luvdunhill Posted July 12, 2010 Report Share Posted July 12, 2010 Has anyone played with biasing capacitors that normally only see AC with a small amount of DC? I know some commercial speaker manufacturers have been doing this for a while (Vandersteen, Infinity, JBL, etc. comes to mind) usually using a battery and often accompanied by fancy marketing speak ("Charge-Coupled Linear Definition Dividing Network"). There is a lot of ink spilled on the subject, but what do you say? Quote Link to comment Share on other sites More sharing options...
nattonrice Posted July 13, 2010 Report Share Posted July 13, 2010 I had a search around and found a couple of papers but nothing specific... What properties of the capacitor is dc bias meant to enhance? Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted July 13, 2010 Report Share Posted July 13, 2010 Wow, I never thought about DC "biasing" a capacitor before. I looked up and found an original document from JBL on it and there seems to be at least a little bit of horseshit/random audio voodoo mixed in there but I guess could potentially work. http://forums.klipsch.com/forums/storage/3/860249/page10.jpg http://forums.klipsch.com/forums/storage/3/860250/page11.jpg http://forums.klipsch.com/forums/storage/3/860252/page12.jpg He's comparing it to biasing transistors into Class A but it doesn't seem like a good analogy, since the transistor is an active device that needs to switch on if it isn't biased into class A whereas a cap is, well, passive, and "biasing" pretty much just means charging it all the way up with DC unless I'm missing something here. The piezoelectric effect seems to me like random horseshit/voodoo unless you're using ferroelectric dielectric caps, and even then I don't know how much the capacitor would actually "move". Who knows though, I haven't done the measurements, but neither has he. Needing double the capacitance and double the caps (which means double the ESR?) seems like a bad trade-off for supposedly getting rid of whatever effects dielectric absorption has, though I think I saw some other design with just a 2.2M resistor? Have you thought about implementing a Zobel network or altering phase? Quote Link to comment Share on other sites More sharing options...
Looser101 Posted July 13, 2010 Report Share Posted July 13, 2010 I had a search around and found a couple of papers but nothing specific... What properties of the capacitor is dc bias meant to enhance? Linearity? The Sound of Capacitors This in particular... The Sound of Capacitors - Electrolytics Quote Link to comment Share on other sites More sharing options...
Bidoux Posted July 13, 2010 Report Share Posted July 13, 2010 Is this the point of C1, C2 and R8 ? BF862 Preamp - diyAudio Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted July 13, 2010 Report Share Posted July 13, 2010 mikhail used this technique in the squarewave... all poly/teflon caps exhibit some piezo electric effect. and electrolytics just don't belong in the audio chain. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted July 14, 2010 Report Share Posted July 14, 2010 mikhail used this technique in the squarewave... all poly/teflon caps exhibit some piezo electric effect. and electrolytics just don't belong in the audio chain. Mikhail was a genius! That's cool to know, so I guess it wasn't BS. Anybody with poly/teflon caps want to play around with this? Quote Link to comment Share on other sites More sharing options...
Nebby Posted July 14, 2010 Report Share Posted July 14, 2010 Mikhail was a genius! But the question remains.....is he at a MarkL level of genius? Quote Link to comment Share on other sites More sharing options...
guzziguy Posted July 14, 2010 Report Share Posted July 14, 2010 I'm sure that Mikhail brought in a lot more money than Markl has dreamed of. So you have the question backwards IMO. Quote Link to comment Share on other sites More sharing options...
Nebby Posted July 14, 2010 Report Share Posted July 14, 2010 You are absolutely correct, though I was just trying to link that "genius" comment to the one made here. My attempt at humor simply fell flat, that's all Quote Link to comment Share on other sites More sharing options...
guzziguy Posted July 14, 2010 Report Share Posted July 14, 2010 That's OK, I think that he has it backwards too. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted July 14, 2010 Report Share Posted July 14, 2010 (edited) Mikhail was a genius! That's cool to know, so I guess it wasn't BS. Anybody with poly/teflon caps want to play around with this? Not exactly. In fact mikhails amplifier was a fully dc coupled amplifer with a HUGE amount of dc drift over time and temperature. And the drift was not necessarily positive or negative, and it was well over 1 volt or more. So mikhail had to put in an output cap, and since he did not know the direction of the drift, he had to put in 2 caps back to back in series. But then because of the caps he picked, and the time it took them to actually charge up, he biased up the center pin, so that it did not suck so bad (meaning no bass for the first hour or so) and then told people to keep it turned on all the time. Serious clusterfuck, every part of the amp. http://gilmore.chem.northwestern.edu/dinglepower2.jpg Edited July 14, 2010 by kevin gilmore Quote Link to comment Share on other sites More sharing options...
jcx Posted July 15, 2010 Report Share Posted July 15, 2010 biasing back-to-back electros is a very old recommendation - past its "use by" date Bateman's "Capacitor Sound" articles showed lower measured distortion from bi-polar Al electros which have full thickness oxide grown on both foils ploarizing V will increase microphonics - just like a condenser microphone Quote Link to comment Share on other sites More sharing options...
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