The OP has a bad habit of editing the original posts.TheDirty:
Those connectors are still way too small!Man, those things are giant.
We have now lost the continuity of changes made to
the original design by the OP. The original use of 25mil
square pin headers was a poor choice. The revised
connectors are better (but undocumented). They are
also too fat for the physical space, hit other part’s
outlines, and allow no room for fingers to grip them.
On the topic of conductor and connector specs, it has
less to do with the physical size and a lot to do
with the contact resistance. For a 150Watt audio amplifier,
driving a 4 ohms load (speaker):
V = IR, I=V/R, R=V/I, P=IV, P= IIR, I = (P/R)^1/2
I = (150/4)^ 1/2 = 6.123Amps (RMS)
For a sub one watt power loss in each connector:
R(max) = Rload/150 = 4/150 = 26milliohms.
Even allowing for 50W per amplifier, it’s connectors
and PCB traces would have to be less than 78 milliohms.
The original design used three amplifiers to drive a
common load (the 4 ohms speaker).
The output AC impedance of the amplifier IC is also
very low (guess at less than 10milliohms).
In the original desing three amplifiers are combined,
with 200 milliohm ‘matching’ or ‘sharing’ resistors.
For this to work at all the three amplifiers need a
very low impedance path to the load. How low?
Much less than 100milliohms!
The use of 25mil square pin headers was just wrong.
In the original article the author used screw terminals
for all external connections and chassis wiring. These
provide the low impedance and low resistance needed
to reliably deliver the heavy load current, heavy supply
current, and equalize the load over six amplifier ICs,
three in parallel, two sets in push-pull or
BTL (Bridge Tied Load).
Here’s an [on-line calculator for trace width.
Here’s the results to deliver 6.2Amps over two inches length:
http://www.stonard.com/SFE/trace_width_1.jpg](ANSI PCB Track Width Calculator)
