Author |
Message |
Sprak
Joined: Oct 19, 2005 Posts: 15 Location: Stockholm, Sweden
|
Posted: Mon Dec 26, 2005 5:03 am Post subject:
PSU instead of batteries? |
|
|
Hey all, was wondering.. what kind of modifications would I have to do to power my Soundlab with a 9V power supply adapter instead of batteries? Just spent half an hour trying to find out why my prototype wasn't sounding anymore, looking for shorts etc., before figuring out that the batteries had gone dry.... _________________ http://www.covox.net |
|
Back to top
|
|
|
Uncle Krunkus
Moderator
Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
G2 patch files: 1
|
Posted: Mon Dec 26, 2005 5:49 am Post subject:
|
|
|
The problem is to make it a +/- 9V power supply. This you will probably not find off the shelf. I'm setting mine up to run off a +/-12V PSU which I custom built.
There is a way of deriving a +/- supply off one battery, but it almost certainly will not deliver the goods as far as running a Soundlab goes.
Have a look at this if you want to experiment: -
http://www.geofex.com/circuits/+9_to_-9.htm _________________ What makes a space ours, is what we put there, and what we do there. |
|
Back to top
|
|
|
Macaba
Joined: Jul 13, 2005 Posts: 160 Location: UK
|
Posted: Mon Dec 26, 2005 7:13 am Post subject:
|
|
|
You could in theory set up a 18V power supply to function as a +/- 9V supply. This would fulfil your aspirations. To get an efficent power supply from 18V (using resistors would be quite inefficent I think) you'd use lots of diodes in series (each diode has a typical drop of 0.7V) or EVEN better, use a 9.1V zener diode. If you need more information on how this is setup, reply with such a request. |
|
Back to top
|
|
|
Sprak
Joined: Oct 19, 2005 Posts: 15 Location: Stockholm, Sweden
|
Posted: Mon Dec 26, 2005 7:30 am Post subject:
|
|
|
Macaba, please teach me how I have a bunch of 9.1v zener diodes lying around. _________________ http://www.covox.net |
|
Back to top
|
|
|
Macaba
Joined: Jul 13, 2005 Posts: 160 Location: UK
|
Posted: Mon Dec 26, 2005 7:53 am Post subject:
|
|
|
If somebody can see a reason why this wouldn't work, feel free to criticise. Sprak- breadboard it and feedback how nicely it works.
(Credit must go to http://www.kpsec.freeuk.com/powersup.htm for the original diagram that I butchered up) |
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18198 Location: Durham, NC
Audio files: 213
G2 patch files: 60
|
Posted: Mon Dec 26, 2005 8:02 am Post subject:
|
|
|
Be careful using systems like this. If you are careful it will work, but now you have two grounds which are 9 volts appart. This could be dangerous. You probably won't kill yourself but sooner or later you'll blow something up.
IMHO, if you need a +/- 9 volts power supply, then get a good one, don't kludge something like this just to use up parts you already have or to save a little bit of money. _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
Macaba
Joined: Jul 13, 2005 Posts: 160 Location: UK
|
Posted: Mon Dec 26, 2005 8:20 am Post subject:
|
|
|
The circuit shown is the basic principle of a voltage regulator anyways. The issue with two grounds is the same in any PSU, you have a ground before and after the transformer. So basically, you just never hook anything up to the battery ground, always being careful to hook it upto the voltage regulator ground. So its not an issue really? |
|
Back to top
|
|
|
Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
Audio files: 2
|
|
Back to top
|
|
|
Wild Zebra
Joined: Apr 28, 2005 Posts: 806 Location: Ohio
Audio files: 5
|
Posted: Mon Dec 26, 2005 9:47 am Post subject:
|
|
|
I'm sure you have your reasons for a power supply, but one of the awesome things about this synth is that it runs off batteries. I put some duracels in mine about 3 or 4 months ago and there is no sign of slowing this puppy down. _________________ "your stripes are killer bro" |
|
Back to top
|
|
|
Macaba
Joined: Jul 13, 2005 Posts: 160 Location: UK
|
Posted: Mon Dec 26, 2005 9:57 am Post subject:
|
|
|
Hey Wild Zebra- theres a point:
Two 9V batteries should last AGES. Sprak- Are you sure you've got low power consumption components? If you used exactly the same components as Ray specified, then it should last ages. If it doesn't last a reasonable amount of time, check for a short. It seems worth it to stay with batteries, because you get FAR less mains interference, a cleaner sound. |
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18198 Location: Durham, NC
Audio files: 213
G2 patch files: 60
|
Posted: Mon Dec 26, 2005 10:01 am Post subject:
|
|
|
Macaba wrote: | The circuit shown is the basic principle of a voltage regulator anyways. The issue with two grounds is the same in any PSU, you have a ground before and after the transformer. So basically, you just never hook anything up to the battery ground, always being careful to hook it upto the voltage regulator ground. So its not an issue really? |
I assume the 18v supply is a DC supply. Never connect anything else up to it if you connect your SoundLab with such a power supply circuit. If the 18v supply is connected to the mains ground, then you are running your SL at a different ground. Never connect the SL to anything else: an external mixer, preamp, amplifier or other synth if you use such a circuit.
What you have is a very basic +9v Zener diode voltage regulator. These work OK for supplying voltages for LEDs, lamps and such, but they are not great for audio circuits. To top that off, you are kludging it to a +-9V regulator by coming up with a derived ground. That's where the prolem comes in.
You have a lot of time invested in your DIY circuits. Give them the respect they deserve and use a well designed power supply. _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
Wild Zebra
Joined: Apr 28, 2005 Posts: 806 Location: Ohio
Audio files: 5
|
Posted: Mon Dec 26, 2005 10:13 am Post subject:
|
|
|
Also I used cheap Alkalines from my local "dollarstore", and these were not lasting very long. Then I said F-it and got some good name brands. Haven't had a problem yet. _________________ "your stripes are killer bro" |
|
Back to top
|
|
|
Macaba
Joined: Jul 13, 2005 Posts: 160 Location: UK
|
Posted: Mon Dec 26, 2005 10:52 am Post subject:
|
|
|
mosc wrote: |
I assume the 18v supply is a DC supply. Never connect anything else up to it if you connect your SoundLab with such a power supply circuit. If the 18v supply is connected to the mains ground, then you are running your SL at a different ground. Never connect the SL to anything else: an external mixer, preamp, amplifier or other synth if you use such a circuit.
What you have is a very basic +9v Zener diode voltage regulator. These work OK for supplying voltages for LEDs, lamps and such, but they are not great for audio circuits. To top that off, you are kludging it to a +-9V regulator by coming up with a derived ground. That's where the prolem comes in.
You have a lot of time invested in your DIY circuits. Give them the respect they deserve and use a well designed power supply. |
Ah yes, that seems to check out apart from a few things you could possibly explain. 0V is the point with 0 potential difference. So if you wire a soundlab using my PSU to an external amplifier, connecting the grounds, they are still the points with 0V's, the amplifier circuit won't "see" 9.1V above ground? Especially as the amplifer is likely to be powered off the mains, which brings up another point:
You can have many different rectifying configurations such as the half-bridge and the full-bridge which result in essentially different ground configurations (center tapped, and not) and there isn't a problem?
I'm eager to learn about this, thanks for taking the time mosc to educate me. |
|
Back to top
|
|
|
Uncle Krunkus
Moderator
Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
G2 patch files: 1
|
Posted: Mon Dec 26, 2005 5:11 pm Post subject:
|
|
|
You tell 'em Mosc!
Yes, big problems when you deviate from PSU convention.
The problem with a derived 0V is that back in the PSU the earthing will end up on the -ve rail. When you connect an output to an amp, etc it's shield on the amp side will be 9V below the sheild from the SL (because your earth is 9V above)
It sounds complicated, but it's really just relativity!!
At the very best, you'll short the -ve side of your SL (and everything that entails) If there are other circuits, synths, effects units etc. in the loop which have their earth's commoned (through shielding connections usually) you'll get a special kind of earth loop hum,..... well it's more of an earth loop bang!! And all that very expensive smoke will escape from vital components. (it's really hard trying to get it back in!!!) _________________ What makes a space ours, is what we put there, and what we do there. |
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18198 Location: Durham, NC
Audio files: 213
G2 patch files: 60
|
Posted: Tue Dec 27, 2005 7:24 am Post subject:
|
|
|
Macaba,
If you look at your power supply circuit, you have labeled one end of a wire 0 V and the other end -9.1 V. You know you are in trouble whenever you do that. _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
Wild Zebra
Joined: Apr 28, 2005 Posts: 806 Location: Ohio
Audio files: 5
|
Posted: Tue Dec 27, 2005 1:08 pm Post subject:
|
|
|
Here is a topic at a stompbox forum http://www.diystompboxes.com/smfforum/forums.html?topic=40268.from1135713069;topicseen#msg289300
Quote: | BTW, for those Soundlabbites out there, Electronic Goldmine has a +/-12V wallwart that would power the Soundlab nicely. It's a low current wart, but the Soundlab is very miserly on its current requirements (Ray's told me it would work as well). Myself, I'd regulate it down to +/-9V internally just to give it some stability. Soundlab itself would have no problem running at +/-12V. |
_________________ "your stripes are killer bro" |
|
Back to top
|
|
|
|