Home > Studio Recording DIY Projects>PM1001 Mic Preamp
Next Step:
The next step is I need to design the mic preamp circuit that will go in front of this line driver circuit. Stay tuned.
Finished designing the rest of the PCB, added 20dB pad, phantom power switch and terminals for the input transformer.
I'll be trying Sowter transformers for the input and output transformers and see how they sound. Sowter Transformers are made in the U.K.
They're already on order, and will be arriving next week!
Specifically,
I'll be using Sowter 8751 Output Transformer
... equivalent to Neve-Type 1073/1272 Output Transformer (P/N LO1166)
and Sowter
9145 Mic/Line Input Transformer
...equivalent to Neve-Type 1073/1272 Input transformer (P/N 10468)
Quick
Update:
The transformers arrived! I got to try the output transformers... Man! I
couldn't believe my ears. I thought the MCI transformer ones were good, but
these Sowter (Neve replacement trafos) are excellent! The MCI are still good,
but has a different sounding flavor... more dark/warmer than the Sowters.
I love the high freq response of the new Sowter transformers. Excellent!
I tried placing the input trafo in the open space of my printed PCB layout and it won't fit. Bummer! So that means, I have to make the PCB dimensions a little bigger and arrange some components to free up some real estate for the input trafo.
To
do:
-------
1. Design and build 2nd prototype PCB with input transformer
2. Determine values of stepped attenuator for mic preamp
3. Redesign PCB layout for 2 layers (try to reduce size)
4. Fabricate (2) prototype boards at commercial PCB Fab House
5. Build and test (2) working prototypes (Serial #001, #002)
6. Initial production run of 25 PC boards (2 layer, silk screened, etc...)
7. While waiting for boards, get components for kits... Yikes! I did a quick
calculation, I'll need thousands of dollars in parts to jumpstart this kit
business...
8. Sell, Sell, Sell....
I'm planning an introductory price for early birds... then I'll sell at regular prices. If you're interested, email me to be on the list. audio@fivefish.net
I may do complete preamps too, with rack case, power and everything but these will sell for much more than just the kits. Pricing TBD.
Stay tuned.
Some pics of the prototype: Prototype #001 and #002. #001 prootype is just the line driver section. #002 includes the mic input transformer, first stage and the line driver section. Not shown is the output transformer.
Here,
you can see a closeup of the mic preamp. Notice the Sowter Mic
input transformer and the 2 big hunky power transistors.
And here's a more complete picture showing the giant output transformer.
The pen is there for size comparison.
I've tested the preamp with my MXL condenser mic, applied phantom power,
and it sounds nice!
