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Author Topic: u67 running warm  (Read 5187 times)


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  • Real Full Name: Jeff Bosley
Re: u67 running warm
« Reply #15 on: January 17, 2015, 04:30:58 pm »

I think most UPS, line conditioners, etc limit current, especially the switching based designs.
That;s why I like Tripplite's tapped transformer, no semiconducters in line with the load.

You will still have the large EMI choke, but's it's only .25 ohms.

If you your power line variation is only 1-2 volts, relax, that's less than 2% change in downstream power supply voltages.


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Re: u67 running warm
« Reply #16 on: January 18, 2015, 09:08:22 pm »

Variations of ±10% of nominal line voltage are inconsequential for the performance of an U67 microphone and its NU67 power supply. For an explanation of the microphone running warm, please see this thread in the forum of the Neumann website:


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Re: u67 running warm
« Reply #17 on: January 19, 2015, 02:22:49 am »

Good additional information. Thanks, Uwe!
I would still feel more comfortable with a B+ of around 210VDC, ± 2VDC, rather than running it at -10% @ 190VDC!
Every precious dB of lowered noise floor counts in a tube mic whose polarization voltage is derived from the B+.
Klaus Heyne
German Masterworks®
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