ac/dc

[ildar]

If a rack unit calls for 16vac, and I use a 16vdc power supply (hypothetically, of course  :wink: ), how long will the rack unit last?

[David]

2.5 seconds.

I don't know.  But if your unit calls for AC, it needs AC.  Why would you want to feed it DC?  You can't substitute at will.

[Ansil]

what is the rack unit.  probally it has an internal rectifier and filter cap section. if so then dc wouldnt' do muh of anything for it.

[ildar]

Well, I came across a 16vdc adapter and was playing around. It's a cheap Peavey Addverb unit, and I was just wondering if it would work. It did power up and switch programs, but that's as far as I pushed it. I'm having a hell of a time finding a proper 16vac adapter.

[niftydog]

it will probably work... but it might use the 60Hz for some internal timing... it's a stretch, but it's possible!

Like Ansil said, rectifier and filter section will sort it out, but 16VDC has less energy in it than 16VAC, so the voltage might be drooping, perhaps the regulators (if present) won't be regulating.

[sir_modulus]

won't be 16 volts will it? I thought that when you rectify it it's x 1.4. That would be 22.5V DC if 16VAC is fed to an onboard rectifier.

[dolhop]

The rack unit will have a rectification section internally - and will use the 16 Vac to provide +22Vdc and -22Vdc for the audio section, but will probably just use one side for the digital display sections - which is why you'd be able to power up the unit and see activity (since the DC will pass on either the +ve or -ve side depending on how it's connected).  It is possible that it does use only +ve rectified DC, but unlikely.  

If the 16Vdc supply you have is servicable, you could open it up and take out the recification and use it as an AC supply.  You could also try to find a supply that is somewhat lower voltage like a 12Vac supply - it will work, but it's more likely that you'll experience clipping.

If you can find an old/cheap external computer modem, they usually use AC wallwarts.  Check the local recycled computer store.

[Paul Perry (Frostwave)]

It is easy to get a 16v AC plugpack (or any other wart) from www.jameco.com. Really.

As for what happenms when you plug a DC supply into something expecting AC, it all depends what is in there... if it is a transformer, possibly you will burn it out (because, there is no AC impedance resisting current inflow). Or, in the case of my commercial Frostwave Quad MIDI-CV unit, the logic circuit will work OK (if you fluke the right polartity) but, supriose, the analog section has half the power supply missing, think it might go out of calibration :shock:  :oops:

[lightningfingers]

Take your 16VDC wall wart, pull the diodes out of it and there you go. It will probably be slightly lower than 16 but it might work.

[Ansil]

http://www.jameco.com./webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=119405

7.95  ac adaptor.

[ildar]

You could also try to find a supply that is somewhat lower voltage like a 12Vac supply - it will work, but it's more likely that you'll experience clipping.

What would happen if I run it with a higher voltage, say 18?

[Alex C]

What would happen if I run it with a higher voltage, say 18?

You run the risk of damaging components that aren't rated for a higher voltage than the intended 16V (or whatever it's converted to after rectification).  You can always safely go down, but there can be side effects, such as the clipping that was mentioned.

Alex

[Paul Perry (Frostwave)]

What would happen if I run it with a higher voltage, say 18?

Well, I've seen a filter cap explode, for a start.. I guess it was a bit underrated to start with, but still... can you say Jameco??

[dolhop]

Slightly higher voltage will be acceptable - the 18V ac supply should work where a 16V ac supply is requested.  Music gear is quite robust and designed to be able to deal with such things - remember, there are fluctuations on the 120V ac supply line.  It the manufacturers put capacitors rated for only slightly higher than the voltages they deal with - they would be spending a lot of money in warranty repairs.  As well, they'd get a bad name.  Capacitors will last much longer if you run them well below their voltage rating.

[Ansil]

Slightly higher voltage will be acceptable - the 18V ac supply should work where a 16V ac supply is requested.  Music gear is quite robust and designed to be able to deal with such things - remember, there are fluctuations on the 120V ac supply line.  It the manufacturers put capacitors rated for only slightly higher than the voltages they deal with - they would be spending a lot of money in warranty repairs.  As well, they'd get a bad name.  Capacitors will last much longer if you run them well below their voltage rating.

i dont know how much i buy into this.. [no offense] but most of all my roland stuff. ie sde3000 and such were only a few volts higher than there intended voltage.

also alot of pedals i have seen are like that too.. i dont 'remember which one it is. but one of visual sounds pedals had a bunch of 10v capacitors in there. and i was shocked.

[RDV]

Great band.

Oh......Power Supply.

Terrible band!



RDV

[dolhop]

That is surely a recipe for disaster.  I've read a lot about people replacing electrolytic capacitors in pedals, and wasn't quite sure why.  I know that if you run them close to the limit they will degrade - so I guess that explains it.  I'd be quite surprised to see 10V caps in pedals.  Many "9Vdc" walwarts are 9V under load, but 14V or so when unloaded - this would surely be a problem for the unsuspecting user.

[smoguzbenjamin]

Well I gotta say I fried a Boss once feeding it about 10.5v. So much for over-rating caps. :|