So i found out that the capacitors that make the 3 time constants used by dolby b/c ic's in some of the best Pioneers and Nakamichi cassette decks aren't polystyrene capacitors, but green or brown drop polyester film/foil type capacitors.Am i wrong about it?Are they so good that the biggest manufacturers in the industry used them in every filter built in top of the line cassette decks?It's true that i refer mostly to these dolby ic's that use high values capacitors(150nf...1uf) and polystyrene would be unpractical , being to big, but are the pet film/foil capacitors doing right with temperature and other parameters? I put two pictures one with the inside of Nakamichi cr-4 which has usual transparent polyester capacitors around the CX20188 dolby b/c chip and another image from a crt tv set with the usual green drop mylar/pet capacitors that are used in some nakamichi decks and other decks for time constants around dolby b/c ic.It seems that they work pretty well at high frequencies too...
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> doing right with temperature
How hot/cold does it get in your listening room?
PET caps are typically 400ppm/C. Even if you live from freezing to boiling, 100C, that's 40,000ppm or 40,000/1,000,000 or 4% change. Since the initial nominal value may be 5%, this is small. Much smaller in non-military environments; under 1%.
First-order filters, most of the Dolbys, are *very* tolerant of value changes, because the slopes are so gentle. Dolby S may be more fussy; the professional Dolbys would of course take all this into consideration.
I've always been fond of little green caps.
How hot/cold does it get in your listening room?
PET caps are typically 400ppm/C. Even if you live from freezing to boiling, 100C, that's 40,000ppm or 40,000/1,000,000 or 4% change. Since the initial nominal value may be 5%, this is small. Much smaller in non-military environments; under 1%.
First-order filters, most of the Dolbys, are *very* tolerant of value changes, because the slopes are so gentle. Dolby S may be more fussy; the professional Dolbys would of course take all this into consideration.
I've always been fond of little green caps.
Well i actually looked first into a pioneer ct-777 which is using unipolar electrolytics for this task...so polyester film-foil should be a clear improvement 🙂
Many of the caps around the Dolby in the CT-777 are listed as film. Too many for me to sort out which are value-critical and which just need to be big-enough. Yes, I have seen caps listed one way on the plan but other types actually installed.
While this was a pretty spiffy deck when new, it is distinctly "Consumer", "plays nicely", not Professional plays-to-exact-specs.
While this was a pretty spiffy deck when new, it is distinctly "Consumer", "plays nicely", not Professional plays-to-exact-specs.
In one passive filter network i also have a 1uf unipolar nichicon muse capacitor with 9v dc over it.What would you use preferably to change that : a 1uf bipolar es nichicon muse or a 1uf poliester film /foil? I don't have a good quality new 1uf unipolar , just bipolar nichicon muse. I think that at some moment i saw some measurements that were telling that unipolar electrolytic capacitors behave better than bipolar when used with significant dc voltage across. I thought of using a 1uf copper polystyrene as i have some, but they are really big and heavy. I was also thinking about the fact that piezzo effect in low voltage polyester should be significantly higher than in an electrolytic though i have no evidence.
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