#511

[@a-job7276]

I like the idea. You could try placing a resistor in parallel to the LDR and another in series on the same feedback branch. It is to limit the maximum and minimum value of the LDR, it could be Trim pot, or better yet, a digital SPI potentiometer to control with an arduino or stm32. I'm wondering if it should be a full-wave peak detector, or does it not matter? If you control the charge and discharge of the capacitor with 2 variable resistors, potentiometers or JFet, you would adjust the attack and release. One thing about the LDR is that its resistance is not linear, it is logarithmic or quadratic, or something like that. I don't know if it would be necessary to "calibrate" or adjust the intensity range of the LED, or the curve in mA according to the threshold of the compressor. I have seen one circuits with OPamp to "linearize" the curve of the LDR with a diode in the feedback, I don't know if it is really necessary for this case, but I would like to see a video where it explains how it works. Another option, if you use an MCU to control the digital potentiometers or JFet, is to use DAC and ADC of 12bit or more. I would also use a pushbutton rotary encoder and LCD display. Cliping-detector and vu-meter. Many things could be done without using an i2s DSP, which is much more complicated, and is reserved for a few people, no, I have no idea, although I looked over and found some DSPs from "Analog Devices" that are configured by USB and its SigmaStudio software. Apparently very simple. www.analog.com/en/design-center/evaluation-hardware-and-software/software/ss_sigst_02.html#software-overview An advantage of digital pots is the precision between L and R, far superior to a dual pot. Although with JFet something could be done, but you depend on them being identical. This would be the volume control that I plan to use in the audio output of the TV, a lot of difference between background sounds and loud sounds, not to mention the damn "commercial advertising", which purposely has more LUFS to stand out or sell more ... In PC, for audio programs, there are some VST plugins, the one that interests me is a "Gain Rider", "Vocal Raider", "Bass Rider" (the concept is the same), adjusting the audio level to a threshold, and it is not a compressor. If it is below, it raises it, and if it is above, it lowers it. It has its parameters so that the change is not much noticeable. Another very complete VST plugin, "MaxxVolume" www.waves.com/plugins/maxxvolume#image "High- and low-level compression in one plugin Intuitive and simple controls for quick dynamic optimization Brings out room ambience and detail Adds body and detail to any instrument Great for dialogue and post-production leveling " Well that, a compressor with 2 thresholds, which raises and limits the audio, and gain raider. What is missing is a DeEsser and if you add a Noise Gate, well ... www.waves.com/plugins/deesser#image In case you don't know how it is, it is a compressor that works only with the hissing frequencies (Hiss, S, Z, F...) on the voice, they are very annoying frequencies. With a band-pass filter in the detector, it compresses only when that super annoying "zone" is loud. If you already put an EQ of 10 bands or more ... I put the example of the plugins, to try to explain how useful it would be in a pre-amp, even if it is not ultra precise or high-end, less is nothing. Sorry for the long text. Greetings.

[@audiofreq]

IMSAI guy with another informative video! Thank you

[@1dimtim]

what was the resistance of the LDR can you use another colour led, is there a difference?

[@t1d100]

Thanks for this! Clever! For clarity, if I wanted to avoid the lack of control before the LED comes on, I would simply need to forward bias the LED to have it be just barely on at all times; correct?

[@IMSAIGuy]

a good application of offset on an op-amp

[@AnalogDude_]

According to Veritasium on analog computers, it should be possible to use differential amplifiers to measure the excess above line level audio. is the there a way to "enable" a opamp to start measuring above a "custom" peak level to extract the excess voltage and use that voltage to reduce audio. I asked Thonk for a High end LDR a few days ago. 100K in dark mode.

[@IMSAIGuy]

Yes, just a peak detector to monitor the high voltage. then use a percentage of that voltage into a comparator. I use this in an audio circuit to gate (mute) the audio when there is no signal from the microphone: kzbin.info/www/bejne/eJazoqVpqdVmb7M

[@bk8biokiller8]

Did you meassure the compression curve?

[@IMSAIGuy]

nope

[@ianitang8409]

Can I used optocoupler?

[@IMSAIGuy]

maybe. it is nice to have a resistor change and not a transistor. you can use an FET too. The photoresistor is an easy way to make a voltage controlled gain stage.

[@AnalogDude_]

there exist some optocoupler that has a FET inside, used by Mystic circuits in their powerless low pass filter circuit.

[@hobbyrob313]

this could have been interesting, If only IMSAI Guy had drawn it a little better! a waste of time and effort Regards Rob

[@sean_miller]

I think it's time for HobbyRob to get glasses.

[@kevinyounkins214]

dumb question here....... does the color of the light matter to the sensor?

[@Linguae_Music]

I believe it does, all materials have a specific spectral absorption pattern. I don't know anything more specific than that. :P