Assistance needed modifying Tremolo circuit

[jhaneyzz]

I built a Pendulum Harmonic Tremolo from a PCB purchased from PedalPCB.

Everything works fine but I find myself wanting
A) the speed to have more upper range (2X faster would be fine)
B) the depth to be maybe a bit deeper.

Can some please assist me in interpreting how I might go about enabling this based upon the schematic below?

[stonerbox]

Lower R14 from 2.2k to say... 100Ω and you will get a much much faster tremolo. Maybe start with 820. Also make sure to up C6 from 4.7uF to 10uF.
In order to get a sharper tremolo response you have to modify the oscillator (IC2 4) to produce more of a square wave rather than a sine wave. Watch out though, the sharper the wave the higher the risk you run of introducing clicking noise in the circuit. Experiment until you find a good balance.

Make sure to filter the power with a huge capacitor (220-470 uF) to ground to prevent the clicking leaking out into the rest of the circuit.

[antonis]

Lower R14 from 2.2k to say... 200Ω and you will get a much much faster tremolo.

I was just about to scold you for your previous suggestion..
(about raising pot's value..)

[stonerbox]

Lower R14 from 2.2k to say... 200Ω and you will get a much much faster tremolo.

I was just about to scold you for your previous suggestion..
(about raising pot's value..)

Hah! Just woke up and hadn't had any black liquid speed yet.

[stonerbox]

If you need a harder wave shape and higher speed try the following:

Swap Speed pot to a 5K.
Keep the default C6 (4.7uF)
Swap R13 with a 1K
Swap R14 for a 460Ω
Swap R15 with a bridge.

[duck_arse]

Also make sure to up C6 from 4.7uF to 10uF.

why more cap if OP wants faster speed? I'd start with 2u2 at C8 for faster and no change to R14.

[antonis]

I think OP wants to raise (2X) upper range..
(lower speed range remained unaltered..)

[duck_arse]

[I will scream if I have to look at another postimages image - their server continually tells me it's overloaded and then does nothing] so double the pot value and halve the cap? otherwise 2u2 fixed and 2u2 added switch parallel for slower range?

[jhaneyzz]

Thank you all for jumping in to assist.

Antonis is correct, I want to increase the upper speed of the tremolo.

I played it a lot last night and decided the Depth is just fine as it is.

So if i read Stoner's fully caffeinated recommendations correctly.


1 - Swap Speed pot to a 5K. (I don't have any 5k C pots on hand but I'll make do)
2 - Swap R13 with a 1K
3 - Swap R14 for a 460Ω
4 - Swap R15 with a bridge

When you say:
"Make sure to filter the power with a huge capacitor (220-470 uF) to ground to prevent the clicking leaking out into the rest of the circuit"
Where would this go?
Does it replace C100? or C7? those seem to be the only caps filtering the power input.
Or do you mean that the this would be an ADDITIONAL cap that goes somewhere not already defined in the circuit?

[antonis]

To upper legs of R11 and R17 resistors..

[jhaneyzz]

Just a ceramic or ploy cap I assume.

[jhaneyzz]

Wait, obviously Electrolytic... does polarity matter?

[stonerbox]

Thank you all for jumping in to assist.

Antonis is correct, I want to increase the upper speed of the tremolo.

I played it a lot last night and decided the Depth is just fine as it is.

So if i read Stoner's fully caffeinated recommendations correctly.


1 - Swap Speed pot to a 5K. (I don't have any 5k C pots on hand but I'll make do)
2 - Swap R13 with a 1K
3 - Swap R14 for a 460Ω
4 - Swap R15 with a bridge

No problem.
I realized I made some mistakes while working it out in my mind. Do not remove/bridge R15, it will deactivate the entire thing, just keep the original 220k. I also suggest to lower R14 to 200Ω for even faster speed, but set it to your taste.

1 - Swap Speed pot to a 5-20K.
2 - Swap R13 with a 1K
3 - Swap R14 for a 220Ω
4 - Leave R15 alone

When you say:
"Make sure to filter the power with a huge capacitor (220-470 uF) to ground to prevent the clicking leaking out into the rest of the circuit"
Where would this go?
Does it replace C100? or C7? those seem to be the only caps filtering the power input.
Or do you mean that the this would be an ADDITIONAL cap that goes somewhere not already defined in the circuit?

If noise/clicks does pop up after modifications you can start by replacing C100 for as big as you can. If that does not help then try to limit the noise by separating the power between amplifier sections and the IC2 with an additional tiny resistor (22-47Ω) and huge cap to ground.

[stonerbox]

I think OP wants to raise (2X) upper range..
(lower speed range remained unaltered..)

Yep, that makes no sense. Not a stoned-box but still.. I can be very confused at times.

[jhaneyzz]

You're killin me smalls...

[jhaneyzz]

Good thing I socketed everything i was swapping or i'd be popping solder pads off the board like popcorn...

[jhaneyzz]

Hmmm...

Kinda not hearing any tremolo at this point. Maybe very faint. no matter the depth.

Not sure what's going on.

What was recommended:
1 - Swap Speed pot to a 5-20K.
2 - Swap R13 with a 1K
3 - Swap R14 for a 220Ω
4 - Leave R15 alone

What I did

1 - swapped Speed pot from C50k to C10K
2 - swapped R13 from 220k to 1K
3 - swapped R14 from 2.2k to 220Ω
4 - Leave R15 alone (I put the 220k back in)

I soldered individual socket pins to the vcc side of R11 & R17 and have tried inserting a 470uf electrolytic cap in both polarities (This doesn't seem to have any effect)

[jhaneyzz]

Oddly enough (at least to me) the following is working quite well:

1) I put R13, R14 and R15 back to the originally specified values
2) I have a C10K pot for speed rather than the C50K specified,
3) I have the 470uf Electrolytic cap between upper (vcc side) leg of resistors R11 and R17

and this works great...

FYI, If i remove the 470uf cap, the tremolo speed goes way down. this seems to be the major contributor to the fix.

[pacealot]

It's well after the fact now, so my chiming in at this point is probably of no use to anyone, and admittedly Duck taught me what little I know about LFOs, so I'm certainly biased (as it were), but I would've thought the easiest solution would've been his — C100K pot and 2.2µF/2.7µF-ish C6, and maybe a slight tweak to R14 to taste, and Bob would have very likely been your uncle. But glad it's working as it is — I've no idea how though (mainly mystified by how 570µF's worth of power filtering could change the range of the LFO that much)...

[jhaneyzz]

OK.

The plot thickens...

While I thought all was well, it turns out that big old 470uf cap effectively completely disables the depth control.

I'll try again with Pacealot's suggestions tonight.

Incidentally,,, how does one go about obtaining the knowledge to determine what values = what modulation through this circuit?

Is there a formula for this, or can you model the circuit in Eagle or something (says he, pretending to know how to use eagle...)