(http://www.geofex.com/FX_images/q+dosc.gif)
I had to sub 22k resistors for the 27k... would that be the problem... also subbed a 2n5088 tranny
i was running it straight in to an amp, and did not use the 2nd transistor.
any help?
Haven't tried the actual circuit. But the subbed resistors may be enough to keep it from oscillating. However, it shouldn't be too hard to get a twin-T to oscillate. Maybe eliminate the emitter resistor? Maybe recheck the wiring? Pinout?
It should work as is. Have you used 4.7k resistors in both positions?
When you connect it to the amp use a 100nF or larger cap in series with the output. The output level is a little high for a guitar amp input too.
I'll try it again....
Now that i look at it, It looks like a band pass filter.... makes the tranny resonate..... Didnt really think about how it worked until after i built it... some times that helps a lot when you understand what is going on.
I know it is a little high for a guitar input. I had it plugged in to a cheap crate amp... the only thing i can think of is that maybe the cheap amp has some sort of protection built in, but i dont think that is the problem.
maybe the trannys i tried are all bad. I'll test them
I'm not sure about 2N5088 vs 2N3904, but it's happened to me that an audio amplifier will only work with a 2N3904 and not a 2N2222. I would doubt that would be the problem, but subbing values is about 30% of the time the cause of your demise.
-Colin
think maybe it is saturating to one side, because the filter is too wide to bring it back... ill check it out.
bri
It works. That's the circuit I use right now. I built it exactly as shown.
I wasnt saying that it shouldnt work.... i was asking if the parts i changed would bake a difference. it certainly seems like it should work.
I think my tranys are bad, or maybe i am reading a resistor value wrong. I'll try it again today.
Test your resistors for their value if you're not sure, that can clear up a whole lot of confusion.
I checked my notes and nothing so I guess I got it to work.
However, I did make a wiring mistake early on which made me think it didn't work as shown.
Maybe you just have a similar problem?
well i went back and put it on bread board again...., and it worked just fine. found a number of ways to adjust the frequency, but the wider the sweep the more harmonics seem to come through.
Brian
I built this as well.. it seemed to work, but I didn't find it particulary useful in testing, maybe with and oscilloscope it would be more useful. I found it more useful to just hook up my keyboard, for variety reasons.
Am I looking past an important test feature of this curcuit?
Thanks
Quote from: TriffidI built this as well.. it seemed to work, but I didn't find it particulary useful in testing, maybe with and oscilloscope it would be more useful. I found it more useful to just hook up my keyboard, for variety reasons.
Am I looking past an important test feature of this curcuit?
Thanks
No, except it is battery powered and small.
Aron
Yeah, haulig my 61 key keyboard out to my garage evertime i need a sine wave is a pain....
Quote from: Brian MarshallYeah, haulig my 61 key keyboard out to my garage evertime i need a sine wave is a pain....
hehehehehe!!!!!!!