Getting old is not recalling the alternatives offered, so I'm a dummy. I
found the filament xfmr first and tried it but it reduced volume so I
assume my radio which is non-military doesn't have 600 ohms like the
military manual I have. So I guess mine is commercial, either a
SP-200-SX or more likely a SP-210-SX and I think it has a 3.2 ohm
output transformer.
I can't find any info and I wonder if anyone knows for sure on the
commercial models output transformer's impedance.

--
Thanks & 73
Hank WD5JFR









"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
What's an easy way these days with limited audio xfrmrs around to get
the 600 ohm spkr output to 4 or 8 ohms?

70V PA distribution transformers.

A 70V distribution transformer with an eight-watt input tap will give
you
600 ohms input.

Old 70V equipment is usually available free for the asking from your
local
installed sound company.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Henry Kolesnik" wrote in
message ...
Getting old is not recalling the alternatives offered, so
I'm a dummy. I found the filament xfmr first and tried it
but it reduced volume so I assume my radio which is
non-military doesn't have 600 ohms like the military
manual I have. So I guess mine is commercial, either a
SP-200-SX or more likely a SP-210-SX and I think it has a
3.2 ohm output transformer.
I can't find any info and I wonder if anyone knows for
sure on the commercial models output transformer's
impedance.

--
Thanks & 73
Hank WD5JFR


All of the Super-Pro models from the SP-100 on had 500
ohm outputs for the loudspeaker and a loosly coupled 8K
winding for headphones. The 500 ohm output will drive a
loudspeaker at much reduced volume. A 12.6V filiment
transformer has about the right impedance ratio (100:1) to
drive a 4 to 8 ohm speaker from this tap. These tramsformers
have enough core material to work down to low audio
frequencies and surprizingly good high frequency response.
70V public address transformers also work very well as Scott
Dorsey pointed out. The original Hammarlund speakers for the
Sp-200, 400, 600, had matching transformers built-in.
The SP-100 has a front panel switch for the loudspeaker
but the later versions do not. You need to mount a switch
(maybe in the loudspeaker cabinet) to cut it off. Use a DPDT
switch with a 500 or 600 ohm resistor switched in when the
LS is turned off to provide a load to the audio transformer.
It should handle a couple of watts.
The headphone winding is not critical of load impedance
and will work with phones from 50ohms to high impedance.
The military and commercial versions of the SP-200 and
210 were identical except for the use of hermetically sealed
transformers and chokes and oil filled filter capacitors in
the military versions, and some variations of panel finish.
There is an owner's manual for the SP-210 somewhere on
the web, maybe on BAMA, I have a copy but don't remember
where I downloaded it.
Most of the communications receivers built up to
perhaps the 1950s had 500 ohm or 600 ohm outputs. A few even
had the output transformer in the loudspeaker cabinet.
--

--
Richard Knoppow
Los Angeles
WB6KBL

Richard
The volume decreased with the filament transformer so I need to open it
up and see if someone made some mods. I downloaded the military manual.
It seems to me that someone at Ham went nuts changing model numbers for
very insignificant reasons.
"Richard Knoppow" wrote in message
m...

"Henry Kolesnik" wrote in message
...
Getting old is not recalling the alternatives offered, so I'm a
dummy. I found the filament xfmr first and tried it but it reduced
volume so I assume my radio which is non-military doesn't have 600
ohms like the military manual I have. So I guess mine is commercial,
either a SP-200-SX or more likely a SP-210-SX and I think it has a
3.2 ohm output transformer.
I can't find any info and I wonder if anyone knows for sure on the
commercial models output transformer's impedance.

--
Thanks & 73
Hank WD5JFR


All of the Super-Pro models from the SP-100 on had 500 ohm outputs
for the loudspeaker and a loosly coupled 8K winding for headphones.
The 500 ohm output will drive a loudspeaker at much reduced volume. A
12.6V filiment transformer has about the right impedance ratio (100:1)
to drive a 4 to 8 ohm speaker from this tap. These tramsformers have
enough core material to work down to low audio frequencies and
surprizingly good high frequency response. 70V public address
transformers also work very well as Scott Dorsey pointed out. The
original Hammarlund speakers for the Sp-200, 400, 600, had matching
transformers built-in.
The SP-100 has a front panel switch for the loudspeaker but the
later versions do not. You need to mount a switch (maybe in the
loudspeaker cabinet) to cut it off. Use a DPDT switch with a 500 or
600 ohm resistor switched in when the LS is turned off to provide a
load to the audio transformer. It should handle a couple of watts.
The headphone winding is not critical of load impedance and will
work with phones from 50ohms to high impedance.
The military and commercial versions of the SP-200 and 210 were
identical except for the use of hermetically sealed transformers and
chokes and oil filled filter capacitors in the military versions, and
some variations of panel finish.
There is an owner's manual for the SP-210 somewhere on the web,
maybe on BAMA, I have a copy but don't remember where I downloaded it.
Most of the communications receivers built up to perhaps the 1950s
had 500 ohm or 600 ohm outputs. A few even had the output transformer
in the loudspeaker cabinet.
--

--
Richard Knoppow
Los Angeles
WB6KBL

"Henry Kolesnik" wrote in
message ...
Richard
The volume decreased with the filament transformer so I
need to open it up and see if someone made some mods. I
downloaded the military manual.
It seems to me that someone at Ham went nuts changing
model numbers for very insignificant reasons.
"Richard Knoppow" wrote in
message
m...

Before you do any surgery make sure the matching
transformer is connected the right way around, the 120V
winding goes to the 500 Ohm winding on the RX, the filiment
winding goes to the loudspeaker.
The output transformer would have to be changed to
provide a low impedance output, that would be pretty
obvious. The headphone output is also brought out the back
on the terminal board.


--

--
Richard Knoppow
Los Angeles
WB6KBL

"Henry Kolesnik" wrote in
message ...
Richard
The volume decreased with the filament transformer so I
need to open it up and see if someone made some mods. I
downloaded the military manual.
It seems to me that someone at Ham went nuts changing
model numbers for very insignificant reasons.

Note that the military type numbering was not done by
Hammarlund. The Super-Pro went through three versions, the
SP-100, the SP-200, the SP-400. The SP-100 was available in
three versions with different frequency ranges, the SP-400
in two ranges. The SP-100 was also available with or without
the crystal filter (I've never seen one without) but
evidently the filter could be retrofitted. All three were
also available in table or rack mount versions. There were
at least two power supplies, a standard and a 50 hz supply.
The 50hz supply will work on 60hz but not the other way. The
last military versions came with solid state power supplies.
There are some circuit differences between the
different frequency ranges. The standard version and the
aircraft frequency version (100 to 400khz) have series fed
RF stages with some loading on the low frequency range and
broadcast range of the standard version to broaden out the
RF bandwidth. The high frequency version (1250khz to 40Mhz)
has shunt-fed RF to keep the DC out of the RF coils. The
coils have ferrite cores so removing the DC sharpens them up
a bit, which is needed for a single conversion receiver
operating a the higher part of the frequency range. A
similar arrangement is used in the SP-400 and SP-400S (the
last has the same 1250 to 40Mhz range).
The three frequency range receivers had different
military type numbers.
The SP-210 is the same as the SP-200 but came with a 10"
loudpeaker, there was also a SP-220, again the same chaissis
with a 12" speaker. The standard version had an X on the end
of the number (SP-210X) indicating it had the crystal
filter, the high-frequency coverage version had an S on the
model number as well as the X for crystal, vis: SP-210SX.
The first versions, the SP-100 had glass multi-pin tubes
with external sheilds, the SP-200 was redesigned to use
metal octal tubes with do not need external shields.
Otherwise the circuits are pretty much the same.
The main virtue of the Super-Pro was the band switching
arrangement. This is a very complex system of knife edge
switches operated by cams, presumably to reduce lead length.
National achieved something similar with the plug-in coils
on the HRO and the sliding RF box on the NC-100, 101, and
later NC-200 and 240 types. This may actually be a better
arrangement. Hammarlund caught up by using a rotary turret
on the SP-600 and Pro-310. But, except for Hallicrafters
version of the Super-Pro, which also has a turret, I don't
know of many receivers that used this good, but complex
arrangement. One virtue of the Super-Pro is its excellent
interstage shielding and lack of spurious responses,
probably at least in part due to the RF stage arrangement.
It is also a relatively low radiation reciever.
Note that both the sliding coil method of adjusting the
mutual inductance of the IF stages (and hence bandwidth) and
the type of crystal filter circuit were Hammarlund
exclusives. The IF bandwidth arrangement allows symmetrical
expansion of the response curve where some other methods
cause the bandwidth to expand only on one side. The crystal
filter is arranged to vary the Q of the loading coil and,
again, does not change the center frequency or gain as the
bandwidth is changed, plus it uses a butterfly capacitor to
adjust the phasing again so the center frequency does not
vary with the notch position. This is a much more
satisfactory system than the original Lamb filter used on
National and Hallicrafters receivers until pretty late in
the game.
I have the civilian version of the instruction book and
will post it to you via private e-mail if you can't find it.
I am still on a dial-up and its pretty big but its yours if
you desire. BTW, it has a long list of the patents used
(mostly RCA and Hazeltine Labs) some of which are
interesting to chase down.



--

--
Richard Knoppow
Los Angeles
WB6KBL

Richard
Having the dial up goes with the SP, hi hi. I did connect the 500 to
the fil xfrmr pri. I was a GCA tech in he air force, worked as a radio
and TV tech in high school and college and am a grad engr and have a bit
of experience. And I 've had a few SP 600s but this is my first Super
Pro 200. 1.25 to 40 Mcs, xtal filter, S-meter and 60 cps pwr supply and
stamped Type O after all the patents. It's kind of a neat boatanchor
that I've never played with before and for some unknown reason I keep on
playing with it. I wish it had the full BCB but it's nice on CW & SWL.
After being on all day I don't notice that much drift. It is just about
right on on all the WWVs, but all you know about other frequencies is
the first 2 digits. I don't need the manual as I have a copy of a copy
of copy and the TM 11-866 but neither is really clear on the model
number.
I was offered $75 at the last hamfest and maybe I'll be lucky and get
closer to the $150.00 I have in it or trade for some other beast.
73
Hank
"Richard Knoppow" wrote in message
m...

"Henry Kolesnik" wrote in message
...
Richard
The volume decreased with the filament transformer so I need to open
it up and see if someone made some mods. I downloaded the military
manual.
It seems to me that someone at Ham went nuts changing model numbers
for very insignificant reasons.

Note that the military type numbering was not done by Hammarlund.
The Super-Pro went through three versions, the SP-100, the SP-200, the
SP-400. The SP-100 was available in three versions with different
frequency ranges, the SP-400 in two ranges. The SP-100 was also
available with or without the crystal filter (I've never seen one
without) but evidently the filter could be retrofitted. All three were
also available in table or rack mount versions. There were at least
two power supplies, a standard and a 50 hz supply. The 50hz supply
will work on 60hz but not the other way. The last military versions
came with solid state power supplies.
There are some circuit differences between the different frequency
ranges. The standard version and the aircraft frequency version (100
to 400khz) have series fed RF stages with some loading on the low
frequency range and broadcast range of the standard version to broaden
out the RF bandwidth. The high frequency version (1250khz to 40Mhz)
has shunt-fed RF to keep the DC out of the RF coils. The coils have
ferrite cores so removing the DC sharpens them up a bit, which is
needed for a single conversion receiver operating a the higher part of
the frequency range. A similar arrangement is used in the SP-400 and
SP-400S (the last has the same 1250 to 40Mhz range).
The three frequency range receivers had different military type
numbers.
The SP-210 is the same as the SP-200 but came with a 10"
loudpeaker, there was also a SP-220, again the same chaissis with a
12" speaker. The standard version had an X on the end of the number
(SP-210X) indicating it had the crystal filter, the high-frequency
coverage version had an S on the model number as well as the X for
crystal, vis: SP-210SX.
The first versions, the SP-100 had glass multi-pin tubes with
external sheilds, the SP-200 was redesigned to use metal octal tubes
with do not need external shields. Otherwise the circuits are pretty
much the same.
The main virtue of the Super-Pro was the band switching
arrangement. This is a very complex system of knife edge switches
operated by cams, presumably to reduce lead length. National achieved
something similar with the plug-in coils on the HRO and the sliding RF
box on the NC-100, 101, and later NC-200 and 240 types. This may
actually be a better arrangement. Hammarlund caught up by using a
rotary turret on the SP-600 and Pro-310. But, except for Hallicrafters
version of the Super-Pro, which also has a turret, I don't know of
many receivers that used this good, but complex arrangement. One
virtue of the Super-Pro is its excellent interstage shielding and lack
of spurious responses, probably at least in part due to the RF stage
arrangement. It is also a relatively low radiation reciever.
Note that both the sliding coil method of adjusting the mutual
inductance of the IF stages (and hence bandwidth) and the type of
crystal filter circuit were Hammarlund exclusives. The IF bandwidth
arrangement allows symmetrical expansion of the response curve where
some other methods cause the bandwidth to expand only on one side. The
crystal filter is arranged to vary the Q of the loading coil and,
again, does not change the center frequency or gain as the bandwidth
is changed, plus it uses a butterfly capacitor to adjust the phasing
again so the center frequency does not vary with the notch position.
This is a much more satisfactory system than the original Lamb filter
used on National and Hallicrafters receivers until pretty late in the
game.
I have the civilian version of the instruction book and will post
it to you via private e-mail if you can't find it. I am still on a
dial-up and its pretty big but its yours if you desire. BTW, it has a
long list of the patents used (mostly RCA and Hazeltine Labs) some of
which are interesting to chase down.



--

--
Richard Knoppow
Los Angeles
WB6KBL

Harold E. Johnson wrote:
"Henry Kolesnik" wrote in message
...
What's an easy way these days with limited audio xfrmrs around to get the
600 ohm spkr output to 4 or 8 ohms?

120 Volt to 12 Volt power transformer. Good at least down to 50 Hz or
better.

The problem isn't the low end, the problem is the high end. But the ratio
is about right, and if you pick a good transformer you'll be okay.

Problem is that a lot of cheap transformers have poor core material that
leads to a lot of distortion, and a lot of the better transformers are wound
to specifically limit the frequency response. For example, the Talema toroids
from Digi-Key are great at 60 Hz, but down 6 dB at 500 Hz and keep falling
above that. This is a great thing for a power transformer where you don't
want to leak noise into the power line or the other way around, but it's a
bad thing for audio.

But there are a lot of filament transformers out there that are quite
reasonable for audio, and they are cheap enough that you can try a whole
bunch of them and see which work best.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Henry Kolesnik wrote:
Getting old is not recalling the alternatives offered, so I'm a dummy. I
found the filament xfmr first and tried it but it reduced volume so I
assume my radio which is non-military doesn't have 600 ohms like the
military manual I have. So I guess mine is commercial, either a
SP-200-SX or more likely a SP-210-SX and I think it has a 3.2 ohm
output transformer.
I can't find any info and I wonder if anyone knows for sure on the
commercial models output transformer's impedance.

What is the DC resistance across the output?

If you want to know FOR SURE, put the output on a scope with a 1K pot in
parallel with it... tune to interchannel noise, and note the location of
the peaks on the scope. Crank the pot up until the level is exactly half
of what it was, then measure the value of the pot.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Thu, 30 Oct 2008, Scott Dorsey wrote:

Harold E. Johnson wrote:
"Henry Kolesnik" wrote in message
...
What's an easy way these days with limited audio xfrmrs around to get the
600 ohm spkr output to 4 or 8 ohms?

120 Volt to 12 Volt power transformer. Good at least down to 50 Hz or
better.

The problem isn't the low end, the problem is the high end. But the ratio
is about right, and if you pick a good transformer you'll be okay.

And of course, one commonly written about trick in the old days was to
use a "useless" 400Hz transformer as an audio transformer, the operating
frequency being about where you'd want frequency response to start for
communication use. Since it moves the frequency up by six, the frequency
response is probably better at the higher frequencies.

That's only a useful trick, though, when 400Hz power transformers are
commonly available, and cheap because nobody can find a use for them.

Michael VE2BVW

Scott
Good suggestion, I'll try it later and let you know.
Hank
"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
Getting old is not recalling the alternatives offered, so I'm a dummy.
I
found the filament xfmr first and tried it but it reduced volume so I
assume my radio which is non-military doesn't have 600 ohms like the
military manual I have. So I guess mine is commercial, either a
SP-200-SX or more likely a SP-210-SX and I think it has a 3.2 ohm
output transformer.
I can't find any info and I wonder if anyone knows for sure on the
commercial models output transformer's impedance.

What is the DC resistance across the output?

If you want to know FOR SURE, put the output on a scope with a 1K pot
in
parallel with it... tune to interchannel noise, and note the location
of
the peaks on the scope. Crank the pot up until the level is exactly
half
of what it was, then measure the value of the pot.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."