Traverser,

Please update your M13 to the latest firmware of 1.07 and let us know if you continue to get a volume boost.

Regards,

Line6Hugo

It seems to me that your issue might have to do with the fact that your amp's loop is buffered.  What a buffer does is convert a high impedance signal into a low impedance signal, and the M13's converters weren't really designed with a low-Z signal in mind.  So perhaps the fact that you're experiencing this drop is related to that.  I've used a setup basically identical to what you describe with my Spider Valve, and I've not had any problems with the levels.

This is an interesting article about buffers and pedal bypass circuits.

I do not remember where I read it in this forum, or it may have been a Mesa forum I visit, I had to really dial in all my scenes at the individual FX level.  I played with my main Mesa Mark III and then adjusted the mix or gain or volume based upon the FX and type until I had relatively the same gain signal per FX as I went across the scene.  It can become tedious as well when you put a 3 stage gain and internal EQ amp in the mix for me though it does make my life easier then when I had an ocean of FX units across & circling the floor around me.  I will try this with my Heartbreaker and see if I can replicate this db gain problem with the delay FX units in the M13.

Dennis

Same problem! I'm checking for this kind of post since months ago. My M13 is updated to 2.01 firmware and I still have problems in volume increase (or sometimes decrease) with some modulation (analog chorus, some flanger effects) and with filter effects (almost all filter effects) have a significant and irritating volume increase. Even using 4 cables method and simply Guitar-M13-Amp method. Line 6 please fix this problem, it seems almost all M13 owners have this problem.

I'm having the same problem (as discussed in another thread: http://line6.com/community/thread/38553).  I have the latest update and I'm running the M13 straight into the front of the amp.  Most of the time I'm using an overdrive in front of the delay, but it seems to have the same issue (maybe less pronounced) with no overdrive.  I use delay effects most so that's where I notice the most problems.  I've owned the Line 6 DL4 and Boss DD5 so I'm fairly familiar with how delays should work...and there is definitely a noticeable volume increase when engaging the delays of the M13.