Why Does My DIY Theremin Sound Gravelly?

[k_squared]

I protoboarded this circuit:
http://www.popsci.com/diy/article/2008-04/build-pocket-theremin-cheap

alas, it seems to make an extremely gravelly noise - the term "hoarse cat" came to mind. Anyways, what could be causing this? I think I have developed a general idea of how the circuit works, however, it does not explain this given that I simply used a proto board to hook up that exact circuit. I mean, could I have accidentally used a low-voltage 555 (if that does anything?) or, you know, whatever. I'm thinking my part tolerances are close enough (well, radioshack). Thanks!

Oh yea... are my photocells supposed to be of very similar values? I can get a slightly better sound out of it by using a bigger capacitor on chip '2'.

Speaking of which, does anyone know any good (fairly) detailed explanations of the 555 timer? That little thing is ubiquitous. Oh, and uh, thanks a lot for any help.

 

[vk6kro]

The output of a 555 is a square wave which is going to sound distorted if you are used to sinewave or musical sound.

The MP3 on that website disguises this a bit by using a high frequency. This means you can't hear the harmonics so the sound seems acceptable.
If the frequency is lower, you can hear the harmonics and they may sound unpleasant.
You can lower the frequency by making the bottom 0.01uF capacitor larger. Maybe 0.1 uF or even 0.47 uF.


There are lots of 555 sites but the one on Wikipedia would be a good start.
http://en.wikipedia.org/wiki/555_timer_IC
Here is another one:
http://www.kpsec.freeuk.com/555timer.htm
Try Google for others




.

 

[oswaler]

I would first like to commend the effort put into building a theremin using a DIY approach. It is always exciting to see individuals exploring and experimenting with electronics and circuits. However, it is important to understand the potential causes of distortions in the theremin in order to troubleshoot and improve its performance.

One possible cause of the gravelly noise could be due to the quality of the components used. As mentioned, using low-voltage 555 timers or photocells with varying values can affect the overall performance of the circuit. It is important to use high-quality components with consistent values for optimal results.

Another factor to consider is the layout of the circuit on the proto board. If the components are not placed in the correct positions or if there are any loose connections, it can lead to distortions in the sound produced.

Additionally, the 555 timer is a complex and versatile component, and it is important to have a thorough understanding of its functionality in order to properly utilize it in a circuit. There are many online resources and tutorials available that can provide a detailed explanation of the 555 timer and its various applications.

In conclusion, it is important to carefully select high-quality components and ensure proper circuit layout in order to minimize distortions in the theremin. With some troubleshooting and potential adjustments, the theremin can produce a smooth and accurate sound.