In the early to mid 1950's. The AM radio manufacturers bought a
standard 2000Ohm to 3.2 Ohm @ 50ma. DC current with .0015"
paper gag. I will leave it to Patrick to compute the frequency
response.

The transformer had EI375 lamination ala .375" centerleg and .375"
stack with UI frame. 1.75" mounting centers.

1800T 37AWG Pri. 70T 25AWG on secondary. Pri Red 6" and Blue6"
with 3" wire extensions on the secondary.


The price for 100,000 quantities was $.29 each, $.27 each for 250,000
and $.25 each for 1,000,000.

Admiral, Emerson, Philco, Motorola, Zenith and others produced these
AM table radios in great quantities. The radio really did sound
decent. FM was down the road abit.

The low frequency of the transformer was better than the 4" speaker.
60HZ hum was non-existant because the speaker and the transformer
gave up at higher than 60Hz response.

The next large volume output transformer was for Texas Instrument's
transistorized radio. The power output was much less than the tube
AM radio i.e. the output transformer had .187" centerleg x .187" stack
with 10,000 Ohms to 16 Ohms sec. My design is in the bank safety
deposit box so I can't tell you the turns and wire size. The first
year we produced 964,870 units for Regency, Bulova, Automatic
Radio, Emerson and others. The next year was high in the millions.

The Japanese started competing in the market in 1959. The wire
and laminations were sub-standard but they improved their materials
over time (on our money and expertise ala US government help.)

Ah, those were the days...............................

Jerry

Did you ever wind a unity-coupled McIntosh style transformer?

On 5 Jan 2006 13:26:39 -0800, "Bret Ludwig"
wrote:

Did you ever wind a unity-coupled McIntosh style transformer?

I visited their plant on the east coast in the late 1950s??

They said that it had taken them so long to find a transformer
source that could make suitable units that they were not ready
to entertain another source even if they were signficantly
cheaper. We were small and growing quickly so I said
"adios and thank you."

Everyone loved their amps so I presumed that the output
transformes were good. I was already supplying Harmon
Kardon and Fisher etc. at that time and that was a heavy
load.

The real problem was that the OPTs had so many windings
and connections that the winder and connector learning
curves were long. The last thing that I wanted to hear
was that one of the good employees was slightly pregnant.

Jerry

Jerry wrote:
On 5 Jan 2006 13:26:39 -0800, "Bret Ludwig"
wrote:

Did you ever wind a unity-coupled McIntosh style transformer?

I visited their plant on the east coast in the late 1950s??

Binghamton NY. Been there myself.

They said that it had taken them so long to find a transformer
source that could make suitable units that they were not ready
to entertain another source even if they were signficantly
cheaper. We were small and growing quickly so I said
"adios and thank you."

Everyone loved their amps so I presumed that the output
transformes were good. I was already supplying Harmon
Kardon and Fisher etc. at that time and that was a heavy
load.

The real problem was that the OPTs had so many windings
and connections that the winder and connector learning
curves were long. The last thing that I wanted to hear
was that one of the good employees was slightly pregnant.

ROTFLMAO! Yes, I worked in a wind house once. The winders were all
female, but at that time, they worked until they were seven or eight
months along, and they were back a couple of months later. This is
still the case at that facility, although now most of the winders are
mestizas and therefore pregnant more often. In the 50s they stayed home
after the first one until all the kids were in college or the army. Or
hubby took a powder.

I'm hoping I can talk someone else into reproing Mac iron so I don't
have to. But HK and Fisher used good transformers-the Fishers were
mostly in the "not too bad" category and work so well in guitar amps
it's amazing any of the receivers survive (I parted dozens out myself).
HK on the other hand-the Citation OPT is considered first rate along
with Marantz, in the same league as the premium catalog suppliers like
Peerless and OTC. I would buy new Citation iron myself if available.
But the Mac 40/240 and 275 unity coupled multifilar OPTs are where the
market is IMO.

Economics always was a factor affecting the performance
of a tube amp output transformer. Even with HK and Fisher
and others. The good news was that we probably produced
5000 units per run and if it was a boat anchor, we may have
run as few as 500 or 1000.

God created the sine wave but marketing managers created
the "instantaneous peak power" that occurred when lightning
struck the outhouse. I could not believe the ratings on some
of our customer units.

From a design standpoint we just wanted to talk about sine
wave power into a pure restive load. Those figures were
hard to come by on given days. Norman Crowhurst was
a part time consultant to many companies. He was very
helpful. The Williamson "ultra-linear" design was interesting
and became quite popular especially when the new "Mullard"
tubes became available.

I must say that on any amp from 5Watt SE to 50W PP that
a better speaker improved the sound so I always considered
that economics came into play there, as well as the transformer.

Jerry