AMB Laboratories DIY Audio

[bcg27]

Here are links to the two headfi threads I remembered:

http://www.head-fi.org/forum/thread/279 ... s-on-sound

http://www.head-fi.org/forum/thread/446 ... ound-query

The first one is linked to at some point in the second.

[egallego]

Great post NwAvGuy. What about using a balanced in order to double power output?

[NwAvGuy]

Great post NwAvGuy. What about using a balanced in order to double power output?

Is this a job interview?

Balanced outputs, all other things equal, provide a 6 dB increase in level. This is actually 4 times the power into a given impedance. That's why you'll sometimes see things like a 100 w/ch stereo power amp rated for 400 watts when it's bridged (the reality is it usually doesn't quite work out that way).

Power is voltage squared divided by the impedance. So if the Mini3 can manage 3 volts RMS of max output into say 600 ohms that's 9/600 = 15 mW. If we add a second Mini3 to drive the other half of the waveform now you can get, in theory, 6 volts RMS of output and that's 36/600 = 60 mW or four times more.

But each amplifier actually sees half the actual impedance. So the 600 ohm load really looks like a 300 ohm load. Or my inefficient 80 ohm Beyerdynamic headphones are going to look like 40 ohms. And 40 ohms is getting into the "unhappy" high distortion territory for the Mini3 (see my review). So this can be significant.

If, instead, we just double the power supply voltage, you get the same four times bump in output power but the amp sees the true load impedance, not half. So it has an easier time and will (especially for the Mini3) produce much less distortion.

And, in the real world, you'll get more power from doubling the battery voltage compared to bridging two amps due to the way the various losses add up.

Some claim that non-linearities and distortion get canceled out by bridging/balanced configurations. And that can be true for certain kinds of distortions. But other kinds of distortions are additive and you can end up with roughly twice as much distortion from a bridged/balanced design. And that's ignoring the lower impedance issue which nearly always creates more distortion. In the real world, I've yet to see a bridged/balanced design perform as well as a single amp solution with everything else being equal.

So, when you have the choice and a true split power supply, a single amp with higher supply rails will almost yield higher performance than a bridged/balanced solution on lower supply rails. The biggest value for bridging is when you're stuck with a single supply (like in automotive sound) or for really high power levels (pro-sound live concert amps).

[NwAvGuy]

Here are links to the two headfi threads I remembered:

http://www.head-fi.org/forum/thread/279 ... s-on-sound

http://www.head-fi.org/forum/thread/446 ... ound-query

The first one is linked to at some point in the second.

Thanks, I'm wading through them now (the short one was easy)... some interesting reading so far!