[ARC5] HS-33
Richard Knoppow
1oldlens1 at ix.netcom.com
Sat Aug 10 02:42:24 EDT 2019
Receivers were made this way back into the 1930s, for
instance the Hammarlund HQ-120-X, headphones just go to the
speaker winding on the transformer meant for about 8 ohm
speakers. Low impedance phones tend to be too loud so loading
them with a pad can help. On my several receivers with phones
going to the speaker winding the level is OK with 600 ohm to 20K
ohm headphones. I think most of these amps are OK with an open
circuit, certainly old 25Kohm Western Electric phones are close
to that for a 4 or 8 ohm output.
The very high impedance magnetic phones were meant to produce
good volume from crystal detectors.
Crystal headphones originated around the mid-1930s. Most
were made by Brush, who held the patents. The impedance was
extremely high, on the order of 100K ohms. Unlike magnetic or
moving coil phones they were connected in parallel. The impedance
is almost purely capacitative so they won't work in series. Brush
made various models, some with very wide frequency response and
low distortion. They also had good low frequency response. The
trouble with crystal phones is the same as for crystal
microphones; they are sensitive to moisture, heat and shock. If
you have a pair that works you are lucky. While Brush held the
master patents their microphones and headphones did not seem to
be as well protected as those made by Astatic. I have six or
seven Brush headphone capsules; one works, the others are
literally just mush inside.
Another type of phone that was popular in the 1920s and 1930s
is the Baldwin balanced armature headphone. These use a reed
armature driving a mica diaphragm by means of a rod. The winding
is on the magnet. These have the advantage of high sensitivity
and relatively less distortion than the familiar clamped edge
diaphragm type magnetic phone. However, they are heavy and
uncomfortable.
On 8/9/2019 2:18 PM, D C _Mac_ Macdonald wrote:
> Since it appears that "modern" receivers simply put the
> headphones in a jack that breaks the line to the speaker, a 600
> Ohm impedance would probably not "load" that audio output very much.
>
> To me, the HS phones are horribly uncomfortable to wear as my
> ears have a considerable protrusion of cartilage but what I have
> was all I could afford back in 1956!
> I got a set of crystal (probably) high impedance phones from my
> grandfather to use with my Walter Ashe WAR-25 regen receiver as a
> Novice! I suspect he had had them since the 1920s!
> I also have a Roanwell headset w/ boom mic from my days on a B-52
> crew in the mid-1960s. Receivers are H-443/AIC and mic (dynamic)
> is M-87/AIC. I don't have the four-conductor female jack to
> receive the plug on the headset.
>
> 73 de Mac, K2GKK/5
> Since 30 Nov 1953
> Oklahoma City, OK
> USAF, Retired ('61-'81)
> FAA, Retired ('94-'10)
>
> ****
>
> -----------------------------------------------------------------
> *From:* arc5-bounces at mailman.qth.net
> <arc5-bounces at mailman.qth.net> on behalf of Kenneth G. Gordon
> <kgordon2006 at frontier.com>
> *Sent:* Friday, August 9, 2019 14:50
> *To:* Joseph Orgnero <josepho at shaw.ca>
> *Cc:* ARC5 at mailman.qth.net <ARC5 at mailman.qth.net>
> *Subject:* Re: [ARC5] HS-33
> On 9 Aug 2019 at 12:42, Joseph Orgnero wrote:
>
>> Thank you Ken for the info.
>> I was curious as to whether the HS-23 or HS-33 were designed for specific
>> equipment.
>> It appears that is a matter of "taste"!
>> 73's
>>
>> Joe Orgnero VE7LBI
>
> Well, not necessarily, Joe. The output impedances of the various
> mil receivers changed
> over the course of WWII.
>
> 600 ohms became, at least for the Navy, the defacto "standard",
> but there were still many
> receivers in use which showed output impedances higher than that.
>
> Higher impedance does give you greater audio sensitivity, and I
> prefer them for that.
>
> Also the crystal-radio crowd swears by them. For them, the higher
> the better.
>
> My best phones right now are a set of those from a sound-powered
> deck-talker set.
>
> The difference in greater audio sensitivity between those and my
> set of ANB-H1s is quite
> apparent.
>
> However, I used a set of HS-33s (600 ohm) with my RAL-7 for many
> years and liked them.
>
> Ken W7EKB
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--
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL
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