Anderton Comparator Fuzz

[Aph]

Great idea. I'll try that out!

[Elektrojänis]

So, I tried a 741 in several combinations of your circuit and Ranko's circuit to try and get the "Anderton sound" while keeping it daisy chain compatible.
No go. They all worked to some extent, but I think the way he applied power has a lot to do with the sound and sustain!

How about using the offset null pins of the TL072 or µA741 to tune the sustain / "noise gate" with the new version... Or maybe just make the bias voltage through R7 (or R4) slightly adjustable?

[Aph]

I did a little bit of bias adjusting, but it just made the sustain worse. Haven't tried the null pins. Maybe I will.

[caspercody]

Sorry it took so long to post images of my build with the LT1054.

Thanks for helping.

[Aph]

Okay, thanks for the nice big pix!
The only thing that I can see is that the power jack is not grounded. All grounds must be connected together.
Now, hold on... I know you said it doesn't work like that. So, it could be something I can't see, which is... (sorry) the solder side of the boards.
If you could take some nice big clear pictures of the underside of both boards that would be great.
Thanks for hanging in there 

[Elektrojänis]

I did a little bit of bias adjusting, but it just made the sustain worse. Haven't tried the null pins. Maybe I will.

I'm not sure how you adjusted the bias, but the problem is you need to try adjusting the balance of the biases between pin 2 and pin 3. (I'm referring to Jack's schematic on reply #33 btw.) So... You would need another bias network like R2, R3 and C1 for the other of the pins to adjust teh bias on just one of them.

The idea is to balance them better. With the same bias source they should balance perfectly if the opamp was perfect... Well... It never is. This would also be very sensitive for very little changes. I bet that if one of the resistors in the bias source was made adjustable it would probably go from very little sustain to more sustain and then very little sustain again within a range of 1 kohm (out of 100 kohm). So, it may be easier to use the offset null pins. I quess they are meant for that kind of balancing, but I could be wrong.

In fact I could be wrong about the whole bias thing as I haven't tried this at all, but I'm pretty sure the sustain of this circuit depends a lot from the balance of the opamps inputs.

[rankot]

Rob, what is you final schematic for supply? LT1054 with ±9V or something else?

[caspercody]

LT1054 for 9 volts positive and negative.

The pedal works when plugging into my OneSpot power supply, but if I daisy chain it to power other pedals it does not work.

[anotherjim]

As intended by Mr Anderton with the "floating" bi-polar +4.5/-4.5 supply, the open ground symbol that Jack has labelled Vbias should be THE circuit ground including your in/out jacks and case.
The solid "ground" symbol should be the -ve supply rail connecting battery- , R3 and U1 pin4 BUT nowhere else and never to ground.
As shown, it must be battery powered. AC adapter might work but ONLY if it has no ground connection at all anywhere else, including to the AC power ground pin if it has one.

To convert that to an AC adapter that can be daisy chained and -ve wire grounded...
R2, R3 and C1 are deleted.
R4 & R7 to ground.
Add -9v supply regulator and connect -9v to U1 pin 4 ONLY.

Note that a dead easy comparator fuzz can be made using most CMOS op-amps, since they don't mind the input going negative and no negative power supply is required.

[diffeq]

The idea is to balance them better. With the same bias source they should balance perfectly if the opamp was perfect... Well... It never is. This would also be very sensitive for very little changes. I bet that if one of the resistors in the bias source was made adjustable it would probably go from very little sustain to more sustain and then very little sustain again within a range of 1 kohm (out of 100 kohm). So, it may be easier to use the offset null pins. I quess they are meant for that kind of balancing, but I could be wrong.

Considering the offset voltage of TL072 and 1% tolerance of bias network resistors, it needs a 5k trimmer between 100k "shoulders" of comparator reference input to bias it with precision. Those multi-turn Bourns trimmers could come in handy.

[amz-fx]

As shown, it must be battery powered. AC adapter might work but ONLY if it has no ground connection at all anywhere else, including to the AC power ground pin if it has one.

Jim, you linked the wrong image. It seems you meant to reference the original CA design. The one in your post is the revised version that has the grounding changed so that it plays well with other pedals 

Best regards, Jack

[Mark Hammer]

Given that the intended output of the Comparator circuit is a square wave, it seems like a perfect match for square-wave shaping:  http://www.diystompboxes.com/smfforum/index.php?topic=73149.0

[amz-fx]

Given that the intended output of the Comparator circuit is a square wave, it seems like a perfect match for square-wave shaping:  http://www.diystompboxes.com/smfforum/index.php?topic=73149.0

From an old issue of Polyphony magazine, as I recall.



regards, Jack

[Mark Hammer]

The more deluxe version:

[amz-fx]

The more deluxe version:

Nice. I had forgotten about that one.

Thanks, Jack

[caspercody]

Here are pictures of the solder side, of the LT1054 power board and fuzz board.

Thanks

[Aph]

Thanks for the pix. I can't see anything obvious. There may be a short somewhere I can't see.
According to your first statement here, that may be the case:

I hooked up the ground on the Fuzz circuit to the ground from the power, and nothing.

I then cut the ground wire I just installed, and it works, but only powered by itself.

If you have access to a multimeter, connect the negative lead to one of the jack (input or output) ground connections.
Leaving it the way you have it now (fuzz circuit not connected to power ground), and just powering the fuzz pedal (no daisy chaining)...
measure the voltages on the 741 pin 7 and then pin 4.
Now connect the fuzz circuit to power ground and measure the same pins.
Thanks.

[caspercody]

Voltage is 9.49

At pin 7 it is 4.6, and pin 4 it is -4.6

Connecting fuzz ground pin 7 is 9.49, and pin 4 is 0.109

[Aph]

Okay, since you are not using a voltage dropping resistor in the LT1054 circuit, your voltage on pin 7 should be around +9v and the voltage on pin 4 should be around -9v... with or without the fuzz grounded to the power input.
So, doing some experimenting, I removed the 100uf cap that goes to pins 2 and 4 on the LT1054 and I got almost the exact same readings you got... +/- 4.6 and then about +9 and +.14 when properly grounded. So, I think that's where the prblem is.
First start with the capacitor. Is it shorted or open? Is one of the leads broken? Is is soldered properly? Try and replace it with a known good one.
If that doesn't work, then try replacing the LT1054. Also, check the socket. Is it soldered okay? Are the IC pins making contact?
Look for shorts or opens around that area on the top and bottom of the board, etc.

[caspercody]

Thanks, it was a bad LT1054.

But now it has a little hiss noise. If i touch the solder side with my finger hiss goes away. Is there anything I can add to circuit to get rid of hiss?