question about power adapter replacement for batteries

[tedrick]

Hello group -
I've put together a little Vellman microphone kit that uses three AA batteries - 4.5V

I'd like to use the device as a one way intercom and power the device off a small power adapter -

The power adapter I have is 5V - 0.7A --

would this power adapter be too high for this small kit? If so - is there a way I could lower the voltage?

Thanks!
Ted

 

[rayma]

The power adapter I have is 5V - 0.7A --would this power adapter be too high for this small kit?

Do you have a schematic of the preamp? A 5VDC supply would almost certainly be fine,
but some of these supplies put out even more voltage than spec, so check its output voltage
without a load using a DVM first. The op amp used could be a 5V single supply type, some of
which are limited to 5.5VDC maximum.

 

[tedrick]

Thanks Rayma -
yes - I tested the power adapter on my DVM and it measured 5.2 V (no load)
I do have a schem of this little device:
at:
https://www.jameco.com/Jameco/Products/ProdDS/2130984.pdf

I'm not sure what I'm looking for -- would it be the specs of the IC NE5532?

Thanks!
Ted

 

[bill_a]

Yes, the NE5532 - it's rated up to 22V, so your adapter is fine.

 

[rayma]

Yes, the NE5532 - it's rated up to 22V, so your adapter is fine.

Yes, just be really really careful of the power supply polarity when connecting.

 

[tedrick]

cool - thanks -
the power supply has black and red wire -
I'll use this method to confirm that black is - and red is +
How to quickly determine the polarity of your DC power supply with a multimeter

 

[tedrick]

here's what I found....

my 3 AA batteries deliver 4.5V and the preamp circuit draws 9 mA

now I'll try the phone charger again and see how many mA the circuit is drawing on the phone charger -