Author Topic: Reducing POP when changing settings in GT2  (Read 6228 times)

ggedamed

Re: Reducing POP when changing settings in GT2
« Reply #20 on: January 14, 2016, 11:35:17 AM »
The output offsets in GT-2 are not small, at least not in my builds. The bias network was not quite simetrically loaded so the outputs were maybe 1V off. I recall trying to bias the op amp inputs precisely to Vb and not succeeding, then leaving it be.

Actually I'm not so sure anymore, I'll try to find a living GT-2 clone and measure it.
« Last Edit: January 14, 2016, 11:39:11 AM by ggedamed »
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potul

Re: Reducing POP when changing settings in GT2
« Reply #21 on: January 15, 2016, 05:07:21 AM »
If I recall it correctly, my Vb is around 4.8 v

I measured DC at the opamp non-inverting input and it goes approx from 4.5 to 4.85 depending on the pot position.
So there is quite a step of voltage when switching from pot1 to pot2 depending on the position. What puzzles me is that the pop appears even when the 2 pots are at the same position.

I guess the only effective way to avoid this pop will be to use some jfet switching and make the transition slow enough to remove it from the audible spectrum.

Mat

potul

Re: Reducing POP when changing settings in GT2
« Reply #22 on: January 21, 2016, 08:56:05 AM »
Hi all

I've decided to leave the POP as it is by now... if in the future I have time I will try to improve it. The reason is that this week I was able to test it in a rehersal, and in the band context, the noise is acceptable.

In fact, I'm very pleased of the performance of the stompbox. The GT2 ended up being much less noisy that during my tests in the workbench.... I guess one of the reasons is I could play at lower volumes settings (lower in the GT2) and there was much less hiss and pops. In fact, I purchased a noise gate and I will probably not use it  :icon_mrgreen:

BTW, let me explain what the pedal is....

My everyday setup with the band is completely ampless. I connect my POD X3 live directly to the PA, and I'm quite satisfied witht it, but I've been searching for an analog alternative since I realized I'm using only 4 presets in my POD :).
My first attempt was  a pedalboard with 2 tech21 character series pedals (chinese clones) and a loop box to choose which one to use (like having 2 channels). But I had to add a reverb, a booster and another overdrive in order to cover all my sonic needs... So it ended up being too bulky.

So, I decided to build my own cusomized solution, by combining in one box:

-Sansamp GT2 (I had a tonepad pcb around), modified to have 2 "channels".
-A booster (SHO from guitarpcb)
-A brick-based reverb (a Musikding kit)

The GT2 is always on. The channel selector footswitch changes gain and volume pots.
The booster has a selector to put it before or after the GT2, and a footwitch to bypass it.
Reverb is always on but mix can be rolled back to 0.

Here  you have a picture of the box as it is now (still missing status LEDs and finish)




And this is how I plan it to look like once I finish it.



With this one I don't need much more for small gigs. And for our regular gigs I just need to add a wah and a delay and I'm set.

When I finish it I will post some more pics and a guts shot (it's a wiring madness, I can tell you)

Thanks for your help!

Mat