Power supplies - MFOS/Doepfer

macmoc · Joined: May 29, 2011 Posts: 2 Location: US/NewHampshire

Hi all,

My first post. Am new to the DIY community. I'm still in the planning stages, and i'm wondering about how easy it is to power modules of one company with the power supply from another.

Case in point: MFOS and Doepfer. Most modules from both companies require +/- 12va. From the MFOS site I know their supply is +/- 12vac regulated. Doepfer is harder to verify. From their site i see this statement for the A-100MINT:
"requires an AC/AC adaptor with 7...9va / 500mA AC output (not DC !!!), "
So, i know the *adaptor* is AC output, but can i assume that the output of the *power supply* is also AC. Anyone know?

Ultimately, i'm trying to minimize the number of power supplies i need to purchase - which might mean using a doepfer supply to power MFOS or vice versa. Or should i play it safe and only power modules with a power supply from the same company?

Thanks

blue hell · Posted: Sat Jun 04, 2011 2:53 pm Post subject:

macmoc

You mess up a couple of things it seems ... you'll always need a DC supply for all synths, but all DC, unless a battery, starts it life as AC from a mains outlet. It will have have to be converted to a lower voltage and to DC.

Voltage is measured in Volts, the symbol for that is V). VA is also a symbol used, but that stands foe Volt Ampere, or Watts, which is a unit for power, and not for voltage. Power is a product of Voltage and Current (the unit for current is Ampere, abreviated with A).

Now as for the conversion from mains AC to a DC voltage suitable for your synth. The voltage will be transformed down first from 230 V to something like 12 V, or 15 V, depending on the actual DC output voltage needed later.

Then that low voltage AC is transformed into DC by rectifying it and filtering it; usually it will be stabilized too after that.

So for Doepfer, the modules will also run on DC - and the voltage they need is +/- 12 V as well. Now a Doepfer system may come in with a built in rectifier and stabilizer and make use of an external transformer - I dont really know that, but .. it's sort of what you wrote down, and its a sort of sensible design decision to get the mains voltage out of the cabinet.

Antimon · Posted: Sat Jun 04, 2011 3:08 pm Post subject:

macmoc

I think you're talking about the DIY power suppy from MFOS, right? Hence the importance of having a wall wart with AC, not DC. I actually have that kit, though I haven't dared put it together yet - power supplies scare me. I'm a bit of an electronics newbie myself.

Anyway, it seems to output +-12V, and that's what Doepfer takes, so that should be ok. You should also be able to hook up most MFOS modules to a Doepfer power supply, since MFOS accepts both +-12V and +-15V as power. I have a MFOS SoundLab Ultimate hooked up to a Curetronic +-15V power supply myself.

I know we're talking about power supplies, but you should also be aware of the panel difference between Eurorack and the bigger stuff like MOTM (I think it's called). I got a finished panel for my SoundLab Ultimate, and that was in MOTM format, which doesn't fit in a Doepfer (Eurorack) case.

If I'm wrong about anything here, I hope a seasoned DIYer can jump in and correct me.

/Stefan

wmonk · Posted: Sat Jun 04, 2011 3:49 pm Post subject:

Welcome on the forum macmoc!

macmoc · Joined: May 29, 2011 Posts: 2 Location: US/NewHampshire

First, many thanks to the responses. I definitely did not expect such quick responses from the Netherlands and Sweden!

Blue Hell - thanks for setting me straight on my mistakes. Also, I went back to the MFOS site and realized i misunderstood something. What i thought was the output of their supply was actually a specification for the adaptor. However, the most important part of your explanation was that ALL synths use DC - even if the output of the adaptor from mains is AC.

Antimon - yes, i'm referring to the MFOS Wall Wart Bipolar supply. This relies on a "wall wart" adaptor to handle the mains. I definitely do not want to work directly with mains voltage - i don't have the skills. The "wall wort" adaptor seems much safer. But i'm also referring to the Doepfer DIY kit #1 which also uses an adaptor. I'm trying to sort which one to use. The Doepfer is nice because it includes a couple bus boards. MFOS doesn't seem to offer a bus board (unless they've done so recently). I definitely appreciate the part of your response where you stated that you power an MFOS SoundLab with a Curetronic supply.

wmonk/Antimon - Ah yes, the panels. I'm trail blazing here with my own panel format. I'm working on them . . . in my secret underground lair. More on those as i near completion.

Thanks for the welcome and help. Greatly appreciated.
tom

marvkaye · Joined: Mar 14, 2011 Posts: 225 Location: Fla

Since we're talking about power supplies I thought I'd share the first DIY project I decided to jump into... it's the MFOS 9-15v adjustable LM317/337 unit for which Ray sells PCBs. I built it primarily to use for testing other modules, so have added a pair of ammeters to monitor current flow on each rail. While the meters will read up to 1.999A on each leg, the fuses on top of the meter enclosure limit current to 1A JIC I slip and short something out... I figured it was better to be safe than sorry.

Pictures #30 & 60 show how it started out, #140 shows the addition of the meters and the separate +12v supply to power the +15 meter... the -15 one is driven by the -15 side of the PS. (I was going to use a modified wall wart for the meter supply but found the unit shown in the photo at my local surplus store today for a whopping $3.50. Amazing what I find there... if you're ever in Orlando, go to Skycraft, you won't be sorry. Both enclosures came from there as well.) The meters monitor only the rails so I can see exactly what's going on with whatever is under test, the left meter shows current on the -15 rail, the right one +15. Photo #150 shows the PS powering my MFOS 1v/octave calibrator, another fun project that turned out very well in the end.

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MFOS adjustable PS with ammeters

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MFOS adjustable PS and 1v/octave calibrator

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MFOS adjustable LM317/337 power supply

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MFOS adjustable PS "guts"

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