quick question Hollis Flatliner.

[Eddododo]

http://www.hollis.co.uk/john/flatline.jpg
For the rectifier section;
There is gain through IC2 driving the LED. what's going on with it, with respect to the 330R into the complementary arrangement?

I understand that you're getting full-wave positive output from the two 'sides' but why is one side amplified and the other simply through a low resistance?

thanks!

[psychedelicfish]

The 330r is possibly there to limit current. As for the gain of IC2, perhaps it's because of NFB through the rectifier?
EDIT: The 330r could also be there for smoothing, forming a low pass filter with the 100nF capacitor

[PRR]

As you say, you need complementary signals (because the total diode-drop is close to 9V).

It does NOT matter whether the 330 is "in" one side or the other. It is simple series string with the diode mess.

You have a good strong signal from ICa. That can be one side of your complement.

There's no complement available so we have to make one. ICb as an inverter does that.

I do have "a problem", theoretical, with this known-good plan.

On one hand, the complements should be the same, so ICb should be unity gain inverting. Not gain of -5. ICb is doing most of the voltage-work.

On the other hand, the guitar-out should probably be much smaller than the diode-swing. So we probably do want gain.

The "proper" approach would be an additional gain-stage to one side of the diode mess AND an inverter for the other side. But that makes three-halves of a TL072. And loses the elegant simplicity.

[Eddododo]

Glad to see I'm barking up the right tree..


further question in this thread...
http://www.diystompboxes.com/smfforum/index.php?topic=107974.msg982824#msg982824

The thread is about the philosopher's tone, which uses a similar rectification section.. though I don't understand the use of the 741