...and then all of a sudden, it all went to hell!

[ExpAnonColin]

   

Last night, at around 11pm, I was working on my tremolo design... namely the envelope control.  I had the tremolo working just fine, it's astable multivibrator LDR based.  Working quite well.  Then, I start working on my 386 based envelope control for the speed. When I first put it together, I had the standard configuration for high gain (2 and 4 to ground, 1 and 8 connected, input to 3, output from 5, Vs to 6) with the output going into a 1uf cap and then into the + side of the LED, the other to ground.  First, it worked so that the light was always on and when I strummed it got a tiny bit dimmer.  Then, all of a sudden, the LED stopped being always on, and instead got brighter when I strummed.  "OK", I said, "No biggy.  Must have been a bad connetion.  I'll just design the circuit around this".

About 30 minutes later, the LED stopped working.  No nada.  The LED worked just fine when connected to a + voltage and the - side to negative, and the LM386 was sure as heck still amplifying the signal... but something was different, and it was no good.  That was when I noticed the high pitched squealing...

For some reason, after it stopped working, it started squealing, even without the amp plugged in.  It only squealed when my hand was near the capacitor, and I'm assuming it was emitting waveforms through the air and the guitar cable plugged into my amp was picking them up.  But why was it squealing?  I figured it MUST be a bad battery, or even a bad op amp.  So I replaced the battery.  Put a DC jack on there, even.  No cigar.  So I replaced the 386.  No cigar.  So I moved the whole assembly on the breadboard in case there was a bad trace somewhere on there.  NO CIGAR.  I replaced EVERY component in the circuit.  NO CIGAR!  Tried bypassing the internal gain control with capacitors instead of simply connecting them... no cigar.  When I put the output of the circuit into the amp, I definitely got the high pitched sqealing, into the amp now, and in unison with my guitar.  It sort of produced this terrible high pitched distortion.  When I moved my hand around the circuit, the pitch changed.  When I connected pin 8 to a 10uf cap, and the other end to nothing, I get the radio.

So, obviously things are really messed up.

So I've tried the following:

-Moving parts on breadboard
-All new parts
-Different voltage sources (batteries and wall)
-Different breadboards (yeah, I moved the entire envelope control to another breadboard.  Nope!)

And just about EVERYTHING I could think of.  Honestly, I'm totally befuddled.  

Someone, please please please help me.      

-Colin

[Paul Perry (Frostwave)]

OK! let's hear it from those 386 fans <ducks>

Seriously, I find a 386 is great for a solidly laid out audio amp, but it isn't the friendliest for 'experimental' work. My opinon only.

[ExpAnonColin]

OK! let's hear it from those 386 fans <ducks>

Seriously, I find a 386 is great for a solidly laid out audio amp, but it isn't the friendliest for 'experimental' work. My opinon only.

I think 386's are fine... but do you honestly think that could be the source of ALL of these problems?  How could it sabotage my astable from afar?

-Colin

[ExpAnonColin]

You know, it's really funny.

I just fixed an ungrounded wire and moved the 2 pots on the astable vibrator, and the tremolo works.

I added a 4k7 resistor to the output of the 386 in parallel to the capacitor (I swear to GOD I wasn't doing this before), and it works.

Man, I hate my life.  Why must the DIY god taunt me so?

-Colin

[Luke]

Man- that noise must have freaked you out!  I would have thought it was possessed!
Actually, it might be interesting if you could switch between the tremolo AND the satanic theremin effect. It could be a funny little combo! I wonder if you could sweeten the 'squeeling'' of your effect so you could use it this way. That could be really cool!
Just an idea.
Take care,
cheers,
Luke

[ExpAnonColin]

See, the problem is, the squealing is still, for the most part, there.  The pedal just works there.  I think something must not be grounding properly..  And I mean my amp, not so much the pedal.

-Colin

[Luke]

sorry- my mistake :oops:  I didnt understand what you said properly.
I hope you get it going though
Cheers,
Luke

[Brian Marshall]

sounds like you made a theramin and a tesla coil all in one.  hahaha.

what are we going to do tonight brain....?

The same thing we do every night pinky..... try to take over the world.

[william]

amen to the brian.

william