What polarity is the plugpack on Boss pedals? - diyAudio
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Old 19th July 2009, 12:53 AM   #1
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Default What polarity is the plugpack on Boss pedals?

Hi,
Does anyone know what the polarity of the power plug on Boss pedals? (Boss rc-2) Is it positive in the center pin or negative? I have a 9v adaptor that I want to use but I dont know which way to solder the plug on.
I measured the voltage on the center pin with the battery connected and it was negative, with positive to chassis, but I want to be sure in case I blow up my $300 pedal.
Does anyone have the official Boss adaptor to measure?
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Old 20th July 2009, 03:59 AM   #2
Enzo is offline Enzo  United States
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Boss pedals have a negative center. Doesn;t the bottom plate show the polarity symbol? Certainly look at a Boss power adaptor, it has the symbol.
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Old 21st July 2009, 10:34 AM   #3
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Thanks. No, it didnt have the symbol on the bottom plate.
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Old 21st July 2009, 06:32 PM   #4
ChrisA is offline ChrisA  United States
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Default Re: What polarity is the plugpack on Boss pedals?

Quote:
...in case I blow up my $300 pedal.....
Simple mod to prevent the "blow up"... Wire a diode across the power jack. If the correct power supply is connected the diode is reverse biased and does nothing, just like it's not there. But if the wrong polarity supply is plugged in the diode acts like a short circuit and the fuse in the power supply blows.

A slightly more complex mod is to also but a fuse in the pedal in series with the power input jack, now when/if the diode conducts the fuse inside the pedal blows.

This is a very simply safety device that can be used with any DC powered device to protect from reverse power connections. It is so simple and inexpensive that it is common. You might check. Many devices have this already built-in. If it is then don't worry about blowing up anything other then a fuse.
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Old 22nd July 2009, 03:39 AM   #5
Enzo is offline Enzo  United States
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Or wire a small bridge at the power entry - then either polarity power supply will work.
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Old 22nd July 2009, 05:31 AM   #6
ChrisA is offline ChrisA  United States
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Quote:
Originally posted by Enzo
Or wire a small bridge at the power entry - then either polarity power supply will work.

No, the diodes in the bridge will drop the voltage by as much as 1.4 volts. That could be enough to make a three terminal regulator "drop out" The bridge idea is good if you are using a 12V power supply and then dropping down to 9V with a regulator.
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Old 24th July 2009, 06:35 AM   #7
Enzo is offline Enzo  United States
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All depends upon how much headroom the power adaptor has, doesn't it? The original poster is not using the stock wallwart anyway. His nominal 9v adaptor could easily be putting out 14 volts at a light load like a pedal.
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Old 24th July 2009, 04:14 PM   #8
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Default Walwart Headroom?

I have lots of 9v wallwarts, and even under load of the pedal, they read from 11 to 15 volts. Is this harmful to the pedal? Do these wallwarts need to be regulated down to 9v?
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Old 25th July 2009, 02:25 PM   #9
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Cheap wallwarts are unregulated, a pedal such as this one is almost certainly designed to run from an un-regulated wallwart (as they are cheaper).
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Old 25th July 2009, 08:41 PM   #10
ChrisA is offline ChrisA  United States
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Quote:
Originally posted by Nigel Goodwin
Cheap wallwarts are unregulated, a pedal such as this one is almost certainly designed to run from an un-regulated wallwart (as they are cheaper).

This whole thread has been about guessing. The best thing is to check a schematic. Here is one for the DS-1.
http://www.godiksennet.com/images/sch/DS1PG2.jpg
It is the simplest one and makes a good example. Notice a few things

1) There is a diode and 470R resistor in series with the input jack. So go ahead and plug in a reversed power supply. It will not work but nothing will blow up either. Like I wrote above - this is so easy to do that most devices have this minimum level of protection built-in. But you have to check. Some companies would jump at the chance to save 2 cents

2) The ciruit is completely unregulated and would work fine at higher voltage, although I doubt the other Boss pedals are unregulated as they might be using some ICs that require it.


You can get the schematic for almost any Boss pedel just by searching Google
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