HP339A article Charles Hansen

[fmak]

I have been trying to get access quickly to the HP339A improvement article by Charles Hansen in the March 03 issue of AudioXpress. Unfortuntely one web listing in uk appeared wrong, the issue for purchase being Feb 03 but with the March 03 content.

Charles, or anyone else, can you pl help?

[dimitri]

A Digital Pooge for HP's 339A Test Set
audioXpress March 2003 pp.16-21

[Charles Hansen]

Originally posted by fmak
Charles, or anyone else, can you pl help?

I can't help because I'm the wrong Charles Hansen. I design equipment for Ayre in Boulder, Colorado. The other Charles Hansen writes articles for Audio Express and lives on the East Coast somewhere. Sorry....

[slowhands]

Originally posted by fmak
I have been trying to get access quickly to the HP339A improvement article by Charles Hansen in the March 03 issue of AudioXpress. Unfortuntely one web listing in uk appeared wrong, the issue for purchase being Feb 03 but with the March 03 content.

Charles, or anyone else, can you pl help?

The HP product was solid to begin with and does not need any POOGE monkey business. All he does is replace the 80 KHz lowpass with a steeper <30khz board, assuming you won't need this for broadcast work and you will want to use it on CD source.

[dimitri]

Dear Charles,
I suspected that something mysterious should exist, when I read your posts and the wrong Charles Hansen reviews in AX. I even started to conceive of split personality ...

[fmak]

Originally posted by slowhands


The HP product was solid to begin with and does not need any POOGE monkey business. All he does is replace the 80 KHz lowpass with a steeper <30khz board, assuming you won't need this for broadcast work and you will want to use it on CD source.

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Having read the article, I tend to agree. Don't see the point of a 20kHz brickwall filter on top of the CD brickwall filter.

Now a mod to extend dynamic range, reduce residual noise in the instrument will be really worthwhile; perhaps by replacing some of the opamps.

[Charles Hansen]

Originally posted by dimitri
Dear Charles,
I suspected that something mysterious should exist, when I read your posts and the wrong Charles Hansen reviews in AX. I even started to conceive of split personality ...

LOL!! Yes, that would be confusing. We tend to have very different approaches to things....

[Charles Hansen]

Originally posted by fmak
Having read the article, I tend to agree. Don't see the point of a 20kHz brickwall filter on top of the CD brickwall filter.

It's kind of silly, but the real point is to make cheap $99 CD players have better specs than they deserve. Some cheap CD players have poor filters that let through a lot of noise, or they use noisy op-amps. Adding another brickwall filter in the measuring device willl "fix" the numbers for better sales.

If you don't believe me, take a look at the data sheet for nearly *any* audio DAC chip. They will have pins for "Left Mute" and "Right Mute". These will output flag signals when the data on the disc is all zeros. The Japanese manufacturers connect these flags to transistors switches that short the output of the analog stage. This gives incredible S/N ratio measurements on the test bench, even when using noisy op-amps and poor power supplies. Of course it has nothing whatsoever to do with real-world performance....

[jackinnj]

the HP339A oscillator is perhaps the limiting factor -- it's distortion is about 0.0018% -- as if this were a limiting factor anyway, but there are plans for oscillators with distortion two factors of magnitude lower on the Linear Tech website --

as far as "utility" the nice big mirrored analog meter of the hp339 allows you to sweep a control setting on the DUT until you've got the result you want. A digital display (as in the Krohn Hite or Tektronix instruments ) requires some mental gymnastics to derive the same result.

[fmak]

[QUOTE]Originally posted by jackinnj
[B]the HP339A oscillator is perhaps the limiting factor -- it's distortion is about 0.0018% -- as if this were a limiting factor anyway, but there are plans for oscillators with distortion two factors of magnitude lower on the Linear Tech website --

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The limiting factor is actually the filter. There is residual of the fundamental around 93 dB down at 1kHz. The sig gen is around -96 dB down from 1 V.

I bought a machine in calibration for £300. Beautiful inside, very used outside. Compared to my National VP7xxx analyser, the HP is clearly inferior in performance and in ease of use. My problem is that the National is malfunctioning some of the time!

Anyone know where I can get knobs for the HP339A?