SABDDI power supply question

silentstranger · #1 10-30-2008, 11:35 AM

My friend/bandmate liked my SansAmp Bass Driver DI so much that he decided he wants one too (bass isn't his primary instrument but he plays it in a few different situations, usually on crappy house amps that could be significantly improved by a SABBDI). He got one on eBay that came without a power supply, and then ordered a separate "power supply/battery charger" from another seller.

My original Tech 21 power supply is 100mA and that's what he ordered, but received a 200mA instead. All the other specs match, and the seller says 200mA will work fine. Is that true? Will a 100mA pedal draw only what it wants from a power supply with more capacity, or do we have to worry about frying it?

Thanks!

jfenderp · #2 10-30-2008, 11:54 AM

Thats fine, that 200mA is just what you can draw off it. The SABDDI will only pull the amount it needs. I used mine with a 500mA with no issues at all.

JanusZarate · #3 10-30-2008, 12:08 PM

The pedal will only draw as much as it needs from the supply. The one received is fine. The original adapter is 9VDC, regulated, with a 2.1mm center-negative barrel. I forget how much current the BDDI actually draws during normal use, but given that it's analog, it's a small amount. Probably not even over 50mA. It's published somewhere... it'll probably say in the manual.

You'll probably notice on this board that a lot of us using effects have a variety of supplies with high current ratings. That's because we're using just a few (often just one) supplies to power multiple pedals, and more available current is always a good thing for expansion and coping with power-hungry digital pedals.

Long story short: more available current is not a bad thing.

Steve Bennett · #4 10-30-2008, 12:08 PM

As long as the center is negative, the output voltage is 9V, and the output current is at least 100mA, it'll work fine. More current than you need is OK, less is not.

JanusZarate · #5 10-30-2008, 12:26 PM

I checked the manual. Typical power consumption is a mere 6mA.

No wonder my BDDI was so battery-efficient when I had one...

silentstranger · #6 10-31-2008, 07:52 AM

Sweet, thanks guys

Glad to know I don't have to return it; the seller strikes me as one that doesn't do returns well...

Quote:

Originally Posted by Steve Bennett

As long as the center is negative ...

Now that is something I never even thought to consider.

Are power supplies with a positive center common or am I unlikely to ever encounter one unless I'm specifically looking for it?

GreggBummer · #7 10-31-2008, 08:09 AM

Quote:

Originally Posted by silentstranger

Now that is something I never even thought to consider.

Are power supplies with a positive center common or am I unlikely to ever encounter one unless I'm specifically looking for it?

It is my understanding that MOST (I am sure there is an exception somewhere) guitar/bass pedals are wired with a negative center on the power input.

I imagine a good reason to wire something with a positive center, or use some kind of strange voltage, would be to force the consumer to purchase a proprietary power supply. Personally, I avoid companies who engineer this way. It is greedy and not friendly to the industry as a whole.

One last thing: If you daisy chain your power supply using a "one spot" or other similar product, be sure to wind a little electrical tape over the unused plugs. It will keep dirt and debris out of the connections.

Steve Bennett · #8 10-31-2008, 09:15 AM

Quote:

Originally Posted by GreggBummer

It is my understanding that MOST (I am sure there is an exception somewhere) guitar/bass pedals are wired with a negative center on the power input.

That's correct. The only exception I can think of is the Demeter Compulator, which requires a positive center for some reason. There's usually a little diagram on the power supply that shows the center polarity.

gm jack · #9 10-31-2008, 09:48 AM

A lot of non-instrument ones are centre positive. If you get it for instrument use, chances are, it's centre negative.

JanusZarate · #10 10-31-2008, 10:10 AM

Quote:

Originally Posted by GreggBummer

It is my understanding that MOST (I am sure there is an exception somewhere) guitar/bass pedals are wired with a negative center on the power input.

+1

Quote:

Originally Posted by GreggBummer

I imagine a good reason to wire something with a positive center, or use some kind of strange voltage, would be to force the consumer to purchase a proprietary power supply.

You'll see this frequently with positive-ground designs. However...

Quote:

Originally Posted by GreggBummer

Personally, I avoid companies who engineer this way. It is greedy and not friendly to the industry as a whole.

Some positive-ground designs are difficult (and more expensive) to re-create with a negative ground. Using an independent supply is cheaper and sometimes more efficient than redesigning the pedal, given how many of us are using power strips and unusual power supplies already. It doesn't do the ordinary musician and casual effects user much good, though.

To the OP: You will almost never see a center-positive 2.1mm barrel (which is the Boss-sized one). Normally, the industry standard is to use a 2.5mm barrel instead if the center pin is to be wired positive. It prevents some confusion, and also prevents you from inserting the wrong barrel.

silentstranger · #11 11-01-2008, 04:05 PM

Quote:

Originally Posted by MysticBoo

To the OP: You will almost never see a center-positive 2.1mm barrel (which is the Boss-sized one). Normally, the industry standard is to use a 2.5mm barrel instead if the center pin is to be wired positive. It prevents some confusion, and also prevents you from inserting the wrong barrel.

Crap. This isn't a music-instrument-effects specific power supply, and if I'm reading this diagram right, it certainly looks like a center-positive. It's also clearly the opposite diagram of the one on my original Tech 21 wallwart. Sorry for the crappy pic:

I also found out yesterday that my friend did actually try to use it before he realized it was 200mA and it didn't work. Is it likely that he fried his pedal by trying to use an opposite polarity power supply?

JanusZarate · #12 11-01-2008, 11:03 PM

It doesn't have to be an "effects specific" supply. It just needs to be (for most pedals including the BDDI):

9VDC
Regulated
100mA or more (as you saw from the actual usage of 6mA on average, this number isn't too important)
2.1mm barrel
Center-negative

In the photo above, the center of the diagram is blurry. If it's center-positive, the line from the (+) will go straight to the center dot, and the (-) will have a line which connects to a "broken" circle (the gap in the circle is around the line which went to the dot). Center-negative is the opposite.