hurricane hugo Posted August 9, 2017 Share Posted August 9, 2017 [font:Comic Sans MS]...or you could just enter this raffle:[/font] Moog Foundation Memorymoog Raffle Quote http://blip.fm/invite/WorkRelease Link to comment Share on other sites More sharing options...
Karl Schmeer Posted August 10, 2017 Share Posted August 10, 2017 Did you end up changing out the caps on the DMUX board? Yes I did. Those white polyester caps have a limited age. That was a big job but seeing this is an early unit from 1982 and the caps are 30+ years old then it was justified, especially for critical CVs. I will eventually do that to my own unit. How about polypropylene caps. The only caps I know of besides mica, that have zero drift with temperature change. I suppose it's possible that this could alter the sound. You see these in the filter circuits of pro audio graphic/parametric EQ's, Oberheim synth DMUX circuits etc.. Panasonic used to make them but I can't find them anymore. Quote MPCX, RD-800, Vsynth, Matrix 12 Link to comment Share on other sites More sharing options...
The Real MC Posted August 10, 2017 Share Posted August 10, 2017 Did you end up changing out the caps on the DMUX board? Yes I did. Those white polyester caps have a limited age. That was a big job but seeing this is an early unit from 1982 and the caps are 30+ years old then it was justified, especially for critical CVs. I will eventually do that to my own unit. How about polypropylene caps. The only caps I know of besides mica, that have zero drift with temperature change. I suppose it's possible that this could alter the sound. You see these in the filter circuits of pro audio graphic/parametric EQ's, Oberheim synth DMUX circuits etc.. Panasonic used to make them but I can't find them anymore. You won't find a large range of values for mica caps as they get impractical beyond a certain range. Polyester is considered the "economy style" for film capacitors. Their low cost come with trade-offs that are a compromise for an industry where cutthroat retail prices rule. Polypropylene is a good dielectric for S&H and tuned circuits. They are good for S&H because they have better dielectric absorption than the original polyester. They are better for tuned circuits like filters and EQs because their tolerance, ESR, and tempco are better than polyester. The phasor in my ARP piano sounded a lot better when I replaced the original polyester caps with polypropylene. Walt Jung did some pretty extensive studies with caps of different dielectrics and also found that there was a marked change in tuned circuits. Yes they will alter the sound; whether it is better is subjective. This is a pretty good primer on capacitors, although it's a little out of date (polycarbonate caps are unavailable). I usually buy film caps from WIMA or TDK, had good luck with them. Quote Link to comment Share on other sites More sharing options...
Markyboard Posted August 10, 2017 Author Share Posted August 10, 2017 Polypropylene is a good dielectric for S&H and tuned circuits. They are good for S&H because they have better dielectric absorption than the original polyester. They are better for tuned circuits like filters and EQs because their tolerance, ESR, and tempco are better than polyester. The phasor in my ARP piano sounded a lot better when I replaced the original polyester caps with polypropylene. Walt Jung did some pretty extensive studies with caps of different dielectrics and also found that there was a marked change in tuned circuits. Yes they will alter the sound; whether it is better is subjective. Other then maybe the 18 auto-tune signals I don't think the type of caps used on the DMUX board will change the "sound" as these are simply control signals. Quote Link to comment Share on other sites More sharing options...
The Real MC Posted August 10, 2017 Share Posted August 10, 2017 Polypropylene is a good dielectric for S&H and tuned circuits. They are good for S&H because they have better dielectric absorption than the original polyester. They are better for tuned circuits like filters and EQs because their tolerance, ESR, and tempco are better than polyester. The phasor in my ARP piano sounded a lot better when I replaced the original polyester caps with polypropylene. Walt Jung did some pretty extensive studies with caps of different dielectrics and also found that there was a marked change in tuned circuits. Yes they will alter the sound; whether it is better is subjective. Other then maybe the 18 auto-tune signals I don't think the type of caps used on the DMUX board will change the "sound" as these are simply control signals. I meant to say that. Thanks... Quote Link to comment Share on other sites More sharing options...
Karl Schmeer Posted August 10, 2017 Share Posted August 10, 2017 How about polypropylene caps. The only caps I know of besides mica, that have zero drift with temperature change. I suppose it's possible that this could alter the sound. You see these in the filter circuits of pro audio graphic/parametric EQ's, Oberheim synth DMUX circuits etc.. Panasonic used to make them but I can't find them anymore. You won't find a large range of values for mica caps as they get impractical beyond a certain range. Polyester is considered the "economy style" for film capacitors. Their low cost come with trade-offs that are a compromise for an industry where cutthroat retail prices rule. Polypropylene is a good dielectric for S&H and tuned circuits. They are good for S&H because they have better dielectric absorption than the original polyester. They are better for tuned circuits like filters and EQs because their tolerance, ESR, and tempco are better than polyester. The phasor in my ARP piano sounded a lot better when I replaced the original polyester caps with polypropylene. Walt Jung did some pretty extensive studies with caps of different dielectrics and also found that there was a marked change in tuned circuits. Yes they will alter the sound; whether it is better is subjective. This is a pretty good primer on capacitors, although it's a little out of date (polycarbonate caps are unavailable). I usually buy film caps from WIMA or TDK, had good luck with them. Thank you much for this. I need to find a new supply of these for upcoming projects. I will check out WIMA and TDK I have been asked a few times from folks wanting to recap their M12's if they should also replace the poly's in their DMUX circuit. I advise not to because: 1) the self-healing effect of polypropylene 2) scarcity of parts. As far as I can tell they last darn near forever. Thanks Again!! Quote MPCX, RD-800, Vsynth, Matrix 12 Link to comment Share on other sites More sharing options...
The Real MC Posted August 11, 2017 Share Posted August 11, 2017 While I was surfing Markyboard's pictures I spotted replacement caps on the voicecards, then checked mine. Sure enough, the original caps that Moog installed for the timing caps on the 3340s were the drifty polyester caps, despite the CEM spec recommending low drift caps such as mica. I just ordered 5% tolerance low PPM mica caps to replace C5, C12, and C22 on the voicecards. Those should be an improvement. Later I will check what timing caps are installed in my OBSX... better not be one of those mylars! Quote Link to comment Share on other sites More sharing options...
Markyboard Posted August 11, 2017 Author Share Posted August 11, 2017 You have way more knowledge regarding specifics of caps then I do. Still you might find this a good source for caps. If not I'd like to know why for future reference. Quote Link to comment Share on other sites More sharing options...
Karl Schmeer Posted August 11, 2017 Share Posted August 11, 2017 You have way more knowledge regarding specifics of caps then I do. Still you might find this a good source for caps. If not I'd like to know why for future reference. All right!! they have poly's. Thanks for this Markyboard!! The downside I see, is it's surplus. Which means that once they have sold them all that's it. Need to do a "lifetime buy" if you are using for production. Also no factory to complain to if you have problems. Serious Thank You! Quote MPCX, RD-800, Vsynth, Matrix 12 Link to comment Share on other sites More sharing options...
Markyboard Posted August 11, 2017 Author Share Posted August 11, 2017 I've bought most of my caps from here and ebay including silver micas. Prices are quite a bit lower then Allied or the other big distro places. Never had a problem but of course I'm dealing with small quantities for personal use. Still I know Michael has mentioned counterfeit parts several times. Can you counterfeit a cap? Quote Link to comment Share on other sites More sharing options...
Karl Schmeer Posted August 11, 2017 Share Posted August 11, 2017 I guess anything is possible, but it would be like counterfeiting dimes. Not really a big money maker. Quote MPCX, RD-800, Vsynth, Matrix 12 Link to comment Share on other sites More sharing options...
The Real MC Posted August 11, 2017 Share Posted August 11, 2017 Can you counterfeit a cap? No, but the big unknown is their true age. There's no "datecode" for passive components. These shops that pass counterfeit ICs - most located in Asia - basically buy scrap circuit boards and scavenge the ICs, then re-label them. It wouldn't be beyond them to scavenge caps and sell them as "NOS", which is sort of true but the age is unknown. And I'm not anxious to put old caps in my synths. Outside of Mouser/Allied/Digikey, there aren't many small quantity outlets I would buy from but it does become necessary sometimes. I was troubleshooting a guitar preamp for a friend and found a dead Z80. Those cpus have been out of production, you're not going to find them at Mouser et al. So I found one through Jameco, and it worked. I've never had trouble with Jameco. I had a dead 80C98 in my OBX, also unobtanium; had to get one from synthparts.com - the guy who runs it is a friend of a friend and he's legit. Quote Link to comment Share on other sites More sharing options...
The Real MC Posted August 11, 2017 Share Posted August 11, 2017 You have way more knowledge regarding specifics of caps then I do. Still you might find this a good source for caps. If not I'd like to know why for future reference. Besides caps, they have a HUGE selection. Hard to find good surplus places anymore. I built a good summary table of capacitor families, pulled from Harry Bissell and other sources - I'll have to put it up on my webpage. Even though my current day job utilizes little of my EE skills (which is why I restore synths), I still read up on things I didn't learn in college. Quote Link to comment Share on other sites More sharing options...
Markyboard Posted August 11, 2017 Author Share Posted August 11, 2017 had to get one from synthparts.com - the guy who runs it is a friend of a friend and he's legit. Believe me , Doug's gotten a few mortgage payments from me over the years. Always been happy with his CEMs. Quote Link to comment Share on other sites More sharing options...
ElmerJFudd Posted September 13, 2019 Share Posted September 13, 2019 Tasty bit of Memory Moog goodness, [video:youtube] Quote Yamaha CP88, Casio PX-560 Link to comment Share on other sites More sharing options...
Marzzz Posted September 13, 2019 Share Posted September 13, 2019 And of course, there is another raffle up and running... Moog Foundation Raffle Quote Link to comment Share on other sites More sharing options...
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