Note: Digital ground is on bridge neg. and Analog on 0v, and bridge goes to the transformer, so it's connected together in a kind of way. antdes45@netscape.net a écrit: > > Buzzing in rear out is signal ground noise, all pcbs have sepparate > analog grounds to PSU but linked together on the psu. > > --- In k5synth@yahoogroups.com, "nelsonj_sce" <nelsonj_sce@y...> > wrote: > > > > Antdes, > > Good information in the note below. It sounds like the good news is > > that the digital (D) and analog (A) have seperate grounds. From > > everything I have been reading that is good news. If they had the > > same ground on the same PCB we might be completely out of luck. > Today > > I ordered the latest OS ROM and schematics from Kawai so hopefully, > > once I have the schems, I make more informed suggestions on how to > > reduce the ground noise. > > > > I did read something today that said that, although you should have > > separate A and D grounding, ultimately both the A and D should be > > grounded at the same point. Otherwise, the D might inject noise in > to > > the A ground. Based on your note, this might be just what is going > on > > in the K5. > > > > Based on this observation, one thing to try would be to take the D > > ground off of the power supply board and connect that ground > directly > > to the A ground on the transformer. We need to make sure the power > > supply board is still fully grounded even if we remove the D ground, > > but you should be able to check the schem and see if it looks like > > this is an easy move. > > > > Anyway I don't want to do anything too fancy until I look at the > > schems, but if it looks safe, this is the first thing I want to > try. > > (Or if you feel adventurous you could try it and tell me if it > works!) > > > > Thanks for the note and let me know if you find anything else out. > > > > > > > > > > > > --- In k5synth@yahoogroups.com, "antdes45dragonmaster" > <antdes45@n...> > > wrote: > > > Digital Ground is plugged to one bridge's negative pole and > analog to > > > 0v line of the transformer(Black wire). I know it's a noisy ground > > > because when I transfer MIDI between K5 and computer, I hear some > low > > > volume beeps in the noise, and my intermittent inverter whines(Is > on > > > DGround) in the headphones when it wants. I looked at the > schemes, and > > > every different PCB's DGrounds are plugged together on the PSU > > > mainboard, but are going to it thru different wires.(Same for > > > AGround). Problem is I don't remember how to filter ground. > Something > > > to try. Also, when I unplug the brown socketed black bus wire > going to > > > outputs board, there is no signal from the headphones, but still > > > noise. So it's not coming from the opamps(Headphones noise). > Might be > > > that the LM386's ground has no filter. While for the rear outputs > > > noise, the opamps might be too noisy(-45dB with some TL072 > instead of > > > some TL062, which might have not changed anything noise talking, > using > > > some OPA????, don't remember which, will have to re-find the name > on > > > DIYAudio, might be a lot less noisy, because a signal passing 4 > times > > > in pretty noisy OpAmps in series might not be really good). > > > > > > --- In k5synth@yahoogroups.com, "nelsonj_sce" <nelsonj_sce@y...> > wrote: > > > > It looks like you have already changed out the op-amps and > found that > > > > the noise is still there. Have you tried anythink to fix the > noisy > > > > ground? Is it that the digital and analog all share the same > ground? > > > > Is there a way to "split" the ground or add a new ground plane > and > > > > reroute say the digital chips to the new ground plane? Are all > the > > > > analog parts on a single board so that we could just cut the > ground to > > > > that board and then wire up a new, "independent" ground? Are > there > > > > just a few key digital parts that are creating the noise that > can be > > > > rerouted to a seperate ground plane? > > > > > > > > Has anyone at Kawai told you how to solve this problem? Even > if I can > > > > get a hold of the schematics, if Kawai or others can identify a > few > > > > key components it should not be that hard to create a seperate > ground > > > > for those parts. > > > > > > > > Any thoughts? > > > > > > > > --- In k5synth@yahoogroups.com, Antoine Deschênes > <antdes45@n...> > > wrote: > > > > > The LM386 doesn't produce any noise. Even if you unplug the > signal > > > > there > > > > > will still be some. Sctually the problem is a noisy ground. > It's > > > > sharing > > > > > the same ground for all the board(s). > > > > > > > > > > nelsonj_sce@y... a écrit: > > > > > > > > > > > Here is the latest, it is good news. > > > > > > > > > > > > Today I got my parts for DigiKey. As below I replaced my > > backlight > > > > > > with a blue backlight from nightlaunch. It worked with my > > stock K5 > > > > > > inverter. However, my stock inverter was very flakey, even > > after I > > > > > > did the resolder job so I decided to replace the stock > > inverter with > > > > > > the DigiKey part. (Digikey part #289-1032-ND). The good > news > > > is that > > > > > > inverter works (even though it is only about 95V @ about > > 550Hz). It > > > > > > is a slightly different color than before, but it still > looks > > great. > > > > > > Also- THERE IS VIRTUALLY NO HUM! > > > > > > > > > > > > The only warning is the Digikey part is not the exact same > size > > > as the > > > > > > original inverter - it is a bit smaller in footprint and a > lot > > > > > > shorter. The stock inverter has only three connections > (in - > > out - > > > > > > ground) and the new inverter has a fourth pin for mounting. > > Because > > > > > > the part is smaller, I used the original hole for > the "out", but > > > I had > > > > > > to wire up jumpers to the "ground" and the "in" - not a big > > deal but > > > > > > it is some extra work - and you don't want to see pictures > of > > > my ugly > > > > > > job. :). But so far so good. > > > > > > > > > > > > Also, I did the 147K resistor hack and it seems to have gone > > > well. My > > > > > > K5 is a louder, but the headphones have even more noise > now. > > I have > > > > > > been looking things over and I think the headphone noise is > > because > > > > > > they use a cheap LM386 op-amp and a bad overall design for > the > > > > > > headphone amp. I am trying to see if I can replace this > with a > > > better > > > > > > op-amp, otherwise I think the only good solution is to just > bypass > > > > > > their circuit completely and make a better headphone amp and > > wire it > > > > > > up to the K5. > > > > > > > > > > > > Anyway, again the good news is that for less than $30 > > delivered you > > > > > > can get nightlaunch backlight and a Digikey inverter and > have > > a new > > > > > > backlight that does not hum! :) > > > > > > > > > > > > Now for the headphone amp... > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > --- In k5synth@yahoogroups.com, "nelsonj_sce" > <nelsonj_sce@y...> > > > > wrote: > > > > > > > Update: > > > > > > > Well today I ordered a new inverter from > www.DigiKey.com. I > > > > found an > > > > > > > inverter that looks like it will do the job - for those > > interested > > > > > > it is: > > > > > > > > > > > > > > Digikey part # 289-1032-ND and it only cost $11.90 - > not > > > bad. > > > > > > > > > > > > > > I am not sure if it will fit exactly in the same slots as > the > > > > original > > > > > > > inverter so it might require some additional wiring. > > > > > > > > > > > > > > Anyway, I had my K5 open to look at the power supply to > plan > > > the new > > > > > > > inverter install when my K5 started "humming", and guess > what, > > > I now > > > > > > > have a beautiful blue backlight. It looks great, a very > cool > > > blue. > > > > > > > So it appears my inverter was not bad, but it just has bad > > solder > > > > > > > joints. It is working for now but tomorrow I will likely > take > > > > out the > > > > > > > board and redo all the solder joints. > > > > > > > > > > > > > > Just some additional info I learned in researching > > backlights and > > > > > > > inverters. The "brightness" of the backlight is a > function > > of the > > > > > > > voltage and frequency applied to the backlight. It > appears one > > > > has a > > > > > > > lot of flexibility in selecting the inverter output > voltage and > > > > freq. > > > > > > > For example, nightlauch says you can "test" the backlight > by > > > > plugging > > > > > > > it directly in to a wall socket (120V AC @ 60 Hz here in > the > > > > US)! The > > > > > > > higher the voltage and freq the brighter the backlight. > > > > However, the > > > > > > > backlight will "burn out" quicker the higher the freq. > So there > > > > is a > > > > > > > trade off, high freq = bright but shorter life. > > > > > > > > > > > > > > Right now my stock inverter is putting out about 102V @ > 380 > > Hz. I > > > > > > > think the inverter I ordered will put out about 95V @ 540 > Hz and > > > > > > > should work with a 3 - 6 V DC input. > > > > > > > > > > > > > > Next step, 147k resistors (also ordered from Digikey > today). > > > > > > > > > > > > > > > > > > > > > > > > > > > > --- In k5synth@yahoogroups.com, "nelsonj_sce" > <nelsonj_sce@y...> > > > > wrote: > > > > > > > > Well I replaced my backlight with one I ordered from > > > > > > > www.nightlaunch.com. > > > > > > > > > > > > > > > > It took less than two weeks from when I ordered and the > > > parts look > > > > > > > good. > > > > > > > > > > > > > > > > Good news/bad news though on my backlight. > > > > > > > > > > > > > > > > The good news: I had no problems removing the LCD, > taking out > > > > the old > > > > > > > > backlight and sliding in the new backlight. The new > light has > > > > some > > > > > > > > wires and a plastic "tab" that kind of gets in the way, > so I > > > > soldered > > > > > > > > the backlight wires to where the wires connect to the > LCD > > board. > > > > > > > > Hint:You have to cut the new backlight to size, so make > the > > > > backlight > > > > > > > > a little longer (say 1/4 inch) than the original to make > > things > > > > > > easier. > > > > > > > > > > > > > > > > Bad news: My backlight does not work but I think my > inverter > > > > is the > > > > > > > > problem. I am only getting about 1/2 Volt at the > output of my > > > > > > > > inverter, and I am supposed to get 120V @400Hz if I > > > understand the > > > > > > > > part correctly. I tested my inverter before I did the > > backlight > > > > > > > > install and saw it had low voltage, but I was hoping > that my > > > > existing > > > > > > > > "dead" backlight was causing the problem (i.e. it was > > > shorted.) I > > > > > > > > guess not because even with the new backlight I get > very low > > > > voltage. > > > > > > > > > > > > > > > > Anyway, it looks like I need to get an inverter. I can > get an > > > > > > > > inverter from nightlaunch for $17.99+s/h but it needs 9V > > DC. I > > > > > > > > understand the inverter in the K5 uses 5V DC. > > > > > > > > > > > > > > > > Q1: Does the K5 inverter use 5V DC? > > > > > > > > Q2: If I measure the voltage on the two wires to the > left > > of the > > > > > > > > inverter, should I get 120V if everything is working? > (My > > > > Fluke says > > > > > > > > it is good <=1kHz) > > > > > > > > Q2: Does anyone know where to get a compatible K5 > inverter > > > and how > > > > > > > > much it will cost? > > > > > > > > > > > > > > > > Thanks again for all the help. This group is great. > > > > > > > > > > > > > > > > > > Yahoo! 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Groups is subject to the Yahoo! > Terms of > > > > > > Service <http://docs.yahoo.com/info/terms/>. > > > > > > > > > > > > > > > > > > > > > > -- > > > > > antdes45@n... > > > > > Yahoo! Groups Sponsor > ADVERTISEMENT > <http://us.ard.yahoo.com/SIG=1294uag9n/M=315388.5455589.6541277.2248467/D=grplch/S=1705032144:HM/EXP=1097243362/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: How to fix a noisy ground?
2004-10-07 by Antoine Deschênes