TL071 chip problem?? for New clipper device

[user]

I recently built the perfboard for the New clipper pedal from Runoffgroove.com

I used a TL071 chip as advised.
The legs and pinouts go like this:
2. Inverting input
3. non-inverting input
4. Ground
6. Output
7. 9 volts positive
The rest of the legs are connectedd to nothing.
I probed around with a jack connected to my amp. I am not getting anything at the 6th leg of the chip and nothing further. Have i a damaged chip? am i not supplying enough voltage? WOt am i supposed to do?

[David]

Are you certain you're getting at least 8.5V to the circuit?
Do you have an input plugged into it?
Do you have the output pot (if you have one) actually turned up?
Have you used the probe on both the input jack and the non-inverting input of the chip?
Do you have any breaks in your wiring?
Do you have any solder bridges?

Have you followed the "What to do when it doesn't work" thread?

[user]

Thanks for replying.
Yes im pretty sure i have the enough voltage supplied. Actually, im supplying it with 12 volts straight out of an adapter.
Yes i have an input plugged in through a discman, i didnt want to use my guitar and strum all the time.
I have set my pot to the max. I have a question, will the pot present at the far end of the schematic affect the output of the op-amp?? I mean i dont have any output at the 6th leg (and obviously, nothing further).
I dont have solder breaks. Today i heard some output from the op-amp, i couldnt figure out how. well i shook the perfboard and it was gone. At least the op-amp isnt damaged. BTw, i am using the audio probe method to debug.

[GibsonGM]

weird problem 
If you get audio probe signal at the + and - inputs, and the power supply pin reads V batt, make sure you in fact have that 22k resistor in series with the battery.

I'd then check the values of the 150K/150 ohm feedback resistors...possibly if it wasn't getting the proper feedback voltage, it could have less than unity gain (?).  Maybe a short in this area, too.

You could still have something wrong with the OA, in my opinion - you could swap it out if you have another...if shaking it changed something, maybe a component isn't soldered well (cold solder joint)? Bad IC socket? Check for continuity at the socket and the solder joint below it for each pin....the volume pot should have zero effect on what comes before it...effects run full-tilt up to the volume pot.

[Mark Hammer]

I suspect this circuit needs a fixed resistor between the junction of the 22k+22k voltage divider and the + input pin.  Try 220k-470k and stick a 10uf cap from the junction of that resistor and the 22k pair to ground.

The 150R/4u7 combination provides a) tons of gain (x1001) and b) a low-end rolloff around 225hz.   I feel pretty confident in suggesting that dropping the gain a wee bit won't hurt things.  For instance, sticking in a 220R resistor instead of 150R gets you a gain of 682 (still pretty punishing) and a low-end rolloff around 153hz, which will keep in more of the bass.  Since the bass is where the high ampliude stuff lives, by restoring more bass, you won't even notice that drop in gain.

I like the use of the 10k resistor with the .0033uf cap to form a 4.8khz lowpass filter. 

[puretube]

with 2  22k`s, 11k is quite a low input-Z...

[David]

with 2  22k`s, 11k is quite a low input-Z...

THANKS, PURETUBE!

I wondered what looked "funny" about that schematic! 

A couple of other questions:  Is it possible to move those diodes to the op-amp feedback loop to do soft clipping instead of hard?  If you switched the diodes out, it would just be a booster, right?  Is there a reason the fixed resistor couldn't be replaced with a pot for gain control?  Lastly, if you switched out the diodes and feedback resistor, and replaced them with a jumper, wouldn't it just become a non-inverting buffer?

[3/4 North]

The original resistors were a 200k and 240k.
If you remove the diodes i think you'll find out that the ic itself is clipping
I played around with this in this thread http://www.diystompboxes.com/smfforum/index.php?topic=48486.0

[Mark Hammer]

The original resistors were a 200k and 240k.
If you remove the diodes i think you'll find out that the ic itself is clipping
I played around with this in this thread http://www.diystompboxes.com/smfforum/index.php?topic=48486.0

With a gain of 1001?  Damn straight!!

Do the math.  What do you get when you multiply a 75mv peak by 1001, and how do you get a "clean" version of that when power is provided by a 9v battery to a device that will not even swing rail to rail?

That's not a criticism.  Merely a comment to note that adding diodes to this is a bit like making "habanero and scotch bonnet stew" and adding some jalapenos afterwards "just to spice it up".

[David]

The original resistors were a 200k and 240k.
If you remove the diodes i think you'll find out that the ic itself is clipping
I played around with this in this thread http://www.diystompboxes.com/smfforum/index.php?topic=48486.0

With a gain of 1001?  Damn straight!!

Do the math.  What do you get when you multiply a 75mv peak by 1001, and how do you get a "clean" version of that when power is provided by a 9v battery to a device that will not even swing rail to rail?

That's not a criticism.  Merely a comment to note that adding diodes to this is a bit like making "habanero and scotch bonnet stew" and adding some jalapenos afterwards "just to spice it up".

I think it's safe to say that the feedback resistor could be decreased considerably...   

Hmmm...  "can't swing rail-to-rail"...  Ah, but a 5532 can, IIRC.  Wonder how half of a 5532 would do here?

[user]

weird problem 
If you get audio probe signal at the + and - inputs, and the power supply pin reads V batt, make sure you in fact have that 22k resistor in series with the battery.

I'd then check the values of the 150K/150 ohm feedback resistors...possibly if it wasn't getting the proper feedback voltage, it could have less than unity gain (?).  Maybe a short in this area, too.

I dont have a signal at the - input. I checked the continuity between the ic socket and the solders below. Theyre fine.

[Mark Hammer]

The original resistors were a 200k and 240k.
If you remove the diodes i think you'll find out that the ic itself is clipping
I played around with this in this thread http://www.diystompboxes.com/smfforum/index.php?topic=48486.0

With a gain of 1001?  Damn straight!!

Do the math.  What do you get when you multiply a 75mv peak by 1001, and how do you get a "clean" version of that when power is provided by a 9v battery to a device that will not even swing rail to rail?

That's not a criticism.  Merely a comment to note that adding diodes to this is a bit like making "habanero and scotch bonnet stew" and adding some jalapenos afterwards "just to spice it up".

I think it's safe to say that the feedback resistor could be decreased considerably...   

Hmmm...  "can't swing rail-to-rail"...  Ah, but a 5532 can, IIRC.  Wonder how half of a 5532 would do here?

Even if it could swing rail to rail, you can't expect miracles from a 9v power supply when a chip is asked to amplify a guitar signal 1000 times.

And just so we're clear here, it's not a "problem", since this IS a distortion circuit we're discussing.  Headroom limitations may be fundamental to what is being sought.  The real issue would seem to be how much one wishes the audible output to be a function of chip limitations, how much it should be a product of the diodes, and how much it should be a product of both.  Some circuits (e.g., fuzz channel on a Blue Box, Black Cat OD) can produce fairly desirable istortion in the complete absence of clipping diodes.

As for the amount of gain, that can be addressed by the feedback loop OR the ground leg.

[David]

The original resistors were a 200k and 240k.
If you remove the diodes i think you'll find out that the ic itself is clipping
I played around with this in this thread http://www.diystompboxes.com/smfforum/index.php?topic=48486.0

With a gain of 1001?  Damn straight!!

Do the math.  What do you get when you multiply a 75mv peak by 1001, and how do you get a "clean" version of that when power is provided by a 9v battery to a device that will not even swing rail to rail?

That's not a criticism.  Merely a comment to note that adding diodes to this is a bit like making "habanero and scotch bonnet stew" and adding some jalapenos afterwards "just to spice it up".

I think it's safe to say that the feedback resistor could be decreased considerably...   

Hmmm...  "can't swing rail-to-rail"...  Ah, but a 5532 can, IIRC.  Wonder how half of a 5532 would do here?

Even if it could swing rail to rail, you can't expect miracles from a 9v power supply when a chip is asked to amplify a guitar signal 1000 times.

And just so we're clear here, it's not a "problem", since this IS a distortion circuit we're discussing.  Headroom limitations may be fundamental to what is being sought.  The real issue would seem to be how much one wishes the audible output to be a function of chip limitations, how much it should be a product of the diodes, and how much it should be a product of both.  Some circuits (e.g., fuzz channel on a Blue Box, Black Cat OD) can produce fairly desirable istortion in the complete absence of clipping diodes.

As for the amount of gain, that can be addressed by the feedback loop OR the ground leg.

Not to sound flippant, but "We doan need no steenkin 9 volts, man!  We got 18!"  Don't want to hijack the thread.  I'm learning too.
My questions relate to a "proof-of-concept" I'm thinking of trying.  I have an idea for a switching slave circuit where you use a PIC to rotate through n possible states using pushbuttons to change the "state" up or down.  So for something like this, your possible states might be:
*  full distortion with clipping diodes
*  op-amp boost only
*  buffered output only

[Gilles C]

Looking for some info onn the Blue Clipper, I found this new version of it with sound clips.

http://www.vintagetoneproject.com/DARipper.htm

It could help to know how it should sound.

Gilles

[user]

It could help to know how it should sound.

Thanks dude. But the tone isnt the problem. The problem is that it doesnt work at all.

[Gilles C]

Oh... so parts values are not a problem there.

I just noticed that you said it kind of work once and stopped after shaking the board. I would check every connections "from the top" if possible to make sure what needs to be connected together really are.

Did you use an IC socket? If not, the IC could be bad (wonder about the sound you heard one...)

You can not have any signal at the (-) input if you have no output at pin 6. The signal at pin 2 (-) in coming from the output through the 150K. No output = no feedback at (-) input.

Gilles

[user]

Yes, it actually worked once. Im using a socket, i even checked for continuity between the socket pin and the solders below. Everything seems to be fine. I even got mad once and bent the board for checking any broken solders. Theyre fine. I am beginning to get really frustrated. Mother nature sure is very rude when it comes to saying that "it isnt perfect".

[Gilles C]

Did you check the DC voltage at the pins of the IC?

It would be helpfull to know that.

Gilles

[user]

Did you check the DC voltage at the pins of the IC?

It would be helpfull to know that.

Gilles

Yes, its 12 volts straight from an adapter at 7th.

[Mark Hammer]

Um, is the adaptor the right orientation?  Possible you're feeding -12vdc to pin 7?  Worse, possible you're feeding 12vAC to the circuit?  Sorry if the questions are insulting.  Just trying to cover all the bases.  Some adaptors are less obvious than others about their properties.  You wouldn't be the first person to fall victim to mistaken assumptions about an adaptor.