Novice and PSU dudes....

[fizzicato]

Hello everyone!

I´m a really novice in DIY practices, and after some circuit bending experiments I have started with a MBFM project. My first dude is that in the main page of MIDIbox FM Synth there is 2 PSU mentions:

1 - PSU 5V Wall adapter (Power supply) 9V / 500 mA "MW 17-GS/6" ca. 6 EUR 

2 - PSU +/- 12V Any hint? I'm using a 2x12V transformer which was really cheap, but tinkering with high voltages is only suggested for electronic experts! Please inform me about cheap alternatives!

The first one is for the general power supply of the MBFM?

and the second what is exactly (function).

I´m doing a buy in www.reichelt.de, and i have find the first one but i can´t search anythig of the second PSU, because i can´t speak german, and i can´t understand what is exactly this module. Any of you can give me a lin in reichelt.de of this kind of PSU?

Thanks a lot!!

[tobsen]

hi, i´m planning a fm box too ;D

The 5V PSU is needed to provide the core module.

the 12V PSU is needet for the opl3. But take care!:

the 12Volts are symetrical, this means there are 12V+ | 0V | 12V- rails.

i suggest that you solder your own psu out of a 15V or 18V Transformator.(it´s also good practise and very cheap) all parts are available at reichelt...

i used this very often, its easy to modify and cheap

http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf

sorry for linking to another page ::)

if you would do it on breadboard, take care of the diffrent pinout of the voltage regulators...

[Wilba]

sorry for linking to another page ::)

Linking to another page is encouraged!

That's a great link, and explains in more detail the idea I got from Paia's website.

You don't need to use your own transformer and mains power wiring etc. You can plug an AC adapter that outputs AC (not DC) and connect it instead... this is essentially a transformer with power plug and wiring done for you.

ALSO it is a little known fact in the OPL3 module schematic that you could run the whole PCB with +/-5V instead of +/-12V. I haven't tried this, but if so, it makes it a lot easier and only one bipolar supply is required... you would supply the Core module directly with the 5V coming out of the bipolar supply, NOT through the Core's own 7805. I'm going to try this approach on a breadboard first and will post some results soon.

[fizzicato]

Thanks guys!

Uff very difficult for a beginner this kind of themes.

In resume:

The 5v one is for the core module. Right, but why a wall adapter?.

I have found this on Reichelt:

http://www.reichelt.de/?;ACTION=3;LA=4;GROUP=D483;GROUPID=597;ARTICLE=35113;START=0;SORT=order_col_artnr_besch;OFFSET=16;SID=22g82lmdS4ARYAAClSULg10a93bf2b3204575ebff62674953c120

What do you think about?, can i use the 5v rail for the Core and the +/- 12v for the OPL3?

Sorry my novice questions then..... ::)

[tobsen]

for me, it looks possible, but when i see the price...

i would spend this money defenately for some other things...

[fizzicato]

Yeah, the price is really not good. I´ll try another options. Your link is so good then, but then I need another 5v power suply for the CORE then. But how can i put the 2 PSU in one out for the main wall 240v?

Thanks!

[TK.]

ALSO it is a little known fact in the OPL3 module schematic that you could run the whole PCB with +/-5V instead of +/-12V. I haven't tried this, but if so, it makes it a lot easier and only one bipolar supply is required... you would supply the Core module directly with the 5V coming out of the bipolar supply, NOT through the Core's own 7805. I'm going to try this approach on a breadboard first and will post some results soon.

Razmo tried this, and it didn't work in the first place. After some emails it turned out, that there is a DC offset at the output of YAC512, which will be amplified above 5V after IC3 and IC5. This completely removes the AC part if OPAs are only supplied by +/- 5V, so that the audio output behind IC6 is silent.

Workaround was to add a cap/resistor pair after each IC3/IC5 output in order to remove the DC part

Note also, that using the 5V supply of the digital domain will add some noise to the analog domain. Razmo used a seperate transformer.

Best Regards, Thorsten.

[Wilba]

Thanks TK... I think I'll start using a +/- 9V supply and regulating +5V from the +9V.