Rebote 2.5 diagnosis

[Bradski]

First build.  Rebote 2.5 w/ Tonepad board.  Works.  Sort of.  Sound is way too dark and there is a lag between pick attack and actual sound.
Do these symptoms point to something in particular I should look at first before I start pulling/ replacing indiscriminate components?

Oh, total newb here ...like you couldn't tell already.

Thanks,
Bradski

[.Mike]

Hi there,

The Rebote splits your signal off to two different places. One is passed pretty much straight through to the output, and the other goes to the delay chip, where it is delayed and filtered. The delayed signal is then mixed into the dry signal.

It sounds to me like you have the delay side working. It is heavily filtered, and so it should sound dark. If the delay side is working, the delay knob should be controlling the lag between pick attack and sound. But the dry path-- the instantaneous, no delay, almost like it isn't there dry path-- probably is not working properly.

If you take a look at the schematic, you will see a 24k resistor that is connected between pin 7 and pin 2 of the opamp. That is the dry path. Check, double check, and triple check that area of the board. Look for solder bridges, cold solder joints, incorrect component values, etc.

The Rebote is pretty advanced for a first build. Whatever you do, don't just start replacing components. If you don't find the problem, you can then either follow the debugging topic, or use an audio probe.

Good luck!

Mike

[Bradski]

hmmmm... okay, thanks Mike.  I'll go look into that area ( I think I know where you're talking about) later in the daylight. 

But, oh, one thing I didn't mention ...I had at first soldered the op amp direct to the board. I read of my possible mistake only afterward, so I bought a socket just in case it didn't work.  Sure enough, when the deal didn't work from the get go, I unsoldered it, put in a socket and tried the another spare op amp I had.  I think I put that one in the wrong direction, because the delay didn't work until I turned it around.  It felt a little warm in my hand.

Maybe I'll order a couple more new ones and try them.  Maybe I fried 'em out.

[Bradski]

Hey Mike,

Thanks again for the help. I really appreciate your insight!

I picked up a TL082 at Radio Shack today, put it in (the right way this time) and it works like a charm.  I've got a LM2904 on order that I plan on trying out too. 

But right now, I'm as happy as a little girl.