73 replies to this topic

[Flying Panther]

BTW some of the circuit was stolen from this: http://xkcd.com/730/
but shhh... don't tell him, he may want royalties.

Hahaha, I had a good laugh while reading that schematic! Thanks!

[Hawkeye]

yo, cool background track! mbfm-powered? very nice!

[Siempre La Luna]

yo, cool background track! mbfm-powered? very nice!

TK really brought 'cool educational television theme song' vibe on that track.

[m00dawg]

Will the schematics be posted online? I am trying to be a bit more diligent about testing as I go and really want to make sure I get continuity on the tracks for the SMD devices. Since some of them run under the chips, it would be easier if I could have a PDF I can zoom down into (much like the MB6582 one). If no, I can make due but thought I'd ask

[Wilba]

Wiki updated:

Here is the PDF of the base PCB. Ground plane is removed. Pads with no tracks can be assumed connected to ground.
http://www.mb6582.or...e_PCB_Rev_1.pdf

[m00dawg]

w00t thanks Wilba!

[m00dawg]

Well it took two late nights but my sammichFM now powers up and shows Ready! I'll be trying to load the firmware today, though I haven't been brave enough to supply power to the FM chips just yet.

Wilba, you did a fantastic job with the kit! It has all the wonderful details that made building it fun and even relaxing. The little things, like having the header pins snap-in (which meant I didn't have to take the header down, tack it, then burn my finger while trying to adjust it so it's vertical) and having snap-in sockets. Very cool, and the LCD looks sexah too!

[Ixox]

WOW... Impressive..
Congratulation for this beautifull little box.
I'll definitely have to order one... maybe next month.

I'm surprised to read in the feature list:
"4 simultaneous instruments of 6 voice polyphony each, plus drum kit. Each voice is a 4 operator waveform."

That makes 24 voices of 4 operators + drum kit ??
That sounds much more than in the opl3 spec:
"6 four operators melody sounds + 3 two operators melody sonds + 5 rythm sound".

Did i miss something ?
Thanks,

Xavier

[Wilba]

No, you're right... I'm paraphrasing TK's MIDIbox FM specifications here: http://www.ucapps.de/midibox_fm.html

Maybe it should be written as "4 simultaneous instruments of up to 6 voice polyphony each, plus drum kit. Each voice is a 4 operator waveform."

Or you can propose an alternative.

[Ixox]

OK. thanks for the clarification :-)

Maybe something like :
"6 four operator voices played by 4 simultaneous different instruments plus drum kit."


Xavier

[trilader]

I think there is an error in the voltage testing picture (the one with the colored dots) for the base PCB. Pin 2 of IC9 (2nd from the top on the left row) is connected to GND and not +5V. I noticed that during the voltage/continuity testing phase and looked it up in the PCB layout PDF.

Regards
trilader

Edited by trilader, 07 May 2011 - 19:13.

[m00dawg]

Are you using the 1.0 version of the build guide? I believe that issue has been fixed in that version?

[Wilba]

I emailed the link to the v1.0 build guide but forgot to update the link in the wiki. Fixed now.

Also, until the build guide is updated again, I recommend MIDIbox FM v1.4c which fixes issues with short notes for drum sounds.

http://www.ucapps.de...ox_fm_v1_4c.zip

[fussylizard]

Crikey! I slack for a few months and come back and Wilba's gone and designed a whole new project. Beautiful job as always!

[trilader]

Ok, no problem then. I was on my desktop and didn't look at the version number.

[kristal=]

Maybe a potential PSU candidate for the sammichFM?

http://www.pollin.de...ernetzteil.html

Reichelt doesn't carry suitable PSUs, at least I haven't found one.

[m00dawg]

That looks like a switched PSU to me (though I'm having Google Translate fail). You'd want a linear regulated PSU as the best option typically. Switchmode will work, but can induce noise (and usually causes a big flame-war here on the forums about half the time it's mentioned )

[Hawkeye]

Also quite often, voltage-switchable psus like the one you mentioned do provide the maximum current (1A from specs) only at the lower voltage settings.

[kristal=]

@m00dawg: Well, the description says "stabilisiert" i.e. "stabilized", which to me indicates that it's a transformer based psu. Do switch-mode PSUs need to be stabilized? Probably not. But I'm not sure about this. The product description is quite poor.

@Hawkeye: The sammichFM draws about 200mA according to the sammichFM building guide. If 1A is provided only in the lower voltage range, I guess at least 200mA should be provided at 9V. But still guessing...

@all: Any recommendations for a transformer based (linear) power supply here in Germany/Europe?

[Imp]

Don't you guys have local fleamarkets? There are lots of those PSUs available round here...