"Tone suck" issue---diagnostic regimen suggestions?

[MRH]

I have been a FX8 (original device, upgraded firmware) user since 2016.
Using a 4-cable setup with my Fuchs ODS-II very successfully since then.
(Using two Humbuster cables for send to amp in, and back to amp effects loop return.)

In recent months (not sure exactly when the change occurred), I've noticed some "tone suck" when comparing FX8 presets (even a fully bypassed, no effects patch) with the FX8 "true bypass" mode. There is a noticeable loss of gain and some high-frequency loss. In my earlier programming phase, I did side-by-side comparisons using true bypass and found the FX8 to be essentially transparent, no deterioration in overall gain and timbre. Something has changed.

1) I have removed effects loop cables, problem still occurs
2) I have replaced Humbuster cable from FX8 to amp input (with regular instrument cable), problem still occurs.
3) I have checked various FX8 Global and I/O settings, no changes there.

I am seeking advice to make sure my diagnostic regimen is thorough before I draw any conclusion about the FX8 itself.

Thanks for any commentary on this.

 

[Eduard]

Did you try another guitar already?

 

[MRH]

Did you try another guitar already?

Yes, this is independent of guitar. "True bypass" confirms that.

 

[DLC86]

Out level knobs are all the way up?
Global EQ flat?

 

[MRH]

Yes to both.

 

[MRH]

Thanks to all who responded. It looks like the issue was the need to recalibrate both of my expression pedals. The culprit was the external pedal assigned (continuous controller) to the front-end volume. It was not being recognized for its full 0-100 travel anymore, and therefore attenuated the input signal somewhat at the top of its travel. Recalibration seems to have solved this.

 

[quasimono]

That is a great hint for future prospects with the same problem, thanks m8!

 

[<Paul]

I've seen on some YT stuff that when you do a firmware upgrade, re cal your exp pedals.