Building the tap tempo tremolo

[Taylor]

As far as the wave distort...still does nothing at all and I have no reference to what it should do...lol

The wave distort functions like pulse width modulation, but for all waveforms. You can hear it (on a working build) most easily on the square wave. With wave distort centered, the square wave will have 50% duty cycle - equal time on and off. Turning the knob one way will narrow the pulse width so it's on less than half the time - as you decrease it all the way the square wave will just be a very short blip and mostly off. Once the audio section is working, you'll be able to hear it better and you may find that it actually already is working, since it seems your entire digital portion (the TAPLFO and surrounding bits) is probably working as it should.

you asked if the trimpots had an effect on the trem itself and would say not really. one I notice just seems to turn the led on/off and the other seems to control the strength of the rate led and seems to increase ticking, noise and ads a bit of gain.

That's what they should do, and if you haven't tried to "tune" them, that's definitely going to give you the depth problem. Again if we think only of a square wave (hard on/off, for simplicity), the "off" volume is basically fixed by the dark resistance of the optocoupler. In between the chips, the trimpot on the right (the one you said increased ticking, noise, and gain) effectively controls the "on" volume, and you want this to be as large a difference from the off volume as you can make it without bad ticking. While you're tuning these to get the best response, I recommend you turn down your gain pot or it will make the noise and ticking you might be getting worse. Make sure your wires to the gain pot are not routed physically near the digital part of the circuit or ticking could get capacitively coupled into the output gain stage.

I did have a question related to the opto though, I was trying to see if I couldn't get the phase depth figured out (or just wanted more) if there was any mod I could come up with to increase the input current on the LED side in hopes to increase phase depth (i know this is the function of the trimmers but they have little affect.) I assumed this was thought of when the circuit was designed but was curious why the Nsl-32 was chosen. Of course I bought and used a couple as the BOM recommended them. Just curious because I had some VTL5c3's lying around and never used a NSL-32. Aside from them being cheaper than the VTL I looked at the datasheets and they appear to be damn near identical. However, I did notice that the response time of the VTL5c3 was much faster than the NSL.  Granted the difference in turn on time is marginal and likely impossible to notice, I did notice the decay time is almost 5 times as fast. Was wondering if the faster response times would help with ticking and add any noticeable depth, especially in the square wave and random settings? Have you tried one at all and notice anything or in this type of application would it even make a difference enough to notice? Just curious...Damn! I just nerded out, I need to go have beer and man up a bit...lol thanks for all the help folks.

I think the NSL-32 was chosen originally because it was cheaper and easier to find than the vactrols, especially outside the US, at least in 2010 when the project was created. The 5c3 is probably better in terms of its on and off resistances, which here we want to be quite low and quite high, respectively. The faster response would also mean more accurate LFO waveforms, and more depth at high speeds, although hypothetically might be more likely to tick since the circuit is relying entirely on the slow response of the optocoupler to filter the PWM signal coming out of the TAPLFO into an analog LFO waveform.

[iampoor]

Currently working on this project. Anyone have any oscillation issues when the supply voltage goes below 9v?
Also, how is the noise? My layout seems to add a reasonable amount of hiss and some "thumping" on high depth settings.

[Taylor]

It sounds like you may need to do more tweaking on the trimpots. Lots of noise might indicate you have the gain trim turned up very high, possibly to compensate for not enough current going to the optocoupler LED. Try setting the opto trim higher, and the visible LED and gain trims lower.

[Goosefeathers]

Forgive this post but I am feeling really stupid today sorry. So I had this board for a bit but never finished  it until a bit ago and before boxing it up I ended up robbing the waveform pot cause I was in need of a 10k pcb mount pot.  Anyways, the problem is I wanted to use a rotary switch in its place but couldn't check the voltages as I took the pot. For some reason my computer will not open the Tap lfo datasheet so I'm now confused. I saw another user posted a gut shot of how they did it and from what I could gather from the photo it would appear that the resistors are wired in series from 5k-10k-5k etc. so my assumption is each wave shape is fairly evenly stepping down the control voltage which looks to be pin 12 of the IC, is this correct? I am still making a guess to this based on hard to see pictures but made this little diagram in the picture if anyone can confirm or advice me otherwise if this is right or wrong that would be kick ass and much appreciated. Also, I have never attempted to use switching instead of a POT but if this is wired correctly the 3.6k (R8) would stay in its place right, or is that removed? Thanks

[Taylor]

What you have there is right, except that your switch positions 1 and 10 should not be connecting to the switch - those ends of the 5k resistors should only connect to ground (right pot pad) and 5v (left pot pad). So there should only be 8 positions on the rotary switch.

The 3k6 resistor is connected to the multiplier pot only, so leave it there unless you were going to replace the multiplier pot with a rotary switch as well.

[Goosefeathers]

Thanks for the response, i was questioning that. so is this updated picture wired correctly now? Am i also to assume that the switching would be in this order on the switch?
1. Ramp up
2. Ramp Down
3. Square
4. Triangle
5. Sine
6. Sweep
7. Lumps
8. Random

Also, im guessing i cant get away with this but ill ask. Little did i know i am out of 10ks at the moment I remember there being a fair amount of pot travel before the waveform changed shape so i assume the 10ks need not be perfect tolerance. I have a Crap load of 9.1ks so if i were to use them in place of the 10ks and thus adjust both 5ks to compensate for the difference in value could i get away with that or would i be running into problems some where in the chain?
thanks again.

[Taylor]

Thanks for the response, i was questioning that. so is this updated picture wired correctly now? Am i also to assume that the switching would be in this order on the switch?
1. Ramp up
2. Ramp Down
3. Square
4. Triangle
5. Sine
6. Sweep
7. Lumps
8. Random

Your new drawing looks right, and that should be the order (make sure to move all the resistors down one position so the first throw on the rotary switch connects to the 5k-10k node, etc.)

Also, im guessing i cant get away with this but ill ask. Little did i know i am out of 10ks at the moment I remember there being a fair amount of pot travel before the waveform changed shape so i assume the 10ks need not be perfect tolerance. I have a Crap load of 9.1ks so if i were to use them in place of the 10ks and thus adjust both 5ks to compensate for the difference in value could i get away with that or would i be running into problems some where in the chain?
thanks again.

If you scaled the 5ks down by the same amount, it would work just fine. But, you'd need something around a 4.5k resistor, which most people are unlikely to have lying around.

This circuit is not picky about overall resistance - notice that you can use either a 10k pot or a chain of resistors on your rotary switch which total 80k, and it works the same either way. So a 10% change in either direction won't matter as far as the total resistance, but you need to keep the ratios about the same. If the ratios were too far off, your switch might give you the same wave at two positions and be missing one of the waves. But, honestly it would probably be fine with  9.1k and 5k values. If you find that the switching doesn't line up right you can always add a larger resistor in parallel to get the value down to 4.5k or so.

There are online calculators for lazy people like me. 

[Goosefeathers]

Thanks again. Lazy??? I know all about that, i knew i had the poles wrong on the rotary switch but we both get it, i was just to lazy to redo the graphic. Also i know about resistor calculators too, Theres an app on my phone for that.  4.5k is not in the average parts bin in this particular hobby i would assume but wouldn't think 5k would be either. Anyways, that's what my (or my phones app) calculated as well but got some 4.3ks that should work. if not i also have a bunch of broken stuff littered with 10ks and a few yards of solder wick so will make it happen...then again...lazy. lol I assume you're the one who produced this fun project? if so nice job.

[Taylor]

Thanks, glad you like it. Yep, I designed the board and ship them out and all that. The TAPLFO chip was created by Tom Wiltshire and a few others mentioned in the build doc also contributed, so I don't want to take all the credit.

[joe_t]

I'm having a problem with my build. It makes a loud beeping noise like a fire alarm. I can get it to go away but only by turning down the gain and thus the guitar. The tremolo does work but the beep is at least twice as loud as the guitar. Is there likely a faulty component causing this? I'm a bit lost where to start. No combination of trim pot settings removes the problem. The beep is present on bypass too.

Thanks in advance.

[Taylor]

Hmm... that's a perplexing one. Could you post a video of what it's doing?

There's no audio source in the circuit. Technically, the PWM signal coming out of the TAPLFO chip is an oscillator with a frequency of ~20kHz. Most people can't hear that high (especially musicians due to hearing damage) and even if you could, it wouldn't sound like a beep, so much as that barely perceptible sound of being in a room with an old CRT television.

Thinking outside of the box here, maybe if you used the wrong crystal (one with a lower resonant frequency) the PWM would also come out at a lower frequency. It would turn from a continuous tone into a periodic beep if it's getting into the audio path and going through the tremolo.

But, that all seems unlikely to me especially if you're sure you used the right crystal. Since you mention it's there in bypass, and the effect is true bypass, maybe something that's supposed to be grounded is not, and that's causing hum to get into the tremolo. Can you post a photo of your wiring?

[ElectricDruid]

I'm having a problem with my build. It makes a loud beeping noise like a fire alarm. I can get it to go away but only by turning down the gain and thus the guitar. The tremolo does work but the beep is at least twice as loud as the guitar. Is there likely a faulty component causing this? I'm a bit lost where to start. No combination of trim pot settings removes the problem. The beep is present on bypass too.

Thanks in advance.

If the beep is present on bypass too, what makes you think it's coming from the circuit? The circuit wouldn't be able to produce any output if it's bypassed. Or maybe there's something up with the bypass switch wiring?

Thanks,
Tom

[nammy]

Hello, this pedal interest me a loot, but i am a total noob at this. I only modified my CryBaby yet following things on internet... Is there any way to get a pcb with all components mounted already? and what would be the price? :3 i really would like to do it myself, but seeing a lot of peoples burning things here, i am scared to give it a try...

I am not really at ease with schematics... maybe someone could make a noob-friendly "tuto", by that i mean just post pictures of the pcb with all components mounted, and legends, so telling where are going wires to etc.
It would be awesome and would probably decide me to give it a try myself, and be proud of the result while using it on stage ^^

[Taylor]

I don't sell the boards pre-populated, but if you make a post in the For Sale/Trade section, somebody may be up to do a partial build for you.

You don't really need to be able to read schematics to build this, though. The build document (which you can view here)tells you where the wires go and which parts to buy, and each part is labeled directly on the board. There are lots of photos of built PCBs in this thread, to give some visual context.

It's not the best beginner project, though. If I could give advice to myself when I was first starting with DIY electronics, I'd say to start smaller and get some simple builds fully completed and working, before trying to make the really cool complicated thing I actually wanted. Instead, my first build was so annoying that it took me 5 more years to try building a pedal again. I don't think there's anything wrong with buying a kit. Also consider checking out some of Madbean's projects with only one or two knobs.

[nammy]

thank you!

[Mgt280y]

Can't find the answer in this thread ? On the build docs it states 3x22k trim pots but on the prefab I have just received they are marked as 10k what should I be using?
Also before I mount switches the spst for the tap has anyone got any recommendations for supplier as the tayda ones I have have a click to them prob nothing but didn't know if people used any that were smooth/quieter.
Thanks

[Taylor]

I have used these ones:

http://smallbear-electronics.mybigcommerce.com/momentary-spst-no-soft-touch/

I see you're in the UK so I'm not sure if Small Bear is a viable option for you.

For the trimpots, go with 22k if you haven't already purchased them. That gives you more leeway for tweaking in case you run into ticking with your build.

[Mgt280y]

Cool I have 22k trim pots I'll use them, I'd have to have a reasonable order to use small bear and even then with postage it wouldn't be that cheap,

[Mgt280y]

Can someone double check this before I do it wrong when fitting the pots to the underside as pics which way does the one that I swapped round go and have I got the others right
Don't want to do all legs to realise it's wrong 
https://www.flickr.com/photos/141176322@N02/shares/o221Zh

[Taylor]

You've got the top row of pots right. The depth pot should go underneath the board, like the first photo.