R/E/P > Klaus Heyne's Mic Lab

Vintage U67 With Euro Power Supply - Suggestions for U.S.?

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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

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!

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.

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! =)

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!

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