another pop problem (with a buffer)

[Cabezahead]

Ok - so I too have made a loopbox...  Everything works fine with the LEDs and the sends and returns and EVERYTHING...

I have also built a buffer into it and THIS is where the problem comes in.  The buffer comes directly after the input and goes straight to the first loop.  No matter what is plugged in to the loops... it'll pop.

(Discrete JFET buffer...)

When I remove the power - the pops slowly get quieter and quieter (with rapid-fire pushing)  which leads me to believe that the problem lies in a capacitor somewhere.

I just don't get why the buffer makes everything pop!  Shouldn't it be treated just like another pedal?  This problem occurs where I send the ground (common ground with the loopbox as opposed to it's own ground through the DC jack)  Any help, ya'll?  Thanks!

-CH

[R.G.]

Any time you switch between two different DC levels, you will hear a pop.

That's the problem in a nutshell. Finding the DC may take some time, but it's simply a matter of persistence.

[Cabezahead]

Glad there's a tangible solution!  So... How do I 'find the dc?'

Thanks a bunch!

-CH

[R.G.]

So... How do I 'find the dc?

Just a guess - a voltmeter??

This problem occurs where I send the ground (common ground with the loopbox as opposed to it's own ground through the DC jack)

I would split the grounds, and then measure DC between the two ground points.

Without any kind of schematic of what you're doing, I can't really tell you any more. Your description sounds like there is some DC power supply problem putting DC voltage on the buffer ground, and transferring that to the signal ground when it's connected, but there's really no good way to tell without a schematic. Can you send one, even hand drawn and scanned or digi-photo-ed?

[Cabezahead]

hmmm... Yea - when I isolate the grounds and measure the voltage I get .003 on the meter...

I really don't have time to draw a schematic - but it's really very simple.

The input goes into the buffer into a tuner bypass switch into the cascaded bypass switches (setup like the ones at http://www.singlecoil.com/tb-strip/tbstrip.html)  Into the output jack.  The whole circuit is grounded except for when I isolate the buffer's ground (which changes nothing.)

The LEDs and the buffer work off of seperate power supplies.  The problem occurs with the buffer ground isolated or not - which makes me think the problem is in the circuit itself.  I have also powered the buffer and LEDs with the same power supply - but that didn't work either.  I have swapped out both of the capacitors to no avail.

I think it must be the buffer circuit - because how else would I get voltage between the grounds?

EXCEPT!  I just thought of this - I dunno if this would have anything to do with it - but - I am using a switchmode powersupply to power this thing.  Is that a no-no?  I hope not.  I guess i'll have to go buy some battery snaps tomorrow, if it is...

Thanks a bunch - this is the most helpful forum i've ever seen.

-CH

[Cabezahead]

Just a bump before I head off to bed...  I'll letcha know if the battery thing works when I try it out tomorow. (later today, I guess...)

-CH

[(doug harrison)]

Maybe it's your amp.  Some of my pedals pop on an old Silvertone, but they are fine on a Fender Champion 110. Then on another small modern Fender solid state, they pop. On a Pignose, they're quiet. So the amp itself could be feeding DC back into the pedal's... output capacitor???

But then how would DC voltage get back into the pedal if there was buffer constantly on between the pedal output and the amp input???

[onboard]

I was going to mention something like this, too, but thought I was off my nut.  I measured some crazy DC from output to ground on a preamp that was feeding a so-so tube amp. 500 ~ 600mV IIRC. If I'm measuring correctly, that is...

[Cabezahead]

hmmmm... damn. that would stink.  I've used all of these pedals with both of these amps though in a chain as my main gigging rig for the past four years....  Unless the bypass box changes that -I don't think that's it.

thanks though - good to know.

-CH

[onboard]

Posting a schematic and DMM readings would likely be very helpful.

[Cabezahead]

Just tried the battery thing.  So far it's working.  :-)  I'll letcha know if I have anymore bad news...  Otherwise - thanks a bunch, guys!

-CH

[onboard]

Using DC from a battery instead of plugging into the wall got rid of the noise?

Now I want to know how the 60Hz snuck in there...

[Cabezahead]

Using DC from a battery instead of plugging into the wall got rid of the noise?

Now I want to know how the 60Hz snuck in there...

60hz wasn't the probelm... and this particular wall wart has powered everything on my gigging board for the past four years without fail and without noise no matter how shitty shitty the source.

Freakin smarty pants.

-CH