DIY SSL E series microphone preamp - Built from scratch.

I have been tinkering with a lot of different mic pre designs over the last few months. I've tried the famous $5 pre using the INA217 chip and it gave some pretty good results considering it's transformer-less, but I wanted something a little more classic sounding. A little while back I came across the schematics for the the E series console by SSL. After looking at the main pre schematic it looked quite doable. A couple of low cost op-amps and an input transformer. All I needed was a output section and a input front end to provide some control over your mic, ie: Pad, phase and Phantom power. So I decided to start a prototype basic unbalanced pre and work from there.



Please note: I am not nor claim to be an expert in mic pre's or their design. I am not a trained electronics engineer, just a guy with a passion for audio circuits and a bit of practice with a PCB layout program. like many, I learn something new every day, but at this stage I pretty much paint by number, joining sections together to make "new" circuits. I tinker with guitar pedals mainly, but have built a few rack units which I use to make my own music. Please take that on board when looking at my schematics and if you see anything that is down right dumbass. Please feel free to set me straight, I can use the crit. 

The main gain stage of the pre looks very simple. A couple of mono op-amps (NE5534) which is a low cost operational amplifier available form just about anywhere for a matter of cents. A single gang 10K potentiometer, which to be honest was a big reason I chose this circuit, no need for dual-gang pots, which are not that easy to come by round my neck of the woods. The original SSL schematic has an unbalanced output as if forms part of their console and I assume balancing duties happen elsewhere, so I borrowed an electronic balancing output circuit from Gyraf's GSSL bus compressor which I have some experience with.

To be honest I was skeptical at first, a couple of 50c op-amps, a transformer and a few caps and resistors? Is this all the mighty SSL e-series pre's are made of? Comparing schematics to a focurstie ISA pre, I can see they are both NE553X based, and that pre rocks, I know, I've got one! So I guess its feasible. Only way to find out is to build one. So I isolated the gain amp section and built a little prototype on a breadboard, and to my surprise it worked! A little noisy, but it worked! So I decided to move to a simple first revision PCB and adapt the rest of the circuit from there, in a kind of modular way.

SSL e-series Schematics
I dont know whether this is approved by SSL or whether they release their schematics for general purpose or not, but here is where I found the files. As you can see, nothing very complicated at all, In fact far simpler than many guitar pedals I have built.

SSL e-series schematics found here
I am working from the SSL "82E01" schematic. (Top of the list) Although the actual schematic is labeled T82E001. As far as I can make out there is a difference between the "01" and "001" circuits.

My Schematic (First revision)