Building the tap tempo tremolo

[.Mike]

It's probably the resistor in the power supply-- 10 ohms... 100 ohms... I forget.

It is not critical. Replace it with a jumper. Be happy.

Mike

[isher1992]

I don't think so.

The orientation on the diode matches the way it is shown on the PCB.

It was the 10 ohm resistor.

[isher1992]

Well I jumpered it and no problems.  But now, I don't get any signal when engaged.  I did the alternate switching with the LED soldered directly to the PCB.  I decided not to use the Tap feature, so I left those pads open.  I have double checked my wiring and everything seems in order.

[isher1992]

Oh, I'm an idiot.  I took the tap switch out and that's why I have no continuity when engaged.  DUH.

[isher1992]

I can't for the life of me figure out what is going on.

I have no signal, whether engaged or bypassed.  I have even doubled checked my wiring with other finished PCB's shown in this thread, and everything mates.  All it does is hum and hum and hum.

[Taylor]

If you have no sound whether bypassed or not, the problem lies between your input jack, the bypass switch, and your output jack. Hum tends to point to ground issues. Make sure your grounds are all connected together, meaning the ground on the board, the switch, the power jack and the in and out jacks. Then check the debugging pages stickied at the top of this forum, build an audio probe, and go through the circuit in order to find your problem.

[isher1992]

Well, part of it was I had the polarities on the DC jack wrong.

Now the LED stays lit all the time, so I'm guessing I have the switch wired wrong.

For the alternate switching method (Where the LED is permanently wired to the board), should the switch be wired like this?



Forgive me if I said the wrong value for the resistor there.

I have never used 3PDT switches and am still somewhat of a noob at this.

[JoeyA]

So i built the Tremolo yesterday and plugged it up and I get ticking but no signal through I've checked all my connections all day to day it worked for a couple seconds then it quit again I have no clue what to do now, thanks in advance

Joey

[Taylor]

Check the stickied threads on this forum regarding debugging and "what to do when it doesn't work."

[ianmgull]

So I just built this (after putting it on the to do list for a couple years) and it sounds great. I know some others in this thread mentioned trying the external sync function so I'm wondering if anyone can report a success? I have a semi-success to share:

I thought it would be cool to get the LFO to sync to my MPC sequencer. The MPC doesn't have any CV out but it does have an audio out and I do have snare drum samples.   I set a snare sample to play pretty loud on quarter notes. I connected the tip and sleeve of the MPC's output to the two terminals meant for the tap switch. SUCCESS!!!! Kind of...

The LFO definitely follows the tempo changes. It's not perfect but it's close. As I speed up the tempo of the mpc the tremolo follows with it. There are a few issues however.

1. The LFO seems to be out of phase with the tremolo. Looking at the PIC datasheet from Electric Druid this makes sense. From the datasheet:

The TAP TEMPO input accepts negative-going 5-0V pulses, and times the period between the falling edges of consecutive pairs of pulses to set the frequency. If another device provides a 0-5V clock signal, this can be fed to the TAP TEMPO input and the LFO will synchronize to the clock.

I know the PIC also resets the phase when receiving a "tap" so it seems that the PIC is setting the phase at the end of my snare pulse as opposed to the beginning.

2. On the same page of the PIC datasheet (the last page) Electric Druid outlines a small transistor circuit which I assume acts as some sort of buffer for the incoming CV pulse. Has anyone built this? I don't know for sure that my MPC was outputting the right voltage so I'm considering trying this (it's just a standard line level output).

3. With the MPC output wired directly to the tap switch of the LFO it was, in effect, like constantly tapping the switch. I don't know if this is the best option. I'm considering trying a momentary NO switch to only let the pulse through when I step on it to see if this cleans things up.

4. Also, what is Pin 13 supposed to be used for and how does this differ from the "tap tempo input" (pin 4). Should I be sending my pulse to Pin 13 instead?

I'm open to any suggestions at this point. Also I can confirm that the VTL5C2 opto works very well.

Ian

[ianmgull]

I have an idea I'm toying with in the simulator. Because the PIC expects a negative pulse (as opposed to the positive one the sequencer is putting out). Is the solution as simple as using an inverting opamp in front of the pic? Or would I have to inject a certain amount of DC offset to make the pulses drop down to zero as opposed to negative voltage. Let me know if I'm making no sense.

[.Mike]

Well, I can answer one of your questions...

4. Also, what is Pin 13 supposed to be used for and how does this differ from the "tap tempo input" (pin 4). Should I be sending my pulse to Pin 13 instead?

The LFO can be used in tap mode, or manual control mode. Pin 13 is for the manual rate knob. It accepts 0-5v DC (0 = slowest, 5v = fastest). If you are using tap mode, the rate knob does nothing. BUT, as soon as you touch the rate knob, it kicks out of tap mode, and the speed is based on the rate knob setting. Sending pulses to pin 13 would not achieve the desired result.


I'm not sure on the rest. I am looking for the easiest way to sync two TAPLFOs. I finally bought a few PICs, and plan on doing some testing once I figure out how to program them. It's on the list. If you find anything on syncing two TAPLFOs, please let me know.

Mike

[ianmgull]

Thanks for the reply Mike. I'll definitely post here if I figure anything out.

What you said about pin 13 makes sense. I didn't realize that was the CV pin.

I'm also interested in chaining a few LFO's together eventually. What was your plan for doing this? Pin 5 and 7 both look like candidates for sending clock sync. I assume 5 is a digital pulse and 7 is CV? Did you plan on using the transistor buffer circuit for the 2nd PIC's tempo input?

[.Mike]

Ian,

I PMed you about this, so we don't crap on Taylor's build topic.

Mike

[Taylor]

No worries about that, Mike.  Life circumstances have precluded me from following closely, but I bet others are interested in reading what you guys are cooking up. If you don't want to post here, consider starting a thread so others ca n follow.

[ianmgull]

Thanks for the info Mike, no new developments on the LFO sync...

Ok I've got an unrelated question.

Has anyone ever noticed a clock glitch in the lfo cycle? What I mean is every 20 seconds or so the clock has a bit of a hiccup and it's as if there are two positive cycles in a row.

[.Mike]

I had that problem back in 2009 when I was working with the VCLFO. I couldn't figure it out, but Tom spotted it right away:

You've got the Step Rate CV input tied to Vdd, which will enable the Sample-and-Hold feature. This stepping wouldn't be immediately obvious with a square wave output, but occasionally it might cause it to apparently miss a pulse. Tie its 1K resistor to 0V instead.
You probably wouldn't hear the steps at all on other waveforms since the step rate is at maximum (which is about 25Hz IIRC) and the LDR will provide enough smoothing to hide them.

Granted, that doesn't specifically apply to the TAPLFO, but the same concept may apply. Check the datasheet, and make sure that pins that need to be held at ground are at ground, and pins that need to be held at 5v are held at 5v.



Mike

[ianmgull]

I almost understand what you mean 

I only have four pots on my build (tempo, waveform, multiplier, depth). All are getting 5v on lug1 and 0v on lug3 (with the exception of multiplier because of the 3k6 resistor).

All of my CV pins seem to be getting proper voltage. I'm just confused about what you meant by connecting the 1k resistor to 0v.

Looking at the schematic I see a 1k resistor in series between pin 13 and the wiper of the tempo pot. Are you saying this resistor connects to ground? I'm using Taylor's beautiful PCB if it makes any difference.

Thanks!

[dean owens]

I apologize if these questions have been covered.  I have read through the thread that started this project and got through part of this thread.  I like everything I'm seeing so far.  There are two questions I can think of so far.

- First up should be the simplest... How is the pcb supported?  Is it from the top three pots?  Is that it?

- I have a DD20 and I planned on having it modded so the tempo signal can be sent from it to anything else I wanted... such as a tap tremolo.  I've been thinking I'd get a Seymour Duncan Shape Shifter but after reading through so much on this pedal I think I'm leaning towards this one.  But I read that the tap tempo takes the first two taps and that's it.  If my DD20 is sending a constant signal will this pedal still work?  I was hoping to be able to keep the two in time together.

If these two have been answered already just tell me to keep reading and I will 

[ianmgull]

I apologize if these questions have been covered.  I have read through the thread that started this project and got through part of this thread.  I like everything I'm seeing so far.  There are two questions I can think of so far.

- First up should be the simplest... How is the pcb supported?  Is it from the top three pots?  Is that it?

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

- I have a DD20 and I planned on having it modded so the tempo signal can be sent from it to anything else I wanted... such as a tap tremolo.  I've been thinking I'd get a Seymour Duncan Shape Shifter but after reading through so much on this pedal I think I'm leaning towards this one.  But I read that the tap tempo takes the first two taps and that's it.  If my DD20 is sending a constant signal will this pedal still work?  I was hoping to be able to keep the two in time together.

If these two have been answered already just tell me to keep reading and I will 

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. Below is a video I made trying to sync the tremolo to my MPC 1000. It works better than expected but the square wave is out of phase. I tried using an inverting op-amp to flip the polarity but had no luck.