Problem can be in the OKI coils, opamps other than U4, or something else. And if you remove the VCAs? (Without cutting the pins) Maybe these are just crappy noisy things? nelsonj_sce@... a écrit: > > Per one of my earlier notes, I took out my BB opamp part U4 and > replaced it with a rewired Tl074 where I lifted the ground pins 3, 5, > 10, 12 and rewired them to a different ground. Bottom line: Using a > different ground for U4 made very little improvement in noise. It did > reduce it a bit, but the noise reduction is not worth the effort. I > even tried 4 different new ground locations,including the main ground > by the xmfr, but none of the grounds resulted in any meaningful noise > reduction. > > Anyway, this hack is not worth doing. Back to the drawing board... > > --- In k5synth@yahoogroups.com, Antoine Deschênes <antdes45@n...> > wrote: > > Good opamps might not change the noise amout that much. But I know > wiaht > > 2 opamps in parallel are doing with noise is like what 2 resistors > in > > parallel are doing: reduce it(noise in the case of opamps if it's > not > > series, I've read this somewhere) > > > > antdes45@n... a écrit: > > > > > Well, in my case, the mixer is pretty niosy too(A Kawai MX8R > mixer > > > from the same year), and I've never found Multi louder than Single > nor > > > Singles louder than Multi, nor that Mix is more noisy than > > > Singles(Tried with VU meter too, maybe it's the same for you since > you > > > changed your opamps, but maybe you haven't changed the 4 opamps > as I > > > did). I've already plugged the K5 directly in the SBLive line > in(Which > > > is -90dB), but obtained a -46dB at the volume I get a -90dB > without > > > source on the SoundForge VU Meter. > > > > > > It's pretty noisy I know it, idtheory.com has a 6MB MP3 made with > 2 > > > K5s in 1991. > > > > > > nelsonj_sce@y... a écrit: > > > > > >> > > >> You wrote: "I only use MIX output and headphones" > > >> I don't use the MIX now, rather, I stack everything in a Multi > to a > > >> single output , Out 1 usually. It makes the sound cleaner > because you > > >> skip one of the op-amps. You might want to try this trick to > help > > >> clean up the sound. > > >> > > >> --- In k5synth@yahoogroups.com, Antoine Deschênes > <antdes45@n...> > wrote: > > >> > You told a couple of replies before "I suppose you now have > socketed > > >> > opamps, like me", well I don't have some, I forgot to ask them > at > > >> the shop. > > >> > > > >> > "U1 if you use MIX" > > >> > I only use MIX output and headphones. I don't have time/want to > build > > >> > some 4 ½ m wires. And my mixer is 8 channels : 2 for the > first > Roland > > >> > D110, 2 for the second one, and 1 for the K5, if I would do > that, I > > >> > would lose all the 3 other inputs, which I use sometimes. > Also, I > > >> don't > > >> > use the K5 for recording or anything else, I modifiy it even > if I'm > > >> just > > >> > playing it when I've got nothing to do. The K5 is just a kind > of toy > > >> for > > >> > me(And my father owns it, and uses it rarely to use it as a > controller > > >> > in Finale). > > >> > > > >> > nelsonj_sce@y... a écrit: > > >> > > > >> > > > > >> > > You wrote: "They connected the non-inverting(+) input(if I'm > > >> right) to > > >> > > the DG?!?" > > >> > > Not directly. The schem show that the (+) is connected to > the > > >> AG, but > > >> > > it appears from the wiring board layouts that the AG and DG > have > > >> > > ground planes that connect in several places. So basically, > there is > > >> > > no physical seperation of the AG and DG ground planes on > board > > >> MI-004. > > >> > > As a result the (+) is connected to this single ground plane > that has > > >> > > both A and D parts on it. > > >> > > > > >> > > > > >> > > You wrote: "What's the VCA's ground?" > > >> > > The same dirty AG/DG ground as that of U4. The VCAs are > parts > > >> IC6 and > > >> > > IC7. The ground is pin 3, there is also a ground through a > cap on on > > >> > > pin 5 but this look like protection rather than ground. I am > not > > >> sure > > >> > > if pin 3 is the third pin from the top or from the bottom, > but pin 4 > > >> > > is -A6. It can't hurt to move the VCA's grounds to a clean > ground > > >> > > also. Note that it looks to me that the VCA's do not play > the > > >> role of > > >> > > traditional synth VCAs, but rather the are connected directly > to the > > >> > > main volume slider via pin 5. They don't seem to have any > other > > >> > > control voltages so my guess is that all the VCAs do is > control the > > >> > > overall volume of the keyboard. If that is the case, I am > note sure > > >> > > that a dirty ground will inject noise. But again, it can't > hurt to > > >> > > make sure they have a clean ground. > > >> > > > > >> > > So here is my plan: Step 1 is change the ground on U4 (and U1 > if you > > >> > > want to use the Mix output). Step 2 is change the ground on > the > > >> VCAs. > > >> > > Parts U8 and U9 are set up as non-inverting amps and do not > have any > > >> > > direct connections to ground so no grounding to change here, > but they > > >> > > have that shielding that we may be able to improve as Step 3. > > >> > > > > >> > > I may be able to do step 1 tonight - it all depends on how > sleepy my > > >> > > baby is! > > >> > > > > >> > > > > >> > > --- In k5synth@yahoogroups.com, antdes45@n... wrote: > > >> > > > Pulling the DG from the boards not PSU board(Impossible, > without > > >> > > removing a bridge rectifier), I've already used the PSU > without the > > >> > > big brown connector full of wires for power and ground of the > boards. > > >> > > > > > >> > > > They connected the non-inverting(+) input(if I'm right) to > the > > >> DG?!? > > >> > > > Well, sure it will make noise, if that ground is that much > noisy, > > >> > > that would be like to plug a phono playing in the input and > wondering > > >> > > why you hear it.(Well, that's what I think) > > >> > > > > > >> > > > What's the VCA's ground? > > >> > > > > > >> > > > Also, they put two mono DACs for 4 channels, so (My > theory) the > > >> > > analog sound is passing thru a kind of flip-flop that > switches > > >> rapidly > > >> > > the input from 1 to 2 to 1 ... and the other with 3 and 4. As > I only > > >> > > have a part of the output board, the opamp section and the > > >> PSU(Thanks, > > >> > > > > > >> > > > > > >> > > > "nelsonj_sce" <nelsonj_sce@y...> wrote: > > >> > > > > > >> > > > > > > >> > > > >Antdes, > > >> > > > >Ok, I still have more work to do but I did look more at > the schems > > >> > > > >while on a plane today. Some thoughts... > > >> > > > >1) DO NOT simply remove the DG ground on the power supply > and > > >> reroute > > >> > > > >it to the AG (black transformer wire). If you do this > the > > >> inverter > > >> > > > >for the backlight (as well as several caps and part D6 > WILL NOT BE > > >> > > > >GROUNDED. Basically the DG does not terminate on MI-010, > rather > > >> > > > >MI-010 needs the connection <CN1> in order to be > grounded. I > > >> am still > > >> > > > >looking at things but it seems the main ground for the > MI-003 > > >> &MI-004 > > >> > > > >comes from where they are screwed in to the K5 case. > > >> > > > > > > >> > > > >2) Although I am not 100% sure, it appears that for some > > >> reason, on > > >> > > > >board MI-004 the DG and AG are actually connected. Board > > >> MI-003 is > > >> > > > >all digital so the ground is pure digital. If I am > correct, > > >> and the > > >> > > > >AG and DG grounds are not separated on MI-004, this may > be the > > >> source > > >> > > > >of the noisy ground. The bad news is that there is no > quick > > >> way to > > >> > > > >separate the grounds on MI-004. > > >> > > > > > > >> > > > >3) Part U4 (the op-amp right after the VCA that we have > both > > >> replaced) > > >> > > > >has my attention. It has four inverting op-amps, where > the "+" of > > >> > > > >each amp is connected directly to the dirty ground. It > is > > >> possible > > >> > > > >that the dirty ground is basically injection noise to > these amp. > > >> > > > > > > >> > > > >I think we both have replaced this op-amp and it is now > in a > > >> socket. I > > >> > > > >plan on taking out the amp(this is a total hack but if it > works > > >> I can > > >> > > > >make it look nice later), and then bending connections 3, > 5, > > >> 10, 12 > > >> > > > >(the grounds) out so that they do not connect to the > socket/dirty > > >> > > > >ground on board MI-004. Then, I will wire these > connections > > >> directly > > >> > > > >to the K5's case to try and get a clean ground. > > >> > > > > > > >> > > > >4) If that does not help lower the noise, I am looking at > lines > > >> g0-g7 > > >> > > > >that feed the op-amps U8 and U9. These are the only > analog signal > > >> > > > >lines that have Faraday shielding. These are low level > lines > > >> early in > > >> > > > >the analog signal chain. If nosie gets in to these > lines, the > > >> nosie > > >> > > > >will get amplified in each of the following amp stages. > > >> Perhaps there > > >> > > > >is a way to improve the shielding on these lines or to > change the > > >> > > > >grounds related to these singal paths...but I have to > think > > >> about how > > >> > > > >to do it. > > >> > > > > > > >> > > > >Anyway, I will let you know what happens after I reground > U4. > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > > >--- In k5synth@yahoogroups.com, antdes45@n... wrote: > > >> > > > >> That's it, AG is analog ground, DG digital ground, +A6V > dc > > >> analog > > >> > > > >6v. . . > > >> > > > >> The kind of fork for the analog ground is an other sign > for > > >> ground, > > >> > > > >maybe they mean different connection places, as the fork > like > > >> is used > > >> > > > >for antenna too. But I think it's just a country/continent > > >> difference. > > >> > > > >> > > >> > > > >> "nelsonj_sce" <nelsonj_sce@y...> wrote: > > >> > > > >> > > >> > > > . . . Cut the file, was 62k. > > >> > > > > > >> > > > -- > > >> > > > Antoine Deschênes > > >> > > > aka DragonMaster > > >> > > > http://thehotcom.deep-ice.com/ > > >> > > > Files:http://angelfire.com/ca7/hotcomcenter/ > > >> > > > > > >> > > > > > >> > > > > __________________________________________________________________ > > >> > > > Switch to Netscape Internet Service. > > >> > > > As low as $9.95 a month -- Sign up today at > > >> > > http://isp.netscape.com/register > > >> > > > > > >> > > > Netscape. Just the Net You Need. > > >> > > > > > >> > > > New! Netscape Toolbar for Internet Explorer > > >> > > > Search from anywhere on the Web and block those annoying > pop-ups. > > >> > > > Download now at > http://channels.netscape.com/ns/search/install.jsp > > >> > > > > >> > > > > >> > > > > >> > > > > >> > > Yahoo! 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Groups Links > > >> > > > > >> > > * To visit your group on the web, go to: > > >> > > http://groups.yahoo.com/group/k5synth/ > > >> > > > > >> > > * To unsubscribe from this group, send an email to: > > >> > > k5synth-unsubscribe@yahoogroups.com > > >> > > > > >> <mailto:k5synth-unsubscribe@yahoogroups.com?subject=Unsubscribe> > > >> > > > > >> > > * Your use of Yahoo! Groups is subject to the Yahoo! > Terms of > > >> > > Service <http://docs.yahoo.com/info/terms/>. > > >> > > > > >> > > > > >> > > > >> > -- > > >> > antdes45@n... > > >> > > >> > > >> > > >> > > > > > > -- > > > antdes45@n... > > > > > > Yahoo! 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Groups Sponsor > ADVERTISEMENT > <http://us.ard.yahoo.com/SIG=129m2cs7f/M=315388.5500238.6578046.3001176/D=grplch/S=1705032144:HM/EXP=1098142001/A=2372354/R=0/SIG=12id813k2/*https://www.orchardbank.com/hcs/hcsapplication?pf=PLApply&media=EMYHNL40F21004SS> > > > > ------------------------------------------------------------------------ > Yahoo! Groups Links > > * To visit your group on the web, go to: > http://groups.yahoo.com/group/k5synth/ > > * To unsubscribe from this group, send an email to: > k5synth-unsubscribe@yahoogroups.com > <mailto:k5synth-unsubscribe@yahoogroups.com?subject=Unsubscribe> > > * Your use of Yahoo! Groups is subject to the Yahoo! Terms of > Service <http://docs.yahoo.com/info/terms/>. > > -- antdes45@...
Message
Re: [k5synth] Re: Notes on Schems...update on grounding experiment
2004-10-18 by Antoine Deschênes