Robert Baer
Guest
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 Posted:
Fri Feb 18, 2005 3:47 am Post subject:
Re: Back to back aluminum electrolytics |
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Roger Lascelles wrote:
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"John Smith" <kd5yikes@mindspring.com> wrote in message
news:30yQd.1416$IU.1402@newsread3.news.pas.earthlink.net...
Thanks, Roger. That's the kind of information I was looking for. I have an
HP 651 Test Oscillator which, if I recall correctly, has lower distortion.
It also has a 600 Ohm output and a 50 Ohm output.
The 331A's lowest switch setting is .1%, so the meter will read .1% at
full
scale on that range.
I will repeat the test with the better oscillator and an integrating RC
with
a resistor of about 36 Ohms. At 402 Hz, the capacitor should then look
like
36 Ohms and the combination would then have an impedance magnitude of 50
ohms.
Does this sound like a better try at it?
Thanks immensely.
John
I get the 36R and 402Hz numbers too, so looks good.
Maxim have an interesting app note :
"Do Passive Components Degrade Audio Quality in Your Portable Device?"
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3171
In this app note tantalums, aluminium electros and polyester caps are
measured. In the app note, the graphs show distortion rising as you go
lower in frequ, which increases the signal voltage across the cap. There is
plenty of distortion at the frequency where the R and C have equal voltages
(99.5 Hz on figure 8), so this should be a good measurement point.
According to fig 8, below the -3db frequency, the distortion rises, but the
output signal decreases, so the audible effect won't be worse at lower
frequency.
Roger
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"Distortion" is *not* the term to use!
"Filtering" is the accurate and correct term.
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