How far is your SUT from your Phono Pre/Preamp?

Do you wanna rephrase that?

This must be a trick question?

Yeah, it does sound pretty dang silly.

Can I report my own post for being a complete waste of everyone’s time?

Mine is inside. I am assuming that your’s WAS external?

I think I get it. He was using an external SUT instead of the one built into his phono pre-amp but switched back because he was getting hum.

Usually hum is from cables that are not properly shielded, ground issues, things like that. I run a Denon AU-340 SUT with 3' cables going into my Audio Research SP8 that sits about 10" from the SUT. No issues what ever. I have all my grounds attached to the back of my SUT, the ground from the SP8 and the ground from the tonearm cable.

BillWojo

The short answer is no, you need not tolerate hum just because your SUT is close to your phono stage. In fact ideally you want the two to be as close together as practical.

External SUT should be hum free -

Use low capacitance shielded cable between SUT/phono

Make sure SUT chassis is earthed to phono via additional earth wire

Should be close as possible. Above comments correct, use a good phono cable to connect to pre...hum can be reduced greatly by turning the sut....if you cannot hear hum at listening position, then there is No problem.

Cable from SUT to phono stage should be kept short (less than 1 ft) to avoid capacitive loading/hi frequency roll off. Ground wire from SUT to phono.

Got it. I'll try other cables today to see if that's what's causing the hum.

Dear @dhcod  : The orientation/position of the cables ( an even of the SUT it self. You can rotate it for example.  ) running is something to try. Sometimes running the cables in a " weird " position makes the hum disappears. You can try with the cables you are using and that " makes " hum.

Regards and enjoy the MUSIC NOT DISTORTIONS,

R.

All good advice here.

In addition to Raul's comments you might also try a different orientation of the SUT.

You don’t happen to have the SUT plugged into a different electrical outlet? 

I've spent the morning doing a bunch of things, reorienting, finding weird angles, and changing cables to shielded cables. Cables make no difference at all. There's definitely one spot that I found to place the SUT that is the quietest and it's about 14 inches away which is good... but there's still a noticeable hum, although only within 3 feet of the speakers, not in the listening position.

My question now is whether the hum is the fault of the SUT or the phono preamp? Will any SUT that gets near my phono preamp cause a problem? Probably need another SUT to figure that out.

Is the SUT or the phono stage in close proximity to your amplifier? Could the power transformer in the amp be the cause? Just thinking out loud....

@atmasphere  : this comes from my post: " ( an even of the SUT it self. You can rotate it for example.  ).

R.

@dhcod  : Why do you need an external SUT with your Lamm PS De Luxe? 58db plus the line preamplifier gain is enough for your 103R.

Now, in the other side : Have you in the past that kind of hum problem using your Lamm with out external SUT or made any analog rig change when you got the external SUT?

If you made any analog rig change the 103 is an easy to be contaminated and develops some kind of noise as " hum " if those cartridge/tonearm connectors are not tigth secured.

R.

Interestingly the SUT in the Lamm is a real weak point. The external, even a relatively inexpensive one like the AnaMighty one I have, is a huge improvement over the Jensen’s inside. I just A-B’d it again this morning and it sound great with the internal but the external is sublime. 
 

The system change that has caused this problem to become noticeable is a switch to SET and higher sensitivity speakers. The amp change came after I first noticed the hum so it’s not a source of the problem. 

@dhcod ​​​​​​the good news is that if the Jensen's inside the box can be quiet there is no reason an external sut cannot be too. Between grounding, and in a worst case scenario additional shielding, you should be able to get the noise down...

I use a .5 meter Atlas Elements Integra phono specific cable that has very low capacitance between the SUT and the phono preamp. Also, I do Not ground my SUT, as the turntable is already grounded to the phono preamp. Adding too many grounds will add noise. That is what I have found in my experimentation. Of course, all systems are different and I'd advise to do what works.

Up above in this thread, someone suggested experimenting with the physical orientation of your external SUT in relation to the power transformer of your Lamm phono stage. In addition to playing with grounding, have you tried that yet? There is a possibility that will make a difference. Also Jensen Transformers are very very good. I am surprised you find them to be inferior to even a low priced external SUT. Perhaps Lamm does not use the top of the line transformers available from Jensen. You might consider replacing the Jensens in your unit with the best current Jensen SUT.

Interesting. I had a similar problem with an SUT, (not a powered one) as previously referenced by another. Check out your turntable cartridge leads and ground. Also the level or gain if any at the preamp. That was my problem. Too much gain at preamp. Hope this helps. Good luck, these issues can be maddening. 

@dhcod I have real trouble believing that the Jensens are actually worse than your outboard SUT. But in order for them to work right, the Jensens must be loaded correctly at their output. I expect Lamm has a provision for that. The loading changes from cartridge to cartridge and Jensen has published a pdf on their website with the correct loading values based on your cartridge.

It may well be a power transformer associated with the SUT that is causing the hum. IOW look at associated equipment to see if there is a power transformer nearby that might be causing this.

It's pretty well documented that owners have had much better luck with outboard SUTs than the internal Jensens with the Lamm. Lamm has no provision for loading changes and maybe that's the cause. In my case, the SUT is designed for my DL103 variant cartridge. I have to say I've had a lot of experience with loading changes and they wouldn't duplicate what the external SUT does in this case.

It's pretty well documented that owners have had much better luck with outboard SUTs than the internal Jensens with the Lamm. Lamm has no provision for loading changes and maybe that's the cause. In my case, the SUT is designed for my DL103 variant cartridge. I have to say I've had a lot of experience with loading changes and they wouldn't duplicate what the external SUT does in this case.

• Do they have to be loaded at the preamp side?
• Or can they be loaded before the SUT?