I'm thinking about buying a TDA8920 audio amplifier and power supply and I need some help buying the right PSU. See edit below.
So here's what I know.
L (AC) = Live (Brown*)
N (AC) = Neutral (Blue*)
__|__ = This normally indicate natural ground in AC (green/yellow**). ___ _
** in Sweden
So here's where the problem starts. On AC-DC 5V you will get +VCC and GND connectors.
But TDA8920 is a op-amp chip and requires +V GND -V (±12.5 to ±30 V). I have been looking on some SMPS (switching-mode power supply) and there output is as following (see below).
On some units COM are replaced by -V.
How do I wire it all up?
TDA8920 --> SMPS
+V --> +V
-V --> -V (or -V --> COM?)
GND --> Where does this fellow go? Also -V/COM? COM is normally ground on voltage meters and there is no specified output as AC-DC 5V adapters have.
Also I'm hooking up a 24V to 5V step-down.
Ebay item: 191014663436
step-down --> SMPS
IN+ (V) --> +V
GND --> -V/COM?
Audio Amplifier - TDA8920
Ebay: D Class TDA8920 Digital Stereo Audio Amplifier OCL 2*80W Power Amp Board BTL
Item number: 190898639459
+V GND -V
Ebay item: 291031105572
L (AC) N (AC) __|__ ___ _ -V -V +V +V
Ebay item: 231045540508
L (AC) N (AC) __|__ ___ _ COM (-V on some units) +V
As a side note, do you know how many A my PSU will need to power the following:
PSU -> TDA8920
PSU -> Stepdown -> Raspberry Pi
Raspberry Pi -> Arduino (5v from RPI or stepdown)
Raspberry Pi WiFi and USB Soundcard
Raspberry Pi requires 700mA/1A
TDA8920 n/a - can't find any information
Stepdown are rated 5A on the output side
I have been looking on SMPS PSU ranging from 2.2A-4.5A, will this be enough?
EDIT: 20:00 / 2014-03-30
Now I have googled and googled some more. This is what I have come up with:
TDA8920 --> SMPS
+V --> +V
-V --> -V
GND --> GND/Ground/Common
You can't choose one with COM / +V (Not for this board at least) due to the fact it requires a negative voltage. Or you need two power supplies. (So scratch S-50-24 off the list)
Wikipedia Ground (electricity) # 5.1 Circuit ground versus earth
Voltage is a differential quantity. To measure the voltage of a single point, a reference point must be selected to measure against. This common reference point is called "ground" and considered to have zero voltage. This signal ground may not be connected to a power ground. A system where the system ground is not connected to another circuit or to earth (though there may still be AC coupling) is often referred to as a floating ground.
But if you want to build a Audio amplifier for a radio, you must choose another power supply, due to the fact that switching-mode power supply are interfering with RF frequencies.
So back to the drawing board and get me a AC-AC transformer to ~25V and a AC-DC rectified & filtered +-25DC power supply with capacitors.
Now I will search for a way to calculate VA requirements and by the look of things these are huge so maybe I will choose a crappier audio amplifier to fit inside a old 50/60 radio.
EDIT2: 23:24 / 2014-03-30
None of the power supplies I have mention does work with this audio amplifier, I have checked some schematics on similar switching-mode power supply and they don't give you -V on -V pin. It's just COM (common).
You need a "bipolar/split-rail/dual rail supply" power supply
Regarding previous link about radio interference there shouldn't be a problem if your switching-mode power supply are correctly made. If you google "Interference from Switched Mode Power Supplies" you will find a article by UKQRM about this. (Don't have enough rep to link more).