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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
wrapping up Sub Commander, need power help
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the architech



Joined: Oct 29, 2010
Posts: 55
Location: Philadelphia

PostPosted: Tue Jan 07, 2014 8:55 pm    Post subject: wrapping up Sub Commander, need power help Reply with quote  Mark this post and the followings unread

So, I haven't really been working on any of my DIY projects for a few years, and I'd like to finish the projects I have on my shelf. One of those nearly completed ones is the Sub Commander from MFOS. I remember I shelved it after hitting a bit of a wall with how I'd power it. I think I debated building an internal power supply, but now I'd much rather just buy a 12V brick and wire a DC jack. Here's where I'm at though:

I wired a foot switch to the board and 1/4" in/out jacks, but never wired anything to the 2.1mm DC jack. My wiring doesn't match my notes, so I'm not positive I did it correctly, and I never wired anything to the DC jack, so I don't know where that needs to fit in. And I can't remember how to determine which of the three feet on the DC jack is positive, negative, or ground. I've tried finding diagrams online, but most refer to 9V or some other weird config. Anyone know a good diagram or site to show how a 12V jack and foot switch need to be wired into a pedal? Sub Commander is big, but it should interface the same as any other pedal, I think.
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PHOBoS



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PostPosted: Wed Jan 08, 2014 4:22 pm    Post subject: Re: wrapping up Sub Commander, need power help Reply with quote  Mark this post and the followings unread

hmm ,. I haven't build a sub commander but maybe I can help you a bit anyway. I just took a look at the schematics and it needs a dual supply.
I don't see a PSU section so you have to provide that yourself. If you want to use a 2.1mm DC jack then you can only power it with a single DC
voltage or an AC voltage. single DC voltage isn't useful in this case (unless you install 2 DC jacks), but you can use an AC voltage to create a
dual DC supply Very Happy. Here's a link to the MFOS Wall Wart Power Supply.

You mentioned 3 connection on the DC jack, 2 are for power, 1 is a switched contact that is often used when a device can be battery powered
aswell, and this way the battery will be disconnected when you plug in a DC supply. The easiest way to find out which ones you need is to plug the
power into it and then using a multimeter to check what connections carry the voltage. This is also useful if you want to check the polarity with
a DC supply.

I can't really help you with the pedal since I don't know what you want to use it for. (true bypass ?)

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the architech



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PostPosted: Wed Jan 08, 2014 6:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

oh geez, I must've missed that it needs a dual supply. what the hell? I thought I would just wire the 12V DC jack to the +12V & -12V connections on the PCB. I'm so confused... how does that work? I don't really know anything about doing it in AC. I thought about the MFOS Wall Wart, but I'm kind of intimidated by it and wouldn't know how to house it. Can't I just get something like a pedal power supply and distributor brick like you would for any other array of pedals?

I'll be totally honest, I know passable schematics, and mostly get by just by following the instructions. This was a hobby that interested me, but never had a mentor or teacher. I've successfully completed a few small projects, and this is the largest one I've tackled. I've never been any good at improvising or troubleshooting :/ I may have bitten off more than I can chew with this one.

Yeah, I mean I am looking for true bypass with the foot switch. I was surprised one wasn't included in the design.
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PHOBoS



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PostPosted: Thu Jan 09, 2014 7:26 am    Post subject: Reply with quote  Mark this post and the followings unread

the architech wrote:
...I don't really know anything about doing it in AC. I thought about the MFOS Wall Wart, but I'm kind of intimidated by it and wouldn't know how to house it. Can't I just get something like a pedal power supply and distributor brick like you would for any other array of pedals?¨

As far as I am aware pedals work on a single supply (usually can be battery powered) and if they do need a double supply they should have a
PSU that comes with it. So no that's not an option. Don't worry about AC, it's not the mains voltage Wink just the ouput from a wallwart transformer,
the only difference with a DC wallwart is that that one has a rectifier and maybe regulator circuit build in to convert it into a single DC voltage. Dual
supplies are available (for synths) btw, but I think they're a lot more expensive and you might have to connect the mains side yourself.

You could build it on stripboard, there's a layout posted here or order the PCB. As for connecting it, there are 2 inputs for the AC
voltage from your wallwart, and 3 outputs: -12V, GND, +12V which will connect directly to the sub-commander PCB.

Quote:
I'll be totally honest, I know passable schematics, and mostly get by just by following the instructions. This was a hobby that interested me, but never had a mentor or teacher. I've successfully completed a few small projects, and this is the largest one I've tackled. I've never been any good at improvising or troubleshooting :/ I may have bitten off more than I can chew with this one.

It doesn't look like a very easy project, but you can do it! Very Happy And there's a whole forum here with people who have a lot of DIY experience that can
help you with it. And the chat can be a useful place to get some help with your projects too.

Quote:
Yeah, I mean I am looking for true bypass with the foot switch. I was surprised one wasn't included in the design.

I'd have to look into the schematic more to see what kind of output(s) it has, not sure if something like that is possible or at least easy to do. But
you'd need a powersupply and test the circuit before you can add that anyway.

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the architech



Joined: Oct 29, 2010
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Location: Philadelphia

PostPosted: Thu Jan 09, 2014 7:49 am    Post subject: Reply with quote  Mark this post and the followings unread

I mean, the entire build is pretty much complete, except for the power. And perhaps the true bypass footswitch won't work, but I wired it in based on a schematic someone had tossed up on here a while back, so fingers crossed on that.

So, assuming I build the MFOS Wall Wart, how exactly do I get power from it to the Sub Commander? I can wire the Wall Wart output to something like a 2.1m jack right? And then just plug a wire from that jack to another jack on the Sub Commander? Then what, just wire the jack on the Sub Commander to the +/-12V lugs on the PCB? I mean, that sounds straight forward enough.

It gets more confusing when I consider the footswitch I wired in, but I guess I could remove the wiring for it and return it to the standard layout to make sure the thing works out. Anyone try to wire a bypass switch for the Sub Commander? I didn't think it'd be so difficult to switch between clean and effected signal, but then again I've only really worked with small 9V stompboxes before...

Any good resources to help me learn to understand schematics better? Like, I get the symbols and all, but I wouldn't know how to figure out whether or not a true bypass switch would work or how to work it in without someone else giving me a wiring diagram.

Thanks for the help! I'll check out the chat group when I get home. Anyone from the Philadelphia area? I saw there was an events page for there here in the forum, but looks like it's been defunct for a few years.
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PHOBoS



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PostPosted: Thu Jan 09, 2014 9:02 am    Post subject: Reply with quote  Mark this post and the followings unread

the architech wrote:
So, assuming I build the MFOS Wall Wart, how exactly do I get power from it to the Sub Commander? I can wire the Wall Wart output to something like a 2.1m jack right? And then just plug a wire from that jack to another jack on the Sub Commander? Then what, just wire the jack on the Sub Commander to the +/-12V lugs on the PCB? I mean, that sounds straight forward enough.

You would have to put the MFOS supply inside the housing for the sub-commander. Or you would need somekind of 3 prong connector
(don't use stereo phono jacks for this), since you have +12V and -12V but also GND (if you leave that one out you get 24V DC).

Quote:
Any good resources to help me learn to understand schematics better? Like, I get the symbols and all, but I wouldn't know how to figure out whether or not a true bypass switch would work or how to work it in without someone else giving me a wiring diagram.

hmm, I learned most just from looking at a lot of them and reading descriptions, and just building a lot Laughing If the sub commander just has one output a bypass switch should be easy (it won't turn of the power though).


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the architech



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PostPosted: Thu Jan 09, 2014 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, since I've already built the housing and don't have room for it, that's not really an option. Plus, I was hoping to do other builds in the future (like a 16 step sequencer), so I'd like to use it for those as well (that's possible, right? I thought I had read you could use it to power multiple units).

I knew that hardwiring it would be the easiest, and probably most efficient, but since I'd rather have it be independent and not in the enclosure, I'd like to be able to disconnect it. I have 3-prong 2.1mm DC power jacks. Wouldn't those work? I never even thought to use an audio jack for it, haha.

Yeah, there's only one out lug on the PCB. I don't care if it doesn't turn the power off (although, adding a power rocker switch to the back would be nice...). Considering this has similar ins/outs on the board, and inout/output audio jacks, wouldn't the bypass footswitch wire the same as any other stompbox? Does the fact that it's 12V make a big difference?

I really appreciate the help, btw. I wouldn't have gotten anywehre in circuitry without this forum Very Happy
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PHOBoS



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PostPosted: Thu Jan 09, 2014 9:37 am    Post subject: Reply with quote  Mark this post and the followings unread

the architech wrote:
Well, since I've already built the housing and don't have room for it, that's not really an option. Plus, I was hoping to do other builds in the future (like a 16 step sequencer), so I'd like to use it for those as well (that's possible, right? I thought I had read you could use it to power multiple units).

yes that's definitely possible, and actually something I've been doing too. Allthough using a single AC wallwart to create a dual DC suppy isn't the
best option (better would be a center tapped transformer), I doubt it'll give you any problems. Just keep in mind that you can only power so
much with it, at some point you'll need another or 'bigger' PSU.
I'm not familiar with any 3 prong 2.1 mm connectors. do you have a photo ? I use XLR myself btw.

Quote:
Yeah, there's only one out lug on the PCB. I don't care if it doesn't turn the power off (although, adding a power rocker switch to the back would be nice...). Considering this has similar ins/outs on the board, and inout/output audio jacks, wouldn't the bypass footswitch wire the same as any other stompbox? Does the fact that it's 12V make a big difference?

nope voltage doesn't make any difference, the footswitch should just be a toggle switch with selects either the input directly or the output of the
sub-commander. Or even better, use a double toggle switch which also disconnects the signal to the sub-commander. (I think this is actually
the most common way of doing it).

edit: this might be useful.

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the architech



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PostPosted: Thu Jan 09, 2014 12:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I figured if I ended up doing a bunch of stuff, I'd make another one. Right now the Sub Commander and 16 Step Sequencer are the only 12V units I have on my plate.

Yeah, I mean I have jacks like they're showing in those Beavis diagrams. I've used that method of power wiring before on stompboxes, and that's actually what I was going to do, but after this thread I got the impression I couldn't do something like that... I mean, given what people have said, and considering that it's 12V, not 9V, are those diagrams even applicable?

XLR is a good idea. I think I have a few spare 3' XLR cables laying around.

I've been using standard 3PDT foot switches wired like this:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Here's another question, if I'm not going to put the MFOS Wall Wart inside the Sub Commander, any suggestions on using an independent housing? I don't really have good access to a shop anymore and would really rather just buy sturdy aluminum unit if I can.
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PHOBoS



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PostPosted: Thu Jan 09, 2014 1:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

the voltage itself isn't a problem,. the fact that it's a dual voltage is Wink btw. in those diagrams it's labeled as an AC wallwart,. which might be a bit
confusing since it's output is DC. Not that it matter's much it was only to show what the function of those 3 prongs is,. and why it's useles for a dual
supply. It's fine for the AC connection though.

Keep in mind that XLR cables are usually made for microphone signals which is very low power, and I think there is some kind of impedance
thing involved too Rolling Eyes It would be better to make some custom cables for it, soldering XLR connectors kinda sucks though.

switch diagram looks good, nice that it also switches the input of the sub-commander to GND when bypassed, and a fancy LED aswell Very Happy

Can't really suggest anything to house it, I'm using wood mostly myself lately, well MDF actually it's not even real wood. I have used, and
sometimes still use, some plastic project boxes, but I got those at local suppliers. Metal would be a better option though.

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the architech



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PostPosted: Thu Jan 09, 2014 2:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

What I don't get about that Beavis diagram though is what each leg would be if I were plugging into the MFOS PSU. I mean, the two legs are positive and negative, right? and isn't the third just used to bypass a battery? If I'm running the 12V AC though, do the 3 legs then become +12V, -12V, and ground?

And if I'm getting that +12V, -12V, and ground incoming, would I wire the +12V directly to the 12V terminal on the PCB as shown in my diagram? I'm assuming the ground would just wire directly to the GND terminal on the PCB also. Would the -12V wire directly to the ring on the input jack as shown in my diagram, or directly to the -12V terminal on the PCB?

I was trying to talk this out with an electrical engineer in my office (he's never done this sort of thing, but went through schematics in college and understands the principles), and we couldn't understand why the on switch would send positive power to the sleeve of the input jack and negative to the ring. Is that just to ground it? Couldn't you just wire the 3PDT directly to the GND terminal?

Know any good suppliers of metal enclosures? I don't know any local stores that might carry this kind of stuff...
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PHOBoS



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PostPosted: Thu Jan 09, 2014 3:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

the architech wrote:
What I don't get about that Beavis diagram though is what each leg would be if I were plugging into the MFOS PSU. I mean, the two legs are positive and negative, right? and isn't the third just used to bypass a battery? If I'm running the 12V AC though, do the 3 legs then become +12V, -12V, and ground?

You'll only use it to connect the AC wallwart to the MFOS supply, so AC in AC out. (forget about the third prong it won't be used) And from the MFOS
supply you'll get the +12V, GND, -12V which you'll then have to connect somehow (XLR) to the commander, sequencer etc.

Quote:
And if I'm getting that +12V, -12V, and ground incoming, would I wire the +12V directly to the 12V terminal on the PCB as shown in my diagram? I'm assuming the ground would just wire directly to the GND terminal on the PCB also. Would the -12V wire directly to the ring on the input jack as shown in my diagram, or directly to the -12V terminal on the PCB?

ah there is actually something incorrect in your diagram, at least for a dual supply, it would work with a single supply. What you labeled as -
should be GND. The -12V only goes to the sub-commander PCB and the GND goes to both the sub-commander PCB and the sleeve of the
jacks. You don't use the ring which in your diagram is used to switch the power on when a jack is plugged in (it's shorted to the sleeve by the jack).

what might be a bit confusing is that with a single supply - is (usually) GND, while with a dual supply they are seperate.

Quote:
Know any good suppliers of metal enclosures? I don't know any local stores that might carry this kind of stuff...

sorry, I can't help you with that, I only order from local (dutch) suppliers. Rolling Eyes

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the architech



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PostPosted: Thu Jan 09, 2014 4:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah, yeah ok, that makes a lot more sense. Thanks man! I think I get how the switch will work now.

Yeah yeah, I was going to use the 2.1mm jack on the supply to receive the wall wart. I'm not sure I understand what's going on in the MFOS PSU though. Is it simply converting 120VAC to 12VAC? Like I said, I've never worked with AC and don't totally understand it. I'll have to read through the description on teh MFOS site more when I get home.

Could I just use a standard American power cable, like this?
http://www.amazon.com/Belkin-6-Feet-Replacement-Power-Cord/dp/B00000J1UQ/ref=sr_1_1?ie=UTF8&qid=1389310182&sr=8-1&keywords=AC+power+cord

I'm not particularly keen on making my own cables... I know a guy who makes his own XLR audio cable though. I could probably talk to him about making me some power cables.

Dutch, eh? I'm a van der Veen (although at some point it was changed to VanderVeen several generations ago). It's a beautiful country!
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PostPosted: Thu Jan 09, 2014 5:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi.
PHOBoS wrote:
Do you have a photo ? I use XLR myself btw.

I am interested to hear what people use for their dual rail PSU connections. I've been using the 3-pole connectors (below) for mine, which I can only find here, so far:

http://www.esr.co.uk/electronics/products/frame_connectors_multipole.htm

I recently built a PSU using six of them for my synth stuff (also below) plus some terminal posts for prototyping. This is the MFOS adjustable 1.5A +/-9V to +/-15V, by the way.

Gary


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PHOBoS



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PostPosted: Thu Jan 09, 2014 6:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

the architech wrote:
I'm not sure I understand what's going on in the MFOS PSU though. Is it simply converting 120VAC to 12VAC?

nope that's what the wallwart will do,. you'll need one that has a 12V AC output. The MFOS supply will then convert that into 2 DC voltages
(+12V/GND & -12V/GND). So you won't have anything to do with the 120VAC mains except pluggin in a wallwart Wink



That's a very nice looking PSU Gary Very Happy and those connectors look great. Is that DIN ? they look similar to some 5 pin DIN connectors I have.
Banana's are great too but you have to be a bit more careful with those, so you don't create any shorts if only plugged into the supply.
(or connect them the wrong way Embarassed )

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analog_backlash



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PostPosted: Fri Jan 10, 2014 7:58 am    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
That's a very nice looking PSU Gary Very Happy and those connectors look great. Is that DIN ? they look similar to some 5 pin DIN connectors I have. Banana's are great too but you have to be a bit more careful with those, so you don't create any shorts if only plugged into the supply. (or connect them the wrong way Embarassed )

Thanks for that - I was quite happy with how it turned out Very Happy . I used an old case which I only had a rear panel for, so the front was cut out of an aluminium sheet offcut I had.

I've done a bit of detective work and found out that the connectors are Cliffcon Miniature ZC Series connectors (although they are described as DIN elsewhere):

http://www.cliffuk.co.uk/products/cliffcon/zc.htm

Because of this, I've now found other suppliers (which was nice). As for the shorts and misconnections to the terminal posts, I usually check and re-check before I switch the thing on (previous incidents involving "magic smoke" tend to remind me Embarassed ).

Gary
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PostPosted: Sat Jan 11, 2014 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

I was talking the footswitch issue over with a friend and I was wondering if by sending the +12v and -12v directly to the PCB first, wouldn't that be wearing on the board and caps over time? I'm thinking I should rewire the footswitch so that the +12v and -12v go directly to the footswitch and only connect to the board when the signal is made dirty. I might need a 4PDT for this though...
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