SID in a 5,25" cd-rom case - in your PC

[kc]

Hello forum,

some time ago i sat around with Mister S.M., and we racked our brains together about how to integrate the beloved MIDIbox SID design into a standard 5,25" cd-rom case, to have it internal to our PCs. A lot of considerations were made regarding the SID power supply, internal connectivity and the user interface.

The latter is the most obvious problem, as a tiny 5,25" bezel won't allow for much of a display or onboard controls (ingredients as 'sexy' and compact as a NOKIA phone LCD display were not yet in reach at this time), everything has to be done via MIDI. As neither S.M. nor me likes to have to mess around with JAVA, S.M. in the meantime has circumvented this by creating a VST-plugin, which will remote-control your SID straight out of your sequencer. Head over to http://69.56.171.55/~midibox/forum/index.php?topic=5116.0 to learn more about this..

the S.M. SID

the kc SID

-- The S.M. approach:  (currently no further link available)

he went ahead in construction and chose to use a 6581. This led into the requirement of a dedicated 15V power supply, as a common pc only will provide 5 and 12V. S.M. solved this,  controlling it by a 12V relay inside the pc.

[As you can see from the link pictures, S.M. uses quite an unusual pc, whose power supply is unusual as well, to say the least. I also use one of these. Redundant power supplies with prolonged internal 230V wiring and lots of space make things somewhat easier  ;D. These are old siemens server cases, converted to take a standard ATX board]

The S.M. SID normally is connected internally onto the cd-rom port of the soundcard. On the outside you have RCA connectors and switches to determine the way of in/output, accompanied by the MIDI in/out/thru trio and LEDs for indicating what's going on. S.M. decided to give it a 'circly' design to fit with his Microwave pc - which rocks as well.  ;)

-- The kc approach: see http://www.pheuron.de/pics.php#sid

i used a 8580 requiring only 12V, so it runs straight off of a molex plug from the pc power supply. This SID is connected to the cd-rom input of the sound card as well. The power switch has been taken off an old atari ST. Another  difference is the d-sub connector for a bankstick. So is the use of 6,3mm phone jacks, it will match to my external mixing desk. The jacks have built-in switches, which will route the in/out to the internal connections if nothing is plugged in. The front plate is mounted on an u-shaped aluminum carrier which holds most of the front components; both have been brought in shape with a portable electric drill and some rasps. All modules sit on top of the original cd-rom PCB as i wasn't too keen on drilling numerous times through the cd-rom steel sheet [edit: and protruding screw heads would not have been too practical in order to have it fit into a standard 5,25" drive bay].

I have had a serious design mishap that killed at least  one 8580 and left another with 'damaged vocal chords'  :P :

When plugging in something to the front (making connection with said mixing desk), the SID got spikes of 50Hz at... 5V straight to its output! Talk about one deadly ground loop :o See this picture of such a spike happening, measured directly at the SID output:

To prevent this from doing further damage, i added two 1:1 transformers to in/output, which solved the problem. Maybe it was caused by some funny AC wiring in the stone-aged house i lived in then, maybe the two victims fell onto the account of the typical pc switching mode power supply.

Well, i hope this looong read hasn't been a boring one and was somewhat enjoyable. Our next project most likely will be a FM synth in the very same kind of casing; let's see who builds it first  ;D.

kind regards    kc

(edit: urls fixed)

[kc]

two more things:

as you can see from the picture, the largest part of the external sockets is located in the lower half of the cases. This has been done so you still can see or use the upper features without being disturbed by plugged-in cables hanging down. For the very same reason, you might want to install such a cutie -below- cd-rom drives and other protruding things, as, for example, MIDI cables don't quite match with open cd trays  ;) .

On S.M.'s case, the rear end is relatively open. In conjunction with the ex-spindle hole on top this allows for a bit of natural  convection cooling. My case, being an old cd-writer with rear fan, only has an added DC plug on the rear, just in case i want to use it outside of a pc. The rest is still original, even the IDE port still is in place. The fan didn't need to be connected, as there don't seem to be any thermal issues.

kind regards  kc