Adding a External Filter for MIDIBOX SID - how... ?

[smycza]

Hi Everyone

I find the original SID filter to sounds wack, and I'm interested in building a Moog filter to reach more interesting sounds.

I know I can control it using pots/knobs but I would like to control it remotely by midibox sid (like we can control the internal sid filter)

and now, only I have in my mind are questions :)

What is the simplest way to add a external filter to a midibox sid so I could control it the same way I control the internal SID filter ? (I mean - automatation - so I could make patches)

I know that the params of internal SID filters are controlled using midi CC commands, so how could I control the external filter params ?

(not only by it's [filter's] knobs but also by midi commands/events)

I was reading something about DOUT and AOUT and CV outs but I don't fully understand the topic since I'm new to "MIDI world".

Could someone put it out clearly, cause I think I'm not the only one who would be interested in having a external filter working with midibox sid.

best regards, smycza ;)

[Alkex]

Hi!

I would suggest using captain Hasting's digital potentiometer circuit

http://69.56.171.55/~midibox/forum/index.php?topic=2556.msg17995#msg17995

The 4 "electropots" could control your external effects from CCs and patches with a little coding.

I can't wait to get my Ad5204 so I can have a play with them too

Alkex

[raphael]

You can find a CV controlled Moog filter here: http://dropmix.xs4all.nl/rick/Emusic/

Just build a MIDIBox CV (http://www.ucapps.de/midibox_cv.html) and have fun ;D

Read also this thread for more about CV: http://69.56.171.55/~midibox/forum/index.php?topic=5078.msg31431#msg31431

Raphael

P.S.:Digital pots like the suggested one from Alekx are another posssibility. But I think CV is more flexible because nearly every type of analog synth gear uses it.

[illogik]

hi,

you could make the low cost aout (search forum) but you'll have to make it on breadboard (no pcb yet), and i don't think you have to build MBCV; you can connect AOUT to MBSID if you configure it?

D2K did this (or at least with MBFM)

cheers

 

[lemonhorse]

just btw.

i made a SID<=>AOUT interconnecting flip chart  :)

all the best,

- lemonhorse

[smycza]

ok now I understand the concept but [there is always a but ;) ] I have a few more questions, hope not to bore you to death ;)

---------------------------------------------------------------------

FOR captain Hasting's digital potentiometer circuit

---------------------------------------------------------------------

It's a great idea ! Simple, easy to build but how about controlling this stuff ?

On what MIDI event does it reacts ?

I must confess I have no programming skills (microprocs) and for making patches I'm just using JsynthLib.

So is there a possibility to control the externa filter (eg. Moog filter) in the way I'm controlling the internal SID filter ?

how could it be realised ?

--------------------------------------------------------------------

FOR CV outs with AOU module

--------------------------------------------------------------------

It's a bit more compex than  captain Hasting's digital potentiometer circuit but also more efficient.

The same question: how could I controll the params of CV outs ? since on TK web site there is only

a pure schematics wit board layout, and no description how it works or any other documentation, could anybody explain to me

how to control this ?

thanks fo all the answers, hope this could also help the other members and hobbists

best regards, smycza

[Alkex]

smycza,

I havent tried this system yet (Cap hasting's one) but it looks like all that needs doing is this:

-download and add aout AD5204  .INC file to your project folder

-INCLUDE the file to your MAIN.ASM

then if i'm right, the  call  AOUT_AD5204 should be available for use

best regards

Alkex

[TK.]

no description how it works or any other documentation, could anybody explain to me

how to control this ?

thats not true, you only have to read the ChangeLog of MBSID:

   o experimental AOUT support (7 CV out assigned to the existing 
     outputs of the modulation matrix, 1 channel to the filter 
     resonance parameter). For the final version it's planned
     to integrate the AOUT into a seperate modulation matrix,
     and to add new CC's to a seperate AOUT channel
[/code]


For your specific usecase it means: you can control the external filter with the same CCs/LFOs/ENVs, which are assigned to the internal SID filter (this filter can be switched off). Improvements are planned, but it can take some months, since they require a new PIC (with more memory - PIC18F4620), which is currently not usable due to a silicon bug (see MIOS ChangeLog)

However, this doesn't mean that it wouldn't be possible to control external filters --- and in my oppinion, the current implementation is already very powerful (in the meantime I don't use the MBSID without external filter anymore)

There is also a new beta version available (see MBSID board) which provides an alternative "low-cost" AOUT module, see changelog of midibox_sid_v1_7_303beta9:

[code]
   o "ENABLE_AOUT 2" selects a low-cost AOUT module
     (currently it only outputs CutOff as 12bit value, once I got
     the Curtis chips I will do some experiments with 8bit CutOff
     and 8bit Resonance)

The low-cost AOUT module is based on Karl Dalen's schematics: http://69.56.171.55/~midibox/forum/index.php?topic=4037.0

Best Regards, Thorsten.