CHASM REVERB

[bluebunny]

The Chasm already does "tails", so when you hit the bypass switch, whatever's "in there" will reverb away naturally while anything you play subsequently won't be affected.  If you really want it to "hold", then I guess you could make the OSC switch stomp-able - stomp OSC to set it going, then stomp bypass so you can play over it.

And welcome. 

[bluebunny]

...in fact, Rob does exactly this (albeit using the normal toggle switch) about six minutes into his demo on page 1.

[wbgarman]

The Chasm already does "tails", so when you hit the bypass switch, whatever's "in there" will reverb away naturally while anything you play subsequently won't be affected.  If you really want it to "hold", then I guess you could make the OSC switch stomp-able - stomp OSC to set it going, then stomp bypass so you can play over it.

And welcome. 

Thank you bluebunny. Yes, the example Rob plays at the 6min mark in the demo is exactly what I'm looking to achieve, but with the addition of a second footswitch (momentary) to temporarily bypass the reverb instead of using the ON/OFF switch. If I understand you correctly, it sounds like this would be possible to achieve with a Normally Closed switch wired into the OSC switch (toggle OSC switch + NC momentary footswitch).

(and apologies in advance for any comments that may seem rhetorical... I'm a novice and trying to learn more about pedal schematics)

[samhay]

> it sounds like this would be possible to achieve with a Normally Closed switch wired into the OSC switch (toggle OSC switch + NC momentary footswitch).

No, that won't do what you want. It will just reduce the depth of the wet effect.

Because of the slight peculiarity of the switching, paralleling a second momentary switch won't work.
You could replace the footswitch with a DPDT relay and switch this with any combination of momentary or latching switches.
Or, if you wanted to make it true bypass, you could use a latching switch for true bypass and a momentary switch to do the (momentary) tails bypass.

[wbgarman]

Or, if you wanted to make it true bypass, you could use a latching switch for true bypass and a momentary switch to do the (momentary) tails bypass.

samhay,

Can you help me understand how to appropriately implement the true bypass option? I've been staring at the chasm switch and circuit diagrams as well as 3PDT true bypass examples all day and I'm starting to go cross-eyed...

[samhay]

^
Treat 'IN' and 'OUT' as any other circuit input and output and wire to a 3PDT (or DPDT with e.g. Millenium bypass) as per usual. You then wire the standard Chasm on/off switch, which will switch in wet signal when you depress. If this is momentary, I would have thought it will be a PITA for most applications as you will only get reverb when you hold down the switch.

True bypass may also cause switch popping as you don't have pull down resistors on the input or output - you can probably tack these on somewhere though.



Another option is to use a DPDT toggle switch to select between a latching OR momentary switch

[wbgarman]

I may have done a poor job explaining what I'm looking to achieve, so below are a couple of videos that demonstrate the 'HOLD' functionality I'm looking to add to the chasm. Instead of "only get reverb when you hold down the switch", I'm looking to bypass the OSC reverb when holding down the momentary switch.

https://youtu.be/6iDHTTImBS4?t=11m13s

https://youtu.be/Jfrfz4n1jE8?t=3m56s

[samhay]

^
That's achieved the same way as above, but now I can see how that could be useful.
You need a DPDT footswitch regardless, so you can choose to wire it either way - i.e. effect 'on' when switch up or switch down.

[wbgarman]

I'm a visual learner, so I've attempted to sketch up what you've described. The initial issue I see with this diagram is that when the momentary is engaged, then the reverb tails coming for the Chasm Board will end abruptly. Is there any way to have the signal from the chasm circuit continue to be sent to the output when the momentary is engaged?

[samhay]

^ other way round - swap the 2 stomp switches.

[wbgarman]

Of course! Thank you samhay for helping me think through a solution here.

[wbgarman]

I'm hoping someone can help me troubleshoot my modification on the chasm reverb. The pedal has been built to have two footswitches. One latching footswitch turns the effect on/off and a second momentary footswitch temporarily bypasses the effects when depressed. Here are the current scenarios:

1. With the pedal bypassed (off), I get a good guitar signal

2. With the pedal active, I don't get any guitar signal (there is also a loud pop when the pedal is turned on/off)

3. With the pedal active and the momentary switch depressed, I get a clean guitar signal (this is the desired effect of the momentary switch)

When looking at the attached picture of the circuit, the switch on the right is the Bypass footswitch and the switch on the left is the Momentary (hold) switch.




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[samhay]

Did the circuit work before you wired up the footswitches?

[wbgarman]

I failed to test before wiring the footswitches, so I just re-wired to the original design (one footswitch) and I still fail to get a signal with the footswitch engaged (the loud pop has gone away though when engaging the effect). There is a little bit of high pitched whine sound with the OSC switch active and the effect pedal engaged.

I also checked the voltage and I get 9V into the IN pin of REG1 and 5V into pin 1 of the BTDR-2H.


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[wbgarman]

I believe I traced the problem to a bad connection with the volume pot to the PCB... Will update once re-wired


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[wbgarman]

The bad connection from the volume pot to the PCB was the culprit. Everything seems to be working with the two switch system now. Here is the final pedal:



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[samhay]

Excellent.
Has it stopped popping other the bypass switch?

[wbgarman]

Excellent.
Has it stopped popping other the bypass switch?

I still have a pop when depressing the BYPASS (on/off) footswitch. Any thoughts on how to fix this?


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[samhay]

You probably need to add pull-down resistors on both the input and output.
You may be able to tack these onto the PCB, but it may be easier to do this on the footswitch.

[wbgarman]

I've attempted to add pull-down resistors (1M), but the only thing that still seems to fix the 'pop' is cycling the BYPASS footswitch 25x or so. Is there is a correct way of wiring the pull-down resistors into the circuit? I have researched and tried a few different ways, but I don't feel confident that I've come across the proper way.