Tap Tremolo - My “first” pedal project

[dean owens]

Hey All.  I know this isn't supposed to be first project but I'm not new to electronics.  I had two years of it in high school about 20 years ago.  That led to tinkering on things and ultimately designing and building my own personal amps over the last 10 years.  But, solid state is a slightly different world for me so I do have a few questions before I start if you don't mind.

1 - Was the board designed with 1/4 watt resistors in mind?  I have many of those values laying around but they are 1/2 watters.  I'll make what I have work, I just want to know when ordering the values I don't have.

2 - What voltage caps do I need to get?  I'm used to thinking in terms of hundred's of volts.  There's a Mouser part number for the 1uf cap so I figure I'm safe to stay in the same family for the other film caps.  But what about the ceramics and electrolytics?

3 - Is the tap tempo switch a Normally Opened or Normally Closed switch?  Or does it matter?
3b - Any reason I can't put the tap pushbutton on a spdt switch and make it do double duty with the rate switch?  I plan to have my tap tempo at an easier place to reach and run in through a jack but I'm still going to have a tap switch on the pedal in case things change in the future.  But I figure for now that switch could work as a rate switch because I won't have to reach for it as often.

4 - I see some of you don't mount the pcb directly to the pots.  Do you just leave it "floating" or do you secure it in some other way?

5 - Is the LED on the board to let you know the tremolo is on or does it pulse at the rate of the tremolo?  I see some with two LED's and I assume one is to tell you it's on and the other is to tell you how fast it's going.

6 - Is there really a reason for a "Gain/Volume" pot?  I see that some have done it and I'm interested to know why.

I know that's a lot of questions.  I've read through a number of threads here and haven't found those answers.  Any help you guys can give will be greatly appreciated.

[.Mike]

Hi dean,

Assuming you mean this project...

1 - Was the board designed with 1/4 watt resistors in mind?  I have many of those values laying around but they are 1/2 watters.  I'll make what I have work, I just want to know when ordering the values I don't have.

Yes. I just measured. The resistor lead spacing is 0.3", and resistors are spaced 0.1". 1/2 watt resistors might be too big. Resistors are cheap, and the build is tight. Use the right resistors.

2 - What voltage caps do I need to get?  I'm used to thinking in terms of hundred's of volts.  There's a Mouser part number for the 1uf cap so I figure I'm safe to stay in the same family for the other film caps.  But what about the ceramics and electrolytics?
You can use the cheapest capacitors that exceed the maximum power supply voltage that you plan on using. That probably means 16v or 25v electrolytics, although it wouldn't be unusual to use a 50v or 100v capacitor. Pretty much all film caps or ceramic caps will be rated high enough. The higher the voltage rating of the capacitor, the physically larger the capacitor will be. For the film caps, get box caps. The board is designed for them.

3 - Is the tap tempo switch a Normally Opened or Normally Closed switch?  Or does it matter?

Normally open, and yes it matters. Most people use the "Soft Touch" switch from SmallBear.

3b - Any reason I can't put the tap pushbutton on a spdt switch and make it do double duty with the rate switch?  I plan to have my tap tempo at an easier place to reach and run in through a jack but I'm still going to have a tap switch on the pedal in case things change in the future.  But I figure for now that switch could work as a rate switch because I won't have to reach for it as often.

I'm not sure I understand. If you are asking if you can have a remote momentary switch for tap tempo while also having another local momentary switch for tap tempo on the pedal, and the local switch can be switched to sometimes work the next multiplier setting, then yes, I think that is possible. It might even be possible to set it up so that when a remote tap switch is inserted, it automatically changes the local tap switch function. That would require some thought.

4 - I see some of you don't mount the pcb directly to the pots.  Do you just leave it "floating" or do you secure it in some other way?

Leaving it floating is not a good idea. You can velcro it, or double-sided tape it, as two possible mounting methods.

5 - Is the LED on the board to let you know the tremolo is on or does it pulse at the rate of the tremolo?  I see some with two LED's and I assume one is to tell you it's on and the other is to tell you how fast it's going.

There is no "on" indicator. When the pedal is powered up, the LEDs flash with the LFO. You can use a regular LED bypass indicator, or you can have the bypass indicator flash in time with the LFO.

6 - Is there really a reason for a "Gain/Volume" pot?  I see that some have done it and I'm interested to know why.

At some of the extreme settings, there can be a perceived volume loss. For example, if you use the square wave, fast, and use the wave distort to shift the center point so it is more off than on, the volume will be lower. The LFO is very flexible, and you can get a wide range of sounds. Having the ability to alter the gain adds even greater flexibility.



Mike

[dean owens]

Thanks for taking the time to answer my questions.  Sorry it has taken me a while to get back to you.  I was working on a reply the other night and Safari shut down on me so I closed up shop and went to bed.

You understood me correctly on the "3b" question.  I didn't write it well.  I was more or less wondering if they share a common ground and if i could use a SPDT switch just to switch their positive.  I was in a hurry when I was typing.  Doesn't matter.  I'll probably just use a DPDT because I think I have one or two of them laying around.  Although it'd be cool to have it automatically become a multiplier with my remote tempo switch plugged in, I'm not sure I'm going to worry about that.

I think you have answered everything well enough I don't need any of it clarified.  I do have two new questions....

1 - Does the tremolo have to be on to accept the tap tempo or can you tap in the tempo and then turn on the tremolo?

2 - Anyone have any idea how many ma it requires?  Just trying to plan on where to power it.

I have the chassis... the board is ordered... and I plan on ordering the parts tonight.  Probably be some time next week or so before I get to it.  I'll keep y'all up to date.

Thanks

[.Mike]

1 - Does the tremolo have to be on to accept the tap tempo or can you tap in the tempo and then turn on the tremolo?

Whenever power is applied, the pedal is on and ready for tapping. The bypass switch routes the audio either through the tremolo, or around the tremolo.

2 - Anyone have any idea how many ma it requires?  Just trying to plan on where to power it.

It shouldn't pull excessive current, probably in the 20-30mA range, depending on how the LEDs are set.

Mike

[dean owens]

Ok, I have almost all my parts ready to order but I'm not sure about one and have no clue what the other is.

First up is the 20mhz crystal.  Is this it? http://www.taydaelectronics.com/20-000-mhz-20-mhz-crystal-hc-49-s-low-profile.html

Next up is the OPTO.  What is that and where to I get one from?

[.Mike]

Yeah, that crystal should work.

The opto is an optocoupler-- a prepackaged LED and photocell. Taylor recommends the nsl-32, which you can get at a number of different places like Smallbear. If you read the main topic about the tap tempo tremolo, I believe other people have used other optocouplers.

You can even make your own optocoupler with an LED and a photocell.



Mike