How come the "Super Hard-On" crackles?

[Hiwatt25]

I just spent the last half hour watchng Zvex videos and was wondering why the "Crackle Okay" pot crackles when you turn it?  Just curious from a electronics theory standpoint, I'm not asking anyone to reveal any trade secrets or anything. 

[aron]

I think there's DC on the pot, so it crackles. You can do the same too! 

[markm]

I think I read on the forum here about no decoupling caps causing the crackle but, this was some time ago.
Would the lack of decoupling caps cause the crackle?

[aron]

Yes, as I said, DC is on the pot. Try it yourself. Put a pot where DC flows and start turning it. Instant crackle. Use a crappy pot for more fun!

[Hiwatt25]

Okay, I think I've read that before too.  I thought it was a bad thing but that peadal sure sounds cool to me.  Do you think it "had" to be designed so that it crackles or was that just a cool "feature"?

[markm]

I agree.
I certainly does sound fantastic. 

[R.G.]

The "Crackle OK" pot is an intermixed gain/bias control. There is no practical way to elminate the crackle without more circuitry, and as zv as notes in this forum, even though lots of his customers complain about it, it's so "elegant" that he'll never change it. I can look up the tread if you like, it's in the last week or so.

The "Cracke OK" pot is the source resistor that does both biasing and gain for the active device. Any time you have DC running through a pot that you then amplify as a signal, the slight roughness and bumps on the pot's wiping surface causes momentary skips over some places, and a resulting suddent small DC shift as the wiper re-connects. Those sudden shifts are heard as "crackle".
A decoupling cap across the pot would certainly fix the crackle, but it will not let it then change the gain, so that's out. Using the pot as a tapped divider with a big cap on the wiper would also prevent the crackly while changing gain, but would prevent it from doing the bias shift.

There is a longstanding tradition in technical work that if you can't fix a problem, you should advertise it as a feature and make a big hoopla about how good it is that way. Many well respected companies have done this for a long time. Consumers seem to love it that way.

[Hiwatt25]

Thanks again RG!  I finally looked at every video on Mr. Vex's site.  There is some very creative stuff on there especially the "seek" pedals.  I'd never even heard of Zvex till I started posting here. 

[Meanderthal]

 I can appreciate the KISS principle- Keep It Simple Stupid (I try to live by that), but if I were at a gig and had to tweak that knob I'd hate the added complication of having to mute first! On a boost I sometimes find it advantageous to tweak the knob with my foot WHILE I'M PLAYING, and a pot that crackles is totally unacceptable. For me personally as a guy who would potentially be USING an effect, the elegance of an efficient design with low parts count becomes irrelevant when it produces undesirable sounds. For someone fooling around in a bedroom the crackle might be ok. I get the impression that it's elegant to build, not use, and that the elegance is impressive from a designer's  perspective only.

I'd rather have the extra parts and lose the "elegance", from my perspective the SOUND is the whole point of effects to begin with.

That being said, I've never heard a SHO, and have heard very good things about it. But no matter how good it sounds, I have no interest in owning or even building one because of that crackle. It's NOT ok for me! And there are many many other ways to sound good...

[RDV]

I made the mistake of turning that knob with the amp on and loud, people were looking to see what the hell that row was aboot!

RDV

[Meanderthal]

 LOL- that's exactly what I imagined happening RDV!

[jonathan perez]

it doesnt crackle until the later part of the sweep, for me anyways. i use it in the loop of my amp, and is always on super loud hahaaa

probably my favorite boost, mostly because of the BEE. :-D

[nightingale]

Hi,
I think the rangemaster also crackles. It has an interesting way of controlling the output too.

[markm]

Removing the crackle would change the gain characteristics of the circuit hence, it would not sound different.
It would become just another drop in the endless sea of dime-a-dozen boosters that have glutted the effects market.
Read RG's post.

[Meanderthal]

 Yeah, I understood that part- it's not just a volume knob, it also does things to the bias at the same time, changing the character of the sound as well. If these were to be seperate functions they wouldn't interact in the same way. Believe me, I'm not trashing the pedal, I was only explaining why for me the concept wouldn't be practical. Might be fantastic in any situation other than live, or as a set-and-forget thing. But I'm VERY persnikkety about what I use live- I rely on murphy's law and try to eliminate anything that CAN potentially go wrong. I won't even use my V4b head live even though when it's in the right mood it sounds FANTASTIC. But it's moody... Not that it's a bad head or bad design, it's just not practical for live use. For me. Well, and it weighs 65 pounds...

And RDV confirmed exactly what worries me about this...

I wish there were a way around this, but...

[markm]

Yeah, I understood that part- it's not just a volume knob, it also does things to the bias at the same time, changing the character of the sound as well. If these were to be seperate functions they wouldn't interact in the same way. Believe me, I'm not trashing the pedal, I was only explaining why for me the concept wouldn't be practical. Might be fantastic in any situation other than live, or as a set-and-forget thing. But I'm VERY persnikkety about what I use live- I rely on murphy's law and try to eliminate anything that CAN potentially go wrong. I won't even use my V4b head live even though when it's in the right mood it sounds FANTASTIC. But it's moody... Not that it's a bad head or bad design, it's just not practical for live use. For me. Well, and it weighs 65 pounds...

And RDV confirmed exactly what worries me about this...

I wish there were a way around this, but...

Totally understandable. 

[puretube]

conductive plastic pots... 

[R.G.]

Yep - those don't crackle with DC on them until they get dirty or worn.

[Meanderthal]

 OH! (didn't know about the plastic pots) Well look what happens when ya go and make a wish 'round here! THANK YOU!

[gez]

Yep - those don't crackle with DC on them until they get dirty or worn.

Sealed conductive plastic pots (like the nice Omeg ones I use)? 

OK, so they wear out eventually...