Let's design a tap tempo tremolo.

[Taylor]

Like take their odd passive tremolo, and shine the LED on the photocell in the signal path part of a tremulous lune,

That's basically what I had in mind, except I don't want to yoink the Lune directly - I'm not sure it would be ok to make and sell PCBs of Dann Green's design, even modified.

[R.G.]

...but i'd love to offer burned devices for this project. If there is enough interest, i will make a bulk purchase of the PICs, burn them, and ship them to all the contributors. I'm willing to go $10 on the whole system/ shipped.

... and competition drives the cost of a tap-tempo PIC down by half! 

[rustypinto]

...but i'd love to offer burned devices for this project. If there is enough interest, i will make a bulk purchase of the PICs, burn them, and ship them to all the contributors. I'm willing to go $10 on the whole system/ shipped.

... and competition drives the cost of a tap-tempo PIC down by half! 

Ha, i was really just throwing that price out there, mainly to cover shipping and the devices. i'm not at all in the pre-programmed device market. My chip set doesn't have quite the wave-form features, but it does make a very nice LDR trem with shape/rate/depth and tap.

[Taylor]

I've noticed that the square wave modes on the Gristleizer stay really choppy even at fast speeds. Maybe a FET would be a good way to go here?

[.Mike]

Hey guys,

Just to follow up on my first comment in this topic, I heard back from Tom from ElectricDruid about his progress on his tap-tempo chip. Here's some of what he said:

Well, I've done quite a bit to it. I've got a working version of the VCLFO with tap tempo. There are one or two things still to do, like improve the accuracy of the tempo measurement (currently it measures milliseconds) and make it so that you can set the frequency using either the tap tempo or the frequency knob/CV. Currently it is tap-only for testing.
I made one or two changes from the VCLFO version following comments made on the forum I started about it. I altered the waveform selection for a more 'effects friendly' collection, so it now has Ramp up, Ramp down, variable-width pulse/square wave, Triangle, Sine, Sweep wave (the lower half of a sine wave), Lumps wave (the top half of a sinewave), and Random (the classic sample-and-hold random levels).
It also has a "tap tempo multiplier" control which allows you to set the frequency at a multiple of the tempo you set. The are currently 16 options for this, including whole note, half note, up to 1/32nd note and also dotted notes and triplets from wholenote triplets to 1/16th note triplets. I suspect this is too complicated and I might reduce it to the eight most useful options (like the waveform control, which could also easily have more options).
I'll probably publish the code once I'm done so people would be free to make custom versions with more/different waveforms for their own use.

This really might turn out to be a good option for a project like this, and other future projects. I don't mean to knock the folks who make similar chips as these, but it might be more in the spirit of DIY to use a chip with more open, modifiable code than purchasing a locked-down, unchangeable commercial chip. Once the programmer is purchased, the PICs are very cheap.

Anyway, just wanted to give an update in case anyone was interested.

Mike

[Taylor]

Sounds cool, openness is excellent, but for me the main thing is to make this accessible to everybody. If somebody was into programming and selling and shipping the PICs for a reasonable price, that would be great. I just want to make this a simple project for people who have no understanding of digital tech. There shouldn't be the need for folks to program their own parts, etc. (though the option to do that is great for guys who are familiar with it).

[jkokura]

Sounds cool, openness is excellent, but for me the main thing is to make this accessible to everybody. If somebody was into programming and selling and shipping the PICs for a reasonable price, that would be great. I just want to make this a simple project for people who have no understanding of digital tech. There shouldn't be the need for folks to program their own parts, etc. (though the option to do that is great for guys who are familiar with it).

And it's this kind of idea that makes me interested, cause I'm so new at this half this conversation goes over my head!

I really like this kind of open idea is kinda like the PTAP, as in it's a community or a person who create, sell and ship a kit and you can add it to a few projects that it works with. Perhaps this turns into a kit, or at least we come up with a guide for a mod anyone can do using a commercial chip, but isn't part of this that we should come up with a Tremolo we want it to work off of? Perhaps this is presumptuous or preemptive, or perhaps you've already all assumed these kinds of features in this trem, but here are some of the features I'd like this kind of trem to include:

- The ability to choose between a few different wave forms (sine, triangle, square)
- Controls for depth, level (fix any volume drop when turned on from true bypass), and rate/speed (that last would be able to be modded to include the tap function)
- Fit it all in a BB size box
- 9V power
- An LED to give us the speed both when using the knob or with the tap function be a good idea
- I'd like a method for being able to bypass the tap tempo function (tap once for on, hold for 2 second to turn it back to Knob control?)

Questions I'd have:
- For that matter, can we control the tap function even if the effect is bypassed? As in, while I'm playing the verse and expecting to turn the Trem on for a chorus of a song can I be tapping it in so it's already at the right tempo before I turn it on.
- When tap tempo is engaged, what would the rate/speed knob do then?
- Ramp up or down feature? My vote is no - that's starting to emulate the 'commercial' offerings too much for me, and I'd rather build a leslie simulator for that kind of effect.
- Could this tap tempo project end up being used in some other modulating effects? (Vibe, phase, flange, etc.)

Jacob

[Skruffyhound]

I'd love to see both possibilities come to fruition. Right now I'm not capable of burning my own chips (except in the oven  ) but in a few years, who knows, and there are already quite a few projects on-the-go in this forum using programable chips, seems like the trend is set to continue. Maybe one of the forum sections will end up being "Code"
I appreciate what Taylor is saying however, in terms of numbers, the more accessible, the cheaper any eventual PCB prices will be.
Shame not to be able to utilize some free code though, if only we knew someone willing to program chips for us .....

[R.G.]

I believe I posted the overall programming approach to do a tap tempo program here a few years ago. This really isn't any big issue if you've done any microcontroller programming.

Here's an interesting issue though. Let's say that tap tempo was trivial, and that there was a $20 part you could just buy that did it. Do you really want a tap tempo *tremolo*?

Tap tempo makes sense for a delay, because the audible delay always starts when you hit a note. The echo happens one delay time later. Even if you make tiny errors in setting the delay, the error is constant per note because the delay only starts for that note when the note happens.

However, there is always some error in setting a tempo. There exist people who are dead-accurate in tapping a tempo, I suspect. I'm not all that great at it, and I suspect there are many who are as bad as I am or worse. Otherwise, there would be no need for metronomes or click tracks.

If the tap tempo sensing algorithm inside your tapper was *perfect*, it would be very confused when your successive taps to set the tempo were not all at the same time apart. This is why good tap sensor routines take several taps and average or otherwise try to figure out what tempo the silly, no-rhythm human was trying to do. And it's good at this, comes up with something that is least-squared, triple polynomial regression of what you actually tapped into the machine.

What are the chances that what you tapped into the machine is what the drummer is going to beat? It's unlikely - unless your drummers are much better and more willing to please than mine ever were! Mine always expected me to follow them, not the other way round. 

But let's say you're really practiced and you (and your drummer) manage to start playing a beat that's only 0.5% different from what the tap tempo chip thought you wanted.  Ten beats later the tempo in the pedal is off by 5%. A hundred beats (maybe 10-20 measures) into the song, it's 50% off and now the silent part of the sound is on top of the beat, not after it. The tremolo is now 180 degrees out of phase with your playing.

Notice that the problem is one of the machine not following your playing and the error building up. This cannot happen with delays, as the error is always 1X, not once per beat.

So ask yourself... do you feel lucky?   

[aziltz]

good drummers would play to the tremolo.

Would it be more accurate if you tap Quarter notes and use some kind of subdivision setting for faster stuff?

[jkokura]

Here's an interesting issue though. Let's say that tap tempo was trivial, and that there was a $20 part you could just buy that did it. Do you really want a tap tempo *tremolo*?

Tap tempo makes sense for a delay, because the audible delay always starts when you hit a note. The echo happens one delay time later. Even if you make tiny errors in setting the delay, the error is constant per note because the delay only starts for that note when the note happens.

Yes, I do want a tap tempo tremolo. You make a good point that it will obviously go out of sync with the rhythm of the song, but that's ok with me. It's not about having it match up permenantly for a long time, it's about it's relative speed.

For instance, I do use trem in several recordings I've made. When I've played those songs live, I invariable have to reach down and tweak my trem so that it matches with the original sound/feel of the song. I don't have one trem speed setting that appears in all my music, and especially when I'm doing cover work that I use a trem in, it's impossible to reach down and change the speed of the trem every time.

However, with a tap function, I could do that all while standing and not having to worry about reaching down and adjusting a knob on the fly. Moreover, for those short sections of a song (i.e. a bridge, or a chorus) I'm good enough to tap in a tempo so that for that part my trem will match my bands tempo long enough for me to be ok with the slight out of sync that will show up 18 or 24 bars along in my songs.

So in short - you have a point RG, and by all means I'd understand if you disagree, but as a live musician I can see how tap tempo would really be advantageous (and fun).

[Taylor]

I agree with RG in theory, but my experience is that this is only a problem when the band is playing to a click or the drums are programmed, etc. As long as you're playing with live musicians, they will tend to keep in time with the tremolo. The trem almost acts like a metronome.

As for programming chips, I guess it's not that complicated or expensive. I'm actually getting into DSP right now, so it may be good for me to get the skill of burning PICs and the like anyway. So maybe I'll burn the chips and sell them along with the PCBs.

[Skruffyhound]

Great, Taylor, I don't know how you find the time for all this, but I'm glad you are making the effort. I feel a series of tap tempo pedals coming on ....

[Taylor]

edit: Oops, nothing.

[R.G.]

However, with a tap function, I could do that all while standing and not having to worry about reaching down and adjusting a knob on the fly. Moreover, for those short sections of a song (i.e. a bridge, or a chorus) I'm good enough to tap in a tempo so that for that part my trem will match my bands tempo long enough for me to be ok with the slight out of sync that will show up 18 or 24 bars along in my songs.

So in short - you have a point RG, and by all means I'd understand if you disagree, but as a live musician I can see how tap tempo would really be advantageous (and fun).

That is a good reason to want it, OK.

As for programming chips, I guess it's not that complicated or expensive. I'm actually getting into DSP right now, so it may be good for me to get the skill of burning PICs and the like anyway. So maybe I'll burn the chips and sell them along with the PCBs.

It is almost trivial to set up to burn PICs. By far the biggest effort is the mental discipline to do the programming.

[jkokura]

Wow. I'm a super newbie, 'arguing' with one of the giants around here, and he agreed with my point. I don't know whether to laugh at my foolishness or feel satisfied.

[frequencycentral]

I doubt I'd ever build a tap tempo trem, but I do have an idea to fight the Russian Dragon (rushing or dragging - get it?).

The tempo is set at the start of the song, it's going to be a hassle to tap it in again at regular intervals during the song, and would certainly interfere with your playing. So what about a reset function on a momentary footswitch which wouldn't redefine the tempo, but would at least put the tremolo back on the beat. You could tap it once every so often just to tweak back in.

[puretube]

...world needz Tap-Tempo triggered by drummerz (as Mark knowz  )

[Ben N]

...world needz Tap-Tempo triggered by drummerz (as Mark knowz  )

Now that is a cool idea--maybe a hi-hat or kick-drum mounted sensor that you could read with a momentary stomper to set the LFO tempo.

[aziltz]

I doubt I'd ever build a tap tempo trem, but I do have an idea to fight the Russian Dragon (rushing or dragging - get it?).

The tempo is set at the start of the song, it's going to be a hassle to tap it in again at regular intervals during the song, and would certainly interfere with your playing. So what about a reset function on a momentary footswitch which wouldn't redefine the tempo, but would at least put the tremolo back on the beat. You could tap it once every so often just to tweak back in.

my line 6 pedals work to this effect.  tap and play, and if it gets off, just tap some more.  Nothing stops or stutters, it just re-averages the tap time.  I know they're digital effects, but maybe we could apply that feature somehow.