just tried this on bread board, and it didnt work at all....

[Brian Marshall]

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?

[Tim Escobedo]

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?

[Boofhead]

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.

[Brian Marshall]

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

[ExpAnonColin]

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

[Brian Marshall]

think maybe it is saturating to one side, because the filter is too wide to bring it back... ill check it out.

bri

[aron]

It works. That's the circuit I use right now. I built it exactly as shown.

[Brian Marshall]

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.

[smoguzbenjamin]

Test your resistors for their value if you're not sure, that can clear up a whole lot of confusion.

[aron]

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?

[Brian Marshall]

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

[Triffid]

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

[aron]

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

No, except it is battery powered and small.

Aron

[Brian Marshall]

Yeah, haulig my 61 key keyboard out to my garage evertime i need a sine wave is a pain....

[aron]

Yeah, haulig my 61 key keyboard out to my garage evertime i need a sine wave is a pain....

hehehehehe!!!!!!!