Hi Geido – I don’t see a problem with frequency loss here.
The main potential issues are related to the fact that H9 was designed for a guitar input:
1) The 600K input will be noisier than a 10K input, so you want to give it a reasonable level, but ….
2) The H9 is expecting guitar levels, so you should be careful not to overload it either.
Hi Nick, thanks for the quick reply.
I had tried to feed another stompbox’s load of 1M ohms (the double of the H9, about 2000 times higher than a line output impedance) with a line level signal and the result was a loss of higher frequencies: the circuit actually works as a low pass filter. SInce then I use the Radial Engeneering stompbox in between (the one mentioned in the original post). Since the line level and the H9 load ratio is 1/1000 (much more than the 1/10 ratio tolerated in the bridging law) I believed to get similar result (high freq. loss).