Hello everyone... I am new to the DIY world and I am pretty knowledgeable with electronics but, I am still a little confused with impedance matching. I am working on a project that consists of a UTC 0-8 input iron, a Quad Eight AM-10 discrete op-amp, that I built from tracking down some N.O.S. Transistors, an LA-3A Amp section, and an LA-4A gain reduction section. The AM-10 is used as the pre-amp based on the Q8 MP-404 schematic. The LA-3A is straight forward clone of the original schematic as far as the amp and output iron go. I just took the GR amp from the la-4 to drive an LED for the opto. I wanted the LA-3A sound wile being able to have a selectable ratio switch. For now I will be using a 10mm red LED to drive a silonex NSL-5910 LDR. Now here is my issue. Since I am Building this project in the same case, like a channel strip, there is no need to put an output iron after the AM-10 and an Input iron before the LA-3A. Unless I am going to make a balanced insert point, which I am considering. But, for now I want the Am-10 to drive right into the LA-3a. I am wondering if there will be an impedance issue here. I'm a little unsure when it comes to impedance matching. I don't have a scope at this time. I have a couple nice Fluke meters and a tone generator. So my main question is at the input of the LA-3A, on the schematic, there is a 39K resistor, R2, across the secondary of the input iron. Should that be changed/omitted due to the fact that there will be no traffo there? I don't know the impedance of the output of the AM-10. There is a 330uf cap followed by a 10R resistor. and in between the cap an resistor there is a 5.1k resistor to ground. So will this be able to just connect to the la-3a input without any problems? Should I leave the 39K resistor (LA-3A) out/change it? So far the pre amp works and sounds great. The Amp section of the LA-3A works and sounds great passing audio. The LA-4 GR circuit works as well. So all circuits work by them selves, just gotta piece it all together for a nice sounding Pre/Comp. If anyone can help me I would greatly appreciate it. This forum is pretty informative as I've been reading and just finished my Gssl clone. You guys rock!!!! Much respect! -Tony