AC to AC, or AC to DC adapter ?

[Jeehemdee]

This is surely a stupid question  
But I've to change the adapter of the amplified speakers of my cabinet (12v, 1000ma)...
But they do have 2 kinds of adapters at Radioshack:

1) AC to AC
2) AC to DC

I think it's the second one, isn't it ?
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F004%5F001%5F001%5F000&product%5Fid=273%2D1779

Thanks !

[RandyT]

This is surely a stupid question  
But I've to change the adapter of the amplified speakers of my cabinet (12v, 1000ma)...
But they do have 2 kinds of adapters at Radioshack:

1) AC to AC
2) AC to DC

I think it's the second one, isn't it ?
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F004%5F001%5F001%5F000&product%5Fid=273%2D1779

Thanks !

You really have to look for a label on the speakers to see what it says.  Most of the time it's AC-DC, but I actually own some speakers that use the AC-AC type adapter.

The rule of thumb here is:  There is no rule.

RandyT

[Thenasty]

The rule of thumb here is:  There is no rule.



I though the rule was:

1. Try it and find out
2. If it fails, see number 1.

[RandyT]

The rule of thumb here is:  There is no rule.



I though the rule was:

1. Try it and find out
2. If it fails, see number 1.

That rule only applies if you have a spare set of speakers

Seriously though, it probably wouldn't hurt anything, but you never know!

Randy

[liche]

Well, let me put it this way.

The only difference between an AC-DC power supply and AC-AC power supply is that the AC-AC is only a transformer, while the AC-DC power supply contains a transformer with a full-bridge rectifier circuit built into it.

AC-DC case (using 12VDC supply)

If the input to your amplifier is in fact 12VAC, this will most likely be full rectified to about 10 VDC after full-wave rectification (Vout = 2*12*SQRT(2)/pi) and probably won't hurt the amplifier as this goes into a 78XX type linear regulator which can withstand a higher voltage.  In fact after the diode voltage drops, the 12VDC input will be around the 10VDC which is what a 12VAC full-rectified would be equivalent to.

AC-AC case (using a 12VAC supply)

In this case, you have a problem.  Your amplifier requires 12VDC and you are inputting 12VAC which gives peak voltages of almost 18V which could likely damage your amplifier.  Vpeak = Vrms * SQRT(2)

So better, make sure before you plug in a supply.

[Jeehemdee]

Wow !!

Liche,

Thanks very much for a so complete answer !!

[Rocky]

Jeehemdee,

If you use and AC/DC converter it will put you on a hiway to hell!    Just don't do it!


Rocky

[JustMichael]

Jeehemdee,
have you tried emailing the company who made the speakers?  Often they will tell you whether it is ac or dc (and if dc, what polarity) that the speakers need.

[liche]

Actually, if you can open up your speakers (amplifier) and trace your input, you can very EASILY determine whether its AC or DC.


If the input wires / circuit board traces go directly to your other components on the amplifier, or into a 3 terminal device which the identifier LM78xx such as LM7805, LM7809, etc..., then the input is DC.

If the input wires / circuit board traces go to either:

(4) cylindrical devices (usually black with a single stripe on it) - these are diodes for the full bridge rectifier

OR

a single round device which usually has the following designations on it (+, -, AC, AC) or (+, -, "sine wave", "sine wave") where "sine wave" is a small graphical representation of a sine wave

then your device requires 12 VAC.

This is very simple to see, and if you have a digital camera, you could even take a picture and post the link here.  I could easily tell you just by looking at the picture if its AC or DC input.

Then again, just contact the manufacturer as the last person stated.