Hey folks,

Just wanted to share a bit of a saga I had last night trying to track down a pesky buzz in my system. I had previously thought it was an errant ZRock 2 that had been causing a buzzing problem when placed between the preamp and amp and had solved it by moving it before the preamp stage. But now this no longer works to get rid of the buzzing. And when the ZRock is in the chain without the preamp the buzzing isn't there. After a few hours of fiddling (and probably annoying my wife with the mess!), I'm pretty sure I've narrowed it down to my CSP2+.

I should note that this has all reared its head because I've recently upgraded my speakers to 100db efficient Zu Soul 6. Lovely speakers but also very efficient at revealing noise, it seems.

Even with everything else disconnected – just the UFO25 and speakers powered on – if I crank the volume on the UFO past about 2 o'clock, there's a noticeable low buzz. Pull the power plug on the CSP2+, and poof, the buzzing vanishes! There's still a super faint hum if I put my ear right up to the speaker, but that's nothing compared to the buzz.

So, now that I've (hopefully correctly) identified the culprit, what's the next step? Is this a "send it in for repair" kind of situation?
Tried a DC blocker on various components (amp, preamp, ZRock 2) but no luck there, sadly. And trust me, I really wished it was just a dodgy RCA cable after the marathon cable-swapping session I had! Even tried borrowing an Audioquest Niagra 1200, but that didn't solve the buzzing either (jury's still out on whether it improves the sound, but definitely not buying another thing right now!).

The weird thing is, even if the CSP2+ isn't connected to the UFO25, just having it plugged into power causes the buzzing to appear when the UFO's volume goes past 2 o'clock. Unplug the preamp, and the buzz is either gone or so quiet I can't hear it unless my ear is right on the speaker. With the preamp plugged in, I can hear the buzz standing up, and definitely from the listening position at higher volumes.

Sounds like some kind of grounding issue with the CSP2+, but I'm way out of my depth trying to fix that myself. Guess I'll be shooting Decware an email to see if they have any ideas.

Has anyone else experienced anything similar with their CSP2+ or any other gear? Any thoughts or suggestions in the meantime would be greatly appreciated!

Cheers!

I feel for you, with really efficient speakers every buzz or hum showing so clearly, especially
with tube stuff that’s so simple and revealing that the combination shows every fault in the system!

Typically for me, it is either ground issues like you are thinking you’re having, including loops, or IC connections, or it can be tubes. IC connections are usually my first check. Aside from noise in the system and/or environment possibly getting picked up, a weak IC ground connection can potentially contribute to ground quality and path issues. It sounds like you have ruled that out though.

Then there is the issue of noise feeding into the AC.... I still don’t understand the intricacies of noise and ground paths, and really wish someone here would explain it if they do! I feel like if I could actually visualize it, I might be able to get a handle on it and this might help me be better at working to solve it.

Anyway, guessing you checked if it is a ground loop feeding noise by making sure everything is plugged into the same outlet or quality distributor, and that the power cords all have good grounds?

And tubes, guessing you already checked that it’s coming from both channels? And if so, did you try changing the CSP2+ rectifier and the input tube? And if one channel mostly, have you swapped the right and left channel output tubes on the CSP 2+?

I always have some hum or buzz, the higher frequency buzz and other noise coming from pre-stages and clearer when the component and/or system is cranked up beyond how I can listen to them. With lots of Decware tube/transformer based pre-stage components in the chain, and each, if having only a little noise individually, contributes to and compounds that of the next. But with all the cables set up right and relatively quiet tubes, I either can't hear hum at the seat, or it is so faint it is not irritating. But I don't think I have ever heard complete silence with my ear right at the drivers.

I just got a new quad for my Torii, Preferred EL34s from thetubestore in Canada. At first they sounded both a little dull and noisy, a low hum not noticeable everywhere in the room, but with my 97dB efficient speakers and the way they project, I could hear it at the seat. And since I had amped up my pretty live sounding pre-stages more than usual to give more lucidity and dynamics with the dullish new tubes, it was worse. At the seat it was mostly that low 60 cycle hum that I find really irritating if loud enough, and though pretty quiet, this was over my limits for tolerance.

Not having bought new EL34s in a long time, I had forgotten how much I resent the experience of burnin, especially with some things that are notably lacking resolution and speed new. And my system is so resolving now, that lack of burnin hurt! I thought I would have to send them back.

But to be sure, I put them in my other system and burned them in. Then listening to them in the main system, they sound really good, but still hum, less, but still. Hum in my system improves with warm up, but is still there with these tubes. And perhaps relative to your situation, checking today, it hums with no ICs plugged into the Torii, and it is pretty close with no volume as with full volume on the Torii attenuator.

I changed the EL34 tubes right to left, and it was about the same. Then I changed the input tubes, and it got a little better. Then I put in the Preferred 6L6s I had been using for quite a while from the same folks, and they show a little hum right at the speaker, but I can't hear it at the seat.

Also interesting, checking out the the EL34s today, in comparison to the 6L6s the EL34s have notably more resistance putting them in the sockets, like the pins are larger. And one time when I put them in, the hum became a hum/buzz on one side in particular, too noticeable for me, so I gently wiggled the bases of them with the amp on, and at some point the hum improved. But I also got a static sound moving the tube bases, opening up perhaps another possibility... that I need to tighten/even up the sockets in my now pretty old amp?

Anyway, sorry I don't have more, but hopefully this story will help!