Removing the opamps one by one could help: exampe. You remove the 2nd last opamp and there is no more noise, then noise source is not at final stage. 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
2004-10-23 by Antoine Deschênes