Converting VA into amps?
Answer:
While it is true that the peak voltage will be about 1.4 time the RMS AC voltage, once you start drawing current the voltage will drop. But if you can get by with range from 12 to 16.8 you should be OK on voltage, also, if this is an audio application, you might be OK with this transformer even though it can't give you 4 amps continuously, an audio application will draw maximum current for very brief periods, the average should be far less. However if the specifications already accounted for that fact, then this transformer will not be big enough.
VA = volts x amperes --- therefore 30 VA at 16.8 volts yields 30/16.8 = 1.8 amperes max which is below your 4 amps requirement. Therefor that transformer is not suitable for your application.
Have you noticed yet that you have a transformer producing 12 volts output, and you need 16.8 volts?
It's not going to work.
As long as it's single phase, just divide VA by secondary volts to get secondary current.
30VA / 12V = 2.5 A on secondary
So it sounds like that transformer won't quite do it.
You will need a 48 VA transformer (or larger) to make sure that you have the 4 A that you need!
(Paul above has a good point too, you might have a tricky time getting 16.8 VDC from 12 VAC)
In addition to all the good advice already given, don't forget that an underspecified mains transformer can have a deleterious affect on the actual audio quality. This is because an undersized transformer core can saturate at peak load, so that current it supplies hits a ceiling instead of rising to meet demand. This can seriously distort the output waveform, an effect particularly noticeable on loud bass notes.
So it's not just that the transformer might overheat; even if the intermittent nature of the load allows an inadequate mains transformer to survive, you could still suffer inferior sound. There's no substitute for a big, beefy mains transformer in an audio amp that makes any claim to quality.
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: