With respect to the Hammond chokes, are the 193 series required? Since they are in parallel with the AC line, and not drawing a lot of current, couldn't the smaller open frame series (159) works as well? Especially if mounted in the chassis of a preamp or DAC for instance. Resistance is higher for the smaller chokes at the same inductance, but that shouldn't be a problem should it?
Thanks,
Ron
Ron, i hope this could give you a guide from Jon Risch.
"-Inductors-
Preferred units: these are 50 uH 15 amp powdered iron or ferrite
core inductors with very low DCR.
Dale #8401, J.W. Miller #5524, and Renco RL-2226-15-50. Even
though these are all rated at 15 amps DC, these particular models
were tested by UL for AC use when selected for use in a commercial
surge suppressor, so I know they can handle it. Unfortunately, I
have been unable to find a ready source for these.
Other parts in the series, such as the J.W.Miller #5520, a 100 uH,
10 amp part would be useful. Available from Allied, #871-7015 for
$6.71 each. These can handle up to 7 amps AC continuous for a 40
degree C temperature rise, and 10 amps AC for a 60 degree C temp.
rise. I would recommend not using them for a total equipment load
beyond approx. 5 amps (600 watts) to maintain linearity and a safety
margin. For power amps, two can be used in parallel for a total
safe margin AC current draw of 10 amps, 14 amps recommended maximum.
To build a filter or suppressor for an entire system, I would
recommend building separate units for the lower power components,
and a separate unit with paralleled inductors for each power amp.
Other inductors can be used, but the two most significant features
are: very low DCR, preferrably below 0.03 ohms for 10-15 amps
current draw, and below .06 ohms for 5-7 amps. The second is the
proper form factor and core, in this case a powdered iron or
ferrite rod core, not a torroid or bobbin style. The inductor
must also have sufficient AC current capacity for the total load,
plus a safety margin.
When paralleling inductors, use one's leads for the circuit hookup,
and use the others to stand the second inductor as far away as
possible, by making a little hook in the end of the leads, and
using that to make the connection to the other inductor. Keep
inductors away from any steel or conductive parts to minimize
inductor distortion.
Alternate sources for inductors:
Marlin P. Jones Assoc. 1-800-652-6733 Surplus parts outfit.
part# 9117-CH, Dale 7 amp 150 uH powdered iron core inductor,
$1.25 each. Use in parallel for a total AC current capacity of
10 amps maximum AC current draw, 7 amps (860 watts) recommended
maximum loading."
