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SID filter issues


Guest spagano

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Guest spagano

this is my first project in MBHP land.

i built a core and a sid.

everything is lovely except it seems as if the filter in the sid does not work. has anyone encountered this problem ? are there particular components on the sid board that could affect filter performance ?

cc 46 is cutoff and cc 47 is resonance - correct ?

i am working on an editor in max/msp. when it is ready i will make a little announcement.

thanks

- scott

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Hi Scott

This is from the SID page. You might find it usefull.

The two caps between Pin 1/2 and 3/4 of the SID are required by the filter. The ideal values may differ with the SID version you are using, so it's possibly a good idea not only to purchase the recommended 470 pF caps for 6581, 6.8nF caps for 8580 (which have been taken from the original schematics), but also some other pairs: 1nF, 2.2nF, 4.7nF - just to check for any better result.

Good luck

Ian

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Hi Scott,

fine fine - one more MIDIbox SID which is up and running! :)

Beside of the possible problem which has been mentioned by Ian, another reason could be that you forget to select the filter mode and to route the VCO outputs to the filter.

This has to be done with the MIDIbox SID editor, or via CC:

CC # | Hex | Description                                  | Range       | Reset
=====+=====+==============================================+=============+======
  44 | 2Ch | Filter Channels                              |             |    0
     |     |   Bit 0: Filter for Voice 1 on/off           |             |
     |     |   Bit 1: Filter for Voice 2 on/off           |             |
     |     |   Bit 2: Filter for Voice 3 on/off           |             |
     |     |   Bit 3: Filter for Audio In on/off          |             |
  45 | 2Dh | Filter Mode                                  |             |    0
     |     |   Bit 0: LowPass on/off                      |             |
     |     |   Bit 1: BandPass on/off                     |             |
     |     |   Bit 2: HighPass on/off                     |             |
     |     |   Bit 3: Voice 3 off                         |             |
  46 | 2Eh | Filter CutOff frequency                      |  0-127: val |  127
  47 | 2Fh | Filter Resonance                             |  0-127: val |    0
-----+-----+----------------------------------------------+-------------+------

Example:

 CC 44 -> 7

 CC 45 -> 1

Best Regards, Thorsten.

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i am working on an editor in max/msp. when it is ready i will make a little announcement.

Cool!  I was wondering if I needed to do this, but it would be hard to justify the time considering I have no use for the SID module.  Not that the SID is not fun, I'm just at the other end of the spectrum in the way I use MIDI and audio. :)

For those who don't know, an editor written in max will run on almost any Macintosh, and with a Windows version of max due out sometime this year would allow for easy cross-platform development for anything related to the MBHP from firmware updates to an easy editor for custom setup of the MIOS.  If you add msp into the equation (and route your audio through your mac) you could easily write a custom real-time audio processing setup with a control surface.  EQ, delay, reverb, pitch transpose, mic modeling, etc. are all possible and easy.  

A majority of the VST effect plugins out there were written using max/msp.

Let me know if you have any problems writing the editor, I have been in patch cord hell with max since it was an Opcode product.

 :)

Later!

SmashTV

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