That is my goal to have a very small board in my arsenal that keeps the diodes, reservoir, and transformer in a very small loop, with an onboard Quasimodo snubber squeezed in and secondary fuse. Then bring that pulsed DC elsewhere usually a RC or LC filter chain board, but it could be to a capacitor Multiplier board, or a Regulator board, etc. for final clean up. The positioning of the most violent current loop is then inherently detached no matter how you build it.
You'd be surprised how many just don't understand that. Probably from having "star ground"
repeated over and over like a mantra.
repeated over and over like a mantra.
In a power or ground plane, at high frequencies the loop return current will follow back directly
above or below the conductor in which it arrived (path of least impedance).
At low frequencies, the plane return current will return along the path of least resistance (a straight line).
The crossover point between the two modes is around 1kHz in most cases, so this is very relevant to audio.
For both modes, this is why you should not cut the plane. Doing so obstructs the path that the loop return
current is trying to take, and raises the impedance of the path (which is always bad), and also creates EMI.
Some nice illustrations of the behavior are presented here.
https://www.emcs.org/acstrial/newsletters/fall08/tips.pdf
above or below the conductor in which it arrived (path of least impedance).
At low frequencies, the plane return current will return along the path of least resistance (a straight line).
The crossover point between the two modes is around 1kHz in most cases, so this is very relevant to audio.
For both modes, this is why you should not cut the plane. Doing so obstructs the path that the loop return
current is trying to take, and raises the impedance of the path (which is always bad), and also creates EMI.
Some nice illustrations of the behavior are presented here.
https://www.emcs.org/acstrial/newsletters/fall08/tips.pdf
Last edited:
I've done dozens of 4 layer boards with Tango. The latest board 2 years back was KiCad and JLCPCB. You'll find 4
layers to be easier than 2. I would routinely run layer 3 (from top) as a solid ground plane with holes under SOME
opamps that were sensitive to capacitance. The other inner layer was used for traces that will NOT be wrong - power
and control lines with remaining nets on top and bottom. Minimum trace was 10 mil for signal, power at 50 for analog
chips and Motor Drive Amplifier boards with 250 mil traces on 2 of the 4 layers fused at 12 Amps. 2 oz copper on the
MDA boards. I used silk screen on both sides which is now routine. The commercial boards had some alignment
instructions and test point ID in the silk screen to make it serviceable.
G²
I am going to re-do the layout and make the board slightly larger, just a little. I also want to make a full wave version with a CT AC input, that one will need two snubber sets, so both boards will be identical size and similar form factor of the TO220 diodes across the edge, AC on one side DC on the other (maybe come into the narrow sides), fused secondary, etc. I will revise traces to power planes too and I really like the idea of using the two inner layers as a full uninterrupted 2 oz ground plane. The top and bottom can even double up some paths too because there is no worry about carving up the ground plane anymore. Impedances and inductances should be very low.
I'll keep two capacitors, its such an easy way to increase the ripple current rating and decrease esr. Probably increase the max diameters too, but put pads under them for all the standard radial cap pitches 5, 7.5, 10 etc... snap-in sized holes.