Pedal based practice amp TDA 1519b

[Bubesz]

I have some time now (I'm not in the mood to prepare for graduation ), so I brought out your preamp and started to repair it, again This time, after 2 days of trying, soldering and switching parts, I was successful! I updated the parts to your last schematic, though I I left the tonestack as it was. I also substituted the diodes with BAT43s. I made a video about it, http://www.youtube.com/watch?v=Mea9nHy9xT0.
But there's still an octave down-like sound, you can hear it in the clip, what can I do about it?

[Brymus]

Hey Bubz
I listened to your vid,and yeah that doesnt sound like the one I made at all 
It should sound like the sound clips I posted a couple posts back.
Honestly I gave that amp away a long time ago,to a friend of mine, he's been using it ever since with out issue.
I had another on my breadboard for months but after making sure it worked as a pedal and pre amp,I got caught up in other projects.
I really like the range of break up it has from clean to all out dark metal,it just has so many knobs 

Did you etch a pcb for it ?
And have you checked it against the schematic ?
IIRC using a low output 386 and getting the input right was key to good sound from the TDA chip amp.
I dont have time to breadboard it right now,and I still have that EQ project that needs finishing on my breadboard,along with two other pedal projects.(make that 3)
Try drawing out a schemtic from your build and if nothing jumps out then maybe I or someone smarter than me can figuer it out for you.
But it definetly doesnt sound like the two I built.

[Bubesz]

The weird thing that it doesn't sound bad... It's just strange. But I don't like that octave sound.
Yes, I etched my own PCB, I posted the design. I will trace it, but I think it's correct. If I have time in a few days, I'll do it. The soundclip is made through a Line6 amp, not the TDA chip (I fried mine accidentaly... ).

[Brymus]

It could be the 386 overloading the Line 6,
but the octave thing sounds like something to do with the 386 being a problem.
I know I have heard them do an octave thing before when I was messing with them,still doesnt rule out the opamp.
Sorry I cant be more help than that,maybe someone else can offer you some more helpful advice.

[Bubesz]

I traced my build, here's is the schematic: http://img687.imageshack.us/f/kp095.jpg/. Looks good to me, despite from some minor changes in values I was wrong the last time, not the tone, but the first volume knob is jumpered, so what i changed in the video was the tone, not volume    As you can see, I used different (but similar) diodes, but I used the original 386 N-1 and NE5532 ICs (they're not marked on the picture). Btw, I noticed that I used a 47uF cap instead of a .47uF one I changed it to the 0.33 non-polarized cap, but it's not an improvement.

I made some tests with the audio probe from geofex, it sounds like the octave appears way before the 386 After the first IC, you can barely hear it (I'm not sure if I hear it, it's so faint... Or I'm just paranoid )  But at the second transistor, you can clearly hear it (on both channels). Do you have ideas?

[Brymus]

You really need that volume/gain knob it controls how much signal slams the rest of the circuit,by forming a voltage divider.
Your bias resistor combo looks kinda funky that may be introducing some noise too,which is getting amplified and passed on.
IDK this is my first hacked together design,and I am still learning.
I wish I could be of more help than that.

[Bubesz]

I bought a volume pot and also replaced the bias resistor with a real 470k resistor, but no changes I have no idea... It's strange that the problem is somewhere around the first IC.

[Brymus]

I bought a volume pot and also replaced the bias resistor with a real 470k resistor, but no changes I have no idea... It's strange that the problem is somewhere around the first IC.

Yeah I am at a loss on that.
I would make sure you have the power supply decoupled properly ,and try different caps in the FBL of the op amp,maybe its oscillating at a certain frequency? IDK
Other than those two ideas I just dont know what to tell you.
I never had any problems with oscillations or octave like noises when I was messing with it.