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Sony C-800 Bad Tube Noise?
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poncival
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8th January 2010
Old 8th January 2010
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Sony C-800 Bad Tube Noise?

I'm pretty sure this sound indicates a bad tube, I have edited it so you don't have to sit through the whole episode.. but after about 5 minutes the mic starts to sputter and make noise, then gradually increases the noise, the edits are about 5 minutes apart... Thanks for any insight you may have, especially the best place to get replacement tubes.
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File Type: mp3 c800noise.mp3 (1.03 MB, 1892 views)
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poncival
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9th January 2010
Old 9th January 2010
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Nobody?
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11th January 2010
Old 11th January 2010
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This sounds like a ground noise problem.

Did you try using protected/shielded cables?

I had a ground noise Problem and it sounded the same and the noise was also increasing like on your example. Try to put shielded cables through out the whole chain. Put the mic to an other preamp, plug the Powerplug to an other powersocket, and so on...
poncival
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11th January 2010
Old 11th January 2010
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Thanks for the reply, I am using the shielded Sony tube mic cable, I think it's 9 pins, and the power supply is connected to a furman power conditioner, and the output of the mic power supply is connected to the Neve 1064 with a Mogami mic cable, and it makes the same noise no matter what cables I use or where I plug it in.
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11th January 2010
Old 11th January 2010
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The rustling sound reminds me of either a bad valve or a dirty capsule. Does it get worse, or does it drop out if you breathe heavily on it?

Try swapping the valve. You may need to try a few to get a quiet one; go NOS.
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11th January 2010
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Sometimes that noise can come from a bad contact between the tube and the tube socket. Remove the tube, clean the pins with a contact cleaner and a clean old toothbrush. While it is still wet insert it into the tube socket and gently move the tube around in the socket. Remove the tube and clean it again. Let it dry and install it in the mic. That will help remove any of the oxidation that may have built up in the socket.

Best,
Jim Jacobsen
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#7
5th April 2012
Old 5th April 2012
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Problem solved?

Hey Poncival.
Did you ever solve the noise problem?

I´m stuck with the exact same issue with my C800.
Sounds like the ocean, sometimes more sometimes less.

Thank you!
//Ted
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6th April 2012
Old 6th April 2012
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My experience with the Sony C800G is that the tube life is quite short...

Having had this problem with a pair of C800G.
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6th April 2012
Old 6th April 2012
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If you have never taken the C800G apart to replace the tube, be warned that it's not a simple matter. If you had done it before, you would not be suggesting toothbrushes or whatever. I am sure it's a matter of replacing the tube and your problems will be gone. Be aware of the fact that Sony uses the smaller version of the 6AU6 tube inside the body of the mic and you'll need to replace it with the same form factor. These tubes are usually available for reasonable money on ebay however, finding one quiet enough to work in a microphone is a challenge and a crap shoot. If they are still available from Sony, (they used to be) I would buy one directly from them. They are selected and noise tested and expensive but........you will be done the first time. Best of luck.
Charlie Bolois
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6th April 2012
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I totally agree with Charlie. Just to moreover remark that the original tube used by sony has a different shape that the regular with the same nomenclature, and as he sais, replacing the tube in the sony is quite tricky.
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8th April 2012
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The tubes that I have replaced in the Sony mics have been a larger 6au6 foreign variant. The smaller NOS 6au6 is quite noisy in these circuits. Sony sets the tube at a high B+ voltage (235vdc loaded, 275vdc unloaded) thus the high failure rate. I set the voltage on my Akita microphone at 220vdc unloaded and the voltage drops to 165vdc loaded. I have not had a single failure rate on the tubes. I have several hundred of these tubes and have found them to be very quiet with a very low reject rate.

The tube is somewhat difficult to replace on the Sony because of the amount of disassembly and they have a copper foil and heatsink/thermal paste covering the tube.








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#12
9th April 2012
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Also, a common problem is corrosion caused by condensation around the Peltier cooling element.

The tube is almost certainly the Russian 6au6 variant (matches physical appearance and dimensions), I forget it's Cyrillic name.
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