dave wrote:
On 07/27/2014 11:57 AM, Cydrome Leader wrote:
dave wrote:

I worked at a pro audio company using wirewound power resistors to test
Class D power amps. I couldn't convince them to consider the reactance
effects at hypersonic frequencies, not only the switching artifacts but
the Power Factor Controllers too, create a rich VLF stew. It won't hurt
speakers but it may affect efficiency and heat load. Am I nuts?


unless these power resistors were very weird, as long tube shaped things
they'd still have less inductance than a speaker winding.

A very complex reactance anyway. The amps were ca 10KW 12KW bridged into
4 Ohm loads made of 8 Ohm cabs series parallel. There were a lot of
wirewound power resistors, in metal enclosures per OSHA, "switched" with
Banana plugs. I like the resistors you mount on heat sinks like power
transistors.

I hope you used special gold plated, cyogenic magical copper cables for
all that.

I just toured a plant that had gigantic resistor arrays mounted into what
appeared to be bread racks. All the resistors were sealed into oil filled
glass tubes, in house. Any like anything used on a shop floor, it had lots
of banana plugs, but with upto tens of thousands of volts across them when
energized. Each jack for each tap into the string was Dymo labelled. I
can't imagine how much it cost to make each one.

The really scary stuff was done in rooms with dented expaned metal cages.