Midibix SID (3 cores / 3 SIDs / Control surface)

[jdelgoulet]

Hi all !

I've been searching the forum to find information about how to power up a midibox sid but it appears that the majority of posts are about C64 based power supply and I don't have one. So, I need to build a PSU myself.

Here is my question : does anyone has built such a PSU ?

If so, would it be possible to share Schemas/PCB and create a new part on the wiki so we all have a single entry point to build PSU for the Midibox Sid.

Thanks a lot for your answers !

Julien

[stryd_one]

Hi Julien,

You should be able to find several posts and a wiki page or two on this subject, however, most agree that the easiest path to take is the c64 PSU, if you are able to get one?

[jdelgoulet]

Thanks for your answer stryd_one !

However, looking at the wiki :

" Without the C64 PSU it’s better to use seperate power supplies. One for the SID module (15V/100 mA should be ok), another for the digital modules (7V/500 mA are possibly enough)

It can work with a single PSU (Thorsten used this configuration at the beginning), but the 7805 of the core will get very hot, especially when additional consumers (esp. backlit LCD) are connected."

I'm pretty confuse about the use of 2 power supplies. I mean, I'm sure that someone has done a C64 PSU like over here ... and it would be nice to share the circuit, PCB and components list :  like if the Power Supply was part of the midibox project.

[nILS]

I built a power supply for my 4x SID. It's really not that big a deal.

I used two print-transformers from Reichelt. One supplies 9V~ for the Cores and one supplies 15V~ for the SIDs. There's not really much of a schema... My Cores and SIDs all have the 7805s/7809s/7812s stuffed, so I directly ran the AC from the transformers to all the modules. This may not be the most elegant way, but it's really easy =)

Just make sure you have some serious isolation on the 230V parts!

[Manticore]

Since I do not have a C64 PSU, I built a custom PSU. It consists of a transformer with separate coils (this is important to avoid ground loops); mine was from Pollin and has an 8V/1,7A coil, a 12-0-12V/0,8A and 4V coil (which is not used yet). Of course you could take two separate transformers; this is a matter of available space. I made a 5V stabilized output, which serves the cores except the master core; this is supplied by unstabilized 10V and a voltage regulator on the master (this is for the display illumination; ). I also stuffed a -12V regulator in the PSU to have a balanced (symmetrical) supply for op-amps (maybe I will build an audio mixer later). The regulators are attached to a heat sink; this will not get too hot. All voltage grounds are connected in the PSU, so you must take care to not connect the a second time. On the boards the input capacitors (1000uF) are stuffed; rectifier and regulators are replaced by appropiate bridges (except on the master, see above).

There is absolutely no hum and no hiss on the audio outputs.

Best regards,

Manticore

[stryd_one]

There is absolutely no hum and no hiss

... in outer space.... ;)

There's no reason that your PSU should be noisey, it may be the quietest around - but zero noise won't really happen...

If you're after a PSU with schematics and partslists and instructions etc then you should look for NorthernLightX's work, there's a monster thread all about it.

[rutgerv]

I've created a PSU for my 8xSID MidiBox with 8 additional Moog filters. The schematic and some explanation can be found here:

http://www.midibox.org/forum/index.php?topic=9236.0

[Manticore]

There's no reason that your PSU should be noisey, it may be the quietest around - but zero noise won't really happen...

Of course not the PSU is noisy or not, but the audio signal might be, due to wiring; that's what I meant. My first MBSID prototype had a PSU with one-way rectification by a single diode (which is absolutely ok for digital stuff); this caused serious 50-hertz-hum on the audio signal.

...BTW, zero noise happens when you short-cut the audio out... ;). Has anyone already thought of including a noise gate inside the MBSID box and maybe have a simple schematic for it?

Best regards,

Manticore