Hi all,
I'm starting work on an update to the CS42448 6 in/8 out board for the T4 pinouts - similar to the "Rev D" version of the SGTL5000 board Paul has recently published. It will go up on OSHPark and be fully open source, as is the Teensy tradition.
Here's my design thoughts (in order of priority):
1. T4 pinouts
2. Software and connector compatibility with Paul's existing version.
3. Buffered outputs with at least 2 pole filters (Butterworth).
4. Input buffers/preamps - this one is tricky as there are likely to be multiple different requirements, and "universal" preamps have high parts counts, and lots of switches and controls.
My thought is to replicate Paul's simple (straight from the data sheet) single pole passive input filter, and add a header (and some board jumpers) to allow external preamps to be powered.
On the short list:
- a mic preamp with compression and noise gate based on the SSM2167. This would serve the folks who use the audio library for live performances (providing improved noise performance and headroom management).
- a "universal" mic/line/instrument input (probably without phantom power) with gain control, possibly based on the MAX4063.
I2C or a GPIO could be provided (at some small cost to noise performance) to allow digital control of the preamps.
VCC of greater than 5V could be required for some preamps (although SSM2167 and MAX4063 are both 3.3/5V devices).
5. AUX SDIN header for full 8in/8out operation. A SGTL5000 could easily be used if I2C was supplied.
6. Stand alone (as well as USB) powering, possibly from a "universal" 9V instrument foot pedal supply, or 12v plugpack.
7. Keep it as simple and cheap as possible, at least in base format, for practical hand loading of single boards.
- are 0805 or even 1206 SMD components preferable for hand loading (I hate tweezering 0603 parts!).
What's the level of interest, and other desirable features?
I'm starting work on an update to the CS42448 6 in/8 out board for the T4 pinouts - similar to the "Rev D" version of the SGTL5000 board Paul has recently published. It will go up on OSHPark and be fully open source, as is the Teensy tradition.
Here's my design thoughts (in order of priority):
1. T4 pinouts
2. Software and connector compatibility with Paul's existing version.
3. Buffered outputs with at least 2 pole filters (Butterworth).
4. Input buffers/preamps - this one is tricky as there are likely to be multiple different requirements, and "universal" preamps have high parts counts, and lots of switches and controls.
My thought is to replicate Paul's simple (straight from the data sheet) single pole passive input filter, and add a header (and some board jumpers) to allow external preamps to be powered.
On the short list:
- a mic preamp with compression and noise gate based on the SSM2167. This would serve the folks who use the audio library for live performances (providing improved noise performance and headroom management).
- a "universal" mic/line/instrument input (probably without phantom power) with gain control, possibly based on the MAX4063.
I2C or a GPIO could be provided (at some small cost to noise performance) to allow digital control of the preamps.
VCC of greater than 5V could be required for some preamps (although SSM2167 and MAX4063 are both 3.3/5V devices).
5. AUX SDIN header for full 8in/8out operation. A SGTL5000 could easily be used if I2C was supplied.
6. Stand alone (as well as USB) powering, possibly from a "universal" 9V instrument foot pedal supply, or 12v plugpack.
7. Keep it as simple and cheap as possible, at least in base format, for practical hand loading of single boards.
- are 0805 or even 1206 SMD components preferable for hand loading (I hate tweezering 0603 parts!).
What's the level of interest, and other desirable features?