I am trying to figure out a way to control the gain of a amplifier driven by a fixed signal . I would like to have its gain controlled by following the gain of another amps input line . All signal output of preamp , and input signal for amplifiers are unbalanced.... please help . Thanks
First thought would be to use an active or Baxandall type gain stage which can have a gain all the way down to zero.
https://www.ti.com/lit/ug/tidu034/t...is a,can simply be copied for a stereo system.
https://www.ti.com/lit/ug/tidu034/t...is a,can simply be copied for a stereo system.
This doesn't help me , as I am trying to control the gain ( fixed ) of one amp by sensing the line level ( variable ) input of another amp . The reason for this unusual situation is because I need the fixed signal's unprocessed qualities , but need the amps volumes to work in unison .
Look at it like this ... I have a head unit driving one amp via rca cable , I have another amp I would like to drive with a different signal , but this different signal is fixed so no unison in volume control when adjusting head unit ( only on amp is adjusted ) . Maybe something similar to a preamp , one that senses and tracks one channels gain ...., then uses that info to adjust the gain on a different channel.... All input / output connections being unbalanced rca .
I think I get what you are trying to do (no idea why you want to do that though) and I'm going to say its going to be very difficult. These with the skills to implement this in the digital domain could probably devise something. Done in the analogue domain and its going to be complex. There are such things as 'four gang pots' available.
Maybe there are some other ideas around but I just can't think of any.
Maybe there are some other ideas around but I just can't think of any.
Presumably the signal itself also has volume changes (loud and soft parts of the music). In that case, I think you need something with two amplitude detectors and a controlled amplifier.
Feedback method:
Amplitude detector 1 connected to the volume controlled output, fixed output connected to an AGC loop that uses the output of amplitude detector 1 as its set point. The AGC loop comprises an amplitude detector, subtractor, loop filter and controlled amplifier.
Feedforward method:
Amplitude detector 1 connected to the volume controlled output, amplitude detector 2 connected to the fixed output, non-linear block calculating the ratio and controlling a controlled amplifier.
It will be very difficult to make either of these methods work properly without substantially degrading the sound quality.
Feedback method:
Amplitude detector 1 connected to the volume controlled output, fixed output connected to an AGC loop that uses the output of amplitude detector 1 as its set point. The AGC loop comprises an amplitude detector, subtractor, loop filter and controlled amplifier.
Feedforward method:
Amplitude detector 1 connected to the volume controlled output, amplitude detector 2 connected to the fixed output, non-linear block calculating the ratio and controlling a controlled amplifier.
It will be very difficult to make either of these methods work properly without substantially degrading the sound quality.
Agauin, a picture is worth 1000 words.
But I guess what you need is a four-gang pot (2 stereo sections).
The input is two stereo signals to each stereo pot section, one from the 'fixed' signal (where does that go to?) and one from the head unit.
By turning the whole 4-gang control you vary the 'fixed' signal output as well as the head unit signal output in unison.
Does that make sense?
But the fact that you don't seem to be able to put it in a drawing tells me it's probably much simpler than you think.
Jan
But I guess what you need is a four-gang pot (2 stereo sections).
The input is two stereo signals to each stereo pot section, one from the 'fixed' signal (where does that go to?) and one from the head unit.
By turning the whole 4-gang control you vary the 'fixed' signal output as well as the head unit signal output in unison.
Does that make sense?
But the fact that you don't seem to be able to put it in a drawing tells me it's probably much simpler than you think.
Jan
I was trying to get around using a line output converter to get the other amp hooked up because the signal it will receive is processed to that set of speakers... that makes sound adjustments more complicated and time consuming as any adjustment made to the channels driving the loc affect the other set-up and this completely unwanted . I figured the loc could be used for sensing a signals strength to maybe influence the gain of a signal amplifier of some sort .
I didn't plan on having to turn any knobs as the head unit has a remote control. I would have to get off the couch every time I wanted to adjust the volume.... that ain't happening . Thanks for the insight though .
Do you know or can you reverse engineer the remote control protocol, codes and gain steps? If so, maybe you could make a remote controlled volume control for the fixed outputs that responds with equal gain steps to the same codes. It's not straightforward, but less awkward than what I wrote in post #7. There are Arduino programs that can help you to reverse-engineer remote control codes for some common protocols, I have to look up the link.
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I understand, but any volume setup can easily be remoted, as described by Marcel.
It's probably even available as a low cost unit, somewhere, Google is your friend.
https://fr.aliexpress.com/i/32875071575.html?gatewayAdapt=glo2fra
https://shopee.co.th/AIYIMA-M62446-...amp-NE5532-OP-AMP-For-i.549265360.15912435559
https://www.ebay.com/itm/2250697074...efaultOrganicWeb&_trksid=p2047675.c101224.m-1
Jan
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In January 2019, when our cable television provider announced that they would stop providing analogue television signals, I had to reverse-engineer the remote control codes of a digital television receiver (set-top box) to find a way to make it work conveniently with our old hard-disk recorder. I looked around on the internet and found that someone called Ken Shirriff had written a library with infrared remote control send and receive functions for Arduino microcontroller boards.
He also provided example programs that can determine the type of protocol and the IR codes for a large range of common protocols. Unfortunately, the protocol used by our digital television receiver/set-top box was not in the list, so I had to record waveforms and reverse-engineer them myself, but maybe you will have more luck.
For more information about Ken Shirriff's libraries, see:
http://www.righto.com/2009/08/multi-protocol-infrared-remote-library.html
https://github.com/z3t0/Arduino-IRremote
Once you know the protocol and the volume control codes and have figured out what the desired gain steps are, you can use Ken Shirriff's libraries to reprogram the Arduino such that it controls the gain of programmable gain amplifiers. TI has some pretty good ones, like the PGA2311, https://www.ti.com/product/PGA2311 . I have no experience with those at all, but there are people on this forum who have.