Ibanez Bypass Suggestion...

[ryanuk]

Hi

Question/suggestion on Ibanez bypass.

From a reivew of the factory schematics on the net, it appears that the FET FlipFlop bypass is common throughout. I should add at this point that I dont have permission to post a schematic but you can view factory schems on the net for reference (e.g. Analogguru's site has a cleanedup TS808 schem).

Using the TS808 schem as a reference, I understand that Q102 and Q104 have an inverse relationship ie. when one is "open" the other is "closed". Accordingly, the "bypass" function essentially switches the emitter follower (on the output) between the volume pot centre lug and the input buffer. Almost a buffered-half-bypass(?? )

Therefore should you wish to implement a similar bypass, but mechanically, could you not use a DPDT switch? ½ of a DPDT to switch the emitter follower to either the vol pot or the input buffer. 1/2 of the seitch to operate the LED.

This way you could then omit all the "bypass" components, use a DPDT switch instead of the unreliable 3PDT and have LED indication.

I appreciate that this would mean that the circuit is still connected to the input buffer when "bypassed", however, this is case in the original TS's and they dont seem to suffer from loading/tone sucking. Not true bypass, but the buffers in the TS are reasonably nuetral.

Has anyone tried this?

You may gather that I have a limited knowledge of electronics – apologies if this is a noddy idea!

[jacobyjd]

Not at all--that's a pretty straightforward implementation of a buffered bypass In fact, you can use ANY buffer with it, not just the one that Ibanez sticks you with.

Now, if you're talking saving $$, there's nothing better than a flip-flop and a super cheap board-mount tactile switch.

[Mark Hammer]

Has anyone tried this?


Hmmmm.....possibly several thousand.

Actually, many people have posted threads here about "converting a pedal to true-bypass" or "rehousing pedal X".  The general gist of the thread is that they would like to stick a given pedal which uses electronic switching (and accompanying buffers) into another box that can accommodate a shiny stompswitch that goes "click!" and permits them to bypass the pedal completely.  The relative usefulness of doing so has been debated ad mauseum here and elsewhere.  It has its good sides and its bad sides.  One of the common recommendations is to leave the pedal in its native form, and do true-bypass via an external loop selector of some type.  It is generally easier to make a loop-selector box than it is to adapt an existing pedal to a different switching scheme in a different chassis.

One of these days I really have to do a photo essay on adapting one's Boss/DOD/Ibanez/et al pedal for remote switching.  There are advantages to those buffered electronic switches that people don't realize.

[ryanuk]

To clarify, I dont want to re-house a pedal or convert an existing TS to true bypass.

A friend wants me to build a Ibanez STL. I have the STL schem and have been cosndering the bypas options:-

1. True Bypass using 3PDT - 3PDT are expensive and in my experience unreliable - I'd much rather use a DPDT. True bypass has its pros and cons.

2. Flip-flop circuit - bufferred bypass, silent switching, LED but I've never built a flip flop circuit and would have to source the components.

3. Replace flip-flop/fets functionailty with DPDT switch - therefore achieving a buffered bypass but with a reliable switch and LED indication.

Therefore I was just pitching the idea of using 1/2 a DPDT in place of the flip-flop.

Just to confirm, if I did this would the input/output buffers maintain integrity of siganl in the bypassed state given that the circuit would be hanging off the input buffer??

[jacobyjd]

Absolutely--that was mainly my point--the main advantage to using the flip-flop is saving on parts costs for mass-production. The DPDT will do you just fine

The other part of it is this: if you don't like how it sounds in bypass, there are better buffers out there, most likely.

[Ben N]

http://www.muzique.com/lab/tsbuff.htm

[Mark Hammer]

To clarify, I dont want to re-house a pedal or convert an existing TS to true bypass.

A friend wants me to build a Ibanez STL. I have the STL schem and have been cosndering the bypas options:-

1. True Bypass using 3PDT - 3PDT are expensive and in my experience unreliable - I'd much rather use a DPDT. True bypass has its pros and cons.

2. Flip-flop circuit - bufferred bypass, silent switching, LED but I've never built a flip flop circuit and would have to source the components.

3. Replace flip-flop/fets functionailty with DPDT switch - therefore achieving a buffered bypass but with a reliable switch and LED indication.

Therefore I was just pitching the idea of using 1/2 a DPDT in place of the flip-flop.

Just to confirm, if I did this would the input/output buffers maintain integrity of siganl in the bypassed state given that the circuit would be hanging off the input buffer??

Actually, before they went to treadle mechanisms, sometimes Boss would use DPDT stompswitches to actuate FETs, and EHX also does that with some of their current crop of pedals using stompswitches.  So yes, it can be done.  Check out the schematic of the Small Clone.

[ryanuk]

Thanks for all the comments and info guys!!

It appears that I'm not re-inventing the wheel here, and the comments you've posted ceraintly suggest that it'll work!!

I'll crack on and try it in the STL build!!

I note the comment on trying different buffers and will experiment.

Thanks again.

[ianmgull]

To clarify, I dont want to re-house a pedal or convert an existing TS to true bypass.

A friend wants me to build a Ibanez STL. I have the STL schem and have been cosndering the bypas options:-

1. True Bypass using 3PDT - 3PDT are expensive and in my experience unreliable - I'd much rather use a DPDT. True bypass has its pros and cons.

2. Flip-flop circuit - bufferred bypass, silent switching, LED but I've never built a flip flop circuit and would have to source the components.

3. Replace flip-flop/fets functionailty with DPDT switch - therefore achieving a buffered bypass but with a reliable switch and LED indication.

Therefore I was just pitching the idea of using 1/2 a DPDT in place of the flip-flop.

Just to confirm, if I did this would the input/output buffers maintain integrity of siganl in the bypassed state given that the circuit would be hanging off the input buffer??

A 4th option would be a millennium bypass. True bypass and LED with a DPDT.

[R.G.]

Therefore should you wish to implement a similar bypass, but mechanically, could you not use a DPDT switch? ½ of a DPDT to switch the emitter follower to either the vol pot or the input buffer. 1/2 of the seitch to operate the LED.

This way you could then omit all the "bypass" components, use a DPDT switch instead of the unreliable 3PDT and have LED indication.

I appreciate that this would mean that the circuit is still connected to the input buffer when "bypassed", however, this is case in the original TS's and they dont seem to suffer from loading/tone sucking. Not true bypass, but the buffers in the TS are reasonably nuetral.

You may want to read "The Technology of Bypasses" at geofex.com.

What you're proposing would work in principle. However, the mechanical moving parts in a stomp switch are far less reliable than the electronics in a flipflop. And a tactile dome switch as used in the original Boss/Ibanez bypassing is more reliable than an actual stomp switch.

Your idea for reworking the bypass setup is very similar to the "Clinton Bypass" I proposed. The difference is that the switch for the output signal goes from the input of the effect buffer in the Clinton bypass instead of the output of the buffer as you propose.