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InnerTube Audio u87 - high self noise / HUM?
Old 16th August 2007
Lives for gear
dubrichie's Avatar
InnerTube Audio u87 - high self noise / HUM?


has anyone else with an InnerTube u87 experienced quite high self noise from the mic?

particularly HUM... which sounds AC-related?

i'm in Europe so my PSUs are built for 230V by the way.

the tone of the mics is GREAT, but the noise / HUM is quite high really... or is it just me / my mics?

should i get them checked out? if so, i hope to do it locally as shipping between California and Dublin, Ireland would be expensive AND time consuming / awkward... i gotta put these babies to WORK!

Old 16th August 2007
Registered User
Rick Sutton's Avatar

Mine have a bit of tube hiss, probably 3-4 dB above my quietest tube mic (U47) but about the same as my KM56 mics, but has absolutely no discernable hum. Better look into your power supply and grounding scheme. Don't know how the AC works over there but can you temporarily lift the 3rd pin ground on the supplies and see if that makes a difference? Hope you get it worked out as those are really beautiful mics that are useable for so many sources.
Old 16th August 2007
Gear Maniac

I auditioned an InnerTube U87 and ran into a hum problem too. Given that it sounded like 60 Hz hum, I assume it was ground-related, but since I preferred the tone of my Klaus Heyne modified U87 to the InnerTube, I didn't try to resolve the problem.

I wouldn't defeat the grounding prong on the power cable for the supply (potentially dangerous), but you should be able to disconnect the audio ground from the power ground. Incidentally, I've never experienced that kind of hum with any other mic (including my old M49), so I'm not sure why I ran into a problem with the InnerTube U87. Have you emailed Stayne about it? He can probably provide some guidance.

Old 17th August 2007
Lives for gear
dubrichie's Avatar
i'll e-mail InnerTube about it promptly.

i'm sure a bit of hum can be resolved.

was just wondering if anyone else had encountered it and figured out a handy fix.

i dont want to lift the earth at the plug for such a piece of gear and i wouldnt really know what to look for poking around inside a tube circuit or its power supply.

Old 15th June 2011
Here for the gear

u87 hum

im having the same problem it goes away if i stand directly in front of the mic as if i was recording vocals. any ideas or feedback would be awesome ?
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