controlling gain of second amp without connecting wires.

[bob v]

Is there a way that I can use the volume from 1 amp to control the volume of another acoustically? If amp 1 gets louder, amp 2 gets louder, and vice versa, without using permanently connected wires.
I can place a mic in front of the speaker (amp !) to control the other amp.. How can I use the mic output voltage control the gain of the other amp?
Thought of using a Light depentent resistor at the input of amp 2 to control the gain.
thanks fir your help.
Bob Vee

 

[danadak]

Are both amps using same source or do they carry different audio streams ?

You could use an optical approach looking at vol control knobs as one approach.

Or use an agc circuit and modify the source signal amplitude into second amp.

Or use a tone based system that issues vol lev of first amp. couple optically to second amp,
like an IR link, decode the level and adjust vol in second amp.

Quite a few approaches I would think.


Regards, Dana.

 

[ZipZapOuch]

How quickly do you need the second amp to respond to the new volume level? If a knob turn is ok, and 0.5 second is fine, then a wifi interface is possible. One mast volume on a "server" and all downstream devices can check for a new volume setting once or twice per second.

Else, you run into problems of quiet times between sets or when playing quietly vs loudly could cause the gain to change with an AGC concept on the second amplifier.

 

[bob v]

bob v:
Thanks Dana,
i'm using two different sources. one is an analog music instrument (keyboard), the second is a MIDI . would like the analog to conttrol the MIDI. Was thinking (in my limited knowledge): place a mic at the speaker, amplify that then rectify it to get a DC voltage then use that voltage to control an optocoupler at the input of the MIDI amplifier. Can't use footpedals.
.

 

[danadak]

Some thoughts.

First and foremost you need protection from circuit failure causing the
downstream amp from going to max volume, possibly damaging speakers.

Second mic approach means all sources within pickup area, not just the
primary amp, will be a factor in determining secondary amps volume. Is
that desirable or a non consideration ?

Third the relationship between primary amp volume and secondary, eg. the
transfer function of the solution, wants to be linear. What level of distortion
are you targeting as a goal ? Optocoupler, because input to it is I-V relationship
of a diode, logarithmic, has to be "linearized". A consideration, but not a big issue.

The link can be optical or WiFi (simple link, non router involved, like ESP8266 or
ESP32 on each end). ESP-NOW protocol fairly fast, in mS area -

https://github.com/espressif/esp-now/blob/master/User_Guide.md

You will need to develop power for each end of link/solution circuits, battery or AC line,
like walwarts ?

Can you use/program processors or is this targeted to an all discrete design, opamps,
transistors........ ?


Regards, Dana.

 

[rjenkinsgb]

Are you using any external amplifier, or are both devices totally self-contained?

Also, what is the MIDI device?

("MIDI" actually refers to the type of connections a device can use to link with other devices, rather than any specific type of device).

 

[ZipZapOuch]

You said "without permanent connection" but are the two amplifiers physically close to each other or do you need some sort of wireless communication (light / sound / radio) to control the second amplifier? If would be much easier to make a cord with a Y adapter that lets the output jack of one control the signal to the other.