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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Message
Re: Notes on Schems...
2004-10-16 by nelsonj_sce