Finished Neve 1073 Mic Preamp
So, I have been thinking about this amplifier build for a long time. We have longed to have the edgy sound that this famous circuit has been known for, and I have been on a quest to find a good circuit that is easily replicated to prototype for small scale production. I got the idea to start the project from Dan Derloo over at collectivecases.com. He is a DIY master, and he has a good handle on a lot of the projects over at Group DIY. The case is not a collective case, and I am regretting not going with his stuff on this but hey, I have to scope the competition once in a while. (Sorry Dan :/)
This is a unique build. It uses boards from Martin at Group DIY (http://groupdiy.com/index.php?topic=22828.0) The build uses Sowter transformers, and I fit 2 boards in a 1 u rack which presented some design challenges. I purchased my power supply and phase/phantom/pad boards from JLM audio, and I got everything else from various sources around the net.
We are in the testing stage at this point. I ran into challenges finding the correct transistors, because the original bc184c transistors are hard to find and expensive. I went with MPSA 18s. I think that they are a bit higher gain, but the pre still sounds great.
I am also waiting for some shielding tape to arrive so that I can add some shielding to the input transformers. The Sowter transformers are nice but the leads are not shielded. I took some time to really try and isolate the power from the audio, and the input transformers from the output transformers, but I have some audible 60hz hum at 80-90 db gain (which is way deep in the noise floor) a normal condenser mic needs only 30-40db. This should be fixed with the additional shielding and I will post pics when it is completed.
To fit in the 1u rack, I had to order special output transformers with smaller cores, and I had to bend the caps and heat sinks on the boards. This build presented some unique challenges as far as the placement of things went. The machining was tough and even the knobs had to be heavily modified to fit the boards.
The front panel design is my own, and the front panels are hand painted, laser engraved, and filled.
They amps sound great and have a wonderful bandwidth to them. 🙂 We will be including some high quality audio samples for your listening pleasure later this week.
I built 4 of these, but I had some Sowter parts get lost in the mail so only 2 are complete at this point with 2 more that will be finished at the end of the month. I am working on a Pultec project, then I plan to build 8-10 more of these neves hopefully with an entirely new board design. Ill keep you posted.:)