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Message started by EdwardT on 04/15/21 at 18:50:28

Title: Low level distortion
Post by EdwardT on 04/15/21 at 18:50:28

New Rachel and Monolith owner here testing out a ZStage addition to my already used system. Yesterday I noticed some background distortion that I had not heard before in one of me test songs. I took out the ZStage but the distortion remained, in the background but audible. Any suggestions where I might start looking for the source, I’ve heard this particular song many times and this was the first I’ve heard that grit in the background.

Title: Re: Low level distortion
Post by morp on 04/15/21 at 20:31:52

Hi Ed,

What is the nature of the distortion? What does it sound like?

There are many members here who are much more knowledgeable than I am, but the first thing I would do is swap tubes in and out to see if there's a noisy tube in there somewhere causing the issue.

Thanks,
Richard

Title: Re: Low level distortion
Post by EdwardT on 04/15/21 at 21:52:29

Hi Richard,
It was like old fashioned radio drift but it didn’t seem to affect the vocals or drums (but their dynamics are all peaks) just grit on the instruments. I was surprised to hear it or even that I could after a loud career. I’ll spin some other discs and then revisit that song. I don’t have a spare set of input tubes so I can’t really do a logical path thru the amp.

Title: Re: Low level distortion
Post by HockessinKid on 04/15/21 at 23:08:55

Could this be radio frequency interference (RFI) or electro magnetic interference (EMI)?

If you have any unshielded interconnects running in parallel with power cords OR a TV/computer monitor near your equipment can cause problems. Try repositioning cables. If still persists reposition equipment.

HK

Title: Re: Low level distortion
Post by EdwardT on 04/17/21 at 22:38:16

Might be several tubes at the same time. I’m pretty sensitive to wire routing and leaky digital pieces but just in case I pulled the ZStage out of the signal path and off the CD transport. No joy. The mail brought some new 6N2P input tubes so I was able to replace each section, as I did the EL-34s started sounding pretty janky. Eventually after swapping outputs twice I landed on KT-88s that weren’t too unhappy with a GZ-34 rectifier so maybe the Valve Arts 274 is failing and the EL-34s are going with it. I don’t know the age or hours on anything which has prompted a tube order for the whole amp so I can start from the beginning.

Title: Re: Low level distortion
Post by EdwardT on 05/09/21 at 12:45:15

My troubleshooting skills are pretty rusty. After swapping components around and substituting cables and amps I finally realized it was the speakers. A new “as built” set of tubes for the Rachel and the ZStage running my old shop speakers showed the truth; the used Monoliths were distorting, most likely from shipping damage knocking the components out of alignment. So, viola! New tweets and woofs and the distortion is gone. I still want to adjust the tweeter level down 3-6dB so some Mills resistors are on order to build a couple of simple L pads. That should do it. :)