Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: melontracks on May 01, 2019, 04:17:44 PM

Title: CA-9100 Preamp noise - help with diagnosis?
Post by: melontracks on May 01, 2019, 04:17:44 PM
I have a Church Audio 9100 preamp that I've been using for years, mostly to record at relatively loud venues. I'm going to be taping some quiet acoustic stuff in a week or so, and was checking the gear i plan to use when i noticed a new noise in the system, which i've traced by process of elimination to the preamp. It's like a very quiet ticking sound, which increases when the unit's gain is increased. I have a sample of it on soundcloud here, with a few notes on the track. I compared the L and R waveforms, and from what I can tell, the noise is identical on both channels.

https://soundcloud.com/cjdiersen/ca-9100-noise/s-n2QGZ (https://soundcloud.com/cjdiersen/ca-9100-noise/s-n2QGZ)

To be sure it was the preamp, i tested it through two different recorders (Tascam DR-701D and Tascam DR-05), with, and without mics attached. Same effect any configuration. Actual recording was made with no mics attached on the DR-701D through the ext in 1/2 port with phantom power off.

This unit has always had a very noisy pot. I don't know why, and I waited years to ask Chris if he could fix it. At the time, hee suggested I buy a CA-9200. I asked what he thought my prospects were for replacing the pot, and he told me i'd "fuck it up." haha! Reasonable, and I understand...last thing i'd want to deal with is some joker breaking a custom electronic device i'd built, then asking me how to fix it.

I've always worked around the noisy pot by getting my levels set then not touching the pot while recording. But this noise is no good. You can really hear it in that soundcloud track after I turn the gain up at 12 seconds. There are also three instances where you can hear the noisy pot as i adjust the gain, but I'm more concerned about the ticking sound. What might that be?

Is it possible that it's the pot, even though i am not touching it at all while that noise is being produced? I use this thing a lot, and would rather have a stab at repairing it myself rather than replacing it.


Title: Re: CA-9100 Preamp noise - help with diagnosis?
Post by: lsd2525 on May 02, 2019, 09:42:58 AM
I didn't listen to it, but if the pot is noisy anyway, try hitting it with some contact cleaner. May or may not work, but it shouldn't hurt anything
Title: CA-9100 Preamp noise - help with diagnosis?
Post by: vanark on May 02, 2019, 09:50:45 AM
If you use it a lot, get a new one or send it back to be fixed. My $0.02
Title: Re: CA-9100 Preamp noise - help with diagnosis?
Post by: melontracks on May 03, 2019, 07:32:57 PM
I've been using what funds come available lately to get more open taping gear, so I was hoping not to spend to replace something I might be able to repair. I'll give that contact cleaner a whirl. Not sure why I haven't tried that yet. Not thinking so good, I suppose.