AD-9 Dry output with true bypass

[gutsofgold]

I'm trying to understand how the Dry out jack on the Ibanez AD-9 (reissue) works. Here is the schem http://www.dirk-hendrik.com/Ibanez_ad9_analog_delay.pdf

My question is this... when you don't have anything plugged into the Dry out then your regular output is a mixture of wet/dry set by the the delay level pot? so when you plug a cable into the Dry out it connects the RING to SLEEVE thus grounding R48 and turning T8 FET "off" not allowing any dry signal at all to mix with the wet signal? how am I doing so far? Is this right?

I'm trying to understand this so I can make the AD-9 true bypass while still retaining this Dry out jack.

[petemoore]

  Perhaps an audio probe could help designate points of interest that are clean/mix/effect on the schematic.

[Mark Hammer]

No, you've got it right.  Took me a bit to figure out the switching logic.

Look at T12.  When the flip flop feed the gate of the JFET through the 1M resistor and diode, it turns on, such that the drain-source path goes low-resistance, and lets the signal through.

The same logic applies to T8.  With nothing plugged into the dry out jack, R48 is just hanging there, unconnected, leaving 9V to feed the gate of T8 through R46 and R49.  Stick a mono plug into thedry out jack, and R48 is now connected to ground through the shaft of that plug such that the voltage divider formed by R46 (100k) and R48 (1k) drops the voltage feeding the gate well below the forward voltage (or should that be backward, given how its drawn?) of D6.  T8 turns off when you insert a plug into J2.

The overall plan of attack is this: T7 and T12 are actuated by opposite states of the flip-flop.  With nothing plugged into the dry out jack, T8 remains on, despite the state of the flip-flop and the dry signal feeds the main output.  The flip-flop turns T7 on and off, permitting and preventingthe wet signal from reaching that output mixer stage.

If you plug something into the dry jack, you don't want the main out to suddenly go dead when you turn the effect off.  At that point, the dry signal sidesteps T8 and passes through T12, reaching the putput stage such that you have dry signal coming out of both output jacks.

Weird, but it works.

[gutsofgold]

makes sense, even though I agree it seems like an over complicated solution for what they were trying to accomplish. thanks for the help!