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 1 
 on: Yesterday at 05:40:12 PM 
Started by Matt Ogaz - Last post by David Satz
Matt, the switch's contacts should certainly be kept clean, but I don't think a totally silent changeover between patterns should be expected with this type of microphone. I don't know of any "vintage" microphone that was designed specifically so that the pattern could be switched while the microphone was in the middle of picking up production sound. That just wasn't an expectation that the designers of that time sought to fulfill.

Each time you change switch positions, the DC converter disconnects one circuit branch from the rear membrane and connects a different one in its place. The switch physically breaks and makes contacts; current flows into the new branch and charges a capacitor via a resistor over a certain amount of time, and the back half of the capsule shifts its charge according to the new voltage being supplied to it via a high-value resistor.

It's straightforward, and by today's standards you might call it unsophisticated, since there's no filtering to remove switching transients or smooth the transitions. But I think that the recording engineer was expected to choose the microphone's pattern before starting a take, or between takes if an adjustment was necessary, and not during a take.

--best regards

 2 
 on: Yesterday at 01:51:04 PM 
Started by maltesen - Last post by klaus
Are you sure you want to pass on any MG warranty-legal or goodwill? The company is usually very good at this.
Besides: how do you know the capsule is defective if you cannot even see it, let alone test it?

 3 
 on: Yesterday at 01:49:03 PM 
Started by arch801 - Last post by klaus
You are already 3/4 there: a Neumann Nu67 power supply already includes the circuit to operate it with U.S. voltages.
All you need now is a studio tech who can properly calibrate the voltages (no, I will not recommend to do this yourself, given your marginal knowledge in the field. I have no interest promoting premature death by electrocution).

Have the studio tech call me, and I will advise how to set up your system.

 4 
 on: Yesterday at 08:43:47 AM 
Started by arch801 - Last post by arch801
Oh wow, okay that is all very interesting.

It's the stock NU67 with a European plug that I have. It's not the re-issue but it is the actual vintage Neumann power supply that came with the mic originally (both are in excellent condition miraculously). I want to extend the life of the original components as much as possible, so what in your opinion would be the most ideal long-lasting solution using the NU67 on a US power outlet?

I am a beginner when it comes to electrical engineering, so while I have soldered a couple of DIY modular synth kits, that's about the extent. I would probably send away for a professional to handle any type of soldering needed, so I would welcome any path that avoids that if possible. I am open to any suggestions you have.

Thank you so much for the advice!

 5 
 on: Yesterday at 05:40:29 AM 
Started by maltesen - Last post by maltesen
Hi there.

I suspect that my UMT800 has a faulty capsule, but I can't figure out how to dismantle it :o

Does anyone know how to get to the capsule?

Best Regards
Morten

 6 
 on: September 16, 2021, 02:02:43 PM 
Started by arch801 - Last post by klaus
The first question I have: what brand is the "European" power supply?
Because all Neumann supplies I am aware of have multi-taps for the line voltage.
And if it's a budget supply, don't even bother going down that road, because every U67 deserves a well-filtered, well-stabilized high-end supply*

The second issue of concern:
Using a step-up transformer may get you in the neighborhood of 210VDC/6.3VDC, but more than likely the voltages you will find will be off enough that it matters-
for tube life, capsule life, noise floor, distortion.

To correctly dial in the precise voltages, you will need a decent meter and soldering skills,
as high and low voltages are set with dropping resistors that need to be changed (not an issue with the heater voltage on NU67u, which have a trip pot).


* the new NU67V are terrific: they automatically seek the correct voltages, even after a tube change. No more voltage adjustments for life!


 7 
 on: September 16, 2021, 10:13:28 AM 
Started by arch801 - Last post by arch801
Thank you so much for the reply! That is very informative, and a bit of a relief to know that having a bit of variation won't be a huge problem.

You are a legend sir, your informative posts over the year have really helped me down the path towards professional microphone ownership, and it is very much appreciated! =)

 8 
 on: September 16, 2021, 05:46:08 AM 
Started by arch801 - Last post by Kai
These PSU‘s don‘t need much power, and some voltage variation is allowed.
A normal ca. 100 W step up 110 to 230 (220) V step up transformer is more than sufficient for the job.

If you want to make sure, get an inexpensive voltmeter and measure the step up transformer’s output voltage, e.g. something like this:

VC185-VC185TRMS-DIGITAL-MULTIMETER (URL removed, as only available in Germany. KH)


To do so and avoid any danger:

• Plug a power strip into the output of the unpowered step up transformer.
• Then connect the voltmeter and the switched off PSU to it.
• Use the meters 400 V AC range.
• Power up the step up transformer.
• Voltage should be 210 - 260 V.
• Switch on the PSU.
• Voltage should be 200 - 240 V.

 9 
 on: September 15, 2021, 03:57:49 PM 
Started by arch801 - Last post by arch801
To elaborate, if it's just a matter of getting a robust power transformer that's fine with me,
I just need to know if there are any other concerns I should be aware of, and any suggestions
as far as what kind of power converter to get would be very welcome!

And if converting the power from EU to US would be a bit shaky in general,
I would have no problem selling this EU power supply and buying a US one if that is the best option.

Please let me know your thoughts if you can spare the time. Thanks for any help!

 10 
 on: September 15, 2021, 03:49:00 PM 
Started by arch801 - Last post by arch801
Hi,

I'm hoping you wise wizards can point me in the right direction. I had been looking for an early run u67 for many many years and finally found one I could afford (serial is in the 5000s), but the nu67 is for EU power. I want to be extremely safe with this and not take any risks running improper power to it, so any suggestions any of you may have as far as what my best options are to get this working in the US will be very much welcome.

Thanks!

-Tom

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