Shared Tap Tempo with Relays?

[erick4x4]

So I have an idea, I am sure it isn't original, but can't be that hard (I hope).

I currently have several pedals that are tap tempo (a boss dd-20, a line 6 echo park, a seymour duncan shape shifter).

I would really like the ability to sync them together on one tap tempo, that could be linked to our audio click track.

We rarely use midi, so really the drummers click is the master clock for the band, even for recordings. All three of these pedals allow me to set the rhythm (quarter, eight, triplet, sixteenth), so if I had one tap tempo, that could adjust based on the audio click track, I would be golden.

Now before anyone tells me just to buy rack gear

Here is what I am thinking. First of course, I need to take apart the echo park, and shape shifter and wire up a little jack, since both of their taps are internal.

Then could I simple use 3 basic voltage controlled relays to do the on-off to simulate the closing and opening of the momentary jack for the tap tempo?

So I would guess I need a simple amplifier to raise the input click to enough voltage to turn on and off the relays, and then connect all of them to the same output of the amp.

What is my next step? I don't know a ton about this, I would think I would buy the relays, and use an opamp or transistor to get the voltage to the same as the relays need to trigger. My question is what amount of voltage should I be shooting for? You can buy relays in many different voltages. What's an easy way to figure out how much a basic opamp would raise the voltage? And how do I be sure the amplification of the click raises the "click" voltage enough, but not amplifying the white noise enough to create enough voltage to trip the relay?

I know this is a lot but I think it would be cool, and useful, and if I can get it to work, then I can post a schematic for all to use.

Thanks for the help!

-Erick

p.s. This may already exist if it does please point me in the right direction.

[R.G.]

Relays don't necessarily respond fast enough to get the tap time the same on all of those. Relays take some time after the current is applied to move the contacts together/apart. In general, the make and break delays are not the same.  So you can't necessarily start all of your tap tempo pedals at the same place, they'll be slightly off compared to each other.

Tap tempo has a little bit of a built in problem - accuracy.

As you note, your drummer is your master clock. He's human, so he varies. Each one of the pieces of gear that you have uses its own internal software to determine which tempo to play. Each one reads the relay closures it gets and determines how long the interval between repeats for it will be. Unless they can keep on watching the click track, they will start to diverge.

This is OK for the digital delays, because each note is delayed by a fixed amount, and the total difference between the time delay and the actual next note remains low. In effect, digital delays "resync" each time a note comes in and they don't get a chance to do long-time divergence.

However, the tremolo does. It has a fixed oscillation time once it's tapped, and over time its internal tempo is perfect - and slightly different from your drummer's timing. The two will necessarily diverge over a song by some amount; if the drummer can hear and adjust to the tremolo, that's great, he'll make up the differences by following the tremolo. But if he can't, the two will get out of sync.

It may be that none of these are big enough to be a problem. But be aware of it.

[erick4x4]

Well the one thing about the seymour duncan trem, is that when the tap tempo comes in (from my foot), it will reset the oscillation if I am far enough off.

So does anything respond fast enough other than a relay?

[Michael Allen]

What about this:

You have something like an LDR controlling a transistor or opamp circuit, which controls voltage being applied to an output. So you have the Tap footswitch rigged to a piece of metal with hole drilled in it, aligned so that when depressed (or when not depressed) the LDR is active and turns on the transistor circuit which applies voltage to the output. You wire that output to a jack, and then connect to your pedals and when the tap tempo switch is hit it triggers a voltage applied to the pedal to control the tempo.

I don't know what kind of circuit you could build to apply voltage, but there should be a simple one out there. You would use the LDR to control whether the circuit  turns on so that no voltage is applied to the output until the LDR is active. It would take some mechanical working to ensure the piece of metal is aligned with the LDR just right.

Maybe?

[RickL]

Something that might be worth trying, assuming each of the three tap tempo switches simply connects some point to ground when it's closed, is to connect a single momentary switch to three jacks with a diode in line with the tip connection. Connect all of the grounds to one pole of the switch and all of the cathodes of the diodes to the other pole. Each anode goes to the tip of one of the jacks. Each of the tap tempo switches will, of course, have to be connected to a mono jack on each pedal, ground to the sleeve, other pole to the tip.

I'm not sure it will work but it is the way keyboard contacts work. Some three button switches, like those used with Digitech gear, also work similarly - two of the switches simply connect a point to ground, the third connect both points to ground through diodes.

Worth a try anyway.

[erick4x4]

Well that would work for using one switch for the 3, but I really want a way to sync it to an audio click.

My Moog Murf does this. It can use an audio input to trigger the next step. Anyone know how it works?

[Paul Perry (Frostwave)]

This is one of those cases where you wish you had the schematics for the three tap tempo controlled units, so you could see whether they all worked by shorting something to ground, and you could use an opto isolator. (I'm talking a semiconductor one, not a discrete LED/LDR type - though for all I know it MIGHT be possible to use a LED and LDRs as the  tap input!!)
I thought that for tap tempo, you only had a few taps at the beginning though, not a continual series of pulses/ Am I missing something?