Relay Bypass with Tails for Delay

[JFace]

I have an old fashioned 3PDT style bypass strip that I've used for years, and it has come to the point where the pops are actually causing damage. My delay pedal (Boss DD3) get fizzy and low volume when activated. I suspect that the pop from the switching causes enough current to really muk things up on the input of the delay. After switching the DD3 on and off a few times it goes away.

So I got to thinking, is it possible to have a bypass system built specifically for delays that will not echo the pop sounds when switched, and will allow tails of the delay when switched off (no abrupt cut of the effect). Looking into different off the shelf products, I found that the Pedal Sync line by Molten Voltage offers the relay microcontroller MV57. The MV57 mutes the output before switching so that no pops are heard during the switching transition.
http://www.moltenvoltage.com/pedalsync/documentation/PedalSync_MV-57_MV-57B_Relay_Bypass_Datasheet.pdf

Problem is, with a delay pedal the pops will continue the echo long after the output is engaged. So, referencing their datasheet, I drew up a schematic that instead mutes the input upon switching, and ties the return of the effect to the output at all times. I included an input buffer to prevent the effect from loading down the input. Some experimentation would be on order, such as the posibility of series resistors on the send and return, both to reduce switching noise and to isolate the input buffer from the output impedance of the delay.

I am curious to hear any feedback you may have on this implementation.

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/Switch+With+Tails.jpg.html?g2_imageViewsIndex=1

[JFace]

The image tags didn't work, so I'll try the url tag.

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/Switch+With+Tails.jpg.html?g2_imageViewsIndex=1

[trixdropd]

You need a small mixer circuit combined with relay bypass. Kepp in mind that the relay has it's own issues with popping, which need to be designed around.

[electrosonic]

I don't see the point of using a relay if the circuit is not true bypass. Why not make a effects loop pedal with a parallel send? I would use a 4053 or a 4066 CMOS and just ground the send to the delay when bypassed.

The setup I am moving towards  (as I finish building various things) is to have everything true bypass, except my delay pedal so I can have tails on the switching. Since the delay pedal is the last pedal in my signal chain, I don't mind having it buffered bypass as it is driving signal through a 10ft cable to my amp.

Andrew.

[JFace]

I don't see the point of using a relay if the circuit is not true bypass. Why not make a effects loop pedal with a parallel send? I would use a 4053 or a 4066 CMOS and just ground the send to the delay when bypassed.

The setup I am moving towards  (as I finish building various things) is to have everything true bypass, except my delay pedal so I can have tails on the switching. Since the delay pedal is the last pedal in my signal chain, I don't mind having it buffered bypass as it is driving signal through a 10ft cable to my amp.

Andrew.

The reason I used this implementation was the ability to mute the signal momentarily during switching. I don't see how the CMOS would be any different than a relay; once the send signal is switched on, there would be mechanical noise on the input of the delay.

[slacker]

....and ties the return of the effect to the output at all times.

You can't do this, the output of the delay and the output of the buffer will both be a low impedance so if you just tie them together they'll just load eachother down and you'll get virtually no output. You need at least resistors to mix the output of the delay and the output of the buffer.

Here's a little thing I built that adds tails to any delay and has "silent" switching.

[electrosonic]

The reason I used this implementation was the ability to mute the signal momentarily during switching. I don't see how the CMOS would be any different than a relay; once the send signal is switched on, there would be mechanical noise on the input of the delay.

With CMOS there should be no mechanical noise - which was the point of my suggestion. It also makes it easy to add tails.

Slacker - I like that mixer setup, but wouldn't the 1k resistor to ground in bypass load the op amp too much? (unless you are using a NE 5532 or something similar)

Andrew.

[slacker]

Thanks, I haven't noticed any problems using a TL072 but it's a good point, upping them to 10k would probably be a good idea.