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Old 1st November 2006, 12:23 PM   #1
omissis is offline omissis  Italy
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Question Yamaha synth-expression circuit

Hi all, first post here.
Please look at this picture

Click the image to open in full size.

It comes from a Yamaha polysynth; I'm studying this circuit, namely the PH1 and PH2 sections and I'd like to know :

1.Is it a kind of a loudness correction circuit?

2.How the two serial filters interact with the photo resistor?

3.Is that embedding able to make the filters change their slope according to the frequency of the fundamental? This is the main question: on this Yamaha polysynth , if you dropped the pitch down to very low pitches with a ribbon controller the sound became more "filtered" in a continuous way...someone told me that there may be a slope variation from 3dB to 12dB shelf and this may be related with the action of the Vactrol itself which controls the pedal too...
I wish for a simple yet precise explaination of how this circuit works, I'd like to try to build it when my skills will grow .
Thx for your care.
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Old 2nd November 2006, 10:50 AM   #2
omissis is offline omissis  Italy
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Hi
Bumping in. Anybody able to give me any explaination??
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Old 2nd November 2006, 10:50 AM   #3
omissis is offline omissis  Italy
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Excuse me, this topic relates to a musical instrument no doubt but may be a general question about amplification, I'm not really skilled in electronics. Moderators, is this the right place to have any explaination about the questions I put in my first post?
Thx for any reply
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Old 7th November 2006, 03:57 PM   #4
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The picture will not load on my computer.
Maybe that is why?
It tries for ages but then nothing happens. (With Opera and I.E.)
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Old 7th November 2006, 09:11 PM   #5
omissis is offline omissis  Italy
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You can find the picture here , I have an OLD computer with IE6 so you can try even to download the picture by right clicking on the link then clicking on "Save object as"....

Thanks a lot for your reply..
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Old 8th November 2006, 10:47 AM   #6
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Still not working here.
I have even tried a different computer.

Can anyone else see the link or is just me?
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Old 8th November 2006, 08:50 PM   #7
Optical is offline Optical  New Zealand
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picture works fine for me and always has.. cant answer your question though
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Old 16th November 2006, 08:14 AM   #8
omissis is offline omissis  Italy
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*bump*

Any people here can enlighten me about the questions I asked on my first post??
Please, this means lot to me!
M
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Old 20th November 2006, 06:32 AM   #9
Vele is offline Vele  Croatia
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Is that Yamaha DX7?
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Old 20th November 2006, 08:43 AM   #10
omissis is offline omissis  Italy
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No, it comes from a Yamaha CS80, the same circuit is embedded also into the CS50 and CS60 : can you answer to the questions on the first post? Moreover does this kind of embedding give sort of a soft distortion??
Thanks!!!
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