SME 3009 S2 Improved Tonearm problem...possibly

Hey

I have an SME Series II Improved with the fixed headshell

If set up properly, it is an amazing tonearm! I stripped mine down to the last screw, cleaned, rewired and put it back together. (There are parts in the service manual where they say to not open certain areas - its worth heeding that advice...) After some colourful use of language, I got it back in order and it sounds amazing!. There are all kinds of compliance info and null point/overhang etc. info online. 

Could be an issue with the compliance, or with the geometry you chose to use when setting it up. The ground noise you are experiencing doesnt seem like it  would be the cause of the distortion from high intensity passages. 

There is a company here in Canada that does a full rebuild/rewire of the tonearm for around 400? I was going to send mine in to be done, but decided to just do it myself. The wire harness they install wasnt compatible with my turntable (DIY heavy plinth Lenco) as I have the arm connected to RCA plugs on the rear of the TT, and there are no provisions for a wire to run from the arm directly to the phono.

Try lowering your gain setting. I had similar issue with my setup when I went from MM to MC cartridge. 

It appears you have a classic case of cartridge/tonearm mismatch. Everything you're reporting (except the induced hum from the hex wrench, and that will never be an issue when using the cart). The Zephyr is a fairly low compliance (stiff) cart at 10 uM/mN. Your SME is a low-mass tonearm (~6.5 to 9.5 grams) when you do the math, your combination has a resonance frequency somewhere betwween 18-20Hz. It should be about 10Hz. The Shure V15-III has a compliance of 30 uM/mN and in your SME that yields a resonant frequency right at 10 Hz - just about perfect. Here's the reference link: http://www.analogue-classics.com/html/sme_3009___3012.html 

The solutions are either increase the effective mass of the tonearm by about 20 Grams (a big wad of florists putty?), Or find a compatible tonearm, or find a more compliant cartridge. You also might see if you an swap your Zephyr for an Aida High Compliance - they're the same price, but as the name implies the Aida High compliance is intended for low mass tonearms. It is also a high-output cart, so no MC preamp is required - just a regular MM phono stage. https://www.sound-smith.com/cartridge-compliancearm-mass-chart

Good luck.

I will talk with Soundsmith about swapping the cartridge possibly. However, they are the ones that recommended it to me.

This is the link they sent to me when I emailed them asking what do they recommend with my setup. I gave them all the details of what I had and this is what they sent to me:

https://www.sound-smith.com/cartridges/317/low-output

I'm going to get the table and arm 100% functioning correctly and then go from there. I am open to tonearm suggestions. I prefer something like the SME V with dial settings. Would that arm fit my table, Thorens TD125 mkii?

I agree with @dover re feedback coming the turntable, I had the exactly the same problem as you described and had to put turntable on a floor standing rack instead of wall mounted.

General rule for cartridges is low compliance cartridge use a high mass arm and vice versa.

Don't be fixated on arms with dials for downforce and bias always use a cartridge downforce gauge and do final adjustments by ear same for bias.