[sdiy] Linux Synth ?

[Linium]

On Mardi 11 Novembre 2003 11:53, Neil Johnson wrote:

> 	http://www.lionstracs.com
>
> How long before someone on list knocks together their own
> LinuxPC+soundcard+keyboard-in-a-box ??
>
> He he he :-)
>
> Cheers,
> Neil

Nice to see the page after that the slashdot effect is gone. :)

It make sense now that linux is customisable enough and PC hardware cheaply 
available to see that kind of boxes. (there are a few other similar synth 
products around linux). 

Make your own one ? I think it should not be hard (nor expensive) to buy a PC 
in a rack enclosure and add a few DIY midi controllers box... and a flat 
screen ? :)

As far as i am concerned instead of using a proprietary DSP processor, i would 
go for hybridation, use the PC as a super CV generator and keep the other 
parts analog. The anti-aliased oscillators (you can find some free as LADSPA 
plugins) are not so great to my taste :) And i like much analog filters :)

My project is to build soon such a monster. The main concept is to recycle a 
middly aged computer and install a low latency linux. PureData or another 
free synth software (GPL license) will provide the midi handling, CV 
generation, and a few audio i/o for further processing.
There are some nice synthesis possibilities with theses soft synth as well (as 
the recent FOF example i gave few days ago showed it), you will have the best 
of the 2 worlds.

The problem with hybrid synth like that is that you would need a somehow 
expensive soundcard with a lot of audio i/o. So i think it is better to use 
real analog VCO, real VCF ans VCA and just use the computer for what it is 
best, audio and midi sequencing and DC signal generations.
There are plenty of analog schemo, the cost of a DIY filter or VCO can be 
really low, specially if you cut cost on the knobs (you will have to create a 
generic interface though if you don't want to use the mouse).   

To drive all the analog circuitry you need a lot of CV signals as well so the 
other part of the concept is too use a DIY external DAC with a mux. The 
computer with the soft synth generates all the notes, triggers, enveloppes, 
LFOs, modulations, etc you need then it is multiplexed into the 2 audio 
channels of the soundcard on its spdif output. The objectif is to have a 
perfect interleaved signal sample rate accurate.
Then unmux everything with analog circuitry. And you should get a lot of 16 
bits CV outs, corresponding to all the CV inputs of your analog modules...
Sure it will do a nice polyphonic analog monster with patch saving, and 
everything else you want. :)

Well i already talked a little about it last year, probably other people are 
working on something more or less similar ? I intend to create a web page 
about the concept but is yet in its infancy. Feel free to email me if you 
want, i would be happy to share ideas about all this.

Cheers,

Linium