19 Volt DC Output Into 18 Volt DC Input

[Tazz]

Hi all, I don't really post here much although I've been lurking for many, many years. I'll try to make as much sense as I can as I'm not great with electrical work.

I've got a pedal power supply and the original 18v output, centre negative wall plug has blown/failed. It's proven almost impossible to find a replacement with the right polarity (centre negative), voltage and amps. My power supply did come with a couple reverse polarity adapters included in the box and I hooked one up to a 19v centre positive wall plug that I already had laying around. I tested everything with my multimeter to make sure everything was ok and it's now centre negative putting out precisely 19.3v

So my question is will I hurt anything in the actual power brick or pedals by supplying 19.3 volts instead of the 18 asked for? I've only used the multimeter so far and not actually plugged it into the brick. Am I making too big of a deal over 1.3 volts extra or is it a legitimate concern?

 

[bholder]

I wouldn't think so, but subbed to learn if I'm wrong...

 

[bongomania]

Depends on the specific case. Some circuits are designed with some room for over/under voltage, and some are not. The ones that can't take it, the results can vary: shutdown, burnout, features not working correctly. If I understand you correctly, this 19.3 V is to power a distribution brick, that itself has separate outputs for your pedals? The design of that distribution circuit will dictate whether it's a problem for the pedals.

 

[Tazz]

Depends on the specific case. Some circuits are designed with some room for over/under voltage, and some are not. The ones that can't take it, the results can vary: shutdown, burnout, features not working correctly. If I understand you correctly, this 19.3 V is to power a distribution brick, that itself has separate outputs for your pedals? The design of that distribution circuit will dictate whether it's a problem for the pedals.

Correct, it's to a distribution brick.

The new cable is also capable of supplying more than double the amps but only the amount of amps called for by the pedals will run through the cable. A search of the forums confirms that as long as the cable can safely supply enough amps it's not a problem but it's voltage that I need to be more careful of.

 

[Wasnex]

Correct, it's to a distribution brick.

A search of the forums confirms that as long as the cable can safely supply enough amps it's not a problem but it's voltage that I need to be more careful of.

Correct.

Generally the current a device pulls is determined by the voltage applied. So, if the voltage is too far out of spec you could destroy the pedal. The manufacturer should be able to tell you if the pedal can safely handle 19.3V.

If you can't find a proper supply, maybe a 1Spot reverse polarity adapter would work with one of your 18V supplies. Of course that would depend on the plugs mating properly.

You can ask for specifics on the plug dimensions here:
Invalid Link Removed

 

[Tazz]

Correct.

Generally the current a device pulls is determined by the voltage applied. So, if the voltage is too far out of spec you could destroy the pedal. The manufacturer should be able to tell you if the pedal can safely handle 19.3V.

If you can't find a proper supply, maybe a 1Spot reverse polarity adapter would work with one of your 18V supplies. Of course that would depend on the plugs mating properly.

You can ask for specifics on the plug dimensions here:
Invalid Link Removed

View attachment 3103371

This is the brick in question, not a picture of mine but it's the same model. It has eight separate 9V outputs, a 12V and an 18V output. Would I be right in thinking that it must regulate the voltage sent to pedals because even if it was running on the correct 18V the 9V outputs only get 9V? It would be more a case of whether I'd fry the distribution brick?
I'm just speculating at this point but it's looking more likely that I'll have to stop being so cheap.

I got two reverse polarity converters included with my power supply so to be on the safe side I should probably buy an 18V plug that can support a high enough current draw. Should be easy enough really its just that I already had a 19V on hand.

You guys have been helpful as always, thanks for the replies

 

[Ben B]

Since the brick has multiple voltage outputs, it's likely regulated output. You should check the manual to be sure. I know that many brick advertisements state that they produce regulated voltage. If the output is regulated, you should not have to worry about excess voltage getting to your pedals.

A little off topic, but I've encountered some non-regulated power supplies that put out 1 to 3 volts more than their rating and never caused an issue powering an effect or household electronics device. Of course, some devices have their own voltage regulators.

As far as damaging the brick itself with too much voltage going from 18v to 19.3v, hard to say. Based on what a brick does, most likely 19.3 volts is not an issue, but I'm not sure how you would make that determination. I guess it depends on how much variance the designer accounted for.

 

[Wasnex]

This is the brick in question, not a picture of mine but it's the same model. It has eight separate 9V outputs, a 12V and an 18V output. Would I be right in thinking that it must regulate the voltage sent to pedals because even if it was running on the correct 18V the 9V outputs only get 9V? It would be more a case of whether I'd fry the distribution brick?
I'm just speculating at this point but it's looking more likely that I'll have to stop being so cheap.

I got two reverse polarity converters included with my power supply so to be on the safe side I should probably buy an 18V plug that can support a high enough current draw. Should be easy enough really its just that I already had a 19V on hand.

You guys have been helpful as always, thanks for the replies

No picture?

If your power supply has an 18V outlet and you have the polarity converters you just need to make sure the 18V outlet can supply enough current to power your pedal.

I use a pair of Voodo Labs Pedal Power 2 Plus power supplies for my pedal board. I get 18V by using a special cable that connects two of the 9V outputs in series. Available current is limited to the lowest current rating of the two plugs used. Depending upon the settings, the voltage is regulated or not.

I run a couple of Dunlop/MXR 18V pedals off one 18V adapter cable using a 1Spot daisy chain. I looked up the current draw of each pedal and the combined total was well below the limits of the outlets I used. Hopefully you can access the specs for you pedal and also the power supply.

 

[Tazz]

Picture should be sorted now I hope, still getting the hang of things.

 

[Wasnex]

Picture should be sorted now I hope, still getting the hang of things.

There appear to be several near identical products on the market.

The brick may or may not work with 19.3V. I suspect it will, but I recommend using an 18V power supply and one of your polarity adapters rather than risking it. Some simple voltage regulators lower voltage essentially by drawing extra current to pull the voltage down. If this is how your distribution brick works, this will reduce the amount of reserve current the power supply has to offer, and generate extra heat in both the power supply and the brick.

If the brick is not regulated, then you will expose your pedals to high voltage. Probably not a problem, especially for pedals designed to work on 9V batteries. But if you have pedals that were not designed to be used with batteries they may be less tolerant of an over voltage condition.

I did search Ebay UK for "18v dc power supply centre negative". This produced several results, but many of the photos showed center positive...probably stock photos, so maybe best to message the seller to confirm centre negative; barrel positive.

If 1000mA meets your needs and the plugs are the right size, this one shows centre negative in the photos.

18V 1000mA Negative Centre AC-DC Adaptor Power Supply Charger for GMP01 Brick 7625664624602 | eBay

 

[Tazz]

I'd noticed the dozen near identical products available. I imagine it's a case of being mass produced somewhere and badged differently depending on the company.

That looks like just what I might be after Wasnex. My previous supply was 1500ma but the draw of the pedals currently on my board is around 600ma so that should work just fine. The other negative supplies I came across were all in the 5-800ma range, one buyer also said that his was just a positive supply with a converter on the end. I've also been dismissing supplies that showed centre positive in the photos because I never thought about stock pictures.

You've been a big help