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! Groups Sponsor > > > ADVERTISEMENT > > > > <http://us.ard.yahoo.com/SIG=129jk20o5/M=273541.4247512.5496808.2248467/D=g= = > rplch/S=1705032144:HM/EXP=1095918198/A=2061551/R=0/SIG=11sr5b9n1/*http://la= u= > nch.yahoo.com/artist/videos.asp?artistID=1001301> > > > > > > > > > > > > > > ------------------------------------------------------------------------ > > > 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@n...
Message
Re: How to fix a noisy ground?
2004-09-30 by antdes45dragonmaster