Help me wire up my SUT correctly (Tamura TKS-27) - diyAudio
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Old 4th February 2013, 05:26 PM   #1
rongon is offline rongon  United States
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Default Help me wire up my SUT correctly (Tamura TKS-27)

I'm not comfortable with the grounding, etc. of MC step up trannies for phono cartridges.

I've attached a little schematic of the SUT in question. They're mounted in an ugly little electrical enclosure, steel chassis. The box has a pair of RCA jacks for input. The input jacks are floating from the chassis. I will be hardwiring the outputs to the interconnect cable, coming straight from the enclosure.

I want to wire up the SUT with single-ended input, using the 300 ohm primary (lugs 1 and 3). Secondary lugs are 4 and 6, 100k ohms. Secondary will also be single-ended.

My dumb questions:

- For unbalanced input, should lug 3 be grounded? If yes, where? Directly to the chassis? Or should the single-ended input float, leaving only the ground wire from the turntable grounded to the chassis?

- Lug 5 is a shield for the secondary. I'm assuming it should be grounded to the chassis?

- For unbalanced output, should lugs 5 and 6 be shorted and grounded? Lug 4 would then be the output signal 'hot', 5+6 would be output ground?


I think that's it. Any help would be greatly appreciated.

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File Type: jpg Tamura_TKS27_schematic.jpg (13.5 KB, 118 views)

Last edited by rongon; 4th February 2013 at 07:39 PM.
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Old 4th February 2013, 05:38 PM   #2
rongon is offline rongon  United States
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According to this schematic...

Click the image to open in full size.

...if I'm reading it correctly, for the primary, I would ground the input shield and lug 3 (0 ohms), and the input 'hot' would be lug 1 (300 ohms).

I would leave the secondary floating by grounding lug 5, while lug 4 would be signal 'hot' and lug 6 would be signal 'shield' (not grounded until the RIAA preamp).

Maybe I'll just try it that way and see what happens.

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Old 4th February 2013, 05:56 PM   #3
SY is offline SY  United States
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Don't ground the primary. And if you can convert the cartridge-to-transformer wiring to balanced with a shield, that's even better (ground the shield). Secondary grounds from pin 6.
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Old 4th February 2013, 06:20 PM   #4
rongon is offline rongon  United States
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Thanks SY. I think this is what you meant (single-ended input, drawing attached). Did I get it right?
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File Type: jpg Tamura_TKS27_wiring_01.jpg (36.9 KB, 108 views)

Last edited by rongon; 4th February 2013 at 06:28 PM. Reason: picture was wrong again.
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Old 4th February 2013, 06:40 PM   #5
SY is offline SY  United States
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Yep!

If you use twisted wires for cartridge hot and cold, connect to the primary, and then ground the shield, you'll have an even better interface.
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Old 4th February 2013, 06:52 PM   #6
rongon is offline rongon  United States
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Unfortunately, I'm using a Technics SL-1200mk2 'table with its stock tonearm wiring, and I'm not sure how the tonearm is wired. According to this picture...

Click the image to open in full size.

...it looks like the cartridge cold conductors are grounded. But I could be wrong about that. At any rate, thanks for the help!

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Old 5th February 2013, 05:19 PM   #7
rongon is offline rongon  United States
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Well, I thought I should let you know how this all ended up. I have to abandon the project for now. Two things did me in. One, the Soundsmith Gold cartridge (modified DL103R, 14.4 grams!) is way too heavy for my tonearm, and two, my phono stage is too sensitive for the Tamura step-up transformer (too high a step-up ratio). In order to make this all work, I'd need a new turntable/tonearm combo, and I'd need to alter the RIAA amp or make a new one. That's more new stuff than I had in mind.

For now, I'm happy enough with my current modest setup, but this was a great learning experience for me. Thanks for the help.

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Old 5th February 2013, 05:51 PM   #8
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Quote:
Originally Posted by rongon View Post
Well, I thought I should let you know how this all ended up. I have to abandon the project for now. Two things did me in. One, the Soundsmith Gold cartridge (modified DL103R, 14.4 grams!) is way too heavy for my tonearm, and two, my phono stage is too sensitive for the Tamura step-up transformer (too high a step-up ratio). In order to make this all work, I'd need a new turntable/tonearm combo, and I'd need to alter the RIAA amp or make a new one. That's more new stuff than I had in mind.
You can add mass to the stock Technics c-weight. Or, swap the arm out for a Jelco 750d.

Technics SL-1200 mods

Seems odd that you have too much gain. Is the Tamura step-up more than 10:1?

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Old 5th February 2013, 07:15 PM   #9
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I think the Tamura is more than 10:1, and I also know that my preamp has more than the usual 40dB of gain. I think it's more like 50dB. I designed it that way to match the output from my DL110 to that of a CD player. The combination of the Soundsmith Gold, Tamura SUT and my 'hot' preamp is just too much. But the electronic stuff is easy compared to the mechanical requirements of the cartridge and tonearm.

I have the extra 10g screw-in weight already installed on the stock counterweight. I'd have to put some kind of non-standard extra weight on there. I guess I could put a layer of something on the screw in weight to add a bit more weight.

I'll read up on the Jelco 750D option. I guess a Rega RB300 tonearm can't handle a 14.4 gram cartridge?


Wait -- That brass pipe weight looks like it would work. Where can I find details on that? Is that glued to the KAB add-on weight? I don't get it...


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Last edited by rongon; 5th February 2013 at 07:34 PM. Reason: new stuff
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Old 5th February 2013, 07:58 PM   #10
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Originally Posted by rongon View Post
I guess I could put a layer of something on the screw in weight to add a bit more weight.
You could try adding Duct Seal around the KAB weight until you reach the correct balance point. Then, take it off and weigh it, which would give you a reference point for a more permanent solution.

Quote:
Originally Posted by rongon View Post
I'll read up on the Jelco 750D option. I guess a Rega RB300 tonearm can't handle a 14.4 gram cartridge?
For the Rega, you'd have to get an aftermarket "heavyweight" . I went the Jelco route because of the removable head-shell. I found mounting a large-ish cartridge on a Rega to be a real PITA.

Quote:
Originally Posted by rongon View Post
Wait -- That brass pipe weight looks like it would work. Where can I find details on that? Is that glued to the KAB add-on weight? I don't get it...
I'm thinkin' it came from the hardware store, home despot maybe? Don't know how they mounted it.

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