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Does my M149 need repair or am I having a power issue?
Old 23rd January 2020
  #1
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tkaitkai's Avatar
 

Does my M149 need repair or am I having a power issue?

Lately, I'm getting some subtle distortion/"choked" sounding recordings with my M149.

It's not major, but it's there, and I'm really trying to nail that last 10% of my vocal sound.

Obviously, the mic itself is super hot, but I'm using a -20dB Shure inline pad with very modest preamp gain. I've tried different cables, preamps, different converters, I've tried using no outboard, and my room is pretty solid (bunch of ASC tube traps + rockwool absorbers + foam).

From what I've understand, this doesn't sound like the typical effects of a dirty capsule or a bad tube. I don't have noise or intermittent signal or anything. But I could be wrong, in which case, I'll gladly send it off to Tom Onofrio for service.

I'm also wondering if this could be a grounding/clean electricity issue. Again, it doesn't sound typical of dirty power (no noise, buzz, or hum), but I've heard that dirty AC can produce distortion.

This is kind of embarrassing, but I'm running my gear off a cheap Livewire "power conditioner" (basically a glorified power strip), and there are definitely some other home appliances on the same circuit. In particular, I have a portable AC in my studio room, which, in spite of being plugged into a different outlet, causes voltage spikes that are picked up by my outboard (visible on my meters).

Here's a clip for anyone interested:

Again, it's very subtle, but it's there if you listen close enough. I can definitely hear it better on headphones.

Any thoughts?

Last edited by tkaitkai; 3 weeks ago at 06:21 AM..
Old 23rd January 2020
  #2
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Spindrift's Avatar
 

Not exactly your symptom but I had an issue with an M149 PSU that manifested itself as noise like a bad tube. It took the Neumann tech and I two tries to determine it wasn’t the tube but in fact the PSU. After trying a tube replacement, Neumann ended up replacing The PSU and the issue was resolved.

Tom is great but since the M149 is a currently produced and supported mic, I’d recommend sending it to the Neumann/Sennheiser service department in CT. They have a great repair department, quick turnaround, reasonable prices, parts on hand, and they really stand behind their work.
Old 23rd January 2020
  #3
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@ Spindrift That's great info, thanks so much! Glad to hear Neumann is reliable, I was starting to worry from reading through some older GS posts.

FWIW, I did a little more testing tonight, and discovered a hum that's only present when the mic is off. Completely goes away when it's powered on. It's also there when I have certain outboard patched in.

Clearly the wiring in my house is not ideal, so regardless of whether the mic needs service, I should probably invest in a quality UPS or power conditioner...
Old 23rd January 2020
  #4
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House wiring can be reversed from socket to socket and room to room. I have a house built in the late 60s and have ground loop issues. I've got to get in there and align the polarity one of these days. My solution is to keep the CPU and my mixer on the same wall socked, also the converters. It helps but I still get issues from the outboard gear on a different socket across the room. Good luck.
Old 23rd January 2020
  #5
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Dbl post

Last edited by Oldone; 23rd January 2020 at 05:48 PM.. Reason: Dbl Post
Old 23rd January 2020
  #6
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Even a cheap plug tester can test for a solid ground at the outlet you are plugging the PSU into. Do that...if it isn’t present, the mic will probably be noisier/not functioning quite correctly with many tube mic PSU designs.
Old 24th January 2020
  #7
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Quote:
Originally Posted by toledo3 View Post
Even a cheap plug tester can test for a solid ground at the outlet you are plugging the PSU into. Do that...if it isn’t present, the mic will probably be noisier/not functioning quite correctly with many tube mic PSU designs.
True. While a tester will tell you if there is a ground at-all, in my case, I tested with one and all "looked good". Only after the pops started driving me UP THE WALL and messing up paying customer's takes did I start tearing into things. Imagine my horror when I switched off the circuit and took the outlet out to find nothing connected to the grounding lug It was getting it's "ground" via the outlet chassis touching the metal conduit.
Old 24th January 2020
  #8
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Hahah, ohhh man. The little tester in my gig bag seems to be able to give a result for a weak ground like that, but maybe there has been a bit of luck involved as well. I mean, it is not as convenient to use a multimeter and definitely not to actually inspect the guts in every scenario...
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