DIY: VA Hardware synth

Multix · Post by **Multix** » Fri Jul 06, 2007 9:18 pm

Hello

Perhaps I've come onto this forum rather blind, but what the heck!

I've recently decided to start a project (in early stages at the moment) to build a fully functional VA hardware synth. I have the hardware architecture already complete with the casing, and I am planning on building a wooden cabinet to house it in. The motherboard I am using (from an old PC) is really rather....um, large! Compared to that of a micro PCB (this is a big project).

My question is really based around the user interface, though. Are there any communication interfaces to route knobs, buttons, sliders to the motherboard using either PCI/Serial? I thought it would be very cool if a PCI I/O card exists which the interface could map to with numerous ports from that PCI to the motherboard. Basically I'm a little stuck on what to do with the knobs/controller modules (and if I can buy these as a complete set). The synth will run on a customized Linux OS where I am happily writing device/port drivers for any interconnects routed to external controls.

But again, the issue is installing control/knobs/slider modules and where to get them. It would be so much easier if a bank of them exist in the form of USB/Serial modules etc. Writing the software around these shouldn't be a problem...

Overall, it is a very decent project, and I'm going one step at a time. I'll keep you all updated but if you can offer any info/advice, it would be much appreciated!

Cheers.

Post by **nathanscribe** » Fri Jul 06, 2007 10:12 pm

You're mad.

Try Doepfer - scroll down to their OEM goodies on the Products page. Perhaps some of those units might help.

Grief, it's bad enough trying to get a flipping oscillator to work.

eumir · Post by **eumir** » Fri Jul 06, 2007 10:46 pm

maybe you could use this one: http://www.ucapps.de/midibox64.html

Multix · Post by **Multix** » Fri Jul 06, 2007 11:25 pm

nathanscribe wrote:You're mad.

Try Doepfer - scroll down to their OEM goodies on the Products page. Perhaps some of those units might help.

Grief, it's bad enough trying to get a flipping oscillator to work.

Mad but extremely bored! haha

I know what faces me - this job is anything but easy. However, it should be fun getting it to do something interesting at least. Funny how the only thing bothering me is obtaining & routing a decent hardware interface! Cheers for the help guys. I'm planning to start small and add to the project as I go along. No point adding a cluster of knobs if they can't do anything! So a working manipulation of one knob is a start....

I checked out some DIY sites and also articles on the AVRSYN, I wish I could go smaller in regards to the PCB but this motherboard is crying out for some TLC and it's either this or scrap unfortunately. Speaking of scrap, I might take a look through some unwanted electronics and see if there is anything I can 'scavenge'.

In regards to the knob interfaces, well, take the computer keyboard for example. I thought the concept of having the same kind of thing, but with knobs is really very appealing - in one hit of course. I'll check out these sites, and I've just seen some tasty PCI I/O cards too. I'm getting the main board wired up next week all being well.

Cheers

Multix · Post by **Multix** » Fri Jul 06, 2007 11:30 pm

eumir wrote:maybe you could use this one: http://www.ucapps.de/midibox64.html

Nice. You have just hit the nail on the head. Knob based midi controllers.

I notice that has RS232 as well....

MissionBrown · Post by **MissionBrown** » Fri Jul 06, 2007 11:51 pm

http://www.elby-designs.com/avrsynth/avrsyn-about.htm[/img]

Multix · Post by **Multix** » Sat Jul 07, 2007 12:01 am

the_undercutters wrote:http://www.elby-designs.com/avrsynth/avrsyn-about.htm[/img]

Yeah, brilliant little PCB for a synth. I own an Atmel board, but for other purposes - and they really are quite good. The reason my host board is so large is for the fact that it was taken from a disused PC, which was just collecting dust. Everything I need is virtually all there apart from the front interface of the synth. Anything I purchase will need to be hacked anyway, especially the interface - so I will probably end up taking most controllers apart. The size of the board does not justify the operational ability of the finished thing, but at least it has room for lots of I/O expansion

Another option is to use keypads for the interface instead (a bit different and very ugly)

Multix · Post by **Multix** » Sat Jul 07, 2007 1:38 pm

Afternoon all,

Today I have designed a rough schematic & cad outline of a potential interface, and have decided to turn towards something different. Serial / USB / parallel seem the obvious choice as many I/O PCI cards exist for decent connectivity (fully supported by the motherboard). I've decided to use a basic and corny serial computer keyboard hacked and mounted into a wooden panel, as well as a numeral 'soft' keypad (also serial).

As for pans & pots, something customized and similar (in concept) to the drehbank but non commercialized and also a tad smaller too.............

I'm also going for a small but fully functional colorized LCD module (also mounted into the interface) running from a low voltage regulator (these things only use something stupid like 3.5v - 5v) for basic selection with the keyboard & keypads. Two midi I/O cards & hubs which talk to both the knob controllers and keyboard. This thing technically won't be true analog (hence the lack of analog circuitry and dependence on software emulation) but close. An independent pitch/modulation module will be present (also connected to the serial bus) or what ever it is I use...

Running a Linux kernel (latest) with open ended synthesis emulations.

I'm using a beech finish as it is cheaper to obtain.

The prototype outline is quite appealing for this project.

Constantine · Post by **Constantine** » Sat Jul 07, 2007 3:25 pm

Running a Linux kernel (latest) with open ended synthesis emulations.

so you're assembling a small pc dedicated to be a VA synth?

Multix · Post by **Multix** » Sat Jul 07, 2007 4:39 pm

Constantine wrote:
Running a Linux kernel (latest) with open ended synthesis emulations.
so you're assembling a small pc dedicated to be a VA synth?

Kind of yes, but without the other bells and whistles. For example the operating system will be no more than 30mb and I'm not going to be running out of power anytime soon. Despite from being an old motherboard, you can see why this project isn't truly 'analog' as such, I'm just taking it a bit further. Very much a rough DIY synth hack - but with an over sized motherboard.

The real fun starts when you get the motherboard talking with the controller interfaces. It's a pretty weird project but what I have in mind should make it usable at least. I'm not sure the idea of 'keypads' for programming is ideal, but it might offer a cheap alternative and it's different.

Let's give it a go