Hi Terry,

Polypropolyne capacitors are the best sounding types for audio use, with
polycarbonate following closely. It you take a look at the dissipation
factor vs frequency characteristics, you will find out that the
polypropolyne caps are the flattest in the regard.
As far as mechanical filters, you don't run into ringing with these units,
but if the filters are not terminated properly they will not have a
flat-topped response characteristic, and that can sound like ringing.
What I used to do if I didn't have the data on those old disc-wire filters
was to either hook up a network analyzer or an LCR bridge (not the kind that
is an extra function on those inexpensive multimeters) and measure the input
inductance of the filter.
This would allow me to determine the value of the required I/O resonating
capacitors. In addition to this, buy calculating the inductive reactance of
the filter, I would be able to roughly calculate in I/O inpedance.
Nowadays, with the newer Torsional Mode filters, this is not required as
long as you keep the strays in your PC board design below 30pF. The newer
filters (especially the 526-9695-XXX series) have a 2k in/out impedance so
you can use them where those Murata ceramic filters are used.

Pete

"Frank Dresser" wrote in message
...

wrote in message
ups.com...

[snip]

Many radios would sound much better with some attention to the audio
chain.
I used to think that a "little" distortion didn't matter. After all the

signals get pretty mangled by the ionosphere. And I was wrong. It makes
a
great difference. I have spent the day listening to HF and going back
and
forth just to get a feel for it.

The Radio Amateur's handbooks have some interesting articles about
increasing intelligibility in radio transmissions.

The older ones will have articles about AM ham radio transmissions.




While I would love to buy a really "good" receiver like the AOR7030+,
or
one of the better Drakes, or even an NRD, money being rather tight, I
am
happy to get any improvements I can.


Terry


You might want to consider a tube radio. A tube radio will get the best
performance from a simple diode detector. The diode detector works quite
well, except when the voltage across it gets low. As the voltage gets
low,
the diode's equivalent resistance goes up rapidly. Working the diode at
a
higher average voltage and into a high impedance load minimize these
problems.

In general, the consumer SW sets will sound better than the
communications/ham receivers.

Frank Dresser