12v +/- Bipolar Supply

[tuffteef]

sooo im not sure if this is even in the right sub forum

but while i understand 12v +/= im not sure how to recognize a power supply as being 12v +/- bipolar

any clues?

are they tricky to find

[Scruffie]

You don't generally see 12+/-V Supplies (I say generally, not sure they even exist, CBA to look it up).

To get those requirements you'd usually use a transformer (as is the case in old EHX effects) or you can use a Charge pump to split a supply.

[McSpunckle]

Bipolar pedals either use AC power supplies or internal DC converters. Standard wall warts aren't bipolar-- you need 3 connections for that.

You can buy simple to use DC/DC converters that have a bipolar output, and there are some circuits floating around too.

[Scruffie]

Or if he's building something he could also create a virtual ground with a bit of circuit redesign.

What exactly is this for?

[tuffteef]

Or if he's building something he could also create a virtual ground with a bit of circuit redesign.

What exactly is this for?

just to power this
http://www.schumannelectronics.com/lion.html

[McSpunckle]

Google says it uses a 12VAC power supply, and makes it into bipolar DC internally.

[Boxbie]

schumann shipped mine with an EH 12volt ac power supply

[tuffteef]

ohhhhhhhhhhhhh i get it now

input AC
output DC

or output AC

[eatyourguitar]

lets say the wall wart outputs 15VAC. Typically the VAC value of a transformer is it's RMS value. I'm thinking that the transformer manufacturers thought Volts AC was a little more marketable than Root Mean Square (RMS). So a 15VAC transformer puts out a peak voltage of 15 * 1.414V or 21.21V. If you were viewing the output on an oscilloscope you would see a sine wave (50 or 60 hz. depending on your locale) that had positive and negative excursions of 21.21V peak. This value when rectified and filtered by the diodes and capacitors in the wall wart will be capable of supplying voltage to any of the LM78XX/LM79XX regulators.

ok so the internal circuitry in any device that has an AC wall wart and internal bipolar DC supply is this. half wave rectifier on each side. filtered by big caps. followed by 3 terminal regulators for each rail. the output of your bipolar supply is always 3 pins. the power supply is never really out of the case completely unless the cable is 3 pin +15V/0V/-15V or 12 or whatever. you need to look at it on a scope after the rectifier and the filter to see what is a safe voltage to regulate. 15VAC might not be enough to to get bipolar 18VDC but 16VAC is probably enough to get bipolar 18VDC. the distance between the rails is 36V! these are actually very simple passive circuits.

[theavondon]

But...we figured it out earlier in the thread.

[tuffteef]

But...we figured it out earlier in the thread.

im gonna guess ac input ac output
cause it converts to dc inside the lion

rather most plugs the ac is being converted to dc inside the plug and the rectifier dc smooths
i dunno i should read a book

[multi_s]

ilf is the new book.

[tuffteef]

ilf is the new book.

[eatyourguitar]

bahhhh I though he was cloning it and only had the schematic without the power supply. I dont see the point in having more headroom in a distortion pedal anyway. seems counter productive to producing distortion. ohhhhh Schumann. always making questionable moves.

[tuffteef]

im gonna clone it

AND THEN KEEP THEM ALL WUAHUAHAUHAUHA!