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Analog  Outs


msi

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With the move to the pic18 is it possible for the Midibox to control devices via something like an analog out.  I'm trying right now to figure out how to build a mixer using something like the Midibox MIOS to control groups and such.  The dout modual can be used to trigger relays to open/close but controlling something like the level of the channels hasn't come to me.  I'm going to work on this in levels, starting with a small distortion type box using solidstate components with midi controlled gain/vol/EQ and switching.  Then move on from there if I succede.  Anyone have any comments on how this can be done with the current state of the MIOS?  Thank you.

William

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Hi msi,

The cheapest solution  would be to use VCA's for the analog audio path. And then use MBMF fader control voltage to also drive the VCA's.

The easier but more expensive solution is to use motorised audio faders (eg. P&G). They have both a control track and an analog audio track. This is the most preferred method cos the audio does not have to go through another op-amp and the fader just replaces your existing mixer's fader.

Peace

Frank

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Another solution : use LDR and Led! this is a better way than relay (LDR and led is use in tube amps such as Mesa Boogie ect...), and if you can control the led intensity, you can control de value of the LDR... without any VCA, you just replace all the pot by LDR, and maybe a little more, to control them with an Analog signal! The midibox as got no Analog out, but I don't think it's a hard thing to implement... (CAN on DOUT?)

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Nope, no AOUT (yet?). With a digitally out its kinda stupid to realize something like that. You would have to get the DOUTs working as pseudo bits (e.g. 7 Outs as 7 Bits for a solution of 128 steps) having the proper resistors and/or diodes at the outs for regulating the  brightness of the LEDs.

Another soultion would be to have several MIDI to CV devices and then using a VCA as stated above.

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Possibly SmashTV means the DS1801 from Dallas Semi.; this chip provides two digital potentiometers with logarithmic characteristic which can be controlled via a simple serial protocol. Several DS1801 can be cascaded to a long chain.

Datasheet:

http://pdfserv.maxim-ic.com/arpdf/DS1801.pdf

The serial protocol (called SPI) is exactly the same like for the SID module. So, no special MIOS extension is required, you just only have to connect the first DS1801 of the chain to J10 of the core module, thereafter you can transfer the command words with the SID_SR_Write routine in sid_sr.inc of the MIDIbox SID application (note that this routine has been optimized for speed and could be written in a less complicated way ;-))

Best Regards, Thorsten.

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Yeah!! this way it's possible every pot of a mixer channel! I've got schématic of analog mixer (with preamp, eq, aux, buses ect...). BUT! I don't think it's a good idea to replace every pot by DS1801 in a mixer : it will be cheaper to use DSP... :-/ Or another solution with a linux box, a good CPU and multiple sound card (for a mixer, we don't care about sync between card)

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