mike11298 said:
oh ok, well I have a 6 ohm speaker, but when the graph says "24v", is it refering to a +12v, -12v supply or +24v, -24v supply?
Also, is there a ay I can change speaker impendance for better performance? (adding a resistor just doesnt seem right
EDIT: ... and do I
need a split power suply? why can't it just be single supply. Also, there was a schematic in the datasheet for a single supply. Is that OK?
The posted graph has "(+/-V)", right after the words "SUPPLY VOLTAGE", in the horizontal axis label. So it does mean both + *AND* - 24 volts, i.e. a dual or "split" power supply. A +/-24v split supply is equivalent to a 48v single supply.
Also, your original 20v single supply would be worrisome. The datasheet shows 20v as the absolute minimum guaranteed-to-work difference between the supply rails. Plus, it would only give you about 3 Watts per channel.
See page 16 of the LM4766 datasheet, at
**broken link removed** . It says "The typical application of the LM4766 is a split supply amplifier."
You CAN use it in single-supply mode. But it's a little more complicated, and might even compromise the sound quality, slightly, by necessitating electrolytic input and output AC-coupling/DC-blocking capacitors.
But yes, the single-supply schematic, in the datasheet, should be perfectly fine (especially if you have a 48v to 52v supply).
What makes you want to use a single supply, so badly? A split supply is easier. And making a split power supply is easy, too. Just get a transformer with a dual secondary, or a center-tapped secondary, with each secondary having the voltage needed, at a high-enough current. Or, get two separate transformers. Then all you need is a fuse, a bridge rectifier (or individual diodes), and two or more big electrolytic capacitors. That's it! These chipamps work just fine with a simple unregulated power supply. [ NOTE: Be safe. Working with AC mains voltages can kill you.]
If acquiring a transformer, remember that AC mains voltage transformers' "VAC" ratings are usually in terms of RMS, which means their peak voltage is actually 1.414 times that. Here is a very nice, concise page, about linear power supply design, that should have the necessary details:
**broken link removed**
- Tom Gootee
**broken link removed**