When you say the synth sounds thin is this when it’s the only pedal in the loop with no pad or less pad? Unfortunately both the wah and the SY-200 are wanting a high impedance (HiZ) input like from an electric guitar pickups. As an aside, am I correct in thinking the accordion has multiple cables (one for each condenser mic) leading from it and being plugged into separate mixer channels? I took a closer look at the Mixinglink and it may provide some options that may help.
Here are some suggestions:
- try the wah in the SY-200 loop
- run the mixer send to the SY-200 first then wah
- perhaps the “Amp Out” of the Mixinglink is buffered to give a better signal for the wah and/or SY-200 in the loop of either mixer or SY-200
- Perhaps the loop of the MixingLink will be buffered more for guitar level and help
- Does the SY-200 have the ability to connect an expression pedal (it should) and if so, see if it can facilitate the same effect you use the Wah for and lose the Dunlop. I know many times a digital wah isn’t the same.
Basically the signal being output from your accordion and also the Mixer loop is meant for different impedances and levels. A buffer circuit is what commonly would help balances this out and some of your devices may have them built in and suffice. Radial and Lehle make different gadgets that may be more affordable and more specific to your need. Also, check within the SY-200 for any parameters that can adjust the input and/or its loop characteristics for different signals. Let us know if anything helps.