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 Post subject: Two more instruments for Brian Wilson
PostPosted: Aug Thu 05, 2021 12:57 am 
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Location: Texas
I was commissioned to make a duplicate pair of instruments for musician Brian Wilson's tour. These are the third and fourth instruments I've made for them. The instrument is called a Tannerin, named after Paul Tanner who first commissioned and played the one-of-a kind instrument that was used to make the theremin-like "wooo-oooo" sound in "Good Vibrations." Those in the know are aware that a theremin was not used in Good Vibrations, but rather, a sine wave oscillator set in a box that Tanner, a Glenn Miller trombonist, could operate with a slide like a trombone.

The priorities here are reliability and tying down the wires. Brian's tour is still using the instruments I built in 1999 and 2016, and those have held up well. This iteration has some refinements such as being able to remove the board without desoldering.

The wiring routes are slightly different, as I look to improve things the second time around.


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 Post subject: Re: Two more instruments for Brian Wilson
PostPosted: Aug Thu 05, 2021 5:03 pm 
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That is interesting and it looks like a very good build, congratulations.

(On the photo, the wire from the Earth pin of the IEC connector to the chassis looks a little thin. Ideally it is 10A rated and some authorities say 15A. The reason is that the line supply cannot be guaranteed to have a working ELCB(RCD) and a number of fault conditions internal or external to the unit, could attempt to raise the chassis to line potential, so the conductors via the chassis, IEC connector, power cord to the GPO have to support enough current to trip the GPO's current breaker without themselves fusing and allowing the chassis to go live. Hard to tell from a photo though, might just look that way if Teflon insulation)

It looks like your circuit contains some OP amp IC's and possibly a PIC micro ? I wonder what the original Tannerin circuit was like that was used in Good Vibrations, presumably it used discrete transistors, but I just read it was Tube based, it would be really interesting to see the schematic of the original and your unit to compare the designs and improvements if you could post them.
From Wikipedia; The instrument used in "Good Vibrations" was a Heathkit tube-type audio oscillator coupled to a mechanical action that allowed the player to mark notes along a ruler-type scale where notes could be located quickly and precisely.


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 Post subject: Re: Two more instruments for Brian Wilson
PostPosted: Aug Thu 05, 2021 6:45 pm 
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Location: Springwater, NY
A related and interesting set of pages on this subject:

http://www.electrotheremin.com/ET.html


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 Post subject: Re: Two more instruments for Brian Wilson
PostPosted: Aug Thu 05, 2021 8:11 pm 
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ACORNVALVE wrote:
I wonder what the original Tannerin circuit was like that was used in Good Vibrations, presumably it used discrete transistors, but I just read it was Tube based, it would be really interesting to see the schematic of the original and your unit to compare the designs and improvements if you could post them.
From Wikipedia; The instrument used in "Good Vibrations" was a Heathkit tube-type audio oscillator coupled to a mechanical action that allowed the player to mark notes along a ruler-type scale where notes could be located quickly and precisely.

Thanks for the kind and useful comments. I depend on ARF for this type of knowledge.

The Wikipedia information is correct. David Miller, who runs the electrotheremin site referenced in the posting above has pictures of the original Heathkit audio oscillator. If I remember correctly, it used a Wien bridge type sine wave generator in which pitch was varied by a variable capacitor. That would provide good stability but with the range limited by the range of the variable capacitor. I suspect it was less than three octaves, as there was a range selector switch on the panel. The two TV repairman who built the instrument for Tanner also included a touch switch that I believe used body capacitance to actuate. Tanner could touch a wire on the slider, making the tone go "bup bup bup," as he described it.

Some of my original instruments also used a Wien bridge oscillator using either variable resistors or variable capacitors . The variable resistors were subject to pitch drift, and both configurations could not be duplicated consistently from one instrument to another using typical off-the-shelf components. If I ever wanted to go into production that would require a lot of finagling with each instrument and would make building a kit much harder to provide quality customer experience. So I decided to look into digital technology.

The 2016 instrument was my first to go digital. It does use a microprocessor to calculate the pitch from the slide position and then generate a corresponding square wave which is digitally filtered to a sine wave. This way the tone is crystal controlled and will not drift. It's also completely reproducible accurately from one instrument to another. The other ICs are peripheral components to give the filter what it needs, buffering control signals, and converting the incoming control voltage to a 0-5V signal.

The tone is started and stopped by using a levered micro switch mounted on the slide. An effective key-click killer circuit provides a softer start and stop to each note so that there is no loud click or thump at the beginning and end of each note.

I thought about emulating the body capacitance touch switch that Tanner had, as it intrinsically would have a soft start and stop. But I didn't know about how it would respond to different human bodies or weather conditions or the amount of grounding by the human body. So this instrument uses a reliable positive contact micro switch with the soft start-and-stop provided by a separate circuit.


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 Post subject: Re: Two more instruments for Brian Wilson
PostPosted: Aug Thu 05, 2021 10:30 pm 
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Joined: Jan Thu 16, 2020 12:29 am
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Macrohenry wrote:

Some of my original instruments also used a Wien bridge oscillator using either variable resistors or variable capacitors . The variable resistors were subject to pitch drift, and both configurations could not be duplicated consistently from one instrument to another using typical off-the-shelf components. If I ever wanted to go into production that would require a lot of finagling with each instrument and would make building a kit much harder to provide quality customer experience. So I decided to look into digital technology.

The 2016 instrument was my first to go digital. It does use a microprocessor to calculate the pitch from the slide position and then generate a corresponding square wave which is digitally filtered to a sine wave. This way the tone is crystal controlled and will not drift. It's also completely reproducible accurately from one instrument to another. The other ICs are peripheral components to give the filter what it needs, buffering control signals, and converting the incoming control voltage to a 0-5V signal.

The tone is started and stopped by using a levered micro switch mounted on the slide. An effective key-click killer circuit provides a softer start and stop to each note so that there is no loud click or thump at the beginning and end of each note.

I thought about emulating the body capacitance touch switch that Tanner had, as it intrinsically would have a soft start and stop. But I didn't know about how it would respond to different human bodies or weather conditions or the amount of grounding by the human body. So this instrument uses a reliable positive contact micro switch with the soft start-and-stop provided by a separate circuit.


Really great and well thought out design improvements.


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 Post subject: Re: Two more instruments for Brian Wilson
PostPosted: Aug Sat 21, 2021 9:41 pm 
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Location: Monroe GA 30656 (from Coventry, UK)
Very interesting stuff there. I read on your website that there’s a slim chance that in the future a kit might become available. Let us know if that happens. Even the important pieces such as the electronics (obviously), and the slide, plus a wiring diagram and a suggested BOM.


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