Baja stomp low volume? please help

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Baja stomp low volume? please help

Postby Sonic » 28 Jan 2013, 19:36

Hello
I've build the sonic stomp (Sonic maxizer clone), when I turn it on the volume is ok, but after a couple seconds the vulome drops at least 9 to 12 dB. I have mesured the voltage follower output, and it seems to be the bias voltage that's killing the sound?!? any other had the same problem? I have triple checked every component and vero board and I seem to have build it correctly. I have used the right IC's TL071, TL072, TL074.
I hope you can give me some hints out there :-)
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Re: Baja stomp low volume? please help

Postby bajaman » 29 Jan 2013, 09:41

sounds like a missing coupling capacitor or reversed electrolytic - check again :wink:
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Re: Baja stomp low volume? please help

Postby Sonic » 06 Feb 2013, 15:04

Hey thanks for the reply bajaman, and thanks for the schematic ;-) I have looked for reversed electrolytic capacitors, but with no luck, I'll look for missing coulping caps, when I have time :-)
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Re: Baja stomp low volume? please help

Postby Sonic » 10 Apr 2013, 14:20

Hello again :? I have layed this project away for a while, to gain power to solve this :D But it's seriosly confusing me, I can't believe this pretty simple circuit is doing this to me.
I have done some meashurements around the IC's: (using a battery at 8,9V before diode)
TL071:
1: 0,15 (Offset null1)
2: 4,14 (Invert in)
3: 4,14 (Non invert in)
4: 0,0 (Ground)
5: 0,15 (Offset Null2)
6: 4,13 (Out)
7: 8,27 (VCC)
8: 0,0 (NC)

TL072:
1: 4,07 (Output A)
2: 4,03 (Invert in A)
3: 3,66 (Non invert in A)
4: 0,0 (Ground)
5: 4,02 (Non invert in B)
6: 3,71 (invert in B)
7: 7,5 (Output B)
8: 8,04 (VCC)

TL074:
1: 4,02 (Output A)
2: 4,02 (Invert in A)
3: ~3,7 (Non invert in A)
4: 8,03 (VCC)
5: 4,01 (Non invert in B)
6: 4,01 (Invert in B)
7: 4,0 (Output B)
8: 4,0 (Output C)
9: 3,99 (invert in C)
10: 3,99 (Non invert in C)
11: 0,0 (Ground)
12: 3,98 (Non invert in D)
13: 3,98 (invert in D)
14: 3,98 (Output D)

I have double-checket everything lots of times now. Maybe your eyes can see something I can't, my brain isn't working well anymore :-P But the TL074 has suspisioulsy similar voltages on it's pins.
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Re: Baja stomp low volume? please help

Postby Sonic » 27 Jan 2015, 14:07

Found the issue, it was the last resistor before the output soldered on wrong lane on the vero board, so it jumped the output capacitor resulting in unwanted dc on the output.
I found the project in a box hiden away, therefore the long time to find the problem :-) anyway, thanks for the help :-)
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