Building the tap tempo tremolo

[spargo]

Can anyone recommend some enclosure sizes for this project?  I generally like to keep things pretty squished so it's as small as possible and can fit more on my pedalboard.

Also, the best place to get quality SPST momentary switches?  I can't seem to find them on mouser, the all metal ones that look like regular stomp switches.

[Taylor]

I believe I mocked it up in a 125b and it fit, if you really want it as small as physically possible. I built mine in a 1590bb and I like that size, any smaller I find is tough to switch.

I get my momentary stomps from ebay.

[jkokura]

I put mine in a 1790NS. It could easily fit in a 125B, but I wanted two stomps and the 1790NS isn't that much bigger than a 1590BB turned sideways. It fits in nicely with 125B's also because of the height, and I use 125B's for smaller pedals mostly.

Jacob

[spargo]

Thanks.  If I wanted to add the ability for an external tap tempo switch (in addition to the internal one), would it be as simple as installing another 1/4" jack wired to the same point on the PCB as the momentary switch?

[Taylor]

Yep.

[jkokura]

I'm planning on doing that with my second Trem... but first I have to get the first one working...

Jacob

[spargo]

Is it at all possible to control the speed with an expression pedal?  I was listening to something earlier today where the guitarist played a chord with a tremolo and the tremolo speed slowed from fast to slow, I believe through an expression pedal.

[Taylor]

Yes, as with any pot on anything, you can wire an expression jack to the speed pot pads. Make sure you wire it in accordance with the way your exp. pedal is wired; they're all different. Use a switching jack to connect the regular pot when your expression pedal is disconnected.

[Skruffyhound]

Just got back from holiday and literally threw this together last night. It fired up first try with very minimal ticking (on extreme settings), I didn't bother with any of the ticking fixes so I was pleasantly surprised.
Great work Taylor, very useful effect.
One question, I stuffed the board just using the silkscreen, when I checked the bom later for pot values the trims seem to be 22K whereas the board shows 10K. Which value should it be? I seem to be OK with 10K.
Thanks
            - Aston

[.Mike]

One question, I stuffed the board just using the silkscreen, when I checked the bom later for pot values the trims seem to be 22K whereas the board shows 10K. Which value should it be? I seem to be OK with 10K.

The two 10K trimpots that are side-by-side (and marked as 22K on the schematic) are used as current-limiting resistors for the optocoupler LED and indicator LED. Either value should be fine there.

Mike

[Taylor]

Cool, glad you had a nice build and are enjoying it. I appreciate the kind words, and want to pass them on to the other guys who made this project possible: .Mike, Tom Wiltshire, Jkowalski, and Dann Green.

[Skruffyhound]

Thanks Mike.

Quite right. Thanks to all the guys involved. I've actually followed this from the start and read all the associated threads so I know how much work you all did.

Now I'm going to build the next one, I want to hear what they sound like in tandem

[spargo]

Got my board and chip today, thanks!  Will likely order another soon.

One question: the spot for an LED on the bottom of the board with the spots labeled NEG/POS.  The PDF shows this wired to the bypass switch.  Is this just for the bypass?  Is it then optional to connect it to the board here?  I usually don't have my LEDs on my boards.

Also, is there a way to connect a second LED to flash in tempo with the currently tapped tempo?

[Taylor]

The LED does flash with the tempo already.

The bypass wiring in the PDF has kind of been replaced by the diagram in this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=84020.msg713301#msg713301

[spargo]

Thanks.  So if I am correct: the LED is completely off when the circuit is bypassed, and when the circuit is active it flashes with the tempo?  So there is no separate basic on/off LED?  How is its brightness determined compared to a "normal" LED where you would connect it straight to +9V with a resistor?

[Taylor]

Yes, it's off when bypassed, on and flashing to the tempo when the effect is on. There is a trimpot to control the brightness on the board. You can make it as bright as you want, just as bright as an LED wired the usual way.

[spargo]

Cool, thanks.  And what's the tiny hole UNDER the TL072 chip (not part of its 8 pins)?  Does that connect to anything?

[Taylor]

It's called a via. You don't need to do anything with it; it allows a trace to move from one copper layer to another.

[spargo]

Got it, thanks!  Also, I'm assuming crystals are non-polar?

[Taylor]

Yes, that's right.