Re: Choke in the Negative Lead...Another view


John Byrns wrote:
In article <1144878368.372046.247410@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"pfjw@xxxxxxx" <pfjw@xxxxxxx> wrote:

Andrew Jute McCoy wrote:


Bunk. That's a special case for people too cheap to buy a choke and who
therefore use the loudspeaker field coil. It has nothing to do with
hi-fi. It is an amateurish attempt at spin by John Stewart to pretend
that it does.

YIKES:

What-under-heaven do you think a field-coil is? It is a CHOKE. PM-type
speakers have been around well-before field-coils, and when caps became
small, cheap, and (more-so) reliable they came right back. However,
designers loving to kill several birds with a single stone used the
need for a choke together with the need for a large (expensive) magnet
to have their choke do double-duty. Many designs added a second coil in
the system as a hum-buck, further reducing the need for capacitance.
But if COST were the only factor, and if CAPACITANCE was reliably
available at a reasonable cost at the time, betcha that the field-coil
speaker design would never have seen the light of day.

Nothing "too cheap" or "special" about it. Actually a quite-elegant
solution to a fairly difficult problem of the time. For an individual
of your advanced age, you really ought to bone up on your history. Very
likely the first artificial sound you ever heard produced electrically
was on field-coil speakers.

You should count yourself lucky to be around during a time when
excellent, reliable and (relatively) compact capacitance is available
at an incredibly cheap price based on the relationship between
capacitance and choke costs in the past. Maybe you should consider the
simplicity of using capacitors properly configured vs. multiple large,
expensive dual-winding chokes to accomplish such a simple requirement
as making ultra-smooth DC.

You also are clearly too inexperienced to understand that when PM
speakers are substituted for FC speakers today, not only does
additional capacitance have to be added to make up for the smoothing
action of the coil, but usually considerable resistance _in addition_
to that of the original coil must also be added to make up for the
increase in B+ due to that same capacitance and removal of the coil.

Mr. McCoy, there is nothing new under the sun when it comes to
tube-only designs. By looking at past discoveries and solutions, much
can be learned and many silly errors avoided. You would do well to
consider this.


Peter Peter, whatever are we going to do with you? Unfortunately I not
taken an interest in the history of speakers, but I think your claim that
field coil speakers were used mainly to get a free choke for use is the
power supply is just more BS of the type we have come to expect from you.

Never made that claim at all. Once again, you are searching for
exception. What I did claim is that prior to good electrolytics, PM
speakers existed. And that if COST were the only factor, field-coil
speakers would never have seen the light of day... this as Mr. McCoy
made the 'too-cheap' claim. And I also wrote that they more-or-less
'went away' in common radio designs when electrolytics became
inexpensive and compact. Which they did.

That designers utilized the coil as a choke actually is quite clever
rather than having to manage both a choke and a coil, or PM speaker.
That it is a cost-saving also is simply a result of good engineering...
something that seems to be getting lost around here.

Which, of course has absolutely nothing to do with the fact that magnet
science was in its relative youth at the time, so field-coil speakers
were a means to get reliable, powerful magnets for reliable, powerful
speakers. MUCH more costly than the PM speakers of the time, and
certainly more costly than PM technology today. And certainly far more
costly given the need for a separate power-supply, as you suggest.

Do you *ever* read for content?

Rest snipped.

Peter Wieck
Wyncote, PA

.

Relevant Pages

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