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James Bong | 12 Jul 2008 18:17

Re: K5 distorted output from patches using Source-2

Does this chip have a bias circuit to set the min/max
output voltage scale? It could be something as simple
as a cold solder joint finally loosing contact and
changing the bias. I'd check/re-solder the solder
joints to everything connected to the chip, and the
chip it's self.

James

--- narfman96 <narfman96@...> wrote:

> Hi, 
> I've been troubleshooting a neglected K5 I found. I
> replaced the 
> battery. Fixed a missing ground trace on the mix
> output. Verified the 
> power supply voltages. There are a few keys that are
> hit and miss. 
> Etc.
> 
> The output whenever the S2 source is included in a
> patch is cranked 
> and distorted. If I set the S1/S2 balance to -31 I
> can hear S1 at the 
> normal volume with no distortion. As soon as the S2
> source is mixed 
> in even at -30 the distortion appears. At 0 to +31
> it turns into a FM 
> and ring modulated mush fest. It sounds analog to
> me. If I turn down
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narfman96 | 14 Jul 2008 14:44
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Re: K5 distorted output from patches using Source-2

I resoldered everything involved in this part of the circuit. There 
is a feedback resistor on the DAC for the audio output. This measures 
6.8k same as the working one. Maybe tonight I'll try lowering this 
value to see if the gain decreases.

I'm not having much luck finding a PCM55HP DAC. Digikey lists it for 
$38.50 with a long, long lead time... Crap! Anyone know of a source?

Hopefully Kawai gets back to me today about the schematic.

Thanks, Fran

--- In k5synth@..., James Bong <jamesbong <at> ...> wrote:
>
> Does this chip have a bias circuit to set the min/max
> output voltage scale? It could be something as simple
> as a cold solder joint finally loosing contact and
> changing the bias. I'd check/re-solder the solder
> joints to everything connected to the chip, and the
> chip it's self.
> 
> James

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James Bong | 14 Jul 2008 15:28

Re: Re: K5 distorted output from patches using Source-2

You wouldn't happen to have an oscilloscope to verify
that the output of this chip is actual problem, do
you? 

If you do get the schematics, could you possibly get
them scanned to share with the rest of us?

James

--- narfman96 <narfman96@...> wrote:

> I resoldered everything involved in this part of the
> circuit. There 
> is a feedback resistor on the DAC for the audio
> output. This measures 
> 6.8k same as the working one. Maybe tonight I'll try
> lowering this 
> value to see if the gain decreases.
> 
> I'm not having much luck finding a PCM55HP DAC.
> Digikey lists it for 
> $38.50 with a long, long lead time... Crap! Anyone
> know of a source?
> 
> Hopefully Kawai gets back to me today about the
> schematic.
> 
> Thanks, Fran
> 
> --- In k5synth@..., James Bong
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narfman96 | 14 Jul 2008 21:14
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Re: K5 distorted output from patches using Source-2

Yes I do have a scope I just haven't gotten that far yet. Yesterday I 
rebuilt the keyboard. This synth has a nice action when it's all 
greased up and triggers every note. I found the aftertouch 
adjustments and got it more sensitive than the key bending tipping 
over the stand mode it was originally set for. The aftertouch strip 
has a few spots that are less sensitive but hey it's a beast....

If it will help I can post the DAC's datasheet here in the files 
section so you can see what weird output configurations it can have. 
Either current or voltage outputs can be used. There isn't any pot 
for the offset zero. Also it seems like Kawai doesn't use much of the 
gain that's available. Maybe that's why it's so noisy.

The patches sound like they should if I turn the balance so S2 is off 
(-31). Except of course they're thin and lifeless without the other 
voice mixed in. I saved a bank that way so I could check out the 
keyboard. I can see where some of the noise comes from. The high 
frequency response goes way out there. Most of these 80's and 90's 
synths have low pass filters. This thing sounds wide open on top end! 
Probably so you can hear the 128 harmonics in all their glory.

Hopefully I won't be beat when I get home from work so I can play 
around with this some more. Still haven't heard from Kawai yet about 
the schematics. Also they always have me sign their non-disclosure 
form so I'm leery about openly posting them in the group. Of course 
helpful individuals are a different story. Right???

Fran

--- In k5synth@..., James Bong <jamesbong <at> ...> wrote:
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James Bong | 14 Jul 2008 22:26

Re: Re: K5 distorted output from patches using Source-2

How does it sound if you turn S1 all the way down, and
start turning up S2? Same distortion?

Oh, and where was the after-touch adjustment? I'm
always afraid I'm going to tip my stand over when I'm
using after touch modulation!

James
--- narfman96 <narfman96@...> wrote:

> Yes I do have a scope I just haven't gotten that far
> yet. Yesterday I 
> rebuilt the keyboard. This synth has a nice action
> when it's all 
> greased up and triggers every note. I found the
> aftertouch 
> adjustments and got it more sensitive than the key
> bending tipping 
> over the stand mode it was originally set for. The
> aftertouch strip 
> has a few spots that are less sensitive but hey it's
> a beast....
> 
> If it will help I can post the DAC's datasheet here
> in the files 
> section so you can see what weird output
> configurations it can have. 
> Either current or voltage outputs can be used. There
> isn't any pot 
> for the offset zero. Also it seems like Kawai
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narfman96 | 15 Jul 2008 01:20
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Re: K5 distorted output from patches using Source-2

The balance only controls the volume for S1 and S2. If S1 is all the 
way down S2 is cranked. Other than the DDA envelope (oh yeah the DHG 
levels too) ahhh, where can S2 be turned down to sublight.

The aftertouch was easy. There's 2 pots on the backside of the MI-004 
board they say Gain (VR1) and Offset (VR2) on them. Open Midi-Ox and 
watch the pressure change the values for aftertouch from 00 to F7. 
Adjust these pots to get the best performance for your preferences. 
Offset is where it starts to kick in. Then the gain adjusts how 
quickly F7 cranks in. I like a smooth contollable range that doesn't 
rip my tendons out.... That's why I can tell the notes from G3 to D4 
in this K5 aren't as responsive as the rest. 

Whoohoo!!! I'm talking to Kawai about the Service Manual. They are 
soooo gooood in this day and age of crapping on us hardware guys. 
Oops did I say e-mu? Awww darn! Dirty bird!! I want my money back!!!

Anyway the manual should be on its way....  Fran   

--- In k5synth@..., James Bong <jamesbong <at> ...> wrote:
>
> How does it sound if you turn S1 all the way down, and
> start turning up S2? Same distortion?
> 
> Oh, and where was the after-touch adjustment? I'm
> always afraid I'm going to tip my stand over when I'm
> using after touch modulation!
> 
> James
> --- narfman96 <narfman96 <at> ...> wrote:
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Antoine Deschênes | 23 Jul 2008 22:42
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Re: Re: K5 distorted output from patches using Source-2

Hi,

some things that might help you:

Datasheet is here, no need to post it:
http://focus.ti.com/lit/ds/symlink/pcm55.pdf
Product Page: http://focus.ti.com/docs/prod/folders/print/pcm55.html

Texas Instruments still produces the DAC, on the product page you can
see that Arrow and Rochester Electronics have some in stock.

As you might have guessed, one DAC outputs S1 sounds, and the other outputs S2.

Cold solder joints are common in this synth. In the first place, I'll
suggest you to rework all the solders on the PSU regulator board. A
lot of them fail.

The noise comes from the demultiplexing switches, the thousands of
opamps placed after the DAC as well as the VCAs.

Here's the diagram (what I remember) :
DACs ->
demux switches (one chip per DAC divides the mono signal in 4
different ones) ->
Sample & Hold circuit ->
S1 CH1-4 & S2 CH1-4 individual mixing (using high value resistors to
prevent feedback from other channels in the S&H circuit, adds noise)
->
VCAs (specs show they're quite noisy)->
Opamp Buffers ->
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James Bong | 24 Jul 2008 00:37

Re: Re: K5 distorted output from patches using Source-2

Wow, thanks for all that info!

--- Antoine Deschênes <antdes45@...> wrote:

> Hi,
> 
> some things that might help you:
> 
> Datasheet is here, no need to post it:
> http://focus.ti.com/lit/ds/symlink/pcm55.pdf
> Product Page:
>
http://focus.ti.com/docs/prod/folders/print/pcm55.html
> 
> Texas Instruments still produces the DAC, on the
> product page you can
> see that Arrow and Rochester Electronics have some
> in stock.
> 
> As you might have guessed, one DAC outputs S1
> sounds, and the other outputs S2.
> 
> Cold solder joints are common in this synth. In the
> first place, I'll
> suggest you to rework all the solders on the PSU
> regulator board. A
> lot of them fail.
> 
> The noise comes from the demultiplexing switches,
> the thousands of
(Continue reading)

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narfman96 | 24 Jul 2008 17:24
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Re: K5 distorted output from patches using Source-2

Antione you're a wizard on this synth!!! Thank you!!! Hope everything 
is cool at home...

I found datasheets for every non-Kawai IC in this synth. These docs 
have been so helpful. I am waiting for the DAC to get here. I found 
one from Sisitronics on Ebay for $22.00 US shipped. This is less than 
half what they wanted here stateside. I'm not sure how quick they 
will be though... Kawai US had this PCM55HP DAC in stock for $37.50 
so I can always pick one up from them. I love dealing with them after 
all my misgivings with the big three. Yuck!!

I've talked to my engineering and audio repair friends and they all 
agree the problem is from the DAC downstream. The clue is the DAC is 
outputting 4 to 5 times what it should. Kawai is using the output op-
amp for this DAC in bipolar mode. This leads one to believe the 
feedback (gain control) portion of this op-amp is bad letting it go 
to the rails (+/- 6 vdc) and output a wide open distorted signal.

I also have the schematics now and once I figure out how to scan the 
larger pages I can help anyone who needs a copy. Kawai TSD let me 
join the technicians area. They had most of the service docs for the 
K3/K3m and the K4/K4r posted for free on their site. The K4/K4r has 
the schematics posted but the pdf is corrupted. I'm trying to get 
them to fix it.

Enough for now. Additive synthesis in the multi-dimensional universe. 
Who'd have thunk it...

Fran
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narfman96 | 2 Aug 2008 19:23
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Re: K5 distorted output from patches using Source-2

The beast is fixed!!! I replaced the U14 DAC and the distortion on S2 
is gone. Whoohoo!!!

I buzzed out the bad PCM55HP and found the Pin-1 <DACF> data line is 
open internally. This must have caused the 16th bit to be ignored. Not 
sure why that caused the distortion??? But hey at least it wasn't the 
Kawai digital chips causing the problem. Oh yeah and I was wrong about 
the problem being analog.

Now to enjoy this great Kawai additive synth.

Fran 

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Antoine Deschênes | 3 Aug 2008 03:37
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Re: Re: K5 distorted output from patches using Source-2

Hi Fran,

Good to see you got your synth working!

Pin 1 is the most significant bit, that explains the distortion ;-)

2008/8/2 narfman96 <narfman96@...>:
> The beast is fixed!!! I replaced the U14 DAC and the distortion on S2
> is gone. Whoohoo!!!
>
> I buzzed out the bad PCM55HP and found the Pin-1 <DACF> data line is
> open internally. This must have caused the 16th bit to be ignored. Not
> sure why that caused the distortion??? But hey at least it wasn't the
> Kawai digital chips causing the problem. Oh yeah and I was wrong about
> the problem being analog.
>
> Now to enjoy this great Kawai additive synth.
>
> Fran
>

------------------------------------
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James Bong | 15 Jul 2008 01:40

Re: Re: K5 distorted output from patches using Source-2

How much are they charging you for it? 

James

--- narfman96 <narfman96@...> wrote:

> The balance only controls the volume for S1 and S2.
> If S1 is all the 
> way down S2 is cranked. Other than the DDA envelope
> (oh yeah the DHG 
> levels too) ahhh, where can S2 be turned down to
> sublight.
> 
> The aftertouch was easy. There's 2 pots on the
> backside of the MI-004 
> board they say Gain (VR1) and Offset (VR2) on them.
> Open Midi-Ox and 
> watch the pressure change the values for aftertouch
> from 00 to F7. 
> Adjust these pots to get the best performance for
> your preferences. 
> Offset is where it starts to kick in. Then the gain
> adjusts how 
> quickly F7 cranks in. I like a smooth contollable
> range that doesn't 
> rip my tendons out.... That's why I can tell the
> notes from G3 to D4 
> in this K5 aren't as responsive as the rest. 
> 
> Whoohoo!!! I'm talking to Kawai about the Service
(Continue reading)

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narfman96 | 15 Jul 2008 02:01
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Re: K5 distorted output from patches using Source-2

$15.00 US plus S/H and the d/cf they wanted filled out is now DOA...

--- In k5synth@..., James Bong <jamesbong <at> ...> wrote:
>
> How much are they charging you for it? 
> 
> James
> 
> --- narfman96 <narfman96 <at> ...> wrote:
> 
> > The balance only controls the volume for S1 and S2.
> > If S1 is all the 
> > way down S2 is cranked. Other than the DDA envelope
> > (oh yeah the DHG 
> > levels too) ahhh, where can S2 be turned down to
> > sublight.
> > 
> > The aftertouch was easy. There's 2 pots on the
> > backside of the MI-004 
> > board they say Gain (VR1) and Offset (VR2) on them.
> > Open Midi-Ox and 
> > watch the pressure change the values for aftertouch
> > from 00 to F7. 
> > Adjust these pots to get the best performance for
> > your preferences. 
> > Offset is where it starts to kick in. Then the gain
> > adjusts how 
> > quickly F7 cranks in. I like a smooth contollable
> > range that doesn't 
> > rip my tendons out.... That's why I can tell the
(Continue reading)

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Gmane