Humility Lesson
Okay, I blew it.
It's been that long since I got out of school.
And I made the foolish mistake of not checking with Wikipedia BEFORE expounding at length on the overtone series.
The seventh harmonic is the notorious flat flatted seventh, not the 11th. (I should know this. I do. It's the time of day and lack of sleep.)
The 11th is the F# in the key of C that is the notorious sharp 11 of a major 11th chord (but the harmonic is out of tune).
The 13th is the 13th of a chord, the A in the key of C, but it's a way out of tune A-flat.
For some reason (drowsiness, perhaps) I had given the A natural of the C69 chord a place in the overtone series which it does not have.
The D comes in as the 9th harmonic and is also the 9th of a chord.
So the musical math is only strange below the 7th. After that, the numbers equate. Okay, that means that it is even more bizarre than I said it was, but no matter.
The 3rd harmonic is the 5th of the chord (G in the key of C).
The 5th harmonic is the 3rd of the chord (E in the key of C).
The 7th harmonic is the 7th of the chord, but it is so out of tune it can't be used (flatter than B flat in the key of C).
The 9th harmonic is the 9th of the chord (D in the key of C).
The 11th harmonic is the 11th of the chord (out of tune F# in the key of C).
The 13th harmonic is the 13th of the chord (out of tune A flat in the key of C).
Of these, the 3rd harmonic, the 5th harmonic, and the 9th harmonic are in the C major scale and the C69 chord, and are relatively consonant with respect to each other.
How the A natural gets into the C69 chord, has something to do with inversions of intervals, as I now recall, but is too deep for me at this time of day.
Most of what I posted above is correct, except that the first even harmonic that is dissonant is then clearly the 14th, being an octave higher than that flat flatted seventh.
Next time, I will try to remember to check my memory against Wikipedia before I post.
Good night, everyone.
(Now that the sun is coming up again.)
Okay, I blew it.
It's been that long since I got out of school.
And I made the foolish mistake of not checking with Wikipedia BEFORE expounding at length on the overtone series.
The seventh harmonic is the notorious flat flatted seventh, not the 11th. (I should know this. I do. It's the time of day and lack of sleep.)
The 11th is the F# in the key of C that is the notorious sharp 11 of a major 11th chord (but the harmonic is out of tune).
The 13th is the 13th of a chord, the A in the key of C, but it's a way out of tune A-flat.
For some reason (drowsiness, perhaps) I had given the A natural of the C69 chord a place in the overtone series which it does not have.
The D comes in as the 9th harmonic and is also the 9th of a chord.
So the musical math is only strange below the 7th. After that, the numbers equate. Okay, that means that it is even more bizarre than I said it was, but no matter.
The 3rd harmonic is the 5th of the chord (G in the key of C).
The 5th harmonic is the 3rd of the chord (E in the key of C).
The 7th harmonic is the 7th of the chord, but it is so out of tune it can't be used (flatter than B flat in the key of C).
The 9th harmonic is the 9th of the chord (D in the key of C).
The 11th harmonic is the 11th of the chord (out of tune F# in the key of C).
The 13th harmonic is the 13th of the chord (out of tune A flat in the key of C).
Of these, the 3rd harmonic, the 5th harmonic, and the 9th harmonic are in the C major scale and the C69 chord, and are relatively consonant with respect to each other.
How the A natural gets into the C69 chord, has something to do with inversions of intervals, as I now recall, but is too deep for me at this time of day.
Most of what I posted above is correct, except that the first even harmonic that is dissonant is then clearly the 14th, being an octave higher than that flat flatted seventh.
Next time, I will try to remember to check my memory against Wikipedia before I post.
Good night, everyone.
(Now that the sun is coming up again.)
That's probably the best way to "read" Hewlett's Master's thesis.
He wrote it on using an incandescent lamp to control the gain in a Wien-Bridge oscillator to keep it balanced between not falling out of oscillation from too little gain, and not flattening the wavetops from too much.
The first HP tube powered oscillator was the HP200A, which was the circuit on which he wrote his thesis. The realization was that it was a less expensive way to give the audio industry a necessary and easy to use tool than what was formerly a very complex circuit. Using a simple resistor-capacitor frequency-determining network, the lamp made it possible to sweep the entire audio range (and then some) with a constant output level across only three bands using a ganged variable capacitor.
My guess is that Packard supplied the money to finance the first production run, which was made in Hewlett's garage, I think. I understand that they baked the enamel paint onto the chassis in the same oven that his wife was using in the kitchen.
From that modest start, with a product that was instantly in demand by everyone in audio electronics including the major broadcast studios, Hewlett-Packard was born.
Oscillators were their flagship product for quite a while. Then they branched into other test equipment, and the rest is history.
So the HP tube oscillator IS Hewlett's thesis.
And, in a manner of speaking then, you did "read" it.
I have not actually read Hewlett's thesis but I did become "one" with his oscillators nearly 40 years ago. We had about 300 of the 200AB and 200CD series in this plant when we used to do manufacturing here. We had an equal number of 331A distortion analyzers too. I was the factory support tech for several years.
Did you know that it was a Hewlett Packard audio oscillator that made the sweeping tones on the Beach Boys hit Good Vibrations?
During the 1970 to 1973 years I went to the local community college to keep my student deferment alive and avoid Viet Nam. During those years I worked at a local stereo store fixing electronic equipment including guitar amps. The store was about 3 feet from the campus of the University of Miami. I got to know several of the music students there and spent some time hanging out in their synthesizer lab. They had recently acquired an ARP 2600 and no one could figure out how to program it. I got to play with it a bit since I understood how it worked. Some of that "music theory" stuff helped too.
Interesting historical goodies.
I knew nothing of Hewlett's thesis until recently. A few years ago I found a "boat anchor" just lying on the ground at a local landfill. Since it looked intact and was built like a tank with a cool 4" diameter rotary knob with frequencies marked on it, I was "forced" into giving it a good home, so I put it into my truck after shoving out the old sofa and other junk that had brought me there. It's purpose was plainly inscribed on its front panel nameplate--"Audio Oscillator". That spoke to me.
Turns out it's an early HP200C in relatively good condition. I don't know what it might be worth, but I tracked down the schematic online and bought a bunch of parts (caps, mostly) to update it with. (Haven't gotten around to that yet, though I did restore an old HP vacuum tube AC voltmeter/dB meter I found at a local surplus store by replacing its caps and a tube or two.)
The search for information about how to restore my "found treasure" HP 200C led me to Hewlett's thesis. I still wonder what it might be worth.
On that same day I also found a foam-lined military wooden box with two huge pairs of tubes in it. Looks like it was made to protect the tubes in the field. A pair of 813 transmitting tubes and a pair of VHV 816 mercury rectifiers IIRC.
And there was also a U.S Army Signal Corps Frequency Meter BC-221-Q, (125 to 20,000 Kilocycles) with a paper roll of frequency information IIRC. I gave them all a good home.
Haven't yet found any info on the frequency meter.
Especially when writing and playing music!
I knew nothing of Hewlett's thesis until recently. A few years ago I found a "boat anchor" just lying on the ground at a local landfill. Since it looked intact and was built like a tank with a cool 4" diameter rotary knob with frequencies marked on it, I was "forced" into giving it a good home, so I put it into my truck after shoving out the old sofa and other junk that had brought me there. It's purpose was plainly inscribed on its front panel nameplate--"Audio Oscillator". That spoke to me.
Turns out it's an early HP200C in relatively good condition. I don't know what it might be worth, but I tracked down the schematic online and bought a bunch of parts (caps, mostly) to update it with. (Haven't gotten around to that yet, though I did restore an old HP vacuum tube AC voltmeter/dB meter I found at a local surplus store by replacing its caps and a tube or two.)
The search for information about how to restore my "found treasure" HP 200C led me to Hewlett's thesis. I still wonder what it might be worth.
On that same day I also found a foam-lined military wooden box with two huge pairs of tubes in it. Looks like it was made to protect the tubes in the field. A pair of 813 transmitting tubes and a pair of VHV 816 mercury rectifiers IIRC.
And there was also a U.S Army Signal Corps Frequency Meter BC-221-Q, (125 to 20,000 Kilocycles) with a paper roll of frequency information IIRC. I gave them all a good home.
Haven't yet found any info on the frequency meter.
Yes, I have often found that to be the case.
Especially when writing and playing music!
Unfortunately I don't do much of either any more.
I have a friend in the surplus business. I was at his shop one day about 10 years ago and he had a truck full of stuff loaded up and headed to the metal scrapper. There were about 25 HP200AB's and 200CD's along with some RF sweep generators and a couple of TEK scopes. All had been sitting outside in the Florida rain for several months.
I sat down in the parking lot and relieved each and every piece of tube equipment of their tubes, chokes, and power transformers. I still have a few of the HP power transformers and a few dozen 6CW5's left. The power transformers are about the right size for a 35 watt guitar amp. Some were so rusty that I only saved the end bells, yet they still worked. I did also find one oscillator that worked even after a lot of salty rain water. I still have it.
Before I get the flamed for destroying valuable stuff, realize that it was ALL about 3 hours away from the scrap metal guy where it gets shredded then melted.
Hi all, I just got an email saying there was a new post here. Ha!! 5 pages of posts...
My interest in such details is very low. But I do appreciate all the theory everyone has published.
I believe part of this discussion should be put in another thread under "LED resistance etc.." There are 5+ pages on this topic that really has nothing to do with my original question. Or at least it is so detailed, and controversial between a few, that I wouldn't even think of trying or want to experiment.
I have no scopes or generators, etc. My test is voltages, and sound to my ear. Someday I will get into these details a bit more, but I think I've done pretty well w/o them. No hum, no hiss, no buzz, no squeal, and beautiful sound is my only 'scope'.
I do plan on using Tubekit's advice on page 6 or so, the last email I received-Oct. 21st.
I am officially finished w/ this thread. (awhile ago) But if anyone wants to keep discussing, I will check out the advice.
My interest in such details is very low. But I do appreciate all the theory everyone has published.
I believe part of this discussion should be put in another thread under "LED resistance etc.." There are 5+ pages on this topic that really has nothing to do with my original question. Or at least it is so detailed, and controversial between a few, that I wouldn't even think of trying or want to experiment.
I have no scopes or generators, etc. My test is voltages, and sound to my ear. Someday I will get into these details a bit more, but I think I've done pretty well w/o them. No hum, no hiss, no buzz, no squeal, and beautiful sound is my only 'scope'.
I do plan on using Tubekit's advice on page 6 or so, the last email I received-Oct. 21st.
I am officially finished w/ this thread. (awhile ago) But if anyone wants to keep discussing, I will check out the advice.
OP = Original Poster (and a reference to the topic question)
ESPECIALLY THAT THEY WERE USEFUL TO THE OP,
whose purpose in asking a question in the first place I kept reminding people in this thread about, if I recall correctly.
Thank you. I do appreciate the recognition, and the knowledge that my efforts were of use to someone
ESPECIALLY THAT THEY WERE USEFUL TO THE OP,
whose purpose in asking a question in the first place I kept reminding people in this thread about, if I recall correctly.
Why not simply us a pot? Then you have no switching noise. Place the pot in series with the lowest value fixed resistor you want. Use a (say) 500R linear pot and then the bias is adjustable for whatever the fixed resistor is up to 500 ohms on top of that. Yes there will be some noise when you tun the pot.
In conclusion . . .
The noise when using a pot in an audio circuit results when there is DC on the pot. If you look closely, most audio circuits have the volume and tone control pots isolated from DC by capacitors, so there is no DC on the pots, and they don't make those loud and scratchy sounds when you turn them for that reason.
But there's no way to keep DC out of a bias circuit; thus, the OP's original question.
You're welcome.
The noise when using a pot in an audio circuit results when there is DC on the pot. If you look closely, most audio circuits have the volume and tone control pots isolated from DC by capacitors, so there is no DC on the pots, and they don't make those loud and scratchy sounds when you turn them for that reason.
But there's no way to keep DC out of a bias circuit; thus, the OP's original question.
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