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@... 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@... 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@...m, 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: [k5synth] Re: Notes on Schems...
2004-10-17 by Antoine Deschênes