wave shaper

What do you think about this schematic:

Can it be used to expand sound possibilities of theremin? If it's true it would give square, sawtooth, triangle and trapezoid waveshapes. Mixing output with input would give even more sounds.

"What do you think about this schematic" - Arsimantur

Sorry - but my answer is: "not much!" LOL..

The complicated input stage is redundant - the object is to obtain a square wave from an input waveform.. you dont need a transistor - straight into a LM393 type comparator via an R+C, with a reference derived from the average input voltage (another R+C) and, with a bit of +Ve feedback (one resistor for hysteresis) you can convert any reasonable monophonic waveform to a square wave.

The "quality" of this design can be instantly seen if one looks at how P1+P2 are wired directly (via diodes) to the capacitor.. Op-Amps do not like driving capacitive loads, and any competent designer would put a resistor (100R or greater, depending on the op-amp)in series with the capacitor.

The above aside - Yes, you will change the shape, but you wont ever get a true ramp.. Assuming U1 outputs a square wave, P1 set to high R, P2 set to low R .. On the +Ve 1/2 cycle, C will charge slowly, giving a rising ramp - but on the -Ve 1/2 cycle, C will discharge rapidly (nearly instantly) and remain discharged (low) for the whole 1/2 cycle.. Compared to a ramp, this 1/2 wave distorted and rectified waveform sounds horrible.

The other problem (musically) with this design is that there is no "pitch tracking" - The time constants are fixed by the settings of P1+P2 - So if you adjust for a sound you like at one frequency, this sound will be different at every other frequency... Now, changing of waveshape with frequency can be pleasant IF deliberately designed to exploit this (Moog Synths have variable tracking on their VCFs - even the simplest, the Prodigy, has a 1/2 track setting, which gives this lovely variable harmonics effect).. BUT a fixed TC system with the waveforms generated by the above circuit has no way to 'regulate' the harmonics and keep them musical.

Serves its purpose as a distortion unit I suppose - but has no real function as a "wave shaper".

Oh - there is one other big problem.. Unless you insert a circuit like this between the mixer and VCA, its output wont track the theremins volume.. It will 'blat' into maximum volume (distortion) as soon as signal appears, and (if your lucky) go quite when you mute your theremin... Most likely there will be a ill-defined on-off point where all manner of 'breakthrough' horrors will be heard.

Fred.

Here is a theremin wave shaper which DOES work, and is not affected by audio frequency:

http://www.element14.com/community/thread/18199?tstart=0

Fred.

Fred said: "Your insistence on "sound bites" is, IMO, ludicrous - What have you proved by any sound bite you have posted or listened to? You cannot hear the distortions in your bites - so even if I posted something containing shit, you probably wouldn't hear it! .."

As I have said in the past, I am not an engineer and have never worked in electronics, is this unacceptable? I should stay out of conversations that involve all that chest pounding theory stuff. I post sound bytes to get a second opinion, good or bad.

Many years ago when TW was young we had contests at different times of the year to hear each person progressing and what sound they could get out of their model of theremin. Today we have a new group that explores the theremin in an imaginary reality known as LT-Spice and they almost fooled me as I waited years for their non results.!#$%

My theremin journey is about having fun, not getting the crap stomped out of me every time I propose an unusual idea.

Christopher

Arsimantur you worked with the Lev Antenna idea a few years ago, I am almost afraid to ask but what were your results?  Be honest as it is not for everyone. The parameters for it to work are strict, but no tuning is involved. It works or it does not!

If you understand why all sound begins with the basic sine wave no matter what brand of blinkers that rambling engineer accused me of wearing, I would have told you how this sound below was generated, but it has been crapped on like his slamming of every theremin design and designer out there.

Today's transistor version of levs-original-sound.mp3 110k using a simple analog audio enhancement I designed. The magic of analog heterodyning should not sound like artificial whistling with digital reverb added, rather a "voice from nature".

Above is theremin direct to sound card, this has no effects or acoustics added, a completely transistor heterodyne generated electronic sound.

Listening to the transistor theremin sound sample above note that it has perfect pitch field linearity, 12" down to 2" volume shading, drift resistant, still in tune from the night before when turned on in the morning, no warm up necessary. $60 for the pitch components and $65 for the volume control section.

All my theremin designs are old school, I would be curious as to what LT Spice sings like? I would ask someone to send me a sound byte but that's what got this thread going in the wrong direction to start with, I demonstrate results.

Why do so many theremin designers avoid letting others hear what sound their design produces? Everyone should stay clear of being led through endless rabbit holes (go ask Alice) and those that avoid posting the final results of their work?

"True beauty is hidden in simplicity"

Christopher

Report my posts?  What post and report to who?

Interpol, the Pope, FBI...

Christopher

The theremin voice is somewhat of an illusion to the human ear or even a miracle of hearing, this is why theremin sound begins buzzy and smooths in the vocal range.

Fred said: "Simulation saves many hours and highlights problems long before one touches a soldering iron - in most cases.. But for LC circuits and antenna linearization, I have found it almost completely useless..."

Where does the beauty hide in the circuity that can't be seen in simulation?

Christopher