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What we need for testing HV tube supplies
What we need for testing HV tube supplies
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Old 16th January 2018, 01:47 PM   #11
jackinnj is offline jackinnj  United States
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What we need for testing HV tube supplies
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Originally Posted by DualTriode View Post
Please tell me more about instability.

The power supplies that we are speaking of will be used to power tube amplifiers.

What is the issue with connecting the known load, the amplifier, to the power supply under test and using a function generator to sweep, pulse or whatever at the input of the amplifier?
You don't generally regulate the output stage of a tube amplifier although you can regulate the screens if not running ultra-linear.

It's recommended to test for stability with low perturbation current. Omicron-Lab's uses the Pico-Test current injector which provides 25mA -- pretty consistent with what you would expect from the input stage and phase-splitter. From the standpoint of consistency and repeatibility you would want the same kind of standards that a journal would require in the physical sciences.

I think that many of the regulators for tube circuits don't meaningfully contribute to performance, or may hurt...
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Old Yesterday, 10:07 AM   #12
DualTriode is offline DualTriode  United States
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I have the impression that the potential number of regulators used for tube output stages may be under estimated.

Or perhaps I am the exception using regulators as the rule rather than the exception. My complaint about tube amplifiers is the noise, particularly line frequency/harmonics and IM products. Even using a C-L-C pre-filter and LM350 Maita type regulator does a much improved job over a C-L-C filter alone.

In the recent couple of years I have been using audio analyzers to see the influence a voltage regulator has.

There is one brand of regulator kit that does a particularly bad job. This is a linear regulator that uses an IXCP10M45 current source. This regulator creates a huge broad noise hump that centers near 3K Hz. The hump does not flatten out until there is better than 50VDC delta across the regulator.

To see instability and distortion past the traditional 20K Hz BW the recent crop of audio analyzers has much broader BW. The Keysight U8903B has a 1.5M BW option. The Audio Precision APx555 comes standard with 1M BW.

I agree that the 25 ish ma injectors will have limited utility for testing other than low current HV regulators. Perhaps we could repurpose a single end output transformer.

DT
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Old Yesterday, 03:46 PM   #13
jackinnj is offline jackinnj  United States
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What we need for testing HV tube supplies
Quote:
Originally Posted by DualTriode View Post

There is one brand of regulator kit that does a particularly bad job. This is a linear regulator that uses an IXCP10M45 current source. This regulator creates a huge broad noise hump that centers near 3K Hz. The hump does not flatten out until there is better than 50VDC delta across the regulator.
DT
Sorry, I'm not seeing it -- this is Pete Millett's "Engineers Amplifier" which uses the IXCP10M45.
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