Do I need an SUT w/ an EAR 868?

Toying with the idea of an SUT for my EAR 868 & 890 setup. Thoughts of the Goners is appreciated. Have tried a Bobsdevices SUT but am experiencing audible hum when hooked up. Hum is not present when going direct from VPI Aries to preamp. Am I trying to tweak too much?
It depends on the output of your cart and the total gain of your system. KAB has a gain calculator on their web site.
EAR makes some of the best phono SUT's on the planet. Not sure why you'd try anything else. In fact, your 868 may have a SUT already in the signal path which is what might be causing the hum... a sut connecting to a sut...

I'm with Swampwalker, what cartridge, output are you using?

I have a EAR MC4's a killer good SUT. This might be one of the very few instances where the wonderful bob's devices sut is a step down from the sut you already have built in...

maybe one tweak to far ;-)
Jfrech.. I'm using a Cardas Ruby 3. Output volt 0.34 mV at 3.54cm/s. Impedance 38ohms.

I may tweak for tweak sakes only! Recommended by a trusted dealer. But perhaps one step too far.

Hi I found a review on your EAR 868. It does indeed use transformers already in the phono stage. "...the linestage gain is 17dB, the phono gain a variable 50-80dB, and the output impedance a relatively low 600 ohms. The 868 doesn’t invert phase. Also, rather than using another set of tubes for a third gain stage in the phono section with its attendant risk of noise, EAR’s legendary designer, Tim de Paravicini, chose to handle that with custom-designed step-up transformers, with selectable primaries of 10/1, 20/1, and 30/1." This is quoted from:

So seems like you have a massive amount of gain..up to 97 db (17 in line stage and up to 80 in the phono)

Have you played around with your loading via the dip switches? These switches are actually selecting different windings on the you different gain. (Similar to my EAR MC4 SUT)

Those Cardas Ruby's are nice cartridges...What table and arm are you using? I've heard the EAR Pre and Amp before..that gear is VERY good...and likely not a source of improvement...unless you want to spend very big bucks...
Jfrech, I have a VPI Aries 2 with a stereo cart on a 10.5i wand and a mono cart on a Classic 3 arm. Thank you for your responses.

I will look into what you mentioned.