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Groove Tubes Model One microphone
Old 26th January 2013
  #1
Gear Maniac
 
Seeker of Rock's Avatar
 
🎧 10 years
Groove Tubes Model One microphone

I hope this is the right place to ask this and apologize if it isn't. I recently bought a Groove Tubes Model One tube microphone from a member here that appears to have gotten some things knocked loose during its UPS shipping trip to me. When it arrived there was no sound. After pulling the assembly out from the casing of the mic, I noticed that one side of the elastic suspension that holds the capsule in place was broken and as a result (I believe) this had caused the capsule to be unsecure and thus broke the connection of the lead wire to the capsule. So I had my amp tech put a splint to re-join the elastic and re-solder the lead wire to the capsule. I now get sound from the capsule but it is masked by a loud, loud low frequency hum that is constant. I tried switching tubes (12AT7) but that wasn't the problem. It has a little transformer in the mic and I'm wondering if there may be something wrong or damaged with that. Does that sound like the culprit? Any other damage that may cause a tube mic to hum really loud? I've checked the power and it is grounded, I've checked different input channels and chains and even tested it against another tube mic. It is definitely something with this mic and not my power or chain.

Here are pics of the mic's guts if that helps. Thank you for any help or advice.
Attached Thumbnails
Groove Tubes Model One microphone-d.jpg   Groove Tubes Model One microphone-k.jpg  
Old 27th January 2013
  #2
Lives for gear
 
Haz-Mat-Strat's Avatar
 
🎧 10 years
Quote:
Originally Posted by Seeker of Rock ➡️
I hope this is the right place to ask this and apologize if it isn't. I recently bought a Groove Tubes Model One tube microphone from a member here that appears to have gotten some things knocked loose during its UPS shipping trip to me. When it arrived there was no sound. After pulling the assembly out from the casing of the mic, I noticed that one side of the elastic suspension that holds the capsule in place was broken and as a result (I believe) this had caused the capsule to be unsecure and thus broke the connection of the lead wire to the capsule. So I had my amp tech put a splint to re-join the elastic and re-solder the lead wire to the capsule. I now get sound from the capsule but it is masked by a loud, loud low frequency hum that is constant. I tried switching tubes (12AT7) but that wasn't the problem. It has a little transformer in the mic and I'm wondering if there may be something wrong or damaged with that. Does that sound like the culprit? Any other damage that may cause a tube mic to hum really loud? I've checked the power and it is grounded, I've checked different input channels and chains and even tested it against another tube mic. It is definitely something with this mic and not my power or chain.

Here are pics of the mic's guts if that helps. Thank you for any help or advice.


Hi,

In the past month I have had three of these mics in the shop for mods and repair.
Check the wire mesh to make sure it is secure. Also check that all of the screws on the body and xlr connector are tight.

The transformer will not cause a hum. There may be a bad cap in the power supply or B+ circuit. In some power supplies {Rode Classic) a bad regulator can cause hum, however in most cases the mic would not be producing any sound.










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Old 10th March 2013 | Show parent
  #3
Gear Maniac
 
Seeker of Rock's Avatar
 
🎧 10 years
Quote:
Originally Posted by Haz-Mat-Strat ➡️
The transformer will not cause a hum. There may be a bad cap in the power supply or B+ circuit. In some power supplies {Rode Classic) a bad regulator can cause hum, however in most cases the mic would not be producing any sound.
You guessed it, power supply parts. Thanks for your post. The repair sheet listed a replacement Zener diode 120v 5w and two transistor BUX85 NPN 250V. Work was done by a local Miami guy name Hayden who owns Florida Electronics, and has a great rep for repairing professional A/V gear. He repaired my '76 Marantz receiver last year and did a great job on that, too.

The mic sounds fantastic!
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