karlson3 Posted February 26, 2019 Share Posted February 26, 2019 I've piddled with metallized paper/"oil" (Russian MBGO) and some PEPT caps with 9vdc. The technique may give good result with various dielectric and with inexpensive caps, worth experimentation. I know there must be others on these vast forums who have done more than myself with CC caps. Which caps might be worth the extra real-estate and expense? "Type A" with MBGO (small tubs are 4uF - large, 20uF) Quote Link to comment Share on other sites More sharing options...
Schu Posted February 26, 2019 Share Posted February 26, 2019 Mundorf Quote Link to comment Share on other sites More sharing options...
Deang Posted February 26, 2019 Share Posted February 26, 2019 Not necessary on a high a quality product like that. It almost makes sense to me if using really inexpensive metalized types. But ... This is John Warren's take on it. "The idea behind battery bias is to use high-K capacitors like electrolytics and, with bias, achieve film type responses. DA trends with K-value. I've not tried it in a crossover but in small signal processing it's good engineering practice for coupling caps to be low-K dielectrics like NP0 ceramics and Polyester. In active filters where the signal passes thru multiple stages of filtering it's important to have low-K insulators." Quote Link to comment Share on other sites More sharing options...
karlson3 Posted February 26, 2019 Author Share Posted February 26, 2019 I'll assume at a certain price range of capacitor that charge coupling's prohibitive/money wasting or unnecessary. Besides common metallized film caps, I do think it would "work" with some of the vintage Russian pio/foil and PEPT/foil type which are reasonably priced. Maybe some modern foil caps (maybe in tweeter highpass ?) - it takes twice the capacitance plus twice as many caps. IIRC, the "bias" resistor has to be lower in value for electrolytic caps than film/paper. Posted by Jon Risch (B) on March 28, 2013 at 22:46:34 In Reply to: RE: Trade-offs posted by freddyi on March 28, 2013 at 21:52:30: Within the limits of the working voltages of the capacitor/s, and the peak voltage output capability of your power amp, use the highest voltage reasonably practical. With a 9 volt battery, you come out of dielectric bias at about 4-5 watts of power into an 8 ohm load. This could be likened to amplifier classes of operation, analogous to leaving pure Class A operation, and going into Class AB. RE the junction charging, it is not a matter of time constants of charge to reach equilibrium, but rather, a dielectric forming process, which can take days or longer to fully settle and stabilize. This is where a lower value resistor can help speed this process, and make it more stable over the long term. Jon Risch Here's a 2013 thread where resistor values for charge coupling were discussed https://www.audioasylum.com/cgi/vt.mpl?f=hug&m=165533 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 26, 2019 Share Posted February 26, 2019 Quote Link to comment Share on other sites More sharing options...
Deang Posted February 26, 2019 Share Posted February 26, 2019 Also a pain in the *** to build. Aren’t you due for a new battery? Quote Link to comment Share on other sites More sharing options...
karlson3 Posted February 26, 2019 Author Share Posted February 26, 2019 @CECAA850 - What caps are those? - I remember one builder saying he preferred CC electrolytic to film caps but wouldn't know which ones to try. (J. Risch suggested 220K R for quality electrolytic) Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 26, 2019 Share Posted February 26, 2019 14 minutes ago, Deang said: Aren’t you due for a new battery? How can you tell? Last time I checked it was 9v. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 26, 2019 Share Posted February 26, 2019 10 minutes ago, karlson3 said: @CECAA850 - What caps are those? - I remember one builder saying he preferred CC electrolytic to film caps but wouldn't know which ones to try. (J. Risch suggested 220K R for quality electrolytic) I believe they're Daytons. Quote Link to comment Share on other sites More sharing options...
karlson3 Posted February 26, 2019 Author Share Posted February 26, 2019 maybe "these" (?) https://www.parts-express.com/12uf-100v-electrolytic-non-polarized-crossover-capacitor--027-342 Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 27, 2019 Share Posted February 27, 2019 6 hours ago, Deang said: Also a pain in the *** to build. Aren’t you due for a new battery? Careful, or I'll post the pic of the wierdly wired crossover sent to me from Staten Island... what was his name? Quote Link to comment Share on other sites More sharing options...
Deang Posted February 27, 2019 Share Posted February 27, 2019 Speakerfritz 1 Quote Link to comment Share on other sites More sharing options...
glens Posted February 27, 2019 Share Posted February 27, 2019 I had to look it up (biasing capacitors in a high-level crossover)... Have to say I'm not enthralled by the notion. You've got to go twice the capacitance, times two, and only one of them gets "class A biased." I even saw mention of higher IM levels as a byproduct (measured, though inexplicably going unnoticed). Sad to say that's one path I'll most likely never explore; thank you very much, but no thanks. My ears are precious, but they're not that golden. I'd sooner "up" my indiscriminate-length speaker leads from 14-ga. Quote Link to comment Share on other sites More sharing options...
Deang Posted February 27, 2019 Share Posted February 27, 2019 “... and only one of them gets "class A biased." Could you please link me to that? Thanks. “I even saw mention of higher IM levels as a byproduct (measured, though inexplicably going unnoticed).” I believe it was explained (somewhere). The levels are extremely low, and what is demonstrated is the often overlooked dominance of the DA component. Quote Link to comment Share on other sites More sharing options...
glens Posted February 27, 2019 Share Posted February 27, 2019 Just about any page which shows a wiring diagram should suffice. Two caps in series, with 9 volts fed via 2 resistors, one resistor each end of the downstream (from the amp) cap. The upstream cap remains completely unbiased (unless of course it's reverse-biased via a circuit through any other components, including the voice coil and amplifier output, to achieve the same-enough-though-opposite potential from the battery across the upstream cap - especially unlikely if the second pair of caps in a 3rd order high-pass is also so biased) . Every drawing, including those in the JBL Everest manual (PDF) I found shows the same configuration. I'm surprised the drawings don't call for a (mil-spec wire) lead length factor of some derivative of 57.125 inches... Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 27, 2019 Share Posted February 27, 2019 2 minutes ago, glens said: I'm surprised the drawings don't call for a (mil-spec wire) lead length factor of some derivative of 57.125 inches... Silver, you forgot silver. Quote Link to comment Share on other sites More sharing options...
glens Posted February 27, 2019 Share Posted February 27, 2019 8 minutes ago, CECAA850 said: Silver, you forgot silver. I assumed that was implicit in the spec? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 27, 2019 Share Posted February 27, 2019 17 minutes ago, glens said: I assumed that was implicit in the spec? It may be. Apparently there's a lot of things that I don't know. Quote Link to comment Share on other sites More sharing options...
glens Posted February 27, 2019 Share Posted February 27, 2019 3 minutes ago, CECAA850 said: 21 minutes ago, glens said: I assumed that was implicit in the spec? It may be. Apparently there's a lot of things that I don't know. Logically, it would have to be part of the spec, else how could one espouse following the spec by using something which either falls short of or goes beyond it? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 27, 2019 Share Posted February 27, 2019 7 minutes ago, glens said: Logically, it would have to be part of the spec, else how could one espouse following the spec by using something which either falls short of or goes beyond it? We're not doing logic are we? Quote Link to comment Share on other sites More sharing options...
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