Mystery Project: The Basics of Vintage Neve Circuitry August 29, 2018 09:17
I'm just beginning a new project and I thought I'd try something different this time: I'm going to make the entire design process public. That means I'm going to share everything I learn as I go and I'll publish my design files under an open source Creative Commons Share-Alike license.
Choosing the Project
I titled this post "Mystery Project" because right now it's a mystery to me. The project will be some sort of Neve-inspired kit, but that's all I know.
"Neve" refers to a family of analog audio gear, either directly designed by or inspired by the designs of Rupert Neve. Neve's vintage consoles (especially those of the 70's as we'll see later) are famous for their "warm," "larger-than-life" sound. And a whole cottage industry has emerged around cloning parts of these consoles to make the "Neve sound" available for modern project studios that don't possess a console. The 1073 and 1084 preamp/equalizers and the 2254 and 33609 compressors are all console modules that have found a second life as plugins and pieces of standalone audio gear.
Neve 8048 Console. Photo by Neve Sweden [GFDL or CC BY-SA 3.0], from Wikimedia Commons
I emphasized "some sort of Neve-inspired kit" above because I have no idea what it will be. I know I want it to be something more unique than a straight clone. There are already a lot of great "British Console" projects out there from The Don Classics, Martin Adriaanse, and Audio Maintenance Limited, so I want to make sure that anything we do fits a niche not already filled by those folks.
The truth is I know very little about the Neve history and right now. So my immediate goal is to learn as much as I can with the hope that it will eventually lead to me to a cool, unique idea for a Neve-inspired kit.
Vintage Neve Basics
My first step was to invite my friend and Neve expert Jens Junkurth down from New York to school me on the circuitry. He gave me a day long crash course, some of which happened live on our Live Q&A on Youtube (archive). There were three big takeaways from that crash course:
1. There are only a few "classic" circuits. All of the myriad Neve clones and Neve-inspired devices are based on a very small collection of circuits the early 1970's. The 80-series consoles of this era featured the preamp/EQ modules that have become famous like the 1073, 1081, and 1084 as well as the 1290 preamp and 1272 bus amplifier. These circuits are all discrete and class-A. By the mid-70's Neve had switched to class-AB circuits and by the end of the 70's the consoles were all IC-based. So, for this project I'll be focused on a very small sliver of Neve's 50+ year history.
2. The circuits are quite simple. While the 80-series consoles are large and complex, they're built from just a few simple building blocks. These building blocks are small amplifier boards with the prefix BA, for "board amplifier." The most ubiquitous, the BA283, contains two sections: a preamp and an output driver. These two circuits are replicated dozens of times throughout a single console, making up the active parts of the mic preamp, equalizer, master section, etc. And both of these circuits contain only three transistors each. For a bit of perspective, the primitive 741 opamp contains 20 transistors.
The BA283 (6 transistors) vs. the 741 opamp (20 transistors)
3. It's all about the parts. Because the circuits are so simple, every part matters. And unfortunately, almost every part used in the originals is long obsolete. Various revisions and years of repairs also give rise to difficult questions about authenticity. For example, the first BA283s used BC184C transistors. However, Neve officially recommended BC107 and BC109 for repairs, which are arguably found in more classic consoles than the "originals." The same issue applies to capacitors. Like any other console, Neves must have their aluminum caps replaced every few years. So many classic albums featuring the "Neve sound" would not have been recorded with the original caps. Because of issues like these, I anticipate that sourcing will be the most challenging part of this project.
Next Steps
Phase 2 of this project is to build up some circuits and listen, listen, listen. I've started compiling a master bill of materials to collect all of the parts I've seen used in BA283 circuits.
I've also laid out the Preamp and Output amplifiers on two separate PCBs. I plan to order a few of each PCB and every part I can find to build up several different versions of each stage. Then I'll spend a few weeks tweaking and listening, to get a sense of which parts sound best together.
My first layouts of the BA283 Preamp and Output sections
Follow Along
I'm excited to keep digging into this project and to share my results with you. If you want to check out or use the design files for yourself, keep an eye on this Google Drive folder. The schematic and PCB files are for Diptrace, which you can download for free. You're welcome to use these files any way you like (under a Creative Commons ShareAlike license); however, keep in mind that these designs have not been tested yet! For all I know the boards won't be good for anything besides creating smoke.
Please stay tuned for the results of my first builds and listening tests next month. And in the meantime, I'd love to hear your thoughts, ideas, feedback, etc. in the comments.