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The sound of parts
The sound of parts
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Old 17th December 2002, 02:51 PM   #101
dorkus is offline dorkus  United States
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hehe ok, fair enough. i'll just discreetly tiptoe out of this arena now...

p.s. sorry, one last thing, can't resist... someone here HAS indeed measured the differences between the transfer functions of different types of capacitors (paper/oil, polyester, polypropylene, etc.)... it is clearly visible on a scope. lemme see if i can find that thread...
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Old 17th December 2002, 02:56 PM   #102
dhaen is offline dhaen  Europe
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Quote:
someone here HAS indeed measured the differences between the transfer functions of different types of capacitors
Probably referring to Steve Bench's website. He's got photo's.
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Old 17th December 2002, 03:00 PM   #103
dorkus is offline dorkus  United States
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Default yes!

http://members.aol.com/sbench102/caps.html

very interesting test results. though it's hard to see in the photos, there are subtle differences in the transfer functions of the different film capacitors types. and of course the non-film types look completely different altogether.
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Old 17th December 2002, 03:03 PM   #104
Christer is offline Christer  Sweden
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Default Re: yes!

Quote:
Originally posted by dorkus
http://members.aol.com/sbench102/caps.html

very interesting test results. though it's hard to see in the photos, there are subtle differences in the transfer functions of the different film capacitors types. and of course the non-film types look completely different altogether.
It is a bit difficult to see any deviation for some of the caps, yes.
That is the problem with using oscilloscopes, we must use our
poor human vision to evaluate what the scope mesasures.
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Old 17th December 2002, 03:03 PM   #105
HDTVman is offline HDTVman  United States
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Gents; No one is forcing anyone to take part in this little project. If you are not prepaired to look at the results and consider them openly, thats up to you. Negitive posts only clog up the thread. If you think this is pointless then please allow use to play our pointless game. We understand you view now and it doesn't need to be repeated over and over, once is enough.

Next subject:

Sy, Dorkus, I like the random switch box idea. Sy, are you willing to build the box? That would be great, and if you can get Nelson Pass to play with us SUPER.

Mrfeedback had some good suggestions for testing and that got me thinking. I don't have the best or newest test equipment at home and the stuff at work is mostly for RF. How do we want to handle the testing? I will do what I can but others may have gear that will give us more information as well. I have no problem with multiple testers. I know that the results will vary from tester to tester. We are trying to find out how to measure those things that we don't understand after all. I think major errors should be detectable. After all what we are looking for is differences not better or worse at this point, we'll figure that out later after we understand how to do the tests.

We should get together a list of listeners and testers. You can do both if you like. We will also need someone to act as test admin. Sy, could I talk you into this too? You seem to have the required skill set.

Anyone who wants to can e-mail me via the forum if you like.

Later
Bruce
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Old 17th December 2002, 03:10 PM   #106
Joel is offline Joel  United States
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The signal level was held constant at about 70 volts RMS at 600 Hz across the capacitors. (for about 26mA signal current). This is probably more than you would normally expect, and serves to show the results better.

Yeah. It's about 4-5 times what you would expect. So is a peak of 98 volts.
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Old 17th December 2002, 03:11 PM   #107
dorkus is offline dorkus  United States
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what's the circuit gonna be for the box?
something that us subjectivists agree is very sensitive to parts quality. actually, i hear SE triodes are very sensitive, but joel seems to think otherwise. i don't like tubes anyway.
maybe Mr. Pass could suggest a circuit... if not, a simple Borbely JFET buffer may be good, as i already have a power supply built for it. it uses a handful of resistors and two capacitors (one .22uF film feedback, and an output coupling cap). could be a good test, although matching JFETs is a pain in the butt.
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Old 17th December 2002, 03:13 PM   #108
dorkus is offline dorkus  United States
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Quote:
Originally posted by Joel

Yeah. It's about 4-5 times what you would expect. So is a peak of 98 volts.
yeah, well it's necessary to exaggerate the distortion products, because it's hard to see very small distortions on a scope. e.g. a sine wave can look perfect, but easily have 1% THD on it, which is very audible.
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Old 17th December 2002, 03:27 PM   #109
Joel is offline Joel  United States
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Sorry guys. I'll start a new thread. Continue with your testing discussion.
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Old 17th December 2002, 03:39 PM   #110
SY is offline SY  United States
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The sound of parts
You can't really do this easily with an active circuit that generates a lot of heat, since it's got to be potted up thoroughly. I would suggest again something simple like a passive filter (or a cascade of two passives), made with crummy wire and Radio Shack parts (maybe even a dread electrolytic!) versus fabulous audiophile wire, amazing magic capacitors, and incredibly transparent resistors. I mean, in a high resolution system, a cheap electrolytic and copperweld steel wire in the signal path ought to be audible to even a tin ear like me, eh?

I'm perfectly willing to contribute construction labor, executing the protocols, and the crummy parts for the A filter. And the cabinet and potting materials. Someone else will have to donate the approved magic wire, caps, and resistors for the B filter. And I'd sure like it if Mr. Pass would spend a few minutes verifying the circuit before I pot it up and send it to the victi... uhhhh.... test subject.
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