TWIN PEAKS Tap Tremolo (Y.A.H.T: Yet Another Harmonic Tremolo)

[nmbb]

Nice one. Having the TAPLFO already, it's just a matter of a few more components and voila! Probably my next build!

Greetings from Sintra

[drolo]

Greetings from Sintra

Ola !
I am originally from near Castelo Branco. I have been to Sintra once and found it a very strange place (in a beautiful and  good way) :-)

I wish I had the patience (and time) to learn how to code PIC chips ... crazy what you can do with those ...

[nmbb]

Oi oi

My late grandmother was from near Castelo Branco also, I've been there, but many years ago!

The pics are a wonderfull world, besides that we also have arduinos, I've made a switch looper with one of those, but also have plans to do a simpler with PIC, already tested and working!

I've tried the tap lfo yesterday and it worked very fine, now only a matter of time of assemble all stuff into a pcb, perhaps later I'll design one. And if you don't mind, I can post here the drawing!

[drolo]

Sure, I would be glad if you post it, maybe someone else might be intereseted in using it.

[nmbb]

Didn't have time for PCB yet LOL, perhaps this weekend if time allows.

I'm thinking also in a autopan circuit, using the LFO, perhaps to include after this, or even separate building!

[drolo]

I'm thinking also in a autopan circuit, using the LFO, perhaps to include after this, or even separate building!

if you add a switch to remove C1 and C5 from the circuit and feed each channel to a separate output, it should give you a signal panning between the 2, in the "out of phase" lfo mode

[nmbb]

Hello all!

I've made a hand draw diagram, to use also autopan on this!  I'll use only normal tremolo - harmonic and the rest of the switch will made the autopan function!

It's ok for you that I post here or you prefer a new topic?

[drolo]

Hello all!

I've made a hand draw diagram, to use also autopan on this!  I'll use only normal tremolo - harmonic and the rest of the switch will made the autopan function!

It's ok for you that I post here or you prefer a new topic?

Ola :-)
Sure you can post it here, I'm curious to see it.

[nmbb]

Oi!

Using a 4 circuit 3 position, I use the first two for the lfo output. Then the other two, for the outputs of the ldr's and each one goes to a output... In normal mode or harmonic, only goes to output 1, in pan goes to output 1 and 2, (pan in harmonic mode, I didn't bypassed the filter section!)

I'm trying to test it in proteus!!

Later I'll try to scan the draw and post here, during the week ( hope so!) perhaps I'll post the pcb's, trying to design them, but it's like almost 10 years without drawing so i'm a little rusty!

[nmbb]

Here's the draw... now that i'm looking, perhaps it could be even more simple, because the 1st led of the vactrol is always on... and one of the outputs of the ldr also... but i'll try another version and then put here!

For now, here it goes, version 1:

[drolo]

Here's the draw... now that i'm looking, perhaps it could be even more simple, because the 1st led of the vactrol is always on... and one of the outputs of the ldr also... but i'll try another version and then put here!

For now, here it goes, version 1:

you're right you can do the same with a 2P3T, if I look correctly.

Now you made me want to make stereo version .... :-)
If you build it, post a demo!

[nmbb]

you're right you can do the same with a 2P3T, if I look correctly.

Now you made me want to make stereo version .... :-)
If you build it, post a demo!

Shure! If time allows, this week I pretend to make some measures on scope and fine tunning the opamp section. But even if I make a breadboard version, it's still possible to take a few samples

[nmbb]

A pre-drawing of the lfo (without pots), using a double side board. Still rusty,but it can be improved:



First time I draw double sided boards!

[Valoosj]

The LFO's PWM signal goes through 2 inverting op amp stages to drive the Optos. The first one has a trimmer connected to the negative input that allows to apply an offset voltage to get the TAPLFO's signal (0-5V) centered around the half-supply bias voltage.

The biasing is easiest like this:
- Adjust the offset to get the LFO signal centered around the half supply voltage

educate me :-)

Could you educate me on this one? Which voltage should I measure where exactly? If I am understanding this correct, I need to have 4.5V at the negative input of the opamp.

I noticed in your schematic that the multiplier does not have a 3K6 resistor between its pin 3 and 5V. Is this a mistake in your schematic? I would assume that without this resistor, the multiplier pot does not function as it is supposed to. (above 3,75V it goes to its default setting of x1)

[drolo]

Here is how I do it:
Set the TAPLFO Depth to minimum, tat way you get a steady 2.5V signal
Adjust the Offset trimpot until you get 4.5V at the output of the first opamp (U3A)

About the multiplier you're right, but I left it like that intentionally as it provided me an easy to dial in x1 position (the one I use most) when I turn the pot full clockwise but still have all the other divisions available on the left :-)

[Valoosj]

Makes sense. Thanks for the extra info.

[Valoosj]

I was wondering, if I set the output of U3A to be 4.5V, shouldn't I make sure the output of U3B is 4.5V as well? Right now I'm measuring 4.5V at the output of U3A and 3.59V at the output of U3B. Also, instead of attaching the VTL5C1 to 5V, shouldn't this be 4.5V as well to ensure there are no differences in volume? I don't have a dB-meter here or I would measure to make sure.

[drolo]

In that case, your bias half voltage VB2 is probably not not 4.5v, like on my pedal. Measure VB2 and use that as value to obtain at the output of those op amps. Basically, dial the offset pot until you have more or less the same voltage at the output of the 2 op amps. As you turn it, you will notice that while one voltage rises, the other drops.

I just realized that the schematic I posted is not exactly what I ended up working with. As I had no 7808 regulator at hand, I just hooked the power of the op amps directly to R16. I also found out after drawing the schematics that the voltage regulators need around 2V of of voltage drop to operate correctly. So I would have needed a 10V supply ... ideally I would need a 7807 and a rail to rail op amp. But it works as is, I just need to think about setting the offset again if I ever change my power supply.

Concerning your question about the opto being directly connected to 5v in the bass only and treble only positions, it's always a bit of a balancing act, when you try to set a tremolo to have the same perceived level as in bypassed mode. It was convenient as I had a nearby 5V rail at hand on the perfboard and it turned out to sound well balanced. But every one has different taste and ears, feel free to try different settings ;-)

[Valoosj]

I'll have a look-see tomorrow then. Maybe a 9V zener could do the trick in place of the 7808? If I have one I'll try that and I'll also connect the bass/treble only to Vb to ensure equal output levels.

[Valoosj]

Did some research on Zeners ...

When using the following schematic ...


First I would need to find out the equivalent load resistance of the circuit.
I am feeding it with a onespot which puts out 9.4V. Because R = V/I = 9.4V / x (current draw of the circuit) = Y Ohms.

To calculate the series resistance, I need to know which input voltages I would allow. Let's say 9-10V.

My zener is 500mW.

500mW/9.1V =  54.9mA and so,

R1_min = (10V-9.1V)/(x mA + 54.9mA) = z Ohms.

For real zeners a more practical rule of thumb is to ensure the zener current doesn't drop below about 1/10th it's maximum current.  

In this case the minimum zener current would be 5.5mA and

R1_practical_minimum = (10V-9.1V)/(x mA + 5.5mA) = z Ohms

Rs_max = (9.2V-9.1V)/x mA = z Ohms

If this is correct, then I still don't have a solution for the Rs_max if I feed the circuit with 9V. I guess the Zener just does not conduct anything and the circuit functions as before.

Could some mastermind perhaps shed some extra light?