Persistent low-level hum when using Stellar Phono Preamp

Can’t seem to get rid of (or really, change) the low frequency hum I’m getting from the Stellar - can easily hear from 2 feet away. Every other path in my system is dead quiet - Soundsmith Zephyr cartridge through Technics SL-200GR/Ortofon Mono SL1200-mkii turntable (one running to MC, the other to MM) through Blue Jeans Cables RCA cables to the Stellar, then Mogami XLR’s to a Schiit Freya+ and then to a Benchmark AHB2 (had a Parasound A23+ amp previously) and finally to Benchmark Canare cables to Buchardt S400 MKii’s. The system is on its own circuit, normally. I turned off lights, switched power outlets and power strips, defeated the ground on the units, turned off (and unplugged) every piece of unnecessary equipment in the room, moved and separated the remaining pieces around, moved the cabling around, even went so far as to unplug all turntable inputs/ground wires from the Stellar - still that unchanging low frequency hum. Switching out the tube circuit on the Freya just made it quieter, and changing the gain setting on the Stellar changes the volume of the hum as well as the amount of gain. The RCA outputs strangely are less noisy than the XLR connections. I had a PS Audio Power Plant at one time but not anymore - don’t remember if that changed anything. Any other ideas of what I can try? Additional info: unplugged the RCA and XLR Stellar outputs running into the Freya - noise goes away. Again, XLR output has louder hum than the RCAs, probably due to lower gain. Switching RCA/LXR cables to other inputs on the Freya makes no difference, nor just having the RCA’s or XLR’s or both plugged in.

Have you tried swapping the XLRs out for another set? If the hum is present with the XLR and (mostly) gores away with rcas perhaps it could be a cable issue? Additionally are the stellar phono and freya plugged into the same receptacle, or power source? Additionally do you have a ground cable from you TT to the stellar? If I remember correctly some SL1200m2 lack a ground, I think there are some aftermarket kits to add them.

One other idea and this may sound silly, but have you tried jiggling the head shell wires?

Good luck.

Thank you; at this point I’m nearly out of ideas so any suggestion is fine.
1.) Yes, I’ve swapped out the phono preamp/preamp cables (I can use XLR or RCA) and have swapped out the preamp-to-amp XLRs - my only option on that side. I have tried Monoprice, Blue Jeans Belden 1800F and Mogami Gold Studio-03 XLR cables, and Amazon, Monoprice, Blue Jeans and AudioQuest RCA cables. Absolutely no difference between XLRs and RCAs, except that the SE connections are quieter but have less comparative gain.
2.) All of my equipment is/was plugged into the same outlet/power strip; I have not tried forgoing a power strip but I will try that (I’ve tried different ones).
3.) Yes, all of my turntables have ground wires and I attach them to the Stellar; I tried disconnecting each one as well and the RCA leads but no difference in noise level.
I did try removing and swapping headshells, but the telling part is that I still get the hum when I have NO turntable inputs/ground wires attached (nor plugged into an outlet).

I just tried my headphone amp so I can turn off my power amp and listen through headphones (yes, I tried a scenario with the headphone amp disconnected) - there is some noise there from all inputs when I turn the HP amp and preamp up really loud, but not as bad as when using the Stellar phono inputs, and that’s true whether or not I actually have a turntable plugged into it.

So, I only get the low hum when the Stellar inputs are used (with or without a tt attached to it), and the system is silent when I use my DAC or switch to an input on the preamp with nothing connected.

An avalanche of information to digest here. But, if I’ve sorted through all of this correctly I don’t see that you’ve grounded the SPP to the Schiit Freya chassis. If that’s the case, try doing so. I always ground my phono preamp chassis to the chassis of my preamp. Why? Because even a tiny, very low level chassis ground potential difference will drive current through the cables connecting the two and that usually manifests itself as hum (or a ground loop if you prefer to think of it that way). In my experience, it doesn’t typically matter whether all the electronics are plugged into the same circuit, because this phenomenon can be caused by the details of exactly how circuit common inside the box is referenced to chassis. Try it if you haven’t. You have nothing to lose.

Thank you; I did briefly try touching the tips of an RCA cable to both chassis, but it had no effect. I just attached a wire to a screw on back of the Freya and then to the ground post of the Stellar. No difference. Tried touching other screws on the Stellar, all around the chassis of the Stellar. No difference either.

Low-level hum can definitely be frustrating. Here is how I would approach it.

  1. Connect only cables between your SSP Outs and Freya Ins.
  2. Insert shorting RCA plugs into the SPP input.
  3. Then test for hum.

This should be an environmental baseline. If you are still hearing hum at normal volume levels, then I would suggest moving the units to another part of the house and using headphones to test.

If the hum stops with the shorting plugs, then you now have a starting point. Zepher cartridges are moving iron and these are susceptible to airborne hum pickup. I would try to test this by shorting the cartridge wires, + and - together after disconnecting the cartridge . On some integrated turntables the tonearm/headshell are not grounded which can lead to hum pickup.

This should get you started on the path to a solution. Let us know your results.

Thank you; I think I will try the shorting plugs, and maybe move the equipment into another room of the house for my own curiosity; I’m in a mostly-buried basement already but you never know. I did mention that I have the hum with absolutely nothing plugged into the Stellar phono stage, so the Zephyr/tonearm/turntable has been taken out of the equation. I do get more hum using XLR cables connected between the phono stage and the preamp, which seems counterintuitive.

I have experienced the XLR path being noiser with airborne interference. My SGCD experienced this as noise injecting back into the output stage via the feedback loop and then being amplified. I solved my issue with better XLR shielded cables and careful re-routing. In my case it was not hum (60 cycles) but what sounded like schottky noise; however the mechanism can be thhe same as I only needed the output cables connected to the amp.

Even in Fremer’s review a sensibility of the Stellar phono to such problems was mentioned and there were several forum members here describing similar cases. Maybe a service call or trying to get in conversation with Darren helps the fastest.

Thank you, and since you brought up AI I realized that I have my wireless router in the same room; another thing to shut down to see if that makes a difference. I’m also trying to take note of if the hum is less/more at different times of the day. I did test multiple XLR/RCA cables in the Stellar to the Freya and to the Benchmark in order to see if there was an effect (sadly, no), and the fact that the noise is not there when I switch to other inputs tells me the XLRs from the Freya to the Benchmark are not the problem. The noise is also present and unchanging when there is nothing plugged into the Stellar.

Yes, I might have to get Darren or a tech on the line to try to work through potential issues, but I was trying to eliminate all of the obvious possibilities I could come up with before I called them. I did read Fremer’s review of the Stellar and tried the resolutions he/they did, and I would only be too happy to discover that I had to reroute cables or use specific cables to make the hum go away. It’s not loud enough as to be totally distracting, but I would think that a unit that’s been so raved about would not have the level of noise I’m experiencing.

Sorry you’re experiencing a bit of hum. Definitely we can help. I would reach out directly to Darren. Email’s the easiest. It’s his first name at PS Audio .com.

Thanks Paul; will do.

No resolution yet; I sent Darren further information about what it sounds like (different but constant buzz on MC/MM settings, gain makes the hum volume go up/down) but nothing else to try yet. Unusual that the hum is there when there’s no inputs connected, so the only path left is the SPP through cables (tried various, both RCA and XLR) to a Schiit Freya+ (tubes put in and taken out of the path) through XLR cables (tried various brands) to a Benchmark AHB2 and then through Benchmark SpeakOn connector cables to banana plugs into Buchardt S400 mkii speakers. I will reiterate that I get absolutely NO noise when I select other inputs on the Schiit.

While waiting for Darren, what is the result with sorting plugs in either of the inputs? You also now mention a “buzz” which is typically in the 120Hz range. That would indicate its from an offending power supply. You also haven’t said whether it entirely goes away when you select Mute on the SPP.

I installed the RCA shorting plugs into the SPP into the input and output - no difference in hum and it really is a hum around 60 Hz (that’s what showing up on my spectrum analyzer) but the hum was a little different as it was a bit “buzzy” when MM is selected. Muting the SPP does gets rid of all hum.
Darren got back to me and he wants me to send it in.

Since you have test equipment, before sending it in, I would take it to a different room. With the shorting plugs in the inputs and the outputs connected to your analyzer check whether the hum level has gone down. This will likely eliminate environmental sources and give Darren a baseline.

Moved it out of the room, checked the hum, still there in all its glory. Ran long XLR cables to the preamp, still there; didn’t think there’d be any difference since I’m in a partially underground cinder block basement out in the suburbs. The hum is not noticeable at low volumes but if you start cranking it a bit it’s very evident. Thanks all, but I’m done futzing with this. I’m sending it in to see if there’s something actually going on with this particular unit, because I love all of the features on this which allows to run two different turntables with vastly different cartridges without having to change cables or settings on the back or bottom.