Re: How to fix a noisy ground?
I got the schems yesterday and I will take a look at the ground issue.
Although all grounds will eventually get to a single point, one idea
is to make sure the D and A get to the same ground at the same time -
that is make sure there is no path between the A and D grounds.
Anyway, I will try to look at the schems this weekend.
I also just upgraded to OS1.2. I am a bit disappointed that the
Kfuenf editor still does not work for me. Oh well, more on that in my
next post.
Also, I hooked up my J-station to the K5. The J-station has a very
good noise gate, as well as delay+reverb+chorus(ect). I have to crank
the noise gate up to about 65 to kill the line noise. But the K5
sounds great through this unit and I recommend it if you happen to
have a J-station around.
--- In k5synth@..., "antdes45dragonmaster" <antdes45 <at> n...>
wrote:
>
> Buzzing in rear out is signal ground noise, all pcbs have sepparate
> analog grounds to PSU but linked together on the psu.
>
> --- In k5synth@..., "nelsonj_sce" <nelsonj_sce <at> 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@..., "antdes45dragonmaster"
> <antdes45 <at> 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@..., "nelsonj_sce" <nelsonj_sce <at> 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@..., Antoine Deschênes
> <antdes45 <at> 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 <at> 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 <at> 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@..., "nelsonj_sce"
> <nelsonj_sce <at> 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 <at> 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 <at>
> 380
> > Hz. I
> > > > > > > think the inverter I ordered will put out about 95V <at> 540
> Hz and
> > > > > > > should work with a 3 - 6 V DC input.
> > > > > > >
> > > > > > > Next step, 147k resistors (also ordered from Digikey
> today).
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --- In k5synth@..., "nelsonj_sce"
> <nelsonj_sce <at> 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 <at> 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.
> > > > > >
> > > > > >
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