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mb_2069 [2017/09/19 09:01]
antichambre [Choices made during prototyping]
mb_2069 [2017/11/08 12:10] (current)
antichambre [Choices made during prototyping]
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 \\ \\
 ==== Precious information found about the 2069 once prototyped ==== ==== Precious information found about the 2069 once prototyped ====
-<WRAP center round info 60%> +<wrap info>The Absolute Rating Voltage is +/-5V, tried and fried ;)</wrap>\\ 
-The Absolute Rating Voltage is +/-5V, tried and fried ;)\\ +<wrap info>CV inputs are in a 0 to 5V range.</wrap>\\ 
-</WRAP+<wrap info>All audio inputs are bipolar and support OverVoltage. A good hard clipping.</​wrap>\\ 
-<WRAP center round info 60%> +<wrap info>The SIG1 and SIG2 has inverted signal audio inputs.</​wrap>\\
-CV inputs are in a 0 to 5V range.\\ +
-</WRAP+
-<WRAP center round info 60%> +
-All audio inputs are bipolar and support OverVoltage. A good hard clipping.\\ +
-</WRAP+
-<WRAP center round info 60%> +
-The SIG1 and SIG2 has inverted signal audio inputs. +
-</WRAP>+
 <WRAP clear></​WRAP>​ <WRAP clear></​WRAP>​
 It seems all VCA cells invert the signal, then same thing for the VCA part.\\ It seems all VCA cells invert the signal, then same thing for the VCA part.\\
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 </​WRAP>​ </​WRAP>​
 </​WRAP>​ </​WRAP>​
-<WRAP center round info 60%> +<wrap info>LOG CV Input for cut-off Frequency is inverted input.</wrap>\\
-LOG CV Input for cut-off Frequency is inverted input.\\ +
-</WRAP>+
 Lowest frequency is at 5V, Highest at 0V.\\ Lowest frequency is at 5V, Highest at 0V.\\
 This CV needs to be inverted too.\\ This CV needs to be inverted too.\\
 \\ \\
 \\ \\
-<WRAP center round info 60%> +<wrap info>LOG CV Input of the VCA seems unusable.</​wrap>\\
-LOG CV Input of the VCA seems unusable.\\ +
-</WRAP>+
 I've got only some NJM2069**BD** for spare then I used the **D** version present in my EX-800 to test Log CV of the VCA in the 2 versions, and it appears to be definitively not usable for both!\\ I've got only some NJM2069**BD** for spare then I used the **D** version present in my EX-800 to test Log CV of the VCA in the 2 versions, and it appears to be definitively not usable for both!\\
 Maybe some other version (AD, DA...) of the chip release this function. I don't know.\\ Maybe some other version (AD, DA...) of the chip release this function. I don't know.\\
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 ==== Choices made during prototyping ==== ==== Choices made during prototyping ====
-- SPDT function added to the VCF outputs to switch between -12dB and -24dB... Of course.\\+**2P/4P Switch**, ​SPDT function added to the VCF outputs to switch between -12dB and -24dB... Of course.\\
 \\ \\
-- SPDT for ByPass ​function... Of course too!.\\+- SPDT for **ByPass ​Switch**... Of course too!.\\
 \\ \\
-- Polarized caps to all audio inputs of the module, SIG1, SIG2, EXT(named like that to be clear) and 1 polarized cap on the output.\\+**DC Offset**, ​Polarized caps to all audio inputs of the module, SIG1, SIG2, EXT(named like that to be clear) and 1 polarized cap on the output.\\
 I checked, with some low offset Op Amps like NE5532 or NJM4580, this is enough to maintain offset and stability in all the circuit. Then no need of big and expensive bipolar caps between stages in circuit.\\ I checked, with some low offset Op Amps like NE5532 or NJM4580, this is enough to maintain offset and stability in all the circuit. Then no need of big and expensive bipolar caps between stages in circuit.\\
  
-Remember, I want the switching between the configuration modes digitally controllable. (MIDI, Recall...You know why ;) I try all the valid configurations,​ and finally choose the 4 most interesting.\\+**Config Modes**, remember, I want the switching between the configuration modes digitally controllable. (MIDI, Recall...You know why ;) I try all the valid configurations,​ and finally choose the 4 most interesting.\\
  
 <WRAP group> <WRAP group>
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 For this purpose I use 3x DG413 Analog Switch on the breadboard.\\ For this purpose I use 3x DG413 Analog Switch on the breadboard.\\
 I reduced it to 1x DG333 and 1x DG413 on PCB.\\ I reduced it to 1x DG333 and 1x DG413 on PCB.\\
-All OpAmps and Analog Switches ​for Audio purpose ​are connected to +/-12V. We wants 2069 distortion only!\\ +All Audio purpose active components like OpAmps and Analog Switches are connected to +/-12V. We wants 2069 distortion only!\\ 
-The 2069 is supplied by +/-5V, then it will the first to saturate.+The 2069 is supplied by +/-5V, then it will be the first to saturate.\\ 
 +\\ 
 +This is the block diagram of the switching circuit 
 +{{ :​antichambre:​block_mode.jpg |}}\\ 
 +Here the circuit is in default state.\\ 
 +The 2P/4P switch has its own line control.\\ 
 +The two Bypass SPST form a SPDT Switch and have their own control line too.\\ 
 +All others 5 switches are for Mode purpose.\\ 
 +5 is too much lines, remember I've got only 4 modes then I may reduce it to 2bits, 2 coding lines.\\ 
 + 
 +I inserted the Switches in the circuit to get this truth table:\\ 
 +{{ :​antichambre:​truthtable.jpg?​200 |}}\\ 
 +As you can see E=B and D=C then it's reduced to 3 lines.\\ 
 +Now I add my 2 required inputs lines, ModeA and ModeB\\ 
 +We can extract that:\\ 
 +{{ :​antichambre:​truthtable_reduced2.jpg?​400 |}} 
 +It's ok, I need 1x OR gate and 1x AND gate, on PCB I use 2 small 74HC1G32 and 74HC1G08.
  
 +And finally I obtain to <wrap hi>​control everything with 4 lines</​wrap>:​\\
 +  * 1 logic line for Bypassing, Active at High.
 +  * 1 logic line for 2P/4P switching, 4P at Low, 2P at High.
 +  * 2 logic lines to code the 4 Configuration Modes.
 +<wrap tip>​Obviously you're not obliged to use this switching circuit. All I/O are individually accessible on pin header.\\
 +You can use it to access I/O or to set it in the static configuration of your choice.
 +</​wrap>​
  
 +- About the **CV inputs** of the chip:
 +I chose to use some 0 to 5V RRIO OpAmp, for precision, voltage limiting and as DAC/CV Summing(Inverter) function.
  
mb_2069.1505811703.txt.gz · Last modified: 2017/09/19 09:01 by antichambre