WOW, that´s an interesting read and def something worth following! Could all that be integrated in one of MJMPs Monstercabs as well??
I think you'd have trouble fitting the additional board to make the mini-notches because it sits in the spot where the load resistors would be placed. But if you could find the room to squeeze it all in there, there's no reason it wouldn't work.
Here's a gut shot of the modded MicroCab as I was doing the mods. You can see the extra board on the right (it isn't mounted as of that photo, just laid there as I tested it)...
I didn't want to put in load resistors because I modded a Marshall Power Brake to more accurately mimic an actual speaker load. So I didn't need the MicroCab to act as a load box. I took frequency traces of some amps' outputs at their transformers and compared that to their behaviour when connected to various loads (actual speaker cabinet and a few load boxes and attenuators). Then I tweaked the Power Brake to get the amps' signal at the amp's output transformer reacting the same. Speakers don't provide a flat impedance, their impedance changes with frequency and that varying impedance is reflected back to the power amp and effects how amp reacts and distorts. Some people actually prefer a flat resistive load rather than a real speaker (as evidenced by all the Palmer and 'big resistor' users like Satriani and Eddie Van Halen
), but I was going for maximum speaker load 'authenticity'.
Here's what a typical guitar speaker impedance curve actually looks like...
Here's the output of my Marshall JVM (at the transformer) through a 4x12 cab (two Celestion G12T-75s and two G12-65s in the cabinet)...
Here's the output of my Marshall JVM (at the transformer) through a resistive attenuator...
As you can see, the amp is reacting very differently through a resistive load... though, like I said, some people prefer that. (And there are reasons for that, like no resonance at ~130 Hz and the high frequencies tend to sound 'smoother'.)
And here is the output of my Marshall JVM (at the transformer) through a Power Brake modded to mimic the load of my cabinet...
As you can see, that's just about dead-on.
So with the SM57 proximity, do you add some bass for the close mic proximity effect ?
The stock MicroCab already does that as much as you'd ever need it to with the "Thump" control.
I didn't need to touch that.
Another mic worth emulating is a Bayer M88 (in my day often used for kick drum as is designed as a male vocal mic with 80hz enhancement).
From memory, Seni 421's were reasonably flat, also a popular tom mic, but hi SPL capable so good cab mic
57/58 obviously 5khz boost (presence/cut)
EV RE20 flattest of them all
It's great your doing it for real in analogue not using DSP.
As someone with an engineering background, and having done my share of DSP courses, I understand that I shouldn't feel this way... but I don't feel entirely 'comfortable' with the idea of using DSP on guitar. I have some very nice DSP-based effects (like reverbs, delays, modulation effects, and even overdrives/distortions) but given the choice, I still 'like' the idea of analogue more... except for
maybe reverb, delay and chorus. I think the less DSP you can use before the signal hits the board, the better.
I realize the SM57 is pretty much the industry standard for miking electric guitar cabs, but I wanted to give the uCab the option of mimicking different mics purely for the convenience of it. Of course, you could accomplish the same thing with an EQ, but there was still a little space on the front so I thought, "Why not build it in?" I just looked at the frequency responses of some popular guitar mics and tweaked the high-end to match.
I should also mention that I voiced the two channels of the uCab differently. One is based around a particular set of cabs (a Marshall 4x12 with G12M Greenbacks on the Vintage 4x12 setting) and the other mimics different cabs (a Marshall 4x12 with G12-65s on the Vintage 4x12 setting). Because there are enough settings to cover lots of bases there's also a Mesa-Boogie 4x12 with V30s in there, some Fenders, some bass cabs, etc. I used probably 50 real cab responses to match them up as best I could. Even the settings that had to be partially compromised for the sake of other settings with a few dB here and there on an EQ and you can nail them.