Archive of the former Yahoo!Groups mailing list: MOTM

----- Original Message -----
From: <mark@...>

--LH--
At 8:42 PM -0600 03/31/01, J. Larry Hendry wrote:
I use # 14 stranded in all mine.

--Mark--
Really?? That seems a bit much. Are you running them over a long
distance??

--LH--
Well, the best connection for each module is directly to the power supply in
a star type fashion. However, when you get your system up to the 40 +
module range, this is not practical. So, I put the PCBs closer to the
modules they serve and run the larger wire to the PCBs. So the current of
all 12 modules served from that PCB is on the wiring to the power supply.
OK, so whats the big deal? It might be 400 mA or so per PCB. The wire is
not sized to the current flow expected. If it were, # 18 would be oversized
for everythying. It is sized to eliminate small voltage drops between the
power supply and the distribution PCB. These unwanted voltage drops cause
by current draw variations in one module can cause interation with another
module.

---Mark---
My entire studio is run off of two 12/3 cords going from the
wall outlets to the power conditioners. Most gear uses 18/3, including
tube amps that draw so much current you can use them to heat up sandwiches.

--LH--
You are comparing apples to oranges. The voltage drop in these AC lines
really has no negative effect on your gear. Small voltage fluctuations on
your 15 VDC line do. The AC supply voltage at your main panel routinely
varies by as much as 3 or 4 volts (more in California) even before
variations caused by voltage drop is considered. We (power companies, my
vocation) vary the AC voltage delivered to your house on purpose. US code
specifies anything between 114 and 126 as acceptable for residential
service.

--Mark--
I notice that motm uses four conductors, but do all three go to the power
supply?? Since that seems like two grounds, I assume the first one is
common to the supply voltage, but what is the second one -- local, earth,
or what??

--LH--
Paul told me that he has one return for the negative power supply rail and
one for the positive. I am not meaning to quote him here, but in general he
told me this arrangement was for the purpose of lower noise. Correct me
Paul if I said something wrong.

--Mark--
14AWG is more like electrical supply than electronics supply.
I'll have more choices in three conductor cable than four
conductor cable.

--LH--
4 conductor is getting more common. New code is requiring a ground separate
from neutral now on many 240 volt appliances (UL caught on to the fact that
these appliances have 120 volt connections.

--Mark--
Now the big question is whether the PCB will fit, how long is it??

--LH--
The official MOTM power jumper PCB with 12 MTA156-4 connectors is 2 1/2" x 4
3/16" by my measurement. I can send you a photo of one if you like.

Larry H