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Discussion Starter #1
I bought a Digitech Trio from a member here, who let me know in advance that he did not have the adapter.

No problem.

I went down to the surplus place and bought one that I figured should work.

I needed:

9 V DC
500ma
center ground (as indicated on the pedal).

I bought a multi voltage unit clearly marked with the right specs.

IMG_0602.JPG


and then turned the package over.


IMG_0603.JPG



So, as per the BACK instructions, don't use it right?

IMG_0601.JPG
 

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Oops, didn’t catch that. Does the pedal really use 500ma? Seems like a lot. Weird that it says 500 on the front.
 

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Discussion Starter #5
Oops, didn’t catch that. Does the pedal really use 500ma? Seems like a lot. Weird that it says 500 on the front.
Weird for sure. "Weird" wasn't exactly the word I used at first.

My inclination is not to risk frying the pedal but I'm happy to hear from some of our resident electronics gurus.
 

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My main concern is filtering questions. The introduction of noise from power supplies not intended for pedals.
 

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I tried it with a 200ma EHX wall wart and it (adapter) ran hot after about 10 minutes. No issues running it with my Voodoo Lab Digital that has 400ma at the plugs
 

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It's all about safety margin. As I may have noted in another thread, current-capacity recommendations are often predicated on what would likely maintain the power-supply on spec. If the PS is being asked to deliver ALL the current it is capable of, there is a pretty good chance that, as a sealed black blob with little or no ventilation to let heat out, the internal components may drift off spec and not supply the correct voltage or degree of regulation. Run that way for an extended period could result in damage to the step-down transformer. So the Digitech unit doesn't need half an amp. But if you ran it with something that is capable of delivering half an amp, that power supply shouldn't be particularly stressed in any way. The wall wart can provide up to 500ma for a short period without any significant stress. BUt the unit will perform to spec for a lot longer if one doesn't ask more than about 300ma peak from it. The Digitech unit assumes this and makes its request accordingly.

This is one of the eternal shortcomings of wallwarts - they are sealed plastic boxes with no way for heat to escape. You can't look inside 'em to see what degree of regulation/smoothing they provide, and you can't even let them run cool.
 

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Discussion Starter #11
It's all about safety margin. As I may have noted in another thread, current-capacity recommendations are often predicated on what would likely maintain the power-supply on spec. If the PS is being asked to deliver ALL the current it is capable of, there is a pretty good chance that, as a sealed black blob with little or no ventilation to let heat out, the internal components may drift off spec and not supply the correct voltage or degree of regulation. Run that way for an extended period could result in damage to the step-down transformer. So the Digitech unit doesn't need half an amp. But if you ran it with something that is capable of delivering half an amp, that power supply shouldn't be particularly stressed in any way. The wall wart can provide up to 500ma for a short period without any significant stress. BUt the unit will perform to spec for a lot longer if one doesn't ask more than about 300ma peak from it. The Digitech unit assumes this and makes its request accordingly.

This is one of the eternal shortcomings of wallwarts - they are sealed plastic boxes with no way for heat to escape. You can't look inside 'em to see what degree of regulation/smoothing they provide, and you can't even let them run cool.

Much appreciated Sir, and I think I understand but in reading your comment, I still don't see a yay or nay.

Is there a risk? The adapter can deliver 500ma but maybe the pedal only needs 400 or whatever.

Should I just not be a cheapskate and buy a higher amperage unit?

And how do I know how much headroom to allow? if the pedal says 500ma do I need a 750ma or a 1 amp adapter?

Of course that's a moot point if I ante up for the manufacturer's recommended adapter.
 

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A lot of folks will aim for a 50% safety margin. So if the device/s being powered will pull 300ma through the wallwart, then you probably want a wallwart rated at 450ma or more.

As Chuck implies, one needs to think of wallwarts as being a sort of slow-blo fuse. As long as the current passing through only surges briefly, the fuse remains intact. But if the current capacity is reached and things stay at that maximum for any length of time, they blow.

And yes, manufacturers will often insist on using their power adapter. Not because it's the only one that would work, but because it's a whole helluva lot easier to say "Just use this one", than it is to explain about plug polarity, current ratings, degree of regulation, etc. Given the packaging and shipping costs, the companies probably don't even make any money on them. But they DO save on having to provide additional tech support, take in repairs and ship them out, or take on the badmouthing that inevitably results from consumers who don't know enough to avoid mishaps and damage but pin all the blame on "shitty products" anyway.
 

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Discussion Starter #14
Thanks to all who have replied. I'm going to buy the right one.

And a tip of the hat to Chuck, who is going above and beyond to help me.

I know people say this from time to time, but this site has many helpful and expert advisors.
 

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Discussion Starter #16
I just spoke to my local shop and the Digitech adapter is 1.2 amps.

He has one. I'll have it in my greasy hands by 5:00 PM.

Again, thanks for helping avert a pedal meltdown.
 

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Discussion Starter #17
In my opinion, the needed adapter amperage should be reflected on the pedal. Why would 500ma be indicated if such an adapter could seriously damage the pedal?

It seems like a pretty easy mistake to make.
 

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This is new to me and worth noting.
It's not a hard and fast rule, Dave. It's just something where you can rest easy that problems can be easily avoided, without having to go overboard.
Works the same way with electrolytic capacitors. That's why so many pedals use caps rated at 16VDC, even though the pedal uses a 9V battery. And if the manufacturer says the pedal can be used with 12-15V, the caps will be rated for at least 25VDC (the next rating step up).

It's all about making sure things remain true to their stated specification.
 

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I just spoke to my local shop and the Digitech adapter is 1.2 amps.

He has one. I'll have it in my greasy hands by 5:00 PM.

Again, thanks for helping avert a pedal meltdown.
More and more wallwarts are switching power supplies, that use high-frequency switching to attain greater current-delivery capacity in a small lightweight package. Were this 1985, a 1.2A supply would weigh twice as much as the Trio pedal. It is less and less of a problem these days as more manufacturers anticipate and design around it, but the clock pulses riding on the power line from the switching supply can interact with digital pedals having their own internal high-frequency clocks, and create noise. However, that is more true of slightly older digital pedals of, say, 10-12 or more years of age.
 

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In my opinion, the needed adapter amperage should be reflected on the pedal. Why would 500ma be indicated if such an adapter could seriously damage the pedal?

It seems like a pretty easy mistake to make.
The pedal will only draw as much current as required, so using a supply that supplies the correct voltage that is rated for a higher amperage will cause no harm.
 
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