Building the tap tempo tremolo

[dean owens]

There are no mounting holes on Taylor's board; it was designed to be supported by PCB mount pots.

Ok, that's what I thought.

Trying to sync the LFO to an external source is what I've been trying to figure out as well. Have you found a way to get clock pulses from the DD20 yet? I'd be curious if so.

Me?  No.  Pedals are somewhat new for me.  I've been building amps for years but never really messed in pedals.  I was thinking about having my DD20 sent off to this1smyne.  I was looking on this page and saw this mod.  Before that I was just thinking of making a tap tempo with two outputs to send to the DD20 and the tremolo.

[ianmgull]

It looks like you should be able to sync the DD20 to the Tap LFO. The question is if the pulse is positive or negative. At any rate you'll likely need to build the transistor circuit on the last page of the data sheet below:

http://www.electricdruid.net/datasheets/TAPLFO2Datasheet.pdf

[dean owens]

It looks like you should be able to sync the DD20 to the Tap LFO. The question is if the pulse is positive or negative. At any rate you'll likely need to build the transistor circuit on the last page of the data sheet below:

http://www.electricdruid.net/datasheets/TAPLFO2Datasheet.pdf

Thank you.  That seems easy enough.  Now how do I find out if the pulse is + or - before spending the money and having it modded?

Another very simple question (at least I assume it's simple since I can't find where anyone else asked it)... Does the tap switch need to be normally opened or normally closed?  I ask because in the meantime I was just going to build a tap box for both my DD20 and the tremolo and the DD20 needs a NC switch.

[call8797]

I finished my pedal this morning and plugged it in and to my alarm I saw no flashing led...but smoke coming from my board! Now to be fair I was not paying attention and accidentally plugged in a Line 6 pod power supply into my pedal that was sitting around next to my pedal board rather than one of the leads from my power brick. When I opened up the pedal I saw that the 10R resistor right next to the diode/rectifier was the culprit in the smoke show.

Any ideas on what the problem might be? Or do you think it was my mistake in plugging in the line 6 power supply that caused it.

Also, I do have bypassed signal coming through my pedal. But no trem and the led is not lighting up...but all of that is to be expected I guess with a fried resistor.

[Taylor]

Is the power supply 9vdc? Is it wired so that the negative terminal goes to the same place as the negative terminal on your pedal (most people use center negative but it can be iether way as long as they match)?

[call8797]

Is the power supply 9vdc? Is it wired so that the negative terminal goes to the same place as the negative terminal on your pedal (most people use center negative but it can be iether way as long as they match)?

The line 6 power supply is 9vAC instead of DC I believe. Do you think that is what burned up that resistor?

My center along with the gnd from the board, the sleeve from the out jack and the gnd from the bypass all star on the sleeve of the input jack. Is this wrong?

Sorry for all the questions...I researched for hours to build this pedal as it is my first one. I know it has been said it is not a great beginners pedal and I know these are probably silly questions...but the truth is I just really wanted the pedal, and the only way I knew of to get it was to build it.

[Taylor]

You need to power this pedal (and pretty much all DIY projects) with 9vDC. So that's why your resistor burned up and you may have damaged other components like the PIC. I haven't really studied what happens when you plug AC into a circuit like this - I bet RG could tell us in great detail though.

Try a DC power supply and see what happens. You may only need to replace that resistor and possibly the 4001 diode.

By the way, not to discourage you from DIY, but there are tons of people who sell this pedal. Just google tap tempo tremolo and like 95% of the boutique ones (and even a couple made by slightly bigger companies) are either this exact circuit or a slight variation of it, with the same code and everything.

[call8797]

Thanks!

I kinda liked the sense of accomplishment after building it. That is until it started smoking...and it turned into a sense of despair. Haha. I think I might have another go at another pedal in the future. I feel like I learned a lot with this one...and all in all it has been fun!

[bongoben]

So I just finished building my Tap Tempo Tremolo and wanted to test it before I started installing everything in to the enclosure I have.  Basically, I wired up the 3pdt switch as is showing in the diagram from the musicpcb.com site. The ground lines are as such...

-GND line from pcb to Line out ground (sleeve)
-Ground from 3pdt switch (as shown in diagram) to Line In ground (sleeve) then to 9V input ground (sleeve)
-LED isn't coming on.

When I turn on the pedal I get some buzzing intermittently and had some ticking (about 60bpm) that would eventually go away. The internal pots for the LED and octupler as well as the internal gain pot did nothing. No signal coming through whether the pedal is on or off. So basically, it doesn't work. I'll post a pic in a few minutes but I wanted to at least get these notes on here asap so I didn't forget anything. This is my first pedal build but I do have a few years of experience working on arcade and pinball pcbs so I know my soldering is good. Not always pretty... but good. There are no solder bridges anywhere or anything like that.

I'm considering going to one of the 2 LED layouts that have been mentioned in this thread because 1) 2 LEDs are better than 1 and 2) It would help take care of some of the ticking issues once I get this thing working.  Anyways, here are some pics.  Please help.

[ElectricDruid]

Since there's a few people here having trouble with the build, here's a few ideas for debugging. I'm assuming you're using the circuit from:

http://musicpcb.com/wp-content/uploads/2010/09/Tap-Tempo-Tremolo-build-PDF-updated.pdf

1) Is the +5V supply ok on the PIC? (Pin 1 is +5V, pin 14 is 0V)

2) Is there any PWM output?
The output LED should be doing something (showing the LFO output) but if t isn't you can check with a 470R resistor and an LED direct from the PWM output on Pin5. If it's ok there (e.g. test LED lights), the transistor might be dead.

3) If the power is ok and the PWM is ok, the audio path must be the problem.
With the tremolo switched in, check that there's audio at the output of the first buffer on pin1 of the TL072. If you can hear the signal there, but you can't hear it at pin 7, the problem is the second stage, the actual tremolo - that might be the vactrol, or one of R15/C9. If pin 7 is ok, then the problem is C10 or R16.

4) If the power is ok, but the PWM isn't working, then the PIC is not working.
This could be because the clock isn't running correctly - check the 22pF caps and the crystal. It is also sometimes caused by open CV inputs. Check soldering/wiring of pots. Similarly, if the 'Next multiplier' input on pin 8 is left floating, the chip does all sorts of weird stuff - speeds up and down, goes wobbly, etc
If it doesn't work immediately, don't worry. PICs are pretty tough. I've managed to fry one or two (but even then mostly only one IO), but I've also got away with stuff that I fully expected to totally cook the chip.

Ok, that's about all I can think of for starters. Good luck!

Tom

[roseblood11]

I couldn't get rid of ticking in square wave mode. Then I read that adding a cap from the transistor's emitter to base (=gnd) could help. I tried values from 10nF  to 1000µF. 10µF or 22µF worked best, higher values smoothed out the waveform too much. Is it really that simple? Or are there any drawbacks to this solution?

[Ultrakd]

Ok my pedal has been working till now. Now its ticking with the pedal in bypass. The only modes it doesnt tick is in, Sine and Lumps. I need some help cause I love this pedal but it keeps giving me problems and I can figure out why.

[roseblood11]

Use shielded wires for all input- / output connections. Keep these wires as far away as possible from all wires to pots that shape the waveform or go to the rate LED.


This is still unanswered:

I couldn't get rid of ticking in square wave mode. Then I read that adding a cap from the transistor's emitter to base (=gnd) could help. I tried values from 10nF  to 1000µF. 10µF or 22µF worked best, higher values smoothed out the waveform too much. Is it really that simple? Or are there any drawbacks to this solution?

I still don't understand exactly, how the ticking finds it's way into the audio signal (when the pedal is turned on).

[Ultrakd]

Use shielded wires for all input- / output connections. Keep these wires as far away as possible from all wires to pots that shape the waveform or go to the rate LED.

what  Idont get though is this is a new issue it never happened before.

[Ultrakd]

Use shielded wires for all input- / output connections. Keep these wires as far away as possible from all wires to pots that shape the waveform or go to the rate LED.

If the shielded wires dont work what should I try next?

[Taylor]

Check page 3 I think for the alternate wiring diagram. Might help.

[Eric.nail]

Since there's a few people here having trouble with the build, here's a few ideas for debugging. I'm assuming you're using the circuit from:

http://musicpcb.com/wp-content/uploads/2010/09/Tap-Tempo-Tremolo-build-PDF-updated.pdf

1) Is the +5V supply ok on the PIC? (Pin 1 is +5V, pin 14 is 0V)

2) Is there any PWM output?
The output LED should be doing something (showing the LFO output) but if t isn't you can check with a 470R resistor and an LED direct from the PWM output on Pin5. If it's ok there (e.g. test LED lights), the transistor might be dead.

3) If the power is ok and the PWM is ok, the audio path must be the problem.
With the tremolo switched in, check that there's audio at the output of the first buffer on pin1 of the TL072. If you can hear the signal there, but you can't hear it at pin 7, the problem is the second stage, the actual tremolo - that might be the vactrol, or one of R15/C9. If pin 7 is ok, then the problem is C10 or R16.

4) If the power is ok, but the PWM isn't working, then the PIC is not working.
This could be because the clock isn't running correctly - check the 22pF caps and the crystal. It is also sometimes caused by open CV inputs. Check soldering/wiring of pots. Similarly, if the 'Next multiplier' input on pin 8 is left floating, the chip does all sorts of weird stuff - speeds up and down, goes wobbly, etc
If it doesn't work immediately, don't worry. PICs are pretty tough. I've managed to fry one or two (but even then mostly only one IO), but I've also got away with stuff that I fully expected to totally cook the chip.

Ok, that's about all I can think of for starters. Good luck!

Tom

Tom, Thanks for the trouble shooting advice. I do certainly appreciated the step by step!

The issue i'm having with my build is that i've got no signal at all coming through the effect's first buffer. I've redone my wiring now completely a seperate time but no change in the problem which leads me to believe it is in fact a faulty part or issue with the circuit board. I've got all the parts connected and i get the tap LED function going on. The PIC is doing its job for sure, The LED speeds up and slows down with the knobs and tap switches like it's supposed to but no signal through the pedal at all. I tapped the output wire to the first pin on the TLO72 with no signal at all. I'm getting good voltages on the PIC but it's weird. I get a pop whenever i touch the output to the 1st pin on the opamp but other than that there's nothing. it sounds like a capacitor is discharging when i bypass it. It'll pop then if i touch it again there's no noise, but if i wait a second it will pop again. This probably isn't very descriptive...but that's the problem i'm experiencing. Any ideas? I'v also switched out the opamp for a known working one to see if that was the issue. no change.

[Taylor]

Does your audio probe have a cap in series? If not it will pop when you touch biased signals.

Are you certain your optocoupler is in the right way?

If you really genuinely think it's a fault in the board, I would of course replace it. But in my experience these (and faulty opamps) are exceedingly rare in comparison with errors that I have missed.

To be clear, you have signal at the input of the first buffer but not at the output?

[Eric.nail]

The capacitor fixed the popping...Noob move.

I still dont get any signal past the input though. If the pedal has no power i can use the first pin on the opamp and get signal out of it but with power on all it does is slightly hiss with some radio interference. I cant pick up the guitar at all. It's really odd. I'm kind of at a loss. I'm fairly certain the opto is in correctly. It had a white dot on one pin. I assumed that was the polerized side and it is in the positive lead pad. Could the opto be causing me to get no signal at all though the buffer though?

[Taylor]

On the NSL32 the dot is negative.

Can you confirm that you have signal at the opamp's + input but not at the output? The buffer contains several parts so I just want to narrow it down. Also, what voltage do you have on the TL072 pin 8?