[sdiy] Jp-8 head scratcher

[Maarten Halmans]

Hi,
ADC?? the selected oscillator goes thru a multiplexer into a comparator into 
a counter and as I said before the output of the comparator looks for all 
voices the same.
Best,
Maarten
----- Original Message ----- 
From: "cheater00 ." <cheater00 at gmail.com>
To: "Maarten Halmans" <diy at artefacts.nl>
Cc: "synth-diy" <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, November 06, 2013 5:38 PM
Subject: Re: [sdiy] Jp-8 head scratcher


>> ----- Original Message -----
>> From: cheater00 .
>> To: Maarten Halmans
>> Cc: synth-diy
>> Sent: Wednesday, November 06, 2013 4:56 PM
>> Subject: Re: [sdiy] Jp-8 head scratcher
>>
>>
>> On 6 Nov 2013 16:50, "Maarten Halmans" <diy at artefacts.nl> wrote:
>>>
>>> Hi all,
>>>
>>> I have some serious strange thing going on in a Roland Jupiter-8 and I
>>> have no more clues where to look. I tuned all 16 voices and they are 
>>> very
>>> nice in tune over all octaves. They are well tuned on start up (in test
>>> mode) and when the synth is on for several hours. So far so good!
>>>
>>> The problem arrises when I use the auto tune. All voices stay tuned 
>>> except
>>> for 2 voices(on the same voice board). Oscillator 1 of both voices is 
>>> tuned
>>> to high. One voice is 12 cent off the other 6 cent. Oscillator 2 of both
>>> voices is still in tune. So I swapped the voice card to make shure it is 
>>> not
>>> in de keyboard cv sample&holds or auto tune multiplexers and the 
>>> problems
>>> moves with the voice card. I also disconnected all the modulation 
>>> sources
>>> but all with no result. Swapped the CV summing amp and the transistor 
>>> array,
>>> which does not make sense but you have to try something. I am completly 
>>> in
>>> the dark now. Sounds familiar to someone or does someone have 
>>> suggestions or
>>> ideas the find the problem? They are very welcome!!
>>>
>>> Best Maarten
>>>
>>>
>>
>> Those voices are likely too quiet. Check the peak to peak voltage on the
>> scope. The autotune requires a specific output voltage. You wouldn't hear
>> the difference in voltage.
>>
>> D.
>
>
> On Wed, Nov 6, 2013 at 5:29 PM, Maarten Halmans <diy at artefacts.nl> wrote:
>> Hi!
>> thanks for the reply! levels are the same and I don't see any strange 
>> things
>> on the multiplexer input or the comparator output. I recorded the output 
>> of
>> the comparator during the autotune sequence both with my scope and a
>> soundcard, and I can see that tuning of the problem voices takes much 
>> more
>> time. The 2 lower frequencies seem fine but it the highest frequency ( 
>> C8 )
>> takes much more time.
>>
>> Best,
>>
>> Maarten
>
> Is the HF of the signal attenuated when it gets to the ADC?
>
> Maybe you have too much noise on the digital rail, distorting the ADC?
>
> Right now I'm guessing.
>
> Cheers,
> D.