Think I need a buffer?

[GibsonGM]

I want to add a "Y" output to an AMZ Mosfet Boost so I can get a clean guitar signal into my PC pre-effects.  So this would tap off the input jack of the boost, thinking literally just a wire to the Y jack.   Obviously the other way to do it could be a buffer feeding both things, but that seems like more than is needed.   Just wondering if the output Z of a guitar sucks so bad that I should buffer.

Nominal input z of the boost is 10M; my interface is stated at 750k.  I wonder if anything weird will happen by just passive-tapping the input jack of the boost and call it good...thoughts?   thanks

[amptramp]

Adding a jack to the output of the boost rather than the input would be the way to go here.  It is no more complication than adding a jack wired to the input and it solves the impedance problem.

The output impedance of a guitar goes all over the place when you adjust the controls on the guitar.  If the volume control on the guitar is fully up, the impedance may be dominated by the inductance of the pickup, meaning you have a voltage divider with the signal going through the pickup inductance to the output and with a resistance to ground that is the input impedance of the buffer in parallel with the volume control.  As you lower the input impedance, you lose treble because the effect of the inductance is to increase reactance as the frequency goes up.  If the guitar volume control is down, the treble loss is not as great since the pickup inductance is isolated from the input impedance of the buffer by the amount of resistance between the top of the control and the slider.

[GibsonGM]

Yeah, that was sort of at the heart of it, whether the interface & input z of boost would split and be too low...this is for recording, to get the dry sig as well as what's coming thru my chain.  I use the boost a lot to goose my tube preamp, but not all the time (hence desire to take it from the input rather than out).    I just ripped it open and tried this - it worked with only a jack tied to the input remarkably well IMO - I rarely play with the volume down.   

I'll install the jack, but it's only going to be for those 'very big guitars' made with 4 tracks, a real tube preamp, VST tracks and some clean mixed in, LOL.  For things that count, I do have a buffered splitter (A/B - Y), just not enough room on my desk to have all this crap lined up all the time.  Thanks!