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Neumann U-67 problem around 8-10 khz
Old 17th August 2011
  #1
Here for the gear
 

Neumann U-67 problem around 8-10 khz

I am experiencing at distortion kind of noise at around 8-10 k, I have changed the tube and signal chain to eliminate signal change possibilities. Also have changed tube's but still hear it though. Any thought's regarding this issue or anyone having the same problem would be greatly appreciated.
Advanced Audio Design
Old 23rd June 2014
  #2
Gear Head
 

Mzaremba: Did you use a good quality EF86 like a Telefunken, Amperex "bugle boy" or Mullard? Any difference in gain between the first tube and the replacement? There is a lot going on in the U67 preamp. It's unlikely, but has the coupling capacitor from the tube anode to the output transformer primary been checked for leakage? There should be no DC at the high side of the output transformer primary. Check the PSU...the heater and HT voltages should be clean and within correct tolerance (especially the heater supply) with the mic connected. If you have more than one U67, try interchanging the power supplies temporarily and check for noise. The last problem may be the capsule. Be careful when working on this mic...the PSU sends 210 vdc to the mic; if you get across it, you will know...
Old 23rd June 2014
  #3
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kidvybes's Avatar
 

...it's been 3 years since that post...I'm thinking the 210VDC probably got 'em...
Old 24th June 2014
  #4
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Quote:
Originally Posted by kidvybes View Post
...it's been 3 years since that post...I'm thinking the 210VDC probably got 'em...
Old 24th June 2014
  #5
Gear Addict
 
Mo Facta's Avatar
LOL! (No, really, LOL!)
Old 24th June 2014
  #6
Motown legend
 
Bob Olhsson's Avatar
 

It's usually dirt shorting the gold film to the outside of the capsule. Factory service can clean or replace it.
Old 25th June 2014
  #7
Quote:
Originally Posted by kidvybes View Post
...it's been 3 years since that post...I'm thinking the 210VDC probably got 'em...
Unbelievable...

R.
Old 10th July 2014
  #8
Gear Head
 

Be ready to put down some real cash for a capsule job. Neumann USA did a nice job on my U67 a while back. Hopefully you were using a pop filter or screen when recording vocals with it. Both capsule elements are charged, and that attracts dust, smoke, etc. The capsule also works at 400 meg ohms so any contamination in the high impedance circuitry will cause trouble.
Old 23rd July 2014
  #9
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Mo Facta's Avatar
There's a dead horse smell on someone's boots around here...
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