Why isn't this working?

[ExpAnonColin]

I've tried this, except using a 4558D.  Is swapping a bad idea for oscillators, but OK for distortion?  It shoooould be working but it just isnt.  Someone else want to try it to?  The Fout = (1/(4RtC))(R2/R1).

-Colin

[Ansil]

is it doing anything?

[Tim Escobedo]

What's the power supply? The circuit you posted assumes a bipolar supply. If you're using a single 9V battery, the pins shown going to ground need to go to a reference voltage, usually something like 1/2V+.

[ExpAnonColin]

mm... I'm just using a 9v and negative grounding the circuit, could that be my problem?

-Colin

[Ansil]

you didnt' use a voltage bias?

[Paul Perry (Frostwave)]

The circuit as shown requires a + and a - supply to the chip.
You can try using a single supply, with a resistor paitr (say 10k each) across the supply, and the parts of the circuit that were going to ground now go to the 1/2 voltage, at the junction of the two 'bias' resistors.

Note the circuit wont work for ALL possible values of r1, r2!

[ExpAnonColin]

Hmm...  I thought that if I negative grounded it and then sent the ground to my amp, and put the Vs from the 4558 to my 9v it would work.  Guess not.

So I need to put 2 10k resistors in parallel from the 9v+ to the 2 parts marked ground on the schematic?

-Colin

[mattv]

Search the FAQ for Vref. Vref should be connected to the ground points indicated on the schematic. Pin 4 should still be connected to regular ground (black battery wire).

[ExpAnonColin]

I knew what Vref was, but how come I'm connecting grounds to it?

-Colin

[puretube]

you`re not connecting "ground" to Vref (=Vbias),
but the 2 opamp inputs (in your schematic only, grounded),
to Vref.

Don`t forget to put an electrolytic between Vref and ground....

[ExpAnonColin]

you`re not connecting "ground" to Vref (=Vbias),
but the 2 opamp inputs (in your schematic only, grounded),
to Vref.

Don`t forget to put an electrolytic between Vref and ground....

It just seems odd to be connecting it to Vref when the schematic symbol is ground.

Oooooh well.

-Colin

[Peter Snowberg]

I knew what Vref was, but how come I'm connecting grounds to it?

Sorry, it's been a bad day, but answers like that get under my skin really quickly. There's no problem with not knowing. This place is here for people to learn, but if you don't understand something please don't respond with "I know" or "hew now". That gets in the way and stops people from answering.

You need to move past knowing to understanding.

Doesn't it seem odd that you're connecting the PS ground to the opamp's negative terminal instead of feeding it with negative voltage? Hint: It's all relative.

So I need to put 2 10k resistors in parallel from the 9v+ to the 2 parts marked ground on the schematic?

No. Re-read the DIY FAQ under "Power Supply - What is V.R., V.B, VREF, 1/2V+ etc....?"

-Peter

[mattv]

I think the reason the schematic shows those inputs going to ground is this:

In a typical op-amp circuit, you have V+, V- and ground. To make it easy for us stompbox goons, we make a Vref so that we have +9V, 0V, and +4.5V. We don't think of it this way, but the op-amp thinks +4.5V is ground and it's supply voltage is +9V and 0V, therefore 0V is not ground in this case. Those fancy synth cats feed their op-amps +15V, -15V and 0V, so 0V in this case is ground.

I hope this makes sense. Thanks again to the guy at Ampage who helped me understand this.

[ExpAnonColin]

I think the reason the schematic shows those inputs going to ground is this:

In a typical op-amp circuit, you have V+, V- and ground. To make it easy for us stompbox goons, we make a Vref so that we have +9V, 0V, and +4.5V. We don't think of it this way, but the op-amp thinks +4.5V is ground and it's supply voltage is +9V and 0V, therefore 0V is not ground in this case. Those fancy synth cats feed their op-amps +15V, -15V and 0V, so 0V in this case is ground.

I hope this makes sense. Thanks again to the guy at Ampage who helped me understand this.

Thanks, mattv, that makes sense...

Sorry, Peter, it's a problem of mine to do that...  

-Colin

[Tim Escobedo]

It just seems odd to be connecting it to Vref when the schematic symbol is ground.

Like I said earlier, the circuit you posted assumes you're using a bipolar power supply.

Do yourself a favor and hunt down a first edition of Walter Jung's "Op Amp Cookbook".  I think the first edition came out around '74. His "Audio IC Op Amp Applications" is just as good and covers the same ground, but it's unfortunately out of print. You may get lucky at the local libraries. Both these books really helped me understand the hows and whys of using op amps with a single 9V battery, moreso than any other books.

[ExpAnonColin]

It just seems odd to be connecting it to Vref when the schematic symbol is ground.

Like I said earlier, the circuit you posted assumes you're using a bipolar power supply.

Do yourself a favor and hunt down a first edition of Walter Jung's "Op Amp Cookbook".  I think the first edition came out around '74. His "Audio IC Op Amp Applications" is just as good and covers the same ground, but it's unfortunately out of print. You may get lucky at the local libraries. Both these books really helped me understand the hows and whys of using op amps with a single 9V battery, moreso than any other books.

I'll be sure to try to check it out.  Thanks!

-Colin