momentary "delay" when switching on fuzz face

[mordechai]

I just built up a fuzz face circuit (battery power only).  When I plug the guitar cord into the input jack and switch it on, there's a very brief delay before the fuzz tone kicks in...like 1/4th of a second.  I hit the stompswitch to turn it off, then tried it again and the fuzz kicked in right away.  I unplugged the input jack, waited about 5 minutes, then plugged it in again and hit the stompswitch...same problem.  After that first brief delay, the problem disappears when switching it off and then back on again.  But if I disconnect it for more than a few minutes, the delayed signal problem starts each time I switch it on for the first time.

What's causing this problem, and what is the best solution for getting rid of it?  It's like the circuit isn't getting power for the first 1/4 of a second after hitting the stompswitch to turn it on.

The last fuzz face I built had a 47uF power filter cap on the power rail and this wasn't an issue...would putting a similar cap in there help retain a charge every time it's "first" switched on and solve the problem?

[robthequiet]

Wild guess here, maybe it needs to warm up because the transistor is heat sensitive? Can't think of anything else that makes sense. You say the problem recurs after a few minutes but not right away? I would maybe tweak the biasing to see if it turns on cold and then see if it gets out of whack differently when it warms up.

[LightSoundGeometry]

me thinks it has to do with some capacitor charging up to working properties.

what size cap is the input/coupling cap ? a power filter cap would not do this in my lab experiments.

probably a faulty input electrolyte or someplace close to signal input loading 

[mordechai]

Well, the input cap is similar to the "filter" function on the DAM Dragn'fly...signal goes to a pot with a 22n cap (non electro) on one side and a 4.7uF electro on the other side.  Could that be the problem?  If it is...why does it work on the DAM circuit (I'm assuming the issue I have here is not something that D. Main would accept in one of his devices)?

[GibsonGM]

Just an aside, of interest here....

Listen to Hendrix' "Bold As Love"...he begins the solo with a climbing pentatonic triplet thing, then kicks on his FF...you hear the cap charge as the FF fades in.  Headphone music 

[mordechai]

So is this common?  I've never experienced it before in a Fuzz Face build.  What is the best way to work around this issue?

[cloudscapes]

A big cap on the power rails is always a good thing, though may not be the problem.A schematic would help!

Some DC between caps somewhere may be incorrectly biased.

[Phoenix]

Is it just me? Or does this seem like a non-issue?
How often do you need to play IMMEDIATELY after plugging in the input jack? If I'm understanding the OP, it's only the first 1/4 second after inserting the jack (thereby powering the circuit) that it doesn't operate correctly, but after this initial power cycle, it continues working as intended.

For what it's worth, it's probably due to the time constant of the bias network.

Also, it sounds like it's a modified Fuzz Face circuit, a schematic would provide significantly more insight.

[Mark Hammer]

FWIW, I experience the same thing with the Orange Squeezer.

The functional impact of that charge-up delay would depend on the speed of one's picking and extent to which the effect is needed to be instantly imposed.

[induction]

FWIW, I experience the same thing with the Orange Squeezer.

The functional impact of that charge-up delay would depend on the speed of one's picking and extent to which the effect is needed to be instantly imposed.

I had that on an orange squeezer once, but it was caused by the switch. It popped even with pull-downs and the pop triggered the compressor. The fade-in was the compressor releasing. The pop was caused by the switch itself. When I replaced the switch, both the pop and the fade-in disappeared.

And I agree with Phoenix. If there was a fade-in when you engaged the pedal (like with my OS), that would be a problem. If the fade-in only happens when you power up the pedal, that's normal (large caps charging). There's a reason we don't power down pedals in bypass.

[cloudscapes]

Are you turning on the circuit when hitting the stomp switch? As in the bypass switch is also an on-off switch for power?

If so, this is a big no-no.

[duck_arse]

check the orientation of any electro you have on any fuzz pot that might be part of your circuit.

[mordechai]

I figured out the problem...one of the electro input caps was no good. Replaced it and all is well.  The pedal is wired the same way I always wire a fuzz, and the circuit is being powered even when bypassed as per standard practice.  I had just never had that particular type of problem before. 

Just for the record: it's a fuzz face with VERY high gain 2N1378 transistors (Q1=160, Q2=322) with extremely low leakage.   Used a 50K trimmer on the collector of Q1, a 10K external bias pot, and a 250KA volume pot.  The Q1 trimmer was extremely helpful in dialing just the right response from the circuit.  I AB'd this one against a very vintage-y voiced FF circuit using old stock Newmarket NKT 275s with the classic gain ranges (85 and 135), and I much prefer the 1378's.   The pedal gets very, very close to the gainy sound of a BC108 silicon version of the circuit (to my ears) but is warmer and cleans up very nicely.  If you ever get your hands on some 2N1378s, give them a shot, they're fantastic. 

[anotherjim]

I was going to add a +1 to Stephens suspicion of an input cap. The tell-tale for that is that it sounds noisy/scratchy/bumpy when you adjust the guitars volume control - did it?

[LightSoundGeometry]

I figured out the problem...one of the electro input caps was no good. Replaced it and all is well.  The pedal is wired the same way I always wire a fuzz, and the circuit is being powered even when bypassed as per standard practice.  I had just never had that particular type of problem before. 

Just for the record: it's a fuzz face with VERY high gain 2N1378 transistors (Q1=160, Q2=322) with extremely low leakage.   Used a 50K trimmer on the collector of Q1, a 10K external bias pot, and a 250KA volume pot.  The Q1 trimmer was extremely helpful in dialing just the right response from the circuit.  I AB'd this one against a very vintage-y voiced FF circuit using old stock Newmarket NKT 275s with the classic gain ranges (85 and 135), and I much prefer the 1378's.   The pedal gets very, very close to the gainy sound of a BC108 silicon version of the circuit (to my ears) but is warmer and cleans up very nicely.  If you ever get your hands on some 2N1378s, give them a shot, they're fantastic.

a faulty electro will have a incorrect time constant , or if forming an RC network denoted by the greek letter tau - they differ in RL and RC circuits.

http://www.electronics-tutorials.ws/rc/rc_1.html

https://en.wikipedia.org/wiki/Time_constant

https://www.google.com/search?q=time+constant+chart&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjG9rO237TMAhVGOCYKHUIsCbYQ_AUIBygB&biw=1280&bih=556#imgrc=GSUlECeBR39dyM%3A

[mordechai]

I was going to add a +1 to Stephens suspicion of an input cap. The tell-tale for that is that it sounds noisy/scratchy/bumpy when you adjust the guitars volume control - did it?

I don't know, I didn't test for that before replacing it.  I'll do that next time a similar problem presents itself.

[alr300]

I just built up a fuzz face circuit (battery power only).  When I plug the guitar cord into the input jack and switch it on, there's a very brief delay before the fuzz tone kicks in...like 1/4th of a second.  I hit the stompswitch to turn it off, then tried it again and the fuzz kicked in right away.  I unplugged the input jack, waited about 5 minutes, then plugged it in again and hit the stompswitch...same problem.  After that first brief delay, the problem disappears when switching it off and then back on again.  But if I disconnect it for more than a few minutes, the delayed signal problem starts each time I switch it on for the first time.

What's causing this problem, and what is the best solution for getting rid of it?  It's like the circuit isn't getting power for the first 1/4 of a second after hitting the stompswitch to turn it on.

The last fuzz face I built had a 47uF power filter cap on the power rail and this wasn't an issue...would putting a similar cap in there help retain a charge every time it's "first" switched on and solve the problem?

Is your switching set up such that when you turn off the effect, it also cuts power to the circuit? If so, it could be the delay as your caps charge.

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[overdriver999]

This happens on my big box Russian small stone..has a slight delay until it warms up..I've been told this is common..but it does become bothersome sometimes when you need phasing right away..which is usually.

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