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

--- In [email protected], James Bong <jamesbong@...> wrote:
>
> 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
> > 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 ->
> > CH1-4 outputs.
> > 
> > The MIX and headphones outputs are connected to the
> > last buffer stage
> > outputs, mix the signal and go through one more
> > buffer.
> > 
> > I was thinking of experimenting with the output
> > stage by connecting
> > two PGA4311s right at the output of the S&H opamps,
> > and mix S1&S2
> > after the PGAs to see if noise levels would improve.
> > I just lack a bit
> > of time to build the required stuff to program a PIC
> > to control the
> > PGA chips.
> > 
> > Your DAC might have a problem, but since there are a
> > lot of external
> > adjustments, it would be a good idea to check the
> > components around
> > the DAC first.
> > 
> > Cheers,
> > Antoine


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