ON/OFF Timer for an Auto Killswitch/Stutter Pedal?

[Jasonmatthew911]

Hey guys, I'd like to make a simple little timer circuit that could turn a signal off and on while I press down on a momentary footswitch to create Killswitch stutter and Tremolo effects...Maybe just 1 Pot to control the speed or rate of the signal being cut off, and an LED to show the speed of the signal going on and off....I know there's a few pedals out there that do this kind of thing already, like the Perfect Square Hyperslicer, and Idiotbox Mad Doctor to name a couple, but it seems like it should be something very simple, afterall it's just something turning the signal off and on at slow to fast speeds...Does anyone here know a simple way or a simple circuit that I could implement to make this effect myself?...It seems like something simple that can be done with a 555 Timer chip, or am I wrong?....Any help would be great guys, thanks.

[haveyouseenhim]

Burst box. I use it at every gig

[Jasonmatthew911]

Or would a 555/LDR acting as an LFO and Rate knob give the stutter effect for guitar?...If so, I suppose a transistor would have to be used to boost the guitar signal?...Or am I way off on this?

[Jasonmatthew911]

Burst box. I use it at every gig

Couldn't find much on the Burst Box....

[mth5044]

You'd want a tremolo with a square wave LFO. A decent amount of the trem projects out there can do this, do a search for it on this forum. I'd look further but I'm being called to bed 

[haveyouseenhim]

Burst box. I use it at every gig

Couldn't find much on the Burst Box....

Sorry. I was being a smart ass. It was a god awful thread that happened here a while back. Didn't mean to throw you off.

[cpm]

Hey guys, I'd like to make a simple little timer circuit that could turn a signal off and on while I press down on a momentary footswitch to create Killswitch stutter and Tremolo effects...Maybe just 1 Pot to control the speed or rate of the signal being cut off, and an LED to show the speed of the signal going on and off....I know there's a few pedals out there that do this kind of thing already, like the Perfect Square Hyperslicer, and Idiotbox Mad Doctor to name a couple, but it seems like it should be something very simple, afterall it's just something turning the signal off and on at slow to fast speeds...Does anyone here know a simple way or a simple circuit that I could implement to make this effect myself?...It seems like something simple that can be done with a 555 Timer chip, or am I wrong?....Any help would be great guys, thanks.

Yes the 555 would be a nice fit.
Problem with square LFOs is that they produce sharp transients on the power rail, which can easily turn into noise clicks on the audio path. And a hard mute on the audio can make an annoying pop
You will need to work around those issues:
- a clean and separate current and ground routing
- a linear ramping up and down of the audio signal. Short to look like a square mute, but long enough to not make audible "thumps"..

[Jasonmatthew911]

Hey guys, I'd like to make a simple little timer circuit that could turn a signal off and on while I press down on a momentary footswitch to create Killswitch stutter and Tremolo effects...Maybe just 1 Pot to control the speed or rate of the signal being cut off, and an LED to show the speed of the signal going on and off....I know there's a few pedals out there that do this kind of thing already, like the Perfect Square Hyperslicer, and Idiotbox Mad Doctor to name a couple, but it seems like it should be something very simple, afterall it's just something turning the signal off and on at slow to fast speeds...Does anyone here know a simple way or a simple circuit that I could implement to make this effect myself?...It seems like something simple that can be done with a 555 Timer chip, or am I wrong?....Any help would be great guys, thanks.

Yes the 555 would be a nice fit.
Problem with square LFOs is that they produce sharp transients on the power rail, which can easily turn into noise clicks on the audio path. And a hard mute on the audio can make an annoying pop
You will need to work around those issues:
- a clean and separate current and ground routing
- a linear ramping up and down of the audio signal. Short to look like a square mute, but long enough to not make audible "thumps"..

What do you mean exactly by linear ramping up and down of the audio signal. Short to look like a square mute, but long enough to not make audible thumps?

[Jasonmatthew911]

Does anyone have a simple schematic or layout of a 555 Square wave LFO that shows clearly where the guitar input would be?...Should I have some kind of pre-amp section or small transistor Boost circuit to make up for volume loss, or is that not necessary?....I've seen a few circuits like the Tiny Trem and the SunTrem, but I'd like to just have a rate knob, with blinking LED, no depth knob, and do I need to use an LDR/LED?...I happen to have a couple of VTL5C3's laying around...On some of the schematics I found, I'm a little confused as to how to wire my "VTL" (LDR/LED)...Can anyone explain or make this simpler for me, I just want to have a clear picture of what I should and should'nt do from the beginning...I'd rather not deal with issues that probably already have solutions....I also saw a schematic of an LM386 Distortion with a 555 section for Stutter, and I noticed it was very simple with just 2 resistors, 2 caps, and a Rate pot with LED, no LDR, Can I just build a super simple transistor Boost with a simple 555 section for stutter using these minimal amount of parts with success, or will I have issues?...What does an LDR/LED combo actually do?... Hopefully some of you guys can help me further with this, thanks.

[cpm]

if you cut the audio to an intant silence, the waveform gets cut abruptly, and most of the time you can hear som click and pop. This may not be an issue for a fixed switch, like a bypassswitch, but i find it quite noticeable and annoying in a tremolo pattern. Ideally, it should be cut at a zero corssing, or a more simple approach: a progressive change up and down.
Some tens of milliseconds for a softer transition may be enough. But you need a device that can be controlled this way.
An LDR is suitable, because its reaction has a "slow" reaction to light by itself.
A FET can be ramped but will ned some RC filter to get the soft control curve.

Another point to consider is how deep the isolation must be when silenced. I experience that in a square tremolo, you really expect that the silence has to be absolute on the low cycle. Otherwise, you'd still hear faintly the guitar, or not so faintly if there are gain stages after it...
The two design i had done for this effect:
- A very high ratio for a resistor+LDR divider: e.g. 1k + LDR, but needs to be buffered and amplified to unity after the divider
- Using an OTA, still tricky to balance headroom and noise.

[cpm]

What i mean with the LDR:

If the LDR has a range from 1k light to 500k dark:
- Full ON this is a 1k/1k divider. You'll need to amplify after this x2 to get unity (or pre-amplify before)
- Full OFF this is a 500k/1k divider, signal is attenuated to 1:500, quite a lot...

Pre-gain can be just a unity gain buffer
For other specifications of LDR (you can measure it) you'll need to adjust gain to get unity

[Jasonmatthew911]

I'm basically trying to make an Idiotbox Cyclops Mono Stutter pedal it seems....Here's a pic of the inside guts I found, I see a VTL LDR/LED, an IC (probably 555), a couple of resistors, couple of LED's, a transistor etc...Can anyone make out what's going on here, it seems very simple, but I'm not really sure what is connected to what by just looking...
[/img]

[cpm]

http://www.eleccircuit.com/simple-pulse-generator-by-ic-555-timer/
here it says:
the output frequency will be approximately 1kHz and the duty cycle 50-50, The output's frequency is control by R1.
f=1/(1.4*R*C).

probably you'll want something in the range from 10Hz down
take the output through a resistor to limit the current appropiately to the LED and that all for that half of the circuit

The VTL is just a LED and a LDR enclosed in one package.

[Jasonmatthew911]

http://i85.photobucket.com/albums/k46/jasonmatthew911/Cyclops_Inside.png

[Jasonmatthew911]

http://i85.photobucket.com/albums/k46/jasonmatthew911/Cyclops_Inside.png

Have any idea what is wired where in that pic?....That's really how simple I'd like to do this to fit in a very small enclosure, and this Idiotbox Cyclops seems to sound good in the demo videos as well.

[Jasonmatthew911]

Can I just try something like the "Tiny Tremolo" circuit and use a VTL5C3 Vactrol, or should I be using something else for the LDR?...I ask because I happen to have a few VTL5C3's laying around....Also does the "Tiny Tremolo" really need any kind of buffer or is there no volume loss?....This is the version of the Tiny Tremolo I'm talking about trying:

http://www.diystompboxes.com/smfforum/index.php?topic=87322.0http://www.diystompboxes.com/smfforum/index.php?topic=87322.0

Would this Tiny Trem circuit and my VTL5C3 vactrol give me an intense stutter like a killswitch?

[Jdansti]

After playing with 555s I don't recommend them at all, but to answer your earlier question about how to deal with the audio path, you would use the 555 as an LFO to drive the LED side of your vactrol.  Two problems with this approach:

1) As mentioned before, the 555 would drive the vactrol, but you might have a hard time trying to get the signal going through the LDR side of the vactol to be the same volume as the bypassed signal when you press the momentary foot switch.

2) To fix #1, you could use a little preamp circuit to adjust the stutter volume, but now you'd be sharing a ground with the 555 and it's VERY difficult eliminate the popping of the 555.

My recommendation is to get in touch with Jon Patton (Midwayfair) and ask him which LFO he'd recommend. He has at least one simple LFO that doesn't use a 555. You could just use the rate pot and use fixed resistors for the depth and wet/dry controls. As for the footswitch, just use a momentary switch instead of a latching one, and wire it the same as you would any other bypass switch.

I just thought of an option to deal with the volume difference between on and bypass states. Intead of using a bypass switch, use a momentary DPDT on the LED side of the vactrol to select between the LFO output and an uninterrupted voltage from your power supply. The guitar signal would always be routed through the LDR.  The LED would either stutter when the LFO is  powering it, or it would be lit constantly when the switch selects straight power. This option allows you to have two separate grounds and would probably eliminate the popping issue. You might still want to use a CMOS 555 to suppress the noise even further.

The downside of this option is that having your guitar signal always going through the LDR might negatively impact your tone. Also, you might still have popping problems if other pedals are fed from the same power supply as this pedal.

If you get this going, you'd do us all a huge favor if you would name it the Burst Box. The Burst Box is a mythical effect that at least one person believes exists, sort of like the Yeti. It would be good to have a real pedal with this name. See this thread for a laugh when you have some time:  http://www.diystompboxes.com/smfforum/index.php?topic=76932.0

[Jasonmatthew911]

After playing with 555s I don't recommend them at all, but to answer your earlier question about how to deal with the audio path, you would use the 555 as an LFO to drive the LED side of your vactrol.  Two problems with this approach:

1) As mentioned before, the 555 would drive the vactrol, but you might have a hard time trying to get the signal going through the LDR side of the vactol to be the same volume as the bypassed signal when you press the momentary foot switch.

2) To fix #1, you could use a little preamp circuit to adjust the stutter volume, but now you'd be sharing a ground with the 555 and it's VERY difficult eliminate the popping of the 555.

My recommendation is to get in touch with Jon Patton (Midwayfair) and ask him which LFO he'd recommend. He has at least one simple LFO that doesn't use a 555. You could just use the rate pot and use fixed resistors for the depth and wet/dry controls. As for the footswitch, just use a momentary switch instead of a latching one, and wire it the same as you would any other bypass switch.

I just thought of an option to deal with the volume difference between on and bypass states. Intead of using a bypass switch, use a momentary DPDT on the LED side of the vactrol to select between the LFO output and an uninterrupted voltage from your power supply. The guitar signal would always be routed through the LDR.  The LED would either stutter when the LFO is  powering it, or it would be lit constantly when the switch selects straight power. This option allows you to have two separate grounds and would probably eliminate the popping issue. You might still want to use a CMOS 555 to suppress the noise even further.

The downside of this option is that having your guitar signal always going through the LDR might negatively impact your tone. Also, you might still have popping problems if other pedals are fed from the same power supply as this pedal.

If you get this going, you'd do us all a huge favor if you would name it the Burst Box. The Burst Box is a mythical effect that at least one person believes exists, sort of like the Yeti. It would be good to have a real pedal with this name. See this thread for a laugh when you have some time:  http://www.diystompboxes.com/smfforum/index.php?topic=76932.0

I checked out the Burst Box thread....Good stuff!...hahaha...Thanks...
I don't mind if there is a little popping, to me this is a Lo-fi effect anyways, I think a manual killswitch does a little bit of popping as well...Does the Tiny Trem 555 circuit have more popping than a manual killswitch would?...I know I can't expect that much from a 555, but I'll still use the CMOS 555 and a Momentary dpdt footswitch...So does the first version of the Tiny Trem have the volume loss issue?....If so, do you think that the little LPB transistor boost circuit would be a good option, I would want the volume with a fixed resistor, as I just want to have a Rate knob for a very small enclosure I have...Would a 100K resistor be too much for the fixed volume of the LPB boost circuit, or will I just have to test and see?

[cpm]

you could do as simple as this:
http://www.diystompboxes.com/smfforum/index.php?topic=99839.0

on the tremolo part, thats a "brute force" attenuator, bad design and unpredictable interaction, but seems like its what you are asking for.

It can be done into many degrees of better, we have already sahred some hints and experience

[Jdansti]

I haven't tried the 555 tremolo without a preamp (I used the Tillman preamp) so I don't know how much the LDR by itself is going to attenuate the volume.  The trick will be to get the LDR resistance as low as possible when the LED is on. The 555 circuits are pretty simple, so it wouldn't take much to get something going on a breadboard and find out what works and what doesn't.