RE: Re: Notes on Schems...update on grounding experiment

[email protected]
Newsgroups gmane.music.equipment.kawai.k5
Message-ID <[email protected]> 
JRC makes clones eg. the RC4558 is a TI chip but JRC makes some the VCAs are Mitsubishi, but JRC makes some too, send them an e-mail, they can send you infos about obsolete components, but you might receive it after a couple of months.

Note: I saw they rebuilt the site, maybe the support has changed. It's NJR.COM (NewJapaneseRadio's logo is JRC)

"nelsonj_sce" <nelsonj_sce-/[email protected]> wrote:

>
>Hack update:
>Since my last note I replaced the other two op-amps with socketed Burr
>Brown OPA4228.  Replacing these two other op-amps did reduce noise
>levels noticeably.  There is still some noise but with 1)the these
>four super clean op-amps, 2)using Multi, 3)routing everything to a
>sinlge output on the multi rather than mix, and 4)using my noise gate,
>noise is really not an issue any more.  I would love to try and
>replace the VCAs also, but I have not been able to track down a spec
>sheet (or any other info on the) on them so I do not have a clue as
>what might works as an upgraded part.
>
>If anyone can help, the VCAs are part M5222L and they are from
>the same off-brand Japanese JRC company that is used elsewhere in the
>K5.  If anyone can help me with details on the M5222Ls I will see if I
>can find a replacement parts.
>
>My bottom line: If you are willing to lay-out $30 for the four BB
>OPA4228 and sockets, and you if you are willing to remove some
>tough-to-remove parts, I highly recommend this op-amp replacement
>hack.  My K5 has much less noise and just sounds much warmer/classier
>with the new parts.  I would love remove more noise, but right now it
>sounds very good and I am not very motivate to continue hacking.  (I
>do still plan on replacing the headphone circuit though since I
>already made the new circuit and all I have to do is wire it up.)
>
>An interesting aside:  After I did the latest op-amp replacement,
>everything sounded great in multi, but when I went to single I had
>serious problems.  Various ranges of the keyboard worked fine, while
>other ranges sounds like a fried amp circuit.  It turns out that while
>I was removing IC8 I accidentally pulled part of the circuit board
>trace off that connected pins 1 and 2 on IC8.  This trace provides the
>feedback loop between the (-) and output of line G2.  Once I tracked
>down the problem I was able to reconnect pins 1 and 2 and then
>everything in single mode worked great.  What I conclude from this is
>that the K5 in single mode is splitting different ranges of the
>keyboard to different op-amps.  I am not sure what K% is doing in
>multi but multi (ouput 1) DOES NOT use the opamp in IC8 pins 1-2-3.
>
>Hack on.
>
>
>--- In [email protected], "antdes45dragonmaster" <antdes45@n...>
>wrote:
>>
>> Not exampe, example
>>
>> --- In [email protected], Antoine Deschênes
><antdes45@n...> wrote:
>> > Removing the opamps one by one could help:
>> > exampe. You remove the 2nd last opamp and there is no more noise,
>then
>> > noise source is not at final stage.
>> >
>> > nelsonj_sce@y... a écrit:
>> >
>> > >
>> > > Per one of my earlier notes,  I took out my BB opamp part U4 and
>> > > replaced it with a rewired Tl074 where I lifted the ground pins
>3, 5,
>> > > 10, 12 and rewired them to a different ground.  Bottom line:
>Using a
>> > > different ground for U4 made very little improvement in noise.
>It did
>> > > reduce it a bit, but the noise reduction is not worth the
>effort.  I
>> > > even tried 4 different new ground locations,including the main
>ground
>> > > by the xmfr, but none of the grounds resulted in any meaningful
>noise
>> > > reduction.
>> > >
>> > > Anyway, this hack is not worth doing.  Back to the drawing
>board...
>> > >
>> > > --- In [email protected], Antoine Deschênes
><antdes45@n...>
>> > > wrote:
>> > > > 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@n... 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@y... 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 [email protected], 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 [email protected], 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 [email protected], 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/
>> > > > >> > > >
>> > > > >> > > >
>> > > > >> > > >
>> > > ____________________________________________
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-- 
Antoine Deschênes
aka DragonMaster
http://thehotcom.deep-ice.com/
Files:http://angelfire.com/ca7/hotcomcenter/


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