C0G/NP0 as coupling caps? - diyAudio
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Old 11th June 2010, 06:57 PM   #1
Salas is offline Salas  Greece
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Default C0G/NP0 as coupling caps?

Did anybody ever try to use C0G/NP0 ceramics as signal coupling capacitors? If yes, did they work as good as film caps?
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Old 11th June 2010, 07:55 PM   #2
jcx is offline jcx  United States
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acording to Pease' DA article they beat Mica but have higher DA than better film

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np0/c0g are very good but not quite perfect:

I have seen ~ -110 dB 2nd order difference in an amp with 2x series 100V np0 caps in a sallen-key 40 KHz low pass with 20 + 21 KHz 1:1 @ 8V pk sine drive

after replacing the np0 with polystyrene the 1 Khz diff dropped below my~ -160 dB measurement limt ( ~ -130 dB noise floor in a Lynx22 sound card + 30 dB gain @ 1 KHz)
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Old 11th June 2010, 08:04 PM   #3
infinia is offline infinia  United States
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C0G/NP0 ceramics are excellent but not as cost effective in large sizes needed for lowish impedance circuits.
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Old 11th June 2010, 08:19 PM   #4
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33nF//33nF//33nF to form 0.1uF are enough in my case as interstage. The specs are excellent but I don't recall anybody reporting impressions in signal coupling.
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Old 11th June 2010, 08:22 PM   #5
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acording to Pease' DA article they beat Mica but have higher DA than better film
Thanks. Did you do that test in the quote? Interestingly Bateman was seeing minimum distortion near to polysterene. Then again your's another test employing two in series and IMD.
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Old 13th June 2010, 04:49 PM   #6
Salas is offline Salas  Greece
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I did some subjective comparisons. Used a DC coupled B1 with doubled outputs. One left DC coupled, through the other I put capacitors. Made a 0.1uF by paralleling 3x33nF 50V C0Gs. I also used 0.1uF FT-2 USSR Teflon, Auricap, K75-10B USSR paper and polyethilene-terephtalate, Jensen PIO copper foil, SCR PP, SCR Tin foil, Wima MKP10, Wima FKP1, RS 1000V Film&Foil PP yellow radial. Just one same track and did a lot of A-B between caps and DC. Amp's input impedance is 120K, so the 0.1uF could work low enough in frequency. Wasn't trying to make any real conclusions, this is no seriously controlled situation, just wanted to have a general subjective impression of where the C0Gs could roughly stand OK among other signal capacitors or not. Well, I was left with the impression that they can. After DC and Teflon, they present a bit of vagueness and less depth resolution but still more open and tonally good than some PP or PIO. They aren't edgy at all, and they add a bit of enthusiasm in midbass and in the mid, they sound ''together'' though. Bass & treble a bit softer. Where layout size and budget are tight they are not going to embarrass. Still Teflon beats all.
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Old 13th June 2010, 09:55 PM   #7
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Default lets get really stupid

I replaced the electrolytic input dc blockers on the preamps of my H182 organ with 10uf 50v Z5u ceramics.(Ceramics fit better than polystyrene). I liked the result of that so well (more treble, more bass than 40 year old electrolytics) that I replaced the 5 uf tantalum input caps on my Dynakit St120 amp with a Z5U ceramic. AB the record player, amp, and SP2 speakers, versus my own personal Steinway console piano, Peter Nero's Steinway (a grand) sounds better even on treble notes. He had studio reverb, I don't. But I'm really happy with the way the ST120 sounds after the DJoffe mod. Exactly equivalent to a Peavey CS800S built 1998, a split supply amp. Warning- my ears are highly trained but roll off after 15000 hz due to Army service. Mr John Curl now tells me this is a stupid decision because of distortion of high value ceramic Z5U caps. (see tail end of discussion solid state thread objective and subjective results of DC blocking caps in output of amps. )
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Old 13th June 2010, 09:59 PM   #8
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Maybe they enhanced the feeling of reverberation? Keep in mind that anything ceramic bar C0G/NP0 is microphonic.
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Old 13th June 2010, 10:31 PM   #9
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I play the Hammond H182 really loud sometimes (40 W 7591 pair into 15" woofer, 7 w 6bq5 pair each into two 8" midrange speakers) that I think I would notice if these Aerovox SK55's were doing anything microphonic. I can hear no reverb on dead room baroque music on the ST120 - so I think the reverb on RCA Peter Nero "Warm and Wonderful" is a studio effect. The electronic piano sounds better than my real one- as probably his $30000 piano is better than my $2000 one. But on treble not that much. Buy a couple of Aerovox Sk055 10 uf's from Farnell in UK and try them- Z5u's are $7, CPO's +-10% are $17. Or stop by Jville indiana and take a listen - it is only 10000 miles and two airport screenings away. I am tasked with buying some polyprophylene and listening by Mr. Curl - if I can make them fit. No more tantalums for me, please.
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