Buffered/Tails/Spillover or True Bypass box

[benny_profane]

Very cool! Thanks for the quick responses here! This has always been an interest of mine so it's nice to see ideas floating around.

[Marshall Arts]

[...]Anyway, here's how I would do it.

Not sure, if I fully understood this: spillover mode, bypass, lower Opamp used... How does the spillover from the return jack get to the output jack?

[Marshall Arts]

In that context, you can achieve the phase reversal even with only half an opamp: check this : http://geofex.com/Article_Folders/polarity_reverser/polarity_reverser.htm

[benny_profane]

MA: i know you're in the midsts of a board overhaul/redesign but did you make any decisions with this design? Definitely interested to see what comes out of this.

[madbean]

[...]Anyway, here's how I would do it.

Not sure, if I fully understood this: spillover mode, bypass, lower Opamp used... How does the spillover from the return jack get to the output jack?

The reason I used both halves of the op-amp is for lower noise. When you use one op-amp and select between inverted and non-inverted side, you have to use much higher resistor values on the non-inverted side to have a properly high input impedance. Using the first stage as a buffer let's you make those resistors 10k instead of 220k or 470k. So, there's not much advantage the other way unless you really want to use as few parts as possible.

The way the spillover gets to the output jack is through mixing the effect output with the clean buffered guitar, both of which go to the output jacks in spillover mode. Setting up the return signal with the mix pot accomplishes two things: give you a level control for the spillover volume and it acts as a pulldown resistor for C2 and C3.

[Marshall Arts]

Thanks, Brian. But shouldn't Swirch TB/Tails Lug B2 be connected to Switch Phase, Lug 2?

[madbean]

Thanks, Brian. But shouldn't Swirch TB/Tails Lug B2 be connected to Switch Phase, Lug 2?

Yup, you are absolutely right. Funny how another pair of eyes can make all the difference! Now that I look at it again, I see another problem. The Mix pot is a load on the RTN path when the spillover mode isn't used and would act as a second volume pot. So, maybe it would be better to keep that as just a pulldown resistor. I got too busy being clever to see what I was doing Replacing that with a 1M resistor would ensure it has no effect on the RTN output.

You could get fancier and move the phase switch to the RTN path instead and then take advantage of the low impedance output of the effect to do the phase reversal like you mentioned. I think like the example below. Also, when the mix knob is off you have just buffered guitar signal in tails bypass.

(Sorry if I'm taking over the thread. This kind of interests me!)

[Marshall Arts]

That's it. I would breadboard that, omitting the potentiometer. It's great, that you are taking this over, I was hoping for that, actually. We all can learn a lot from you ;-). Furthermore, this is YOUR forum ;-)

BTW - It must have been crazy early in the US when you replied. Do you sleep... at all?

[madbean]

That's it. I would breadboard that, omitting the potentiometer. It's great, that you are taking this over, I was hoping for that, actually. We all can learn a lot from you ;-). Furthermore, this is YOUR forum ;-)

BTW - It must have been crazy early in the US when you replied. Do you sleep... at all?

My daughter had to leave for a school trip at 5:30am this morning so I was up pretty early. Not sure what to do with her gone a whole week!

[Marshall Arts]

My daughter had to leave for a school trip at 5:30am this morning so I was up pretty early. Not sure what to do with her gone a whole week!

I know how that feels ;-)

Anyway, I thought about how to embedd that in the redesign of my looper and thought it would be fancy, if the complete circuit resides on a small daughter board held in place with the jack on the bottom side of the PCB. This would save some space on the main relay board, which I could really use... All the supply voltages are available within the looper, so no need for extra components for power supply on this board (just some more offboard wiring...)




I will add a second gnd pad for the I/O, as I will use shielded wire for that.

[benny_profane]

My daughter had to leave for a school trip at 5:30am this morning so I was up pretty early. Not sure what to do with her gone a whole week!

I know how that feels ;-)

Anyway, I thought about how to embedd that in the redesign of my looper and thought it would be fancy, if the complete circuit resides on a small daughter board held in place with the jack on the bottom side of the PCB. This would save some space on the main relay board, which I could really use... All the supply voltages are available within the looper, so no need for extra components for power supply on this board (just some more offboard wiring...)




I will add a second gnd pad for the I/O, as I will use shielded wire for that.

Were you planning on fabbing the board? If so, I'd be very interested in getting ahold of one if possible.

[gordo]

I'm kinda doing the same thing but as an add on for existing 3PDT switches or relay bypass.  I don't work well with a breadboard so I may just do a test shot as an etch.

Brian, how are you getting those 5-sided tabs (ie: VB).  I thought I had it figured out within Eagle but was wrong.

[Marshall Arts]

Yes, I will get them fabbed - will just take some months, as I will order that with the yet-to-be-designed looper boards.

On Brian's drawings... I would mine to look like his drawings (I like the B/W style), so I'd be interested in some information about that as well...

[benny_profane]

Yes, I will get them fabbed - will just take some months, as I will order that with the yet-to-be-designed looper boards.

On Brian's drawings... I would mine to look like his drawings (I like the B/W style), so I'd be interested in some information about that as well...

Very cool. Keep me updated if you don't mind?

It looks like Brian's drawings are done in Visio (or something similar) if I'm not mistaken.

[Marshall Arts]

I will keep everyone posted about the development in the looper thread, so it would be great, if you could subscribe to that ;-). You can find it here:

http://www.madbeanpedals.com/forum/index.php?topic=28843.0

The Looper-Project will be create some sub-topics - technical discussions about specific issues (like this one here).
I will post these in upcoming, topic-specific threads (rather than bury them in the looper thread), as the discussion will hopefully be fruitful for other projects as well.