Solid-state topologies in the early sixties.

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Ribbledox

Active member
Joined
Oct 15, 2004
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33
Location
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I have a short question... would have helped a lot if I could attach the schematic...well, anyway.

After have gone through quite a few patents of compressor circuits, mostly filed in the early sixties, I've realised that there were a lot of different solid-state topologies around (even that early on). And many of them were variations of one another, based around bipolar transistors and diodes. However, none of these designs seem to have made it to a commercial level...wierd?

One specific that I was looking at was a design from 1962 (a US patent by Martin-Marietta Corporation). Here the input signal is passed through two emitter followers, then rectified and used to charge a capacitor. A negative resistance diode is connected across this capacitor and is connected to the output. As the voltage across the capacitor increases, the resistance of the diode decreases, thus decreasing the signal sent to the output.

Looking at this topology (and similar from this time), where bipolars are used for amplification, and were a capacitor and a negative resistance diode were used for compression, what are the downsides, the disadvantages? Why didn't a design like this one make it commercially? I guess, in the early sixties, a solid-state topology would have been very welcome.

As far as I understand, the audio doesn't actually pass through the diode, which I understand would cause distortion and other problems. And according to the patent applciation, the attack time achieved was very fast.

Wish I could attach the schematic...but unfortunatley I don't have a scanner.

Cheers=)

/R :roll: :cool:
 
> However, none of these designs seem to have made it to a commercial level...wierd?

Are you sure?

"Pro audio" isn't the end of the audio world. Army tank crews need intercoms, which need compression. A million-dollar contract to make tank-intercoms may not be glamorous, but sure is commercial.

No joke. The thinking behind the CBS compressor was developed for a tank, then leaked into every radio station. Your Martin patent may well have been hoping to grab the next wave of that trend.

Then there is the other side. 99% of ideas, even just the ones that are patented, never earn a dime. You can read patents all day and never find anything that made it to market. Don Lancaster says the idea is the least part of the product. And sometimes it isn't the turkey, it is the trimmings.

And many good-looking ideas either don't work well, or don't work a bit better than some other idea.

What neg-resistance diode? I would not think a tunnel diode has enough linearity to threaten the worst forward-diode gain-cell. Certainly a diac or other sharp-knee diode won't do.

> As the voltage across the capacitor increases, the resistance of the diode decreases

This sounds like a simple forward diode. But without seeing it, I dunno.
 
A patent search at http://gb.espacenet.com/ finds:

http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en&DB=EPD&PN=US3242436&ID=US+++3242436A1+I+


Jakob E.
 
:green:

Patent searching
Army Tanks
Tunnel Diodes

you guys need a hobby

oh !!!
:shock:
wait ... you already have a hobby ???


... errr ... I'll shut up now ... carry on. :wink:
 
Now we're talking quantum tunneling - has anyone checked the QTC (quantum tunneling composite) silicone components available at e.g. Farnell (order no 779-104611)?

It's a bit of silicone, that changes it's resistance logarithmically from 10MOhms to 1 Ohm in proportion to applied mechanical force (pressure).

Place it between a fixed and a moving piece of iron in an electromagnetic field...

Am I the only one that sees a new topology for voltage-controlled attenuators? :shock:

And think of the marketing-hype possibilities - "Quantum-effect VCA" :razz:

Jakob E.
 
Those 50 track headstacks that Sony made for their digital multitracks must surely have had another application also - they couldn't have sold enough 48 tk. digital tape machines to the music world to cover all their R&D costs, I imagine they would have made great data loggers for the military though.... I wonder if there are a lot of these units in unusual places?
 
Wow...great! Good Stuff!

I had no idea that one could access these patents online...

And I went all the way to the british library to print them...he he=)

Anyway, there you go. No need for a scanner.

Any comments on the design?

Was the TG limiters using a simlilar concept (just know they used diodes) to achive limiting?

About your "Quantum-effect VCA"...sounds very intresting! Speaking about patents...;=)

:grin:
 
Coming back to PRRs point about compression
Sticking my thinking cap on...
Does using compression mean less bandwidth is used
The military implications of this are huge if you think of it...

Does this mean smaller and lighter radios for the same range? Therefore the Radio Op can carry more equipment

When I used battlefield military radios in the early 1980s - we were just moving from the old WW2 style ones to the new Clansman type ones..
The difference in weight was astounding..
And that was not just down to the size of the batteries - the working parts themselves were much smaller (handheld as opposed to back pack)
 
[quote author="Steve Jones"]Those 50 track headstacks that Sony made for their digital multitracks must surely have had another application also - they couldn't have sold enough 48 tk. digital tape machines to the music world to cover all their R&D costs, I imagine they would have made great data loggers for the military though.... I wonder if there are a lot of these units in unusual places?[/quote]
At the initial price of $150,000 for each one - you wouldn't have to sell thousands...
Count the number of film, post-prod and TV studios in the world and you might have a nice figure...

Data loggers at the time would probably have been whatever proprierty system the ADA porgrammers were writing to (I would gues DEC PDPs) - not big - not clever - but indestructable (the code was the backbone of all milititary, air traffic etc...)
 
I don't see how this got a patent at that time. Or rather: it is a very weak patent.

The gain-control is a simple diode. Lots of prior art on that.

Yes, the text does say "negative resistance", but that isn't right. They suggest using a plain old Ge diode (1N64 is just a better 1N32).

The actual claim seems to be for the 2-stage layout, which is slightly novel but easily changed to a non-infringing plan.

Since it isn't even balanced, it will thump. S/N for reasonable distortion isn't great. This is clearly an intercom-type application (note the carbon-mike power feed), not hi-fi.

> Does using compression mean less bandwidth is used

Mostly it means greater "loudness" for the same power.

If you want your band to sound loud, with only a 100Watt powered-head, put a limiter in there and pump heck out of it to raise average power without raising peak power. Every commercial AM radio station does the same thing, to punch-through the competition as you scan the dial, and to reach more listeners beyond their main coverage area.

Police, taxi, and military radio does the same. First cut out all the bass: the "balls" in male voices eat power but do not add anything to the meaning of the speech. Cut the treble too; that does not reduce power much but does reduce spatter to adjacent channels. Then boost the gain so peaks would be around 10 times higher than the amplifier or transmitter can handle. Then "crunch" the peaks to about 95% of max power, because some amps and transmitters don't clip nicely (overmodulated transmitters can splatt-out a dozen channels).

The simple trick is to just clip the peaks. It sounds awful, but you learn to listen through it. Grossly clipped speech can be about as intelligible as clean speech. When the point is not the beauty of your voice, but a message like "Send more toilet paper!", range (for a given power/weight) is more important than sounding nice. And the 10X boost of average power means a 3X increase of range or 10X increase of coverage area for the same S/N at the listener.

Quick limiting sounds nicer than clipping, and is less critical of voice level (no gain knob).

So the military application of bass-cut and clip/limit is: if you need to send a guy 50 miles out to scout the enemy (or find a toilet-paper depot), you can give him a 100 pound "clean speech" rig or a 10 pound "clip/limit" rig.

If you had actual WWII gear: you had tubes which were very inefficient. Vietnam era stuff was much better, comparable to civilian CB gear a few years later. The most recent advances are improved modulation: SSB and NFM beat the pants off AM, and spread-spectrum digital will recover air-wave signals that are weaker than the local noise.
 
PRR interesting
To add to this - the use of throat mics as opposed to handheld or headphone mics must have done somthing as well
i.e. it is easier (and safer) to whisper than talk into a mic - the throat mic is ideal for this...
Or in my case shout "F**k" very loudly as some Irish guy shot at me...
 

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