So I decided to try and get my new Denon DL-103R (thanks sub ) running on my Technics SL-1210 MK2. 

Mounted it with some temporary hardware that I had on hand and got it all aligned.



I grabbed this Fidelity Research FRT-3G from Dad's stash. 



The trouble is that when I switch to any of the MC settings (low, high) I just get a loud buzzing sound through the system.

No buzzing and decent sounding music (although very quiet, which is expected It think) when on the MM setting, which is a pass through. So I guess that confirms that the cartridge is hooked up correctly?

I have the TT output (and ground wire) going into the SUT, SUT output into Rega Fono Mini 2 and then into an auxiliary input on my amp.

I'm pretty sure Dad has done some work to this SUT (new cardas output cables) so I opened it up to see if anything had come loose. I couldn't see anything obviously wrong but there were some dubious looking connections around the rotary switch.

I don't really know anything about SUTs and I couldn't find a schematic anywhere so my chances of trouble shooting it are low.

Is there anyone around that would be able to repair this? Someone that might be familiar with this type of unit? 

www.jeremyyoungdesign.com

Brian Smith in Foxton 063637774

May 16, 2021 22:45:28 GMT 12 peter0c said:

Brian Smith in Foxton 063637774

Thanks, I might give him a call.

He actually wound the transformer for my OTL tube amp but Dad organized that.

Hopefully he can figure it out.

www.jeremyyoungdesign.com

A couple of things to check. Make sure both sides of the SUT are grounded to the phono stage. I know your Dad was fiddling with grounding at one point so this unit might have separate wires for grounding. Basically, you should have continuity of the grounding from turntable and cartridge negative pins to phono preamp.
Next check the location of the transformer. MC SUTs handle microvolts of signal so you need to keep them well away from any external magnetic fields such as amplifier power transformers, etc. Definitely don’t put it on top of your gainclone amp.

AMR-iFi R&D

May 17, 2021 20:04:11 GMT 12 colinf said:

A couple of things to check. Make sure both sides of the SUT are grounded to the phono stage. I know your Dad was fiddling with grounding at one point so this unit might have separate wires for grounding. Basically, you should have continuity of the grounding from turntable and cartridge negative pins to phono preamp.
Next check the location of the transformer. MC SUTs handle microvolts of signal so you need to keep them well away from any external magnetic fields such as amplifier power transformers, etc. Definitely don’t put it on top of your gainclone amp.

Thanks Colin, I will check that grounding continuity.

Is it best to connect the TT grounding wire to the Phono or SUT?

One other thing, I checked the continuity of the positive (signal) conductors between the input and output of the SUT. Initially I thought that there should be continuity but I've just realised that as this is a transformer the inputs (primary windings) and outputs (secondary windings) aren't actually electrically connected, is this correct?

But I should be able to measure the resistance of the secondary winding though, and the resistance should change as I move the switch?

Cheers,
Jeremy

www.jeremyyoungdesign.com

There is no direct connection between the primary and secondary of your SUT. The only connection is inductive. There should be info on the input and output resistance of the SUT but be careful in measuring it (I'd use a vacuum tube meter) because it will be exceedingly thin wire but not as thin as a cartridge which is easily damaged. Colin will be able to advise.

Ok, so I think I have this figured out thanks to colinf 's tip about grounding.

I went and grabbed the other two SUT's that Dad had, I plugged the FRT-4 and it had the same issue, loud buzzing as soon as it was plugged in. This SUT has also been modified as it is detailed on his blog, no mention of grounding though.




Next I plugged in the other one which looks to be a Bob's Devices SUT. This one worked, but only when the switch was in the "ground" not "lift" position. This got me thinking about colinf 's comments about grounding.



I checked the continuity of the grounds and found that the signal grounds did not have continuity with the ground wire lug, once opened up and found that the ground wire lug was only attached to the shielding of the input cable.

I added the blue wires you can see in the photo below, connecting the ground wire screw with the outer (negative) sleeve of the input sockets.



And it works!

My question now would be, why would you want to lift the ground? How would it have been possible to get this to work without the internal grounding? 

colinf how did you know that Dad had been playing with grounding, had he written about it somewhere?

I will have to open up the FRT-4 and reinstate the grounding as well.



The DL-103R sounds great, much better than my tired old DJ carts. Managed to find some brass hardware as well which I know Dad was fond of.

www.jeremyyoungdesign.com

Glad you got it sorted. If you are tempted to play with the 103 and nude it, fit an after market body or whatever to it.

www.denonaluminumbody.com/

Really good, well worth the money. I gave one of these to Beeman (with a Denon 103) when I bought his spare phono stage.

Good detective work J !

Ground lifts are an easy way to eliminate ground loops.

Very effective on the Plinius amps I've used, interestingly Gary M had discarded ground lift switching on his PureAudio designs.

The 103 cap looks good, fixes the awful open sided cartridge mounting.

jerm which setting sounds best for you with the Denon? Low - 3ohms to 10ohms, or high - 15ohms to 40ohms?

"Is it best to connect the TT grounding wire to the Phono or SUT?".
I connect mine to the amp chassis. But with all things earth grounding wise, it pays to play around. Earthing/ground issues can be a nightmare!

May 18, 2021 15:50:59 GMT 12 jon said:

Glad you got it sorted. If you are tempted to play with the 103 and nude it, fit an after market body or whatever to it.

www.denonaluminumbody.com/

Really good, well worth the money. I gave one of these to Beeman (with a Denon 103) when I bought his spare phono stage.

Before fitting this cart I did some research on it and discovered that people were doing a bunch of mods to them. Part of my job involves product design and a lot of CNC prototyping so my first thought was to potentially make my own body. It looks fairly straightforward, but I realised I should probably install and listen first before modifying it  .

That cap looks interesting, it certainly looks easier than re-housing it into a new body, how does it compare?

I also actually really like the look of the standard body, the shape, angles and gold accents.

www.jeremyyoungdesign.com

May 18, 2021 17:06:08 GMT 12 Citroen said:

jerm which setting sounds best for you with the Denon? Low - 3ohms to 10ohms, or high - 15ohms to 40ohms?

"Is it best to connect the TT grounding wire to the Phono or SUT?".
I connect mine to the amp chassis. But with all things earth grounding wise, it pays to play around. Earthing/ground issues can be a nightmare!

Low seems to sound better, but they are very similar.

Should the volume change when I switch between the two? Gain? Both settings seem to output a similar level but slightly different characteristics.

www.jeremyyoungdesign.com

The Denon 103R is 14 ohms, so falls between the two settings.

SUT's are a black art to me, and while some work well with some carts others are naff (despite the theoretical compatibility specs).

Currently having minor hum issues with Auditorium SUT... No wonder I prefer a good head amp!

imho can't beat straight in !

May 16, 2021 19:25:33 GMT 12 jerm said:

I have the TT output (and ground wire) going into the SUT, SUT output into Rega Fono Mini 2 and then into an auxiliary input on my amp.

I came in late to this, but after reading through, it seems to me that the above is/was the problem. You stopped the ground wire at the SUT?

No need to internally solder grounds to the cart -ve leads - they will eventually meet earth/ground inside the amp.

But the ground wire should have been carried not just to the SUT but also from that to the Rega Fono, and yet again from that to the amp - grounding all those chassis.

I think all you needed to do was continue a ground wire (anything chunky you have around, terminate nicely later but just try it first) also further from the SUT (where from the above description it seemed to end, never made it to the amp!) to the Rega and then another one to carry it to amp phono earth.

If you want to try that (to prove it) you will need to undo the internal links you made (temporarily, tape the ends until sure) otherwise you will / may have a ground loop.

But do you see what I mean? The cartridge terminals are essentially balanced, floating - some phono stages (and I imagine the primary of a SUT) even maintain a balanced input - heck, some amps offer it too - think microphone XLR inputs as well.

But when going in to an unbalanced RCA input, the -ve pins will get connected to signal ground inside the amp.

In a sense you have brought that internal amp connection back out with your mod. But it might be even better as originally intended, just connect all the ground wires.

The purpose of the 5th grounding wire is to connect the body of the tone arm (and perhaps the TT chassis) - as a shield - all the way back to the chassis of the amp.

And so it must also connect all the chassis of the intermediary boxes you have on the way in, too. They all have grounding posts?

Daisy chain that ground wire to & from all the boxes, so to speak, and you won't need (and should undo before trying it!) that modification that you made. IMHO.

Sorry for the repetition! But I hope that makes sense. Your amp will have a ground post by its phono inputs.

I used to own a nice Supex SUT, reluctantly sold after both my MC carts had died; that's how I connected it, no problem.

It could switch two TTs and two amps, and either boost for MC or pass through for MM. Notice the big ground lug. ;=})

Cheers !!

“colinf how did you know that Dad had been playing with grounding, had he written about it somewhere?”

Your Dad wrote a bit on the thread “System Grounding” under Cables and Power. He wrote earlier this year, and one of his diagrams includes SUT grounding.

AMR-iFi R&D

May 18, 2021 17:16:35 GMT 12 jerm said:

That cap looks interesting, it certainly looks easier than re-housing it into a new body, how does it compare?

I also actually really like the look of the standard body, the shape, angles and gold accents.

I started with a standard Denon 103... I've nuded and rebodied around 15 - 20 of these!! It's nerve-wracking doing i, at least for me.

Remove the body (nude it). Improvement in sound

Put a wooden body on it. Improves the sound over nude. You can really play with different wood bodies and get different sounds.

The cap goes here!

Put a Metal body on and the sound improves again.

The cap's not quite as good as nuding one and fitting a metal body. It's really simple to fit. It's cheap. So as an introduction to after market stuff for the cartridge it's a great starting point.

May 18, 2021 19:30:54 GMT 12 RdM said:

May 16, 2021 19:25:33 GMT 12 jerm said:

I have the TT output (and ground wire) going into the SUT, SUT output into Rega Fono Mini 2 and then into an auxiliary input on my amp.

I came in late to this, but after reading through, it seems to me that the above is/was the problem. You stopped the ground wire at the SUT?

No need to internally solder grounds to the cart -ve leads - they will eventually meet earth/ground inside the amp.

But the ground wire should have been carried not just to the SUT but also from that to the Rega Fono, and yet again from that to the amp - grounding all those chassis.

I think all you needed to do was continue a ground wire (anything chunky you have around, terminate nicely later but just try it first) also further from the SUT (where from the above description it seemed to end, never made it to the amp!) to the Rega and then another one to carry it to amp phono earth.

If you want to try that (to prove it) you will need to undo the internal links you made (temporarily, tape the ends until sure) otherwise you will / may have a ground loop.

But do you see what I mean? The cartridge terminals are essentially balanced, floating - some phono stages (and I imagine the primary of a SUT) even maintain a balanced input - heck, some amps offer it too - think microphone XLR inputs as well.

But when going in to an unbalanced RCA input, the -ve pins will get connected to signal ground inside the amp.

In a sense you have brought that internal amp connection back out with your mod. But it might be even better as originally intended, just connect all the ground wires.

The purpose of the 5th grounding wire is to connect the body of the tone arm (and perhaps the TT chassis) - as a shield - all the way back to the chassis of the amp.

And so it must also connect all the chassis of the intermediary boxes you have on the way in, too. They all have grounding posts?

Daisy chain that ground wire to & from all the boxes, so to speak, and you won't need (and should undo before trying it!) that modification that you made. IMHO.

Sorry for the repetition! But I hope that makes sense. Your amp will have a ground post by its phono inputs.

I used to own a nice Supex SUT, reluctantly sold after both my MC carts had died; that's how I connected it, no problem.

It could switch two TTs and two amps, and either boost for MC or pass through for MM. Notice the big ground lug. ;=})

Cheers !!

Yeah, I think you're right. Initially I did try moving the ground wire between the SUT, Phono and Amp but never thought to daisy chain them.

I did want to test this theory so I grabbed the FRT-4 which also had the same hum issue when I tested it. I found that attaching the ground wire to the SUT then running a clip lead to the Rega phono worked well. There was no need to run another from the Rega phono to the amp. I guess the Rega phono may also have internally grounded the outputs?

Another thing that caused some head scratching was that although this unit has 3 inputs, only one of them worked, and the switch didn't do anything. I knew that Dad would likely have had the idea to bypass the selector switch so I opened it up and sure enough he had run the B input directly to the impedance selector switch bypassing the input selector. Luckily he left all the original wiring in so that I could easily reverse the modification, you can see all the green heat-shrunk ends. This SUT will be kept for use with the SP10MK2 setup and will make it easy to switch between the two arm/cart options.

Those two 1MEG resistors are also disconnected (which he does mention on his blog post) I'm not sure what effect that really has but I left it as-is.



I think I may leave the FRT-3G with the internal grounding for now, saves me have another wire connected and doesn't seem to harm anything?

Thanks for your help.

www.jeremyyoungdesign.com

May 18, 2021 21:14:42 GMT 12 jon said:

May 18, 2021 17:16:35 GMT 12 jerm said:

That cap looks interesting, it certainly looks easier than re-housing it into a new body, how does it compare?

I also actually really like the look of the standard body, the shape, angles and gold accents.

I started with a standard Denon 103... I've nuded and rebodied around 15 - 20 of these!! It's nerve-wracking doing i, at least for me.

Remove the body (nude it). Improvement in sound

Put a wooden body on it. Improves the sound over nude. You can really play with different wood bodies and get different sounds.

The cap goes here!

Put a Metal body on and the sound improves again.

The cap's not quite as good as nuding one and fitting a metal body. It's really simple to fit. It's cheap. So as an introduction to after market stuff for the cartridge it's a great starting point.

Very interesting, thanks.

I will give it some thought, if I were to do it I would either go the whole hog and re-body it in aluminium, or perhaps design an aluminium cap.

www.jeremyyoungdesign.com

May 19, 2021 12:49:39 GMT 12 jerm said:

May 18, 2021 21:14:42 GMT 12 jon said:

I started with a standard Denon 103... I've nuded and rebodied around 15 - 20 of these!! It's nerve-wracking doing i, at least for me.

Remove the body (nude it). Improvement in sound

Put a wooden body on it. Improves the sound over nude. You can really play with different wood bodies and get different sounds.

The cap goes here!

Put a Metal body on and the sound improves again.

The cap's not quite as good as nuding one and fitting a metal body. It's really simple to fit. It's cheap. So as an introduction to after market stuff for the cartridge it's a great starting point.

Very interesting, thanks.

I will give it some thought, if I were to do it I would either go the whole hog and re-body it in aluminium, or perhaps design an aluminium cap.

Said so casually.

I envy you DIY guys. I've still not been game enough to rebody a 103, even though I have an alu body waiting for a fitting! 

May 19, 2021 17:37:40 GMT 12 Citroen said:

May 19, 2021 12:49:39 GMT 12 jerm said:

Very interesting, thanks.

I will give it some thought, if I were to do it I would either go the whole hog and re-body it in aluminium, or perhaps design an aluminium cap.

Said so casually.

I envy you DIY guys. I've still not been game enough to rebody a 103, even though I have an alu body waiting for a fitting! 

Haha I guess that's where the fun is for me, I'd struggle to part with $200+ for an aluminium body but I'd love to machine one. Potting it in epoxy would be the tricky part!

www.jeremyyoungdesign.com