AMZ IC Buffer Question

[ECistheBest]

Hello, I built Jack Orman's IC Buffer earlier today, sounds great with close to no tone sucking. But with one problem. It's quiet. Quieter than the bypassed signal. Is there a way to get a bit more gain out of this? Can anybody supply me with some ideas that can cause the quietness? Thanks!

and here's the layout I made myself from Jack's page:


here's a picture of the pedal with no switch or LED, just two jacks and a battery:

[the_random_hero]

I cannot think of a reason why it would be quieter - gain's set at unity by the fact along that you're using the op-amp as a non-inverting voltage follower. You could modify the design so it had a slight switchable boost (a couple of dB is all you would need), but that could be a bit of work as you would have to change your layout.

[burnt fingers]

I built one of these about a year ago.  It was always at unity.  It never was lower.   You may want to double check it to make sure there isn't somehting wrong.

Scott

[amz-fx]

With no signal input, measure the dc voltage of the opamp pins to ground... they should be:

1:  don't care
2: 4.5v
3: 4.5v
4: 0v
5: don't care
6: 4.5v
7: 9v
8: don't care

You are using a TL071 and not a TL072?

regards, Jack

[ECistheBest]

okay so here are the voltages. (Thanks Jack!)

1: 0.13V
2: 3.95V
3: 2.41V
4: 0V
5: 0.11V
6: 2.90V
7: 4.93V
8: 0V

so is it a faulty battery/power supply? or did i fry the IC...?

now it's getting

2: 3.77V
3: 2.74V
6: 4.43V
7: 8.84V

does pin2 and pin3 hate me??

[amz-fx]

now it's getting

2: 3.77V
3: 2.74V
6: 4.43V
7: 8.84V

Pins 2 and 6 are connected by a jumper. They should be the same voltage.

-Jack

[ECistheBest]

pin 2 and pin 6 both read 4.43V now.

Pin7 only reads 3.7V now...

[PerroGrande]

Pin 7 needs to be connected directly to v+.  Your layout shows this - perhaps one of your trace cuts isn't quite all the way through?

Also -- please verify the type of chip you're using...

[ECistheBest]

my IC is a TL071CP. i think it's a Texas Instrument chip.

[the_random_hero]

Take the IC out and measure the voltages while they aren't being dragged down by the IC. You should be getting roughly half the supply voltage shared between pics 2 and 3.

[ECistheBest]

with the IC out, i get 0V in pin 2, 2.96V in pin 3, 0V in pin 4, 0V in pin 6, 8.84V in pin 7.

[PerroGrande]

Something is wrong (obviously)...

With the IC Out, you should read about 4.5 volts on pin 3.   Check for complete trace cuts / solder bridges, etc.

[ECistheBest]

pin 3 is somehow still reading 2.94V. pin 2 and pin 6 are getting 4.44V, and pin 7 is getting 8.84V.