Mic preamp remote control

[Larrchild]

Hello all. It's been about 10+ years. Hope you are all well!
Yeah that's me. No more Fairchild clones as the ITB trend continues but darnit, they still need a mic preamp! So I took a push-pull tube design and gave it remote control and recall with an ESP 32, motor pot and relays. Runs from a browser. I think digital control of analog is the future. Who's with me? lol. Seriously, an industry standard for data exchange might be useful. -larry

 

[gyraf]

Great project. I vaguely recall Neumann having remote preamps where signalling was done via small variations in phantom power?

..darn, it's good to see you here again..!

/Jakob E.

 

[emrr]

Larry!

 

[ccaudle]

Seriously, an industry standard for data exchange might be useful.

The DAW I use (Ardour) can accept Open Sound Control messages for remote control. Possibly AES70/Open Control Architecture might be a possibility as well, a lot of the network connected audio devices support that now.
The OCA Alliance has a demo board and code called OCA MicroDemo that runs on a ST 32F215 using FreeRTOS and lwIP to show that you can make a fully compliant AES70 device with a microcontroller (since a lot of the AES67 audio-over-ethernet devices have relatively heavyweight hardware available some people may assume that you need that much horsepower).

 

[Larrchild]

I'm using Websockets and JSON across WiFi and it's quite robust. I intend to open source the JSON for 3rd party plugins, etc.

 

[ccaudle]

motor pot

Do you have one extra pole on the pot for feedback? Or just use position sensing and that is good enough?

 

[Larrchild]

Do you have one extra pole on the pot for feedback? Or just use position sensing and that is good enough?

I use an extra pot section into an A/D for position feedback. H Bridge on the motor with PWM ramping.

 

[zamproject]

H Bridge on the motor with PWM ramping.

Is it usable real time or only for dump recall due to EMI/RFI ?

I drop PWM for analog driver in my automation/recall design, motor too noisy.
I even implement a driver bypass after few sec of automation inactivity to erase any load on the motor, save consequent current consumption and dead quiet, fader wake up in 2 or 3ms if any change in position value.

Nice project you have

Cheers
Zam

 

[Larrchild]

Is it usable real time or only for dump recall due to EMI/RFI ?

I drop PWM for analog driver in my automation/recall design, motor too noisy.
I even implement a driver bypass after few sec of automation inactivity to erase any load on the motor, save consequent current consumption and dead quiet, fader wake up in 2 or 3ms if any change in position value.

Nice project you have

Cheers
Zam

I moved the PWM up to like 100 kHz to keep it out of the audio. Worked! No extra sounds when you adjust.

 

[Tubetec]

Hi Larry ,
I had an idea about making a tube compressor but instead of going to the trouble of building the control amp ,virtualising it instead , so sort of in the box and out of it at the same time .
Sending control signals by varying the PH48 up or down a bit was something I had been thinking about for a while ,microcontrollers I really dont know much about . Phantom has it own built in limitations in terms of current so what you can put on a mic pcb in terms of space is all very well , but what phantom can actually supply is a bit meagre .
Very interested to hear more about your audio analyser and transformer testing software .

 

[pucho812]

this is cool well done señor

 

[Larrchild]

this is cool well done señor

Looong time my friend. Great to see these familiar names.

 

[pucho812]

Looong time my friend. Great to see these familiar names.

Yeah.. I saw the unit in person out here on the left coast. The web interface is nice, but once you get past that, it delivers on the sonic.