H9 inputs clip when in FX loop of amp

It sounds like your effects loop output is too hot for the H9. Check for a level control on the amp.

Otherwise, if you've set the H9's input gain to its lowest level, you will need a suitable pad or attenuator. Simplest way is to have a tech wire up a few resistors to make an attenuating lead.

Your "passive serial loop" clearly has (lots of) gain, so may not be very passive.

If you pad the signal on the way in, the output will be reduced by the same amount. This is as well, as otherwise the output of the unit would overload. If your loop does not have a return gain, it may be a problem.

While I personally wish we had put a line-in switch on the H9, we did not, so it should be used at guitar level. You might want to contact your amp manufacturer and ask them why they put so much gain on their effects loops – I suspect ours is not the only pedal which would have trouble with it.

This seems to be the biggest issue this pedal has. Is there no way to come up with a software based input pad for the H9 in a future release?

I would have bought an H9 by now but I came across this line level issue.  I want to know if I can use the H9 with my rig.  I am DAW based, and would like know in advance that I can run line outs from a Kronos, Analog Keys, and Minibrute into the H9 directly, and output the H9 to my DAW.  My DAW outputs to active monitors.  

While you say the H9 should be used only with instrument level devices, others say your documentation states it can successfully work with line level devices like synths.

So, will it work sans clipping in my setup?    

When I get back to the 'Tide after the holiday (our decent employers like their staff to have a modicum of rest), I'll report the maximum input level the H9 will tolerate, in both Volts and dBu.

This is made more complicated by the fact that it has a "soft clipper," at the front end, so it will need a lot of signal to actually clip, but distortion will increase when overdriven below this point.

Maybe I should give levels for 0.1%, 1% and 10% distortion. (0.1% is hi-fi, 1% is funky, 10% is nasty).

I think that once this is done, it is entirely reasonable to say that if people are not using it with a guitar, it is wholly (100%, not 10%) their responsibilty to give it the right signal level,.

Looks like I will have to sell the H9. It doesn’t work in a line level situation without clipping. Too bad and misleading. I mean, if it was just for guitar, why would it have stereo inputs?

Moving to Strymon. Should have done this from the beginning. Can I transfer the Algos I purchased to a new buyer?

This pedal may not be designed for synths but it would be great to be able to decrease the input level for use with synths. Especially for older analog synths that are already noisy w/ low dynamic range, I have decrease the output level of thses synths in order for the H9 not to clip. I lose 6dB or more of headroom.