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DIY Stompboxes => Building your own stompbox => Topic started by: soulsonic on April 27, 2008, 03:54:44 AM

Title: Anderton Comparator Fuzz
Post by: soulsonic on April 27, 2008, 03:54:44 AM
Hello everyone,
I finally dug up the book with this one in it. It's an old comparator-based fuzz designed by Craig Anderton. It was originally published in Popular Electronics, July 1972 in an article entitled, "Build the Optimum Fuzz Adapter". I've seen people ask about square wave circuits around here a few times, so I figure folks might enjoy this - it's as square wave as you can get!
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=22322&g2_serialNumber=1)
http://www.aronnelson.com/gallery/main.php/v/soulsonic-fx/AndertonComparatorFuzz.gif.html
I built one of these in high school and it was probably the second thing I ever built. It gets a big buzzy square wave sound that reminds me of the sort of tones you hear on Siamese Dream. One thing to note is the fact that the negative terminal of the battery does not connect to ground, so you wouldn't be able to do the usual input jack shorting trick to switch it on and off. I suppose you could have a switch mounted to one of the pots to switch the power or something like that. Maybe you could have the power switched on the third pole of a 3PDT bypass switch, but I'm not sure if that would make a power-up pop when switching. There's alot of room for more ideas here!
I believe this could be considered an early version of what later became the "Ultra Fuzz" project from Electronic Projects for Musicians, which is also a comparator circuit.
Sorry, I don't have a layout for this; when I built it I wired it point-to-point with terminal strips... seriously! I did a crummy job of building it too, but it still worked! :icon_lol:
Title: Re: Anderton Comparator Fuzz
Post by: R.G. on April 27, 2008, 10:26:22 AM
I always liked that one too. The 741 might not be the best opamp to do that with these days, as there are quieter ones, and also opamps that have a cleaner entry/exit from overload. The opamp is always in overload, either banged against the top power supply or the bottom.

The only thing I didn't like about it is that there's a DC transient at the start of every note. The resting state of the op amp between notes is always either full-positive or full-negative, so the output cap is charged to the full power supply one way or the other. When the note comes along, the DC level on the output changes to half the DC supply, and so the output after the output cap has a transient to be passed along.

I think if I were working with that today, I'd do a side chain which provided a "note present" gate signal that starts the note off a bit softly. That would open the note with a low gain to the DC transient and soften the "snap" a bit.

The other thing that would be interesting is to use a real comparator like the LM339 or one of its eight-pin variants as the comparator. This might produce lower noise.
Title: Re: Anderton Comparator Fuzz
Post by: Dragonfly on April 27, 2008, 10:59:49 AM
Thanks Soulsonic - I probably won't have time to breadboard it anytime soon, but I'll definitely save it for future reference. I appreciate the redraw and posting ....
Title: Re: Anderton Comparator Fuzz
Post by: ollie on April 27, 2008, 11:51:17 AM
Siamese Dream?

:o

Actually need to build me one of these!
Title: Re: Anderton Comparator Fuzz
Post by: Mark Hammer on April 28, 2008, 10:24:56 AM
Quote from: R.G. on April 27, 2008, 10:26:22 AM
The only thing I didn't like about it is that there's a DC transient at the start of every note. The resting state of the op amp between notes is always either full-positive or full-negative, so the output cap is charged to the full power supply one way or the other. When the note comes along, the DC level on the output changes to half the DC supply, and so the output after the output cap has a transient to be passed along.
Q:  Did the EPFM Ultra-Fuzz - another comparator based square-wave generator - manage to get past those hurdles?
Title: Re: Anderton Comparator Fuzz
Post by: CodeMonk on May 27, 2008, 02:32:49 AM
I just finished building this one tonight.
It kicks ass, big time.
Out of the 4 fuzzes I have built (Jordan Bosstone, Mosrite Fuzzrite, Dallas Arbiter, and this one), its my favorite one by a long shot.
I'm gonna call it "ZipTone". I didn't have an enclosure, so I gutted a power adapter for a Zip drive and stuffed it all in there.

RG, would a LM339 be a direct swap for the 741?
Mine is actually a UA741CP (Radio Shack is all I have locally, and even that is 30 miles away).

Thanks
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on November 30, 2017, 03:00:45 PM
I made one of these last night, using a veroboard layout. And I get no sound out of it. I tried a audio probe up to pin 2, i get sound. But nothing out of pin 6. I have 9 volts positive and negative to the IC, with the ground connections connected separately and not to  connected to the negative of the battery.
Title: Re: Anderton Comparator Fuzz
Post by: reddesert on December 01, 2017, 02:00:54 AM
It's a simple inverting comparator circuit. The 100K and 100nf pairs drawn above the opamp are just setting a reference voltage to ground, midway between -4.5V and +4.5V supplies. The Attack pot sets the level of the input signal at which something happens, and the op-amp is running open-loop trying to slam the output against the + or - supply rail depending on the value of the input. You may have a layout problem or some kind of DC offset such that the DC level of pin 2 is different from ground, so that even though audio is present on pin 2, the comparator never switches states.
Title: Re: Anderton Comparator Fuzz
Post by: diffeq on December 01, 2017, 07:59:19 AM
Quote from: reddesert on December 01, 2017, 02:00:54 AM
It's a simple inverting comparator circuit. The 100K and 100nf pairs drawn above the opamp are just setting a reference voltage to ground, midway between -4.5V and +4.5V supplies. The Attack pot sets the level of the input signal at which something happens, and the op-amp is running open-loop trying to slam the output against the + or - supply rail depending on the value of the input. You may have a layout problem or some kind of DC offset such that the DC level of pin 2 is different from ground, so that even though audio is present on pin 2, the comparator never switches states.

This is mostly likely, and pin 7 is on the same vero track as pin 2, offsetting it high above reference point. Maybe checking DC on pin 2 in unconnected state can give any valuable info?
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on December 01, 2017, 09:07:19 AM

(https://s2.postimg.org/vnznphl2t/comparator_fuzz.jpg) (https://postimg.org/image/vnznphl2t/)


Here is the layout I am using. I can get voltage readings later.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on December 01, 2017, 09:30:40 AM
Never mind, it works.

I was testing it with my headphone amp, and it did not work. Plugged it into my Marshall and it works. Plus used a different guitar. But both have passive humbuckers.

Thanks
Rob
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on December 07, 2017, 06:12:33 PM
So, I tried the pedal again and it did not work. Then I plugged it in just by itself, and only powering this one pedal and it worked.

I cannot plug this pedal into the same daisy chain of power cords I have coming from my 1Spot. When i place it in my pedal board I need to use a separate power supply, then it works.

Not sure if this helps anyone, but thought I would share my experience.

Thanks
Rob
Title: Re: Anderton Comparator Fuzz
Post by: thermionix on December 07, 2017, 09:25:47 PM
Quote from: soulsonic on April 27, 2008, 03:54:44 AM
One thing to note is the fact that the negative terminal of the battery does not connect to ground

This is why you can't daisy chain the power with other (neg. ground) devices.
Title: Re: Anderton Comparator Fuzz
Post by: Aph on December 08, 2017, 12:35:51 PM
Quote from: thermionix on December 07, 2017, 09:25:47 PM
Quote from: soulsonic on April 27, 2008, 03:54:44 AM
One thing to note is the fact that the negative terminal of the battery does not connect to ground

This is why you can't daisy chain the power with other (neg. ground) devices.

Or, you could add this to the circuit:


(https://s7.postimg.org/ecdeazvbb/LT1054_Isolated_9v_Supply.jpg) (https://postimg.org/image/ecdeazvbb/)
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 05, 2018, 09:46:05 PM
I added that power supply to the circuit, and still can not use a daisy chain power cord. Works with its own power cord.
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 06, 2018, 01:15:42 PM
And you're sure the adapter power coming in is ONLY connected to ground and to the point marked +9v?
In other words, just like a normal guitar effects pedal.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 06, 2018, 04:37:37 PM
Yes.

I connected the +9 volts power to the Fuzz circuit and pin 8 of the LT1054.

I connected the -9 volts power to the ground on the LT1054 ground connection.

The ground on the Fuzz circuit does not connect to any -9 volt power, or ground connection on the LT1054.

I did forget the 1K resistor on the LT1054 board.

Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 06, 2018, 06:21:52 PM
Ground is ground is ground.


(https://s18.postimg.org/l2ydsx591/Anderton_Comparator_Fuzz-_Isolated.jpg) (https://postimg.org/image/l2ydsx591/)

ALL grounds connect together.
If you make it like this schematic, it WILL work.
Title: Re: Anderton Comparator Fuzz
Post by: Kipper4 on February 06, 2018, 07:31:33 PM
Whats the point of R3, R2. Why not just connect pin 3 (to Ground (Ironically pin 3 (lt1054) too)?
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 06, 2018, 08:15:44 PM
Quote from: Kipper4 on February 06, 2018, 07:31:33 PM
Whats the point of R3, R2. Why not just connect pin 3 (to Ground (Ironically pin 3 (lt1054) too)?

Not real sure. You'll have to ask Craig Anderton. I've taken out C1, C2, R2, and R3 and it makes no difference... at least in the circuit I posted.
I'm not sure what you meant about the two pin 3's. They ARE, of course, connected to ground. I do not know why the original schematic was drawn showing the two capacitor/resistor pairs connected to pin 3. It's just one way of showing that they are connected to ground.
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 06, 2018, 08:44:06 PM
Okay, it looks like the resistors work as a ground reference or something.
With reference to ground, they keep pin 4 at -4.5v and pin 7 at +4.5v. Without them, the pins are lopsided.
I haven't gotten the scope out, so I don't know if this affects the output symmetry.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 06, 2018, 10:24:36 PM
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.

Here is only difference from your posted schematic:

I forgot to put in the 1K resistor on the LT1054

I used a 3pdt switch, and added a led and 1k resistor. The ground from the power goes to the ground connection on the LT1054 board, and to the middle lug on the 3PDT switch, and that is it.

All ground points shown on Fuzz schematic are connected together, but not to power ground.

Thanks
Rob

Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 06, 2018, 11:06:12 PM
Do you have pictures?
You're not building the LT1054 circuit outside of the box and trying to plug it in through the power jack, are you?
I've confirmed this circuit.
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 07, 2018, 08:09:53 AM
This is an odd design, that was meant to be powered with a battery.

The ground of this circuit is biased to 4.5v and this is connected to the in/out jacks, which might be causing some of the problems. What is ground to the circuit is only internal to it, and outside connections have +4.5v on them.

I have redrawn the circuit so that this can be seen better:

(http://www.muzique.com/images2/Optimum_Fuzz.gif)

I had planned on fixing this last night but something came up. I'll try to get it breadboarded tonight to verify.

regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: diffeq on February 07, 2018, 08:24:56 AM
Quote from: amz-fx on February 07, 2018, 08:09:53 AM
This is an odd design, that was meant to be powered with a battery.

The ground of this circuit is biased to 4.5v and this is connected to the in/out jacks, which might be causing some of the problems. What is ground to the circuit is only internal to it, and outside connections have +4.5v on them.

I have redrawn the circuit so that this can be seen better:

(http://www.muzique.com/images2/Optimum_Fuzz.gif)

I had planned on fixing this last night but something came up. I'll try to get it breadboarded tonight to verify.

regards, Jack

Wouldn't it make more sense to bias the input at +4.5 in front of a buffer, then run it into comparator?
Title: Re: Anderton Comparator Fuzz
Post by: rankot on February 07, 2018, 08:53:52 AM
Or use DC voltage invertor to provide -9V, so opamp can be run at ±9V, while ground remains common, as already proposed?
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 07, 2018, 09:30:12 AM
Ground is ground. The circuit I posted Works!
I have it breadboarded right now and it is daisy chained to several other pedals.
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 07, 2018, 10:08:05 AM
Quote from: Aph on February 07, 2018, 09:30:12 AM
Ground is ground. The circuit I posted Works!
I have it breadboarded right now and it is daisy chained to several other pedals.

Your LT1054 circuit will work fine, just as you mentioned, since it is putting the Vbias at essentially 0v.

The original circuit wants to (weakly) pull the ground up to some arbitrary voltage and this can cause problems on certain power supplies, as some have already noted. I'm not sure why, but I have a theory or two  :icon_biggrin:

Best regards, Jack



Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 07, 2018, 11:02:06 AM
Thanks for the clarification, Jack.
Just as a note... The 1K resistor in the LT1054 circuit lowers the voltage to get about +4.5v and -4.5v (referenced to ground), otherwise the voltages would be +9 and -9, which works... But it seems to sound better with the lower voltage.
Title: Re: Anderton Comparator Fuzz
Post by: rankot on February 07, 2018, 03:46:06 PM
Why not like this:

(http://i63.tinypic.com/2uy1vup.jpg)

Single IC (TL072 or similar dual op amp), input buffer biased to vref and that's it.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 07, 2018, 05:46:56 PM
I can get a picture on Friday night

The LT1054 is inside the box and only commutes to this pedal.

I am using a One Spot power supply
Title: Re: Anderton Comparator Fuzz
Post by: amptramp on February 07, 2018, 09:24:16 PM
Quote from: R.G. on April 27, 2008, 10:26:22 AM
I always liked that one too. The 741 might not be the best opamp to do that with these days, as there are quieter ones, and also opamps that have a cleaner entry/exit from overload. The opamp is always in overload, either banged against the top power supply or the bottom.

The only thing I didn't like about it is that there's a DC transient at the start of every note. The resting state of the op amp between notes is always either full-positive or full-negative, so the output cap is charged to the full power supply one way or the other. When the note comes along, the DC level on the output changes to half the DC supply, and so the output after the output cap has a transient to be passed along.

I think if I were working with that today, I'd do a side chain which provided a "note present" gate signal that starts the note off a bit softly. That would open the note with a low gain to the DC transient and soften the "snap" a bit.

The other thing that would be interesting is to use a real comparator like the LM339 or one of its eight-pin variants as the comparator. This might produce lower noise.

There is the possibility of using a window aperture comparator which has a low, middle and high output level so it starts at the zero (or middle level) voltage and has three possible outputs.  This avoids the rail-to-rail snap between states because everything starts at the mid level.
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 07, 2018, 10:22:41 PM
Quote from: rankot on February 07, 2018, 03:46:06 PM
Why not like this:

Single IC (TL072 or similar dual op amp), input buffer biased to vref and that's it.
Breadboarded.
Yes, it does work, but it's not as "responsive" and has even less sustain than Anderton's.
Make the first stage a gain stage?
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 07, 2018, 10:55:09 PM
Here is what I came up with:

(http://www.muzique.com/images2/Optimum_Fuzz_revised.gif)

Breadboarded and verified to turn a small sine wave into a square wave.  :icon_mrgreen:  Will work with a daisy chain power supply. Use a TL071 for best performance.

regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 07, 2018, 11:38:27 PM
Quote from: amz-fx on February 07, 2018, 10:55:09 PM
Here is what I came up with:

Breadboarded and verified to turn a small sine wave into a square wave.  :icon_mrgreen:  Will work with a daisy chain power supply. Use a TL071 for best performance.

regards, Jack

Thanks, Jack. Interesting design.
But... (here it comes), it's still too comparator-ish. The sustain is pretty good. It's a little brighter than Anderton's (but I think I prefer his: slightly darker). Also, the original circuit has quite a bit of sustain and doesn't "splatter out" as much when it finally does die. A lot of comparator circuits can sound too digital. Anderton's circuit sounds more "analog". This all may be due to the difference in IC's... I don't know. Maybe I'll try your version with a 741.
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 08, 2018, 07:50:13 AM
Thanks for the report Jody.

It is related to the IC chip since I could see a definite difference in the output at low levels on the o-scope when I tried it with a 741. The lower output impedance of my version probably contributes to the bright sound too.

I listed the TL071 because it was more synth-like and comparator-ish  than the 741 since I thought that was the object (make it buzzy) :icon_mrgreen:

Not only did I fix the ground issue and lower the output Z but also made it non-inverting.

Thanks again for testing it!

Best regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 08, 2018, 11:26:39 AM
Yes, it's a useful sound. Putting a compressor in front of it helps the sustain and adding a chorus and wah at the end makes it even "synthy-er".

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!
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 08, 2018, 02:32:49 PM
Thanks for the report. Very interesting.

Does your solution with the +/- 4.5v supply using the charge pump sound more like the original battery version?

regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 08, 2018, 04:36:09 PM
Quote from: amz-fx on February 08, 2018, 02:32:49 PM
Thanks for the report. Very interesting.

Does your solution with the +/- 4.5v supply using the charge pump sound more like the original battery version?

regards, Jack

As far as I can tell, they sound identical... with this observation: The original power adapter I used gave me around +/- 4.9v with the 1K resistor in the charge pump circuit. I then switched to an adapter that was giving about +/- 4.2v. But this was a few weeks later, so I thought "still sounds the same". Just now I tried a fairly new battery that was supplying about +/- 4.7v and I COULD tell a very slight difference (battery sounded just a touch more "bitey"  :icon_rolleyes:). So, I lowered the charge pump voltage drop resistor to 820 ohms which gave close to +/- 4.9v. Then there was no difference that I could hear.
Sounds like voodoo, I know  :o
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 08, 2018, 09:04:23 PM
Rather than depend on the voltage drop across the resistor, here is an idea for a specific voltage drop by using a zener diode. The 4.3v drop across the diode lowers the V+ from 9.0v to 4.7v. Any noise contributed by the zener should be filtered by the 10uF on pin 8. Of course, the zener type could be changed to give a different voltage. The 1N748 is 3.9v for example.

(http://www.muzique.com/misc/LT1054.gif)

regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 08, 2018, 09:34:43 PM
Great idea. I'll try that out!
Title: Re: Anderton Comparator Fuzz
Post by: Elektrojänis on February 09, 2018, 03:04:18 AM
Quote from: Aph on February 08, 2018, 11:26:39 AM
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?
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 09, 2018, 05:37:45 PM
I did a little bit of bias adjusting, but it just made the sustain worse. Haven't tried the null pins. Maybe I will.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 11, 2018, 08:46:58 PM
Sorry it took so long to post images of my build with the LT1054.

Thanks for helping.

(https://s18.postimg.org/vbv1gsr51/IMG_0828.jpg) (https://postimg.org/image/vbv1gsr51/)

(https://s18.postimg.org/pnoqpxpdh/IMG_0829.jpg) (https://postimg.org/image/pnoqpxpdh/)

(https://s18.postimg.org/r2qbeniqt/IMG_0830.jpg) (https://postimg.org/image/r2qbeniqt/)

(https://s18.postimg.org/twtgs3d79/IMG_0831.jpg) (https://postimg.org/image/twtgs3d79/)


Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 11, 2018, 09:46:41 PM
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  ;)
Title: Re: Anderton Comparator Fuzz
Post by: Elektrojänis on February 12, 2018, 06:47:47 AM
Quote from: Aph on February 09, 2018, 05:37:45 PM
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.
Title: Re: Anderton Comparator Fuzz
Post by: rankot on February 12, 2018, 11:16:11 AM
Rob, what is you final schematic for supply? LT1054 with ±9V or something else?
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 12, 2018, 12:03:11 PM
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.
Title: Re: Anderton Comparator Fuzz
Post by: anotherjim on February 12, 2018, 04:53:02 PM
(http://www.muzique.com/images2/Optimum_Fuzz_revised.gif)
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.

Title: Re: Anderton Comparator Fuzz
Post by: diffeq on February 13, 2018, 06:32:08 AM
Quote from: Elektrojänis on February 12, 2018, 06:47:47 AM
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.
(https://s13.postimg.org/acwwc1web/image.png) (https://postimg.org/image/acwwc1web/)
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 13, 2018, 07:47:40 AM
Quote from: anotherjim on February 12, 2018, 04:53:02 PM
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  :icon_mrgreen:

Best regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: Mark Hammer on February 13, 2018, 08:48:36 AM
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
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 13, 2018, 09:39:10 AM
Quote from: Mark Hammer on February 13, 2018, 08:48:36 AM
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.

(http://img.photobucket.com/albums/v484/boogdish/slacktavemodschem.jpg)

regards, Jack
Title: Re: Anderton Comparator Fuzz
Post by: Mark Hammer on February 13, 2018, 03:45:47 PM
The more deluxe version:

(http://www.diale.org/tpe123/swsh.gif)
Title: Re: Anderton Comparator Fuzz
Post by: amz-fx on February 13, 2018, 05:57:37 PM
Quote from: Mark Hammer on February 13, 2018, 03:45:47 PM
The more deluxe version:

Nice. I had forgotten about that one.

Thanks, Jack
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 15, 2018, 09:35:58 AM
Here are pictures of the solder side, of the LT1054 power board and fuzz board.

Thanks
(https://s9.postimg.org/x0ugwk3bv/IMG_0833.jpg) (https://postimg.org/image/x0ugwk3bv/)

(https://s9.postimg.org/jjxidp8fv/IMG_0834.jpg) (https://postimg.org/image/jjxidp8fv/)
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 15, 2018, 12:26:55 PM
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:

Quote from: caspercody on February 06, 2018, 10:24:36 PM
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.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 17, 2018, 05:49:43 PM
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
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 17, 2018, 09:50:07 PM
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.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 20, 2018, 08:30:48 PM
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?
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 21, 2018, 04:24:56 PM
Quote from: caspercody on February 20, 2018, 08:30:48 PM
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?

You're possibly hearing the artifacts of the LT1054 clock... which means you have great hearing, as that clock runs around 33kHz!

Check out this revised schematic. Add R7 and C5 and possibly C9 to your circuit. C5 can be as high as 150pf if needed. Read the note under U2 on the schematic.
Make sure you insulate your circuit boards (especially the bottoms) with cardboard or something so they don't short out, and then screw the bottom on your pedal to shield the whole thing, etc.


(https://s18.postimg.org/3ywsi23g5/Anderton_Comparator_Fuzz-_Isolated.jpg) (https://postimg.org/image/3ywsi23g5/)
Title: Re: Anderton Comparator Fuzz
Post by: rankot on February 21, 2018, 04:34:34 PM
Or you have bought relabelled 7660 instead of LTC1054?
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 21, 2018, 06:07:02 PM
Quote from: rankot on February 21, 2018, 04:34:34 PM
Or you have bought relabelled 7660 instead of LTC1054?

Mmmm, interesting, since his first 1054 was defective. The number of people running into bad IC problems on this forum makes me wonder.
I can't remember the last time I had a bad IC.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 21, 2018, 08:51:22 PM
I actually only had a MAX1044 chio, if that makes a difference.
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 21, 2018, 09:15:53 PM
Quote from: caspercody on February 21, 2018, 08:51:22 PM
I actually only had a MAX1044 chio, if that makes a difference.

Connect pin 1 of the 1044 to +9v and add C5. Do not add R7. I couldn't get a 1044 to work with R7 in the circuit.
Let us know.

A 1054 is still better. I would really use one of those. If you use a 1054, just be sure to keep pin 1 unconnected.
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on February 23, 2018, 09:19:29 PM
I connected pin 1 to pin 9 on the MAX1044 circuit, and noise gone.

Works with daisy chain power supply.

Thanks!!!!!!!!!!!!

Rob
Title: Re: Anderton Comparator Fuzz
Post by: Aph on February 23, 2018, 09:38:46 PM
Great, Rob! Persistence pays off!
Title: Re: Anderton Comparator Fuzz
Post by: Ratimus on January 11, 2020, 12:00:31 PM
Quote from: Kipper4 on February 06, 2018, 07:31:33 PM
Whats the point of R3, R2. Why not just connect pin 3 (to Ground (Ironically pin 3 (lt1054) too)?

Bleeder resistors for the power supply bypass caps so they don't stay charged after you power it off.
Title: Re: Anderton Comparator Fuzz
Post by: Andon on May 21, 2021, 01:42:59 PM
Sorry to be bringing up an old topic, but it's one of the most recent (and comprehensive) regarding comparator fuzzes.

I breadboarded the Optimum Fuzz Adapter that Jack Orman revised, and it sounds great with humbuckers, but really lags and gets super gated with single coils, suggesting input impedance issues. I tried just tacking a 10K resistor to the input and that helped a bit, but not enough. Eventually I just took the input and connected it straight to non-inverting input and added a 1M resistor to ground and now it responds perfectly, though it lacks some of the gated charm.

(https://i.imgur.com/GFV9hHul.png)

What I did is highlighted in red. The 500K pot still works as it should, but again with less gating.

Was there another way to do this that I overlooked? Obviously it works, but I'm just looking for a second opinion I guess.

After that I also tried a modified BMP tone stack to the end after C3 and before before the volume pot (put that after a JFET buffer) and that gave it a lot more depth (which is unrelated to my question, but also neat).
Title: Re: Anderton Comparator Fuzz
Post by: antonis on May 21, 2021, 03:20:46 PM
Quote from: Andon on May 21, 2021, 01:42:59 PM
The 500K pot still works as it should

IMHO, it doesn't.. :icon_wink: :icon_wink:

It works more like variable frequency HPF rather than input amplitude set..
Title: Re: Anderton Comparator Fuzz
Post by: Andon on May 21, 2021, 04:05:31 PM
Ha ha, true, fair. Is there anything else I could have done beforehand, though? Op amp gain buffer/stage?
Title: Re: Anderton Comparator Fuzz
Post by: iainpunk on May 21, 2021, 06:12:57 PM
Quote from: Andon on May 21, 2021, 04:05:31 PM
Ha ha, true, fair. Is there anything else I could have done beforehand, though? Op amp gain buffer/stage?
what specific type of opamp did you use? some opamps really don't like being used like a comparator, and the input bias current can shoot off to one side when its pushed into the rail voltages.
some opamps can do the same function as this fuzz without the hassle of Vbias and getting that to work. the TL071 TL081 CA3130 CA3140 and CA3160 work fine when biased to GND instead of Vbias.

cheers
Title: Re: Anderton Comparator Fuzz
Post by: Andon on May 21, 2021, 06:40:45 PM
I'm actually using a TL071, though I've also tried it with a TL022 and an NE4558, etc. to varying success.

EDIT: At this point it may also very well be that my single coils just don't like this fuzz, even though my other guitars do.    :-\
Title: Re: Anderton Comparator Fuzz
Post by: anotherjim on May 22, 2021, 05:39:23 AM
So, you have a device that has a huge gain wanting to drive the output high or low depending on which of the 2 inputs is a higher voltage than the other.
To cope with different guitar output levels, it can help to able to trim the bias voltage on one input so you can set the point at which signal causes the output to switch. This will let you control how sensitive or gatey it is.
You can hack what you have to try it out...
(https://i.imgur.com/GFV9hHul.png)
Remove your extra 1M.
Disconnect R5 wiper and input signal direct to C4.
Connect top lug of R5 to +9v.
Connect wiper of R5 to the point between C4 and R1
Set R5 midway (never turn it full cw or ccw while trying this out).

R5 now gives a variable bias and you can see if you can find a setting to suit your pickups.
This is an experimental hack, the setting of R5 will be very tricky/fine. A better approach is available with a lower value pot in the middle of a resistive divider. The setting needed will be millivolts away from the fixed Vbias.

Personally, I like CMOS opamps for this. As Iain said, the bias can be ground making it super simple (no Vbias network). Also, those opamps tend to already have input offset that already suit guitar levels and the outputs switch slower/smoother. However, I've never got it to work with a TL0xx chip. TLCxxx instead works great, but they are duals. CA3130 would be a good single amp type.

Title: Re: Anderton Comparator Fuzz
Post by: rankot on April 17, 2022, 04:09:33 PM
Quote from: anotherjim on May 22, 2021, 05:39:23 AM
(https://i.imgur.com/GFV9hHul.png)

Could you please reupload this image? This one is lost. :(
Title: Re: Anderton Comparator Fuzz
Post by: Andon on April 18, 2022, 01:29:11 AM
That was me working through a design problem I had when I was brainstorming a circuit and trying to wrap my head around the comparator fuzz architecture. Here's what I ended up going with:

(https://i.imgur.com/LPSxiThl.png)

That then feeds into a series 10K resistor followed by a 10K resistor to ground (a voltage divider of sorts to limit the volume of the comparator fuzz - it's very, uh, loud) and that goes into a BMP-style tone stack with a mid boost at noon rather than a scoop, and then eventually an output buffer.

If you'd like to hear it, here's a demo video (it's the fuzz on the left):

Title: Re: Anderton Comparator Fuzz
Post by: rankot on April 18, 2022, 04:26:36 AM
Very nice pedal!
Title: Re: Anderton Comparator Fuzz
Post by: caspercody on December 22, 2022, 03:44:27 PM
What, if any, tone circuit could be added to this circuit? I tried a BMP tone circuit, but all the way to treble it sounds more bass and treble control seems to be more at noon