Arny Krueger wrote:
"Michael A. Terrell" wrote in
message m
Eeyore wrote:
John Larkin wrote:
True, none of this is relevant for audio. Anything will
work for audio.
Almost anything. RCA's 2N3055s weren't exactly the
fastest in the world. 800kHz fT IIRC. I hate to think
what their germanium predecessors like the OC35 were
like.
RCA's germanium predecessor to the 2N3055 was arguably the 2N2147. If
memory serves, PD = 25 watts, FT = 3 MHz. SOA = negligible. Many of the
first generation mass-market *production* hi fi power amps used the 2N2147
with a driver transformer. This included Knight Kit, Heath Kit, Ten Tec,
Altec Lansing, etc. Mainstream mid-fi producers like H. H. Scott, Sherwood,
and Fisher AFAIK never produced any germanium power amps. Their first
generation products were based on 2N3055 and similar devices.
The 3055 was developed for linear power supplies, so it
didn't need a high fT.
AFAIK the first generation data sheets characterized it as both a power
supply, servo amp, and audio power amp device.
It was scaled down from the RCA 40411, which was a 100 volt device, VS a
60 volt, cheaper
device.
AFAIK the 40411 was introduced several years after the introduction of the
2N3055. I think that there were at least two years of the RCA solid state
book with the 2N305x family in them, before the 404xx family was added.
I bought some 40411 transistors in the '60s, and the product release
for the 2N3055 stated that it was developed as a 60 volt version for
linear power supplies. Pupular Electronics used the RCA sample circuit
for their 'Brute 70' amplifier.
http://www.swtpc.com/mholley/Popular...PE_Feb1967.htm
I had a business partner who, in an earlier venture manufactured SS power
amps for professional use. He based his top-of-the-line products on the
40411. There was also an even more robust device called the 411. Again, my
memory of this is hazy as this was in the late 60s.
According to him, he discovered that the 404xx series of devices were mostly
sold for automotive uses, such as SS ignition modules. For a while RCA was
making these parts literally by the millions. Product consistency was a
problem, which they were very effective at exploiting. The
middle-of-the-road parts went to the car companies under proprietary part
numbers.
The really nice parts, the cream of the crop, were skimmed off sold in
relatively small volumes as 40411s, mostly for audio. Eventually the car
market for 40411-type devices dried up. As the milk dried up, so did the
cream.
According to my friend, RCA tried various ruses to come up with enough
40411-type devices, but could never equal their original product. He sold a
ton of amps that were not durable and was forced out of business.
Eventually, he started cutting open devices, both old and new, and found
results similar to what we've seen far more recently with counterfeit
transistors.. It was his opinion that RCA was sort of counterfeiting their
own product.
This all happened number of decades ago, and should not be taken as a
reflection on the current RCA corp which has been bought and sold at least
once since then, and is thus under a different management.
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