Taptation Issues / Noisy tap

Started by junge87, August 13, 2014, 03:57:44 PM

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junge87

I have built a few taptation based delays in the past, so I know quite a bit about building them.

I have recently decided to make a PCB for my business and a delay that i am about to release.  I had a working circuit delay/taptation, but made some changes with the delay portion of the circuit and kept everything the same on the taptation side of things in eagle. 

Everything works perfectly with the circuit.. sounds great, all functions and knobs work properly, tap tempo works, subdivisions work, but there is a popping when i use the tap tempo footswitch.  SImilar to a true bypass pop, but everytime i hit the tap tempo.  I thought it might be an issue with the autorouter on Eagle messing up, so i reordered the components on Eagle to be easier runs, redid the routing, and waited a couple weeks for the PCBs to come back and same issue.

Here is what i have tried...

3 batches of PCBS
All new ICs/transistors
3 separate footswitches (normally open, normally closed, different manufacturers, etc)
External tap tempo that i know works
Tried attaching the side attached to ground of the tap function to a different ground
Tried attaching the side attached to pin 2 directly to pin 2

Like i said, everything on the PCB schematic is 100% accurate.  I've checked some of the routing on the PCB visually (the part dealing with pin 2) and it all looks good.  Just wondering why i get the pop.  The tap function is accurate and works great.  THis is the last issue with the design and then it is ready for production.  It is a really sweet delay, i've solved most of the inheret problems of the PT2399 and have it going to a full second without hiss/noise.  I just need to figure out this popping.  I've put in 10-15 hours trying to troubleshoot this circuit.

junge87

Forgot to clarify, The first PCB worked perfectly... no popping.  I even have two builds that work perfectly, but had to make the changes to the design offboard.  So essentially the exact same circuitry, it just pops now..

I am mystified and am starting to wonder if that first design had some sort of wizardry invoke on it over at SEEED that made it work and the next two have a horrible pop

Lurco

If your popping is more like a ticking as experienced in many LFO-driven circuits, the taptemo switching might cause a noise like an LFO does similar to the one being discussed and solved in this thread: http://www.diystompboxes.com/smfforum/index.php?topic=107353.0 .
May your flower bloom soon!

junge87

 
Quote from: Lurco on August 14, 2014, 02:54:53 AM
If your popping is more like a ticking as experienced in many LFO-driven circuits, the taptemo switching might cause a noise like an LFO does similar to the one being discussed and solved in this thread: http://www.diystompboxes.com/smfforum/index.php?topic=107353.0 .
May your flower bloom soon!

No... It is not a constant ticking/poppin like an LFO... It is only when you depress the momentary tap tempo footswitch.

samhay

Any chance you could post a schematic?
I'm a refugee of the great dropbox purge of '17.
Project details (schematics, layouts, etc) are slowly being added here: http://samdump.wordpress.com

junge87

Quote from: samhay on August 14, 2014, 07:24:46 AM
Any chance you could post a schematic?

http://tinypic.com/r/rwtapv/8

VD is heading to pin 6 of pt2399 and VB is 5V from 78lo5

armdnrdy

Try tacking a large resistor (2.2M) across both contacts of the momentary switch.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

slacker

Try measuring the current draw of the pedal and then measure it with the taptempo switch held down, does it change much?

junge87

Quote from: armdnrdy on August 14, 2014, 01:33:22 PM
Try tacking a large resistor (2.2M) across both contacts of the momentary switch.

I tried that (kind of as a pull down resistor)...

Quote from: slacker on August 14, 2014, 01:45:32 PM
Try measuring the current draw of the pedal and then measure it with the taptempo switch held down, does it change much?

I will try this tomorrow

polivox

Try a nice large tantalum capacitor in parallel with the button, and/or from pin6 to ground. Some pt2399 do not like sudden (like, square wave like) change of resistance on pin6 - this results in a pop you've described. Not all pt2399s are created the same