Variable LFO

I think it wsa 1971, and I was thinking about that article, but can't remember what was involved. I think that one was more likely from John Simonton, of PAIA fame, if it was from one of the top tier writers.

Michael

PAIA is correct. March 1971, starting on page 51 and it was designed by John S. Simonton, Jr.

My guess would have been April, so when I downloaded that issue and it wasn't there, I kept downloading subsequent issues. March seemed a tad early, it was only the second issue of Popular Electronics I bought.

Michael

ed by them way back in the 80's called the Digital Domain that was really c ool. It was made specifically to show the benefits of digital audio. Some o f the cuts on it were planes landing that really pushed the dynamic range t o the max for the CD standard. Also some of them were just plain weird. The y also included a version of deep note that would blow speaker cones right out of the basket.

ap OSC (sine) that can be varied from zero to approx. maybe 20 cycles conti nuously. Been busting my brain to implement it. This is for a source into a keyboard to act as a Leslie. Any ideas guys. THANKS.

Also as a side story. Back in the mid 80's I worked with USDOS in VA near D C. Made a trip to CA for a secretary of state visit to set up two way comms . This was when George Schultz was SOS. Security detail was using office on 2nd floor of this rickety old garage on the residential section of Stanfor d behind his house. The whole crew had left for a train trip to LA and they had no one to call DC to indicate they had departed. I was elected to perf orm that function. While waiting there was a small earthquake (my first). O ld garage shook and settled and I swallowed my heart. Ahhh the memories. Ha d I remembered CCRMA I probably would have been able to visit them. Kick my self every time I think of it.

heap OSC (sine) that can be varied from zero to approx. maybe 20 cycles con tinuously. Been busting my brain to implement it. This is for a source into a keyboard to act as a Leslie. Any ideas guys. THANKS.

Briefly spoke with him via email back in 2000 on an unrelated issue.

per some of the responses received. Thanks for all the help guys. Will let ya'll know what happens.

If you make a voltage divider that a pair of diodes can be attached to, those diodes can then suppress the output of the timer via a resistor to form a near sine wave on both ends.

Then it can be cleaned up a little..

That will give you the best results for the lowest price with a broad freq sweep.

Jamie

Another quick thought. Try a beat frequency. Have 2 oscillators, 1 fixed at say 40Hz. The other variable from 40 to 45 hz. Mix them together and you will end up with an output freq. of 1 to 5Hz. Remember, the beat frequency is the difference of the 2 components. (

The only problem you really have is the zero Hertz. Just use a switch, and a circuit just like an old guitar amp. Take the tremolo circuit, perhaps extend its range a bit, scale down the voltages and use an FET.

I found some decent regular old style depletion mode FETs at Digikey. I think this would be an excellent use for them, PLUS using them to manipulate the phases or whatevcer from your crossover, or whatever is going to actually create the effect.

The voltages canbe lower, the RC time ocnstants are almost totally immuine to other shit.

I guess you could use a MOSFET as well, but the old JFET would be more fun, and probably in line with your whole idea. The JFET is essentially a triode.

What kind of mixer are you going to use?

Certainly a balanced mixer, and certainly in electronic music circles they do know about the phasing method to get rid of the unwanted sidebands. For single frequency tones, that's all relatively easily done, since you can use methods to generate sinewaves that also have an output 90degrees from the main one. So you get two of those, and two balanced mixers, and you get your sum or difference very easily. It's when you need to mix voice or really complex signals that the phasing method can be limited.

Michael

DDS would be a lot simpler, and the output level wouldn't change with frequency.