be wired up in such a way as they could it could be switched between them (with the addition of a switch in the case I already have)?

Apologies for the slightly rambling nature of the post. I have a couple of moving coil cartridges used presently with an active MM/MC phono stage, I would like to be able to try the World Designs SUT at some point in comparison to the MC stage in my phono amplifier.

Thanks for any advice anyone can offer.
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  #2  
Old 18th August 2019, 10:17 AM
John Caswell John Caswell is offline
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Default Re: WD MCT SUT question

Hi Goomer,
Just doing some drawings, will post later in the day.

John
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  #3  
Old 18th August 2019, 03:44 PM
John Caswell John Caswell is offline
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Default Re: WD MCT SUT question

Hi Goomer,
Attached, I hope, are a couple of drawings that show how to wire up and switch between 10:1 and 20:1 for the SUT.
The toggle switch can either be 2 separate dpdt switches, one for each channel or a 4pdt that does both simultaneously. Note that generally on miniature type toggle switches, the centre tags are the "poles" and that looking from the side of if toggle is up the lower pair are made and vice versa
The rotary switch is generally a 4pole 3 way, physically constrained to 4pole 2 way by means of an insert on the locating mechanism.
Have a look and see if it makes sense to you and others. Any questions ask here.

John
Attached Images
File Type: gif sut1.gif (30.1 KB, 37 views)
File Type: gif sut2.gif (55.2 KB, 28 views)
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  #4  
Old 20th August 2019, 08:28 AM
goomer goomer is offline
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Default Re: WD MCT SUT question

Many thanks for the detailed reply, John, and the drawings. I've decided to stick with wiring them up in a 1:10 ratio only to start with, to keep things simple and to best match the cartridges I am presently using, though will keep your drawings for if/when I decide to add the option of 1:20 too. I hope to have them finished later on today so look forward to having a listen soon.

Thanks again,

Chris.
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  #5  
Old 20th August 2019, 02:07 PM
bob orbell bob orbell is offline
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Default Re: WD MCT SUT question

Just to add my bit, there are far more cartridge's out there that need 1-10 or 1-12 than 1-20, so, I think you will be fine with your selection, the 1-20 will only be required if you ever use a very low output cartridge. Bob
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  #6  
Old 20th August 2019, 02:48 PM
goomer goomer is offline
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Default Re: WD MCT SUT question

That's great, thank you. A small pictorial update of my progress.

What I initially discovered upon opening my mystery parcel:
World Designs SUT 0001 by christogo2, on Flickr

Preparing the case with some lengths of cable for earthing the sockets:
wd step up 002 by christogo2, on Flickr

The transformers with the cables all twisted into their pairs and the blue/yellow pair soldered up and the ends covered. The blue/yellow pair was much harder to twist for some reason which meant they weren't quite as neat as the pink/orange, resulting in an untidy quad arrangement unfortunately:
wd step up 003 by christogo2, on Flickr

The transformers installed and all cables soldered into their various positions, hopefully correctly:
wd step up 004 by christogo2, on Flickr

I make no claims for neatness here, this is my first attempt at making an SUT so am open to criticisms about cable orientation/routing/etc.. If I were starting from scratch, I would elect to get a case with enough internal space for the transformers to be mounted vertically and have the input and output sockets on opposite sides, I think. This would allow a more tidy cable layout although I don't know if there is any technical benefit to such an arrangement.

Thanks again for the advice. I must now install an MC cartridge onto my turntable so I can have a listen; fingers crossed that there will be music and no hum.
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  #7  
Old 20th August 2019, 03:47 PM
goomer goomer is offline
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Default Re: WD MCT SUT question

It works! I have music and with only the faintest trace of hum if you put an ear to the speaker and if the turntable - a Technics direct drive - is spinning.

I haven't experimented with placement yet, just plonked the SUT down next to the turntable, so will try altering that later as well as using a proper shielded pair of cables between the SUT and phono pre amp. I have the tonearm cable earth wire connected to the SUT but no onward separate earth cable connected to the phono pre, is it worth trying the SUT earthed to the phono pre too?
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  #8  
Old 20th August 2019, 04:35 PM
bob orbell bob orbell is offline
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Default Re: WD MCT SUT question

Looking at your assembly, I would remove the two brown wires connecting the 0 volts to ground on the input, the inputs to the SUT should ( in my opinion ) be floating and not have any connection to ground earth, this way you will have a balanced input ( sort of ) to the primary side of the SUT, you may also wish to try the arm earth lead to the phono amp. Bob
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  #9  
Old 21st August 2019, 08:19 AM
goomer goomer is offline
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Default Re: WD MCT SUT question

Thank you for the suggestions, I will give that a try at some point soon.
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  #10  
Old 21st August 2019, 01:50 PM
John Caswell John Caswell is offline
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Default Re: WD MCT SUT question

Hi Goomer et al,
You do not need to be so enthusiastic about twisting your wires together so tightly as you can easily break them without realising it.
After all they are all going to be inside a metal box connected to earth, so are well screened electrostatically.
Contrary to what Bob says you may or may not need to earth your input leads, it will depend very much on turntable/arm and cartridge combination.
If you suffer from hum pickup, and you are sure that the earthing is correct, it is possible that you have electromagnetic pickup into the transformers so try moving the SUT box around, inverting it rotating it and the like. You may be surprised at how big the radiated transformer fields can be.

John
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