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- Опубликовано: 29 июл 2014
- In a recent video (linked below), I presented a circuit that was designed to be used with a scanning receiver, whose function was to provide a constant audio output level from the receiver - thus eliminating the annoying variations in volume of the various received signals. The video can be found here:
• #157: Circuit fun: Aut...
In today's video, the circuit is demonstrated by connecting it up to a scanner and listening to the affect it has on the audio level of different received signals. Note that the automatic audio gain in the camera's recording system will tend to make the results with this circuit seem less dramatic than they really are when listening to it live.
Ludvig, SM6XUN, was kind enough to design a PCB for this design, and has made it available on OSH Park for anyone to order. The project can be found here:
oshpark.com/shared_projects/0...
And here are the schematic:
www.qsl.net/w2aew/youtube/audi...
and PCB placement files:
www.qsl.net/w2aew/youtube/audi... 
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Hi Alan, I want to thank you for the level control. Built it and works great. In the morning I get up before the wife and listen to a net on 2 meters. The stations have a large range of gain. So if I turn the gain up for a low audio level station and the next one with a high gain of audio. It wakes up the wife. So it causes a unhappy wife. Your circuit does a great job keeping it at one level. On CW I think it improves the tones. A big thank you from me. Rick
+Richard Willaman Cool! I'm glad it worked out so well for you.
Very cool project. Thanks much for this video.
Finished installing this circuit in an old Kenwood "SP-520" speaker enclosure along with a LM386 power amp. What is really cool is that if I keep the output of my Yeasu FT 450-D volume to around 100 MV it bypasses the compressor action, and I use the power amp to increase the volume. If I want the compressor to kick it I just increase the output of radio's volume level to around 180 MV. Pretty cool!!!
+Curtis Wilson Very nice!
I'm really enjoying your videos. I may even go back to the beginning (again) and watch some of the ones I skipped. Thanks.
I really need this for watching RUclips videos. Different Creators seem to have wildly varying opinions about standard volume levels. Those who incorporate music clips in their videos frequently let the volume reach 50 to 100% higher than the voice levels.
It would be nice to preserve stereo sound (tracking volume compression), although I think most of the RUclips channels (RUclips machinists - a lot of machine noise as well) I watch are single audio channel.
YES me too, that's very annoying. Some channels I wont click on because their intro music rattles my house and wakes up anyone sleeping, then the content is whisper quiet, I am looking for this device in stereo and with line level in and line level out...please Sir oh yeah great video
Dear sir thanks this circuit work very well thanks again
Excellent. Jut what I need for a homebrew transceiver which has no agc. I can be listening to a weak signal and the next station to call me can blow me out of the chair and leave me half deaf.
Great video! Wondering if this would work with the XR-2206 chip (or your balanced modulator circuit) to level the AM audio input? Or would the DC offset interfere?
Hi, thanks for the great circuit.
I have one question . According to the schematic diagram, there is ONLY 1 electrolytic capacitor 0,47uF, but in the video, we can see another 2,2 uF electrolitic capacitor. Could you please, which normal capacitor should be replaced by the 2,2uF electrolytic? Thanks
I always wanted to build this but googled wrong words, thanks a lot!
Interesting.. Because here in the UK Commercial TV stations audio levels jump when commercials are played between advert breaks, they can be very loud.
This contribution by Your good self may make the evenings more pleasant for those whom care to try it out.
The volume levels don't really jump as such, it is just that commercials are deliberately very heavily compressed. The advert's peak level is the same as the programme, that's regulated by broadcasters, it is just that all the quiet and medium levels have been very heavily boosted. Which is why it sounds so suddenly hectic.
Unfortunately a simple peak detector circuit would therefore have trouble identifying adverts, you'd need something a lot more complicated which was able to detect "apparent" loudness.
Rupert Rooksby
Well there are some TV's that have that circuit built in like AVLS auto volume limiter system and it works ! But they are probably DSP based.
Rupert Rooksby
Thank you. Twice. : )
Rupert Rooksby
This is where you need to have a RMS (or average) detector in the control loop...;)
They are some really Pro units around called "expander" the opposit to the compressor. They expand the incomming signal to a range set by the user. But they are far more complex to set up and operate without the anoying pump-around effect when the input signal differs to much (Crest factor distortion)
Software is also available; often called "de-compressing" or MultibandExpander. These are much more complex and some do have "footprint" libraries of famous compressors to nearly delete them from the audio. But even with today´s computers they are all offline, as there is not enough power to compute the numbers in realtime with enough headroom and artefactial noise free silence. You can "pre-hear" the result, but it sounds like a telephone. The results after processing are quite good....but you need a lot of time to set it up until it works well....
Any chance someone has a part list for this? Not sure what they are using for the audio input and output.
Thx verry 👍 good
Do you have or could you design a simple audio controlled relay circuit. So that when the scanner audio comes on it would activate a relay. The purpose is to open the audio output of another radio so that the scanner audio could be heard more clearly. Thank you for your videos.
I like your Comp very much (as mentioned in your previous video). As it is a complete different way to set it up. Usually Comps are working as VCAs with a attack/decay envelope feed in the control voltage path and the control stroke is formed by the input voltage via a peak detector. To let you have a control over attack/decay and Compression Ratio (1:1 -> nothing, up to 1:infinty for constant output voltage) via external pots.
The overall design is far more complex than your design, woking as a variable load depending on the input signal voltage, i *do* like your way.
Even absolute Pro Audio Compressors, like this ruclips.net/video/C-5iEBR1Ii4/видео.html ( a true Classic! ) and this: ruclips.net/video/sAcCFi4_TX4/видео.html do *not* have an inbuild frequency diversion. If you want to add this you need to have an "aux" input called the "sidechain", where you can split the detector path and insert an equalizer and or some extra filters into it, to let the Comp react different with respect to frequency.
I have designed some Comps, with VCAs, all diskrete (like the urei 1176) and some with tubes....as Comps are an absolute basic you need to have while play/recording music(instruments).
When using software Comps, one can have a completely different way of how a Comp is set up, as they are MultibandComp around. They split the frequency range of the music signal into regions where you can set up its corresponding Comp completely different. Common MultibandComps have 3 to 5 bands, where you can also set up the frequency range to operate independent from one band to another.
Also there is a "lookAhead" function. It lets you set the attack time to zero, for brickwall-limitting in addition with a distortion stage to have more punch (used all together mainly in commertials to make them "loud" in radio/TV stations).
One "TopNotch" transmitting station compressor company is "Orban" they are pretty much standart in radio stations....(OPTIMOD.....RF-guys really can tell something about this....;)
A good circuit and simple one at that most compressor circuit to tend toward more companants. A question I do have is were did you purchase the island cutter from and was it from Qrpme at all would like to get a hold of one. Hope to meet on air 73's David ZL1UTS
Yes, it was from QRPme. Here are a few videos where I discuss the island cutter method, and a few other construction techniques:
Electronic Circuit Construction Techniques - a review of some prototype circuit building methods
and here's a video that shows how I use the island cutter to build a simply crystal oscillator circuit:
Build a crystal oscillator from schematic thru prototype construction and testing - DIY
Can someone provide the parts list? I have purchased the board that was offered on the internet for this project.
I bought the "circuit" board offered by another person for this circuit. The boards are very small and require you to have good eye sight to solder the parts onto. The boards are very professional in quality, but small. I soldered all the parts but needed a magnifying glass to check the solder connections. I just thought I would let every know in case they were planning on purchasing the boards.
It would be nice if we knew where to get the circuit boards from. Thx.
@@acmefixer1 The link is in the description below the video, as Alan stated in the video!
Very useful project. I'm a newbie and building a vu meter circuit based on arduino. What I'm planning to do is, take the signal from earphone out and connect it to your circuit(to keep the output signal constant) before going into next stage. As the earphone signal is way too low to get a decent output level (decent level means around 2Vrms), I'm planning to use a simple audio amplifier to amplify the signal.But this circuit is lowering down the signal from speaker level to 50mVpp. How can I use this circuit for my purpose? Also in the schematic I noticed, there are some additional components added to the circuit diagram.what is d5 and d6? I assume they are also 1N34A diodes. Really appreciate your help. Thank you.
You would need to add an amplifier after the compressor. It distorts the signal and limits the dynamic range, so won't make a good front end for a VU meter. All diodes are 1N34A.
Hey +w2aew, this circuit looks great! I built it and it does limit the volume (Have tried up to 2Vpp using a tone generator from my laptop, the circuit limits my tones down to 50Vpp!) I am, however, noticing distortion in the output, cant figure out what's causing this :/. Any insights greately appreciated! Thank you for your videos!
It is a natural result of this simple circuit. It relies on the non-linear properties of the diodes to do the compression, so it definitely does distort the signal. The distortion is tolerable for communications quality audio, but I would not use it for anything that requires more fidelity. You can see the distortion on the wavefom in the first video I did on the subject:
ruclips.net/video/1h0FZJYXQ_w/видео.html
Great, I'll use it mostly for voice. Thanks again!
What is an island cutter method?
Alan, you have a good understanding of audio circuit . what if i wanted to have my radio alarm start low audio and increase fairly fast to wake me with out un nerving me. do you have a circuit for that?
I haven't got a circuit for that, but initial thoughts would be to use a FET as a variable resistor, with a slow charging voltage on the gate to reduce the channel resistance slowly... This could be employed in an audio amp pretty easily - just need to work out how to have it reset and then start it's ramp at the right time...
@@w2aew the reset easy power to the siren goes out completely in 10sec
This worked great, but will it also work on some of those DVDs that have very loud and then low volumes? On my living room setup, we constantly have to adjust the TV volume when listening to a DVD because some parts will blow you out of the room and others, you can barely hear?
It would likely work, but keep in mind it isn't really a high fidelity circuit.
ok, thanks and thanks for giving an idea that may majorly help. If it works, I'll post and certainly give you credit for the idea
Nearly every DVD player and home theater receiver has an option to limit the dynamic range (difference between loud sounds like an explosion and quiet ones like whispering), usually called "midnight mode", "night listening", "compression", or something similar. Check the user manual to enable it, or browse through the settings menus in the audio section.
also remember this circuit does not take into account the ears' response curve. If you have loud low or high frequencies, everything will sound quiet because the ears dont have a good response for stuff below 500Hz or above 10KHz. The peak is about 4-5KHz (avg voice), so if the input has anything on those ranges, the voices will sound low. It would be cool in a lineal world, but for anything other than just voice or FM signals it's not really a great idea. Unless of course you add a bandpass filter or an equalizer, and tune it so that all the frequencies sound to you at the same level.
Laharl Krichevskoy Very good point.
This is great for listening to cops on the scanner that don't know how to operate a microphone. I swear some of them leave the radio on their belt while talking.
The one problem with this circuit is obtaining the 1N34 diodes. Germanium parts are very difficult to obtain and are expensive. It would be much easier if there was a substitute for these diodes. Thanks.
There's millions of them on eBay, and they're cheap.
Nice sir can i used the circuit in my fm transmitter
It's possible - it really depends on your signal levels, circuit impedance and the required signal fidelity.
Thanks for reply sir
Hey Alan, I am trying to design the circuit but using a Si diode (0.7 V) instead of a Germanium (0.2 V). My simulations seems to be non linear. Any suggestions or thoughts about the same.
Yes, it certainly will be non-linear. The Ge diode solution is non-linear too, just not as bad.
I'd like to vary the audio to a different level, would the 240K at the bottom of the
schematic be a good location to place a Pot.? What would you suggest?
No. The 240k along with C4 sets the decay time of the peak detector. Lowering the series 10K would change the output level, but you have to watch out for linearity issues. Also, the output can NOT drive a speaker - it is a low level, high impedance output that is designed to go into an amplifier. So, simply adjust the volume on the amplifier.
*****
Yes, I understand were driving in mV, not volts. But I do understand what your saying...thanks anyway,
Alan, where did you purchase the island cutters? Did I miss the link?
I got the island cutter from QRPme. This technique and other construction techniques are shown in this video:
Electronic Circuit Construction Techniques - a review of some prototype circuit building methods
I also show this technique in this video where I show how to build a crystal test oscillator:
Build a crystal oscillator from schematic thru prototype construction and testing - DIY
I use one of these for making the pads on a copper clad board, in my small drill press. Picked it up at the local harbor freight, modified it a bit. It works very well!
www.harborfreight.com/3-8-eighth-inch-double-sided-rotary-spot-weld-cutter-95343.html
Dear sir 240k resistor is not available in market can i use the 220k resistor place of 240k resistor please reply me
Yes, 220k will work fine.
Hello W2AEW.......In BITX or uBITX schematic, there is an AF preamp followed by LM386 AF amplifier.
# Could we intercept the point between that preamp and lm386 amp,
so the output of the bitx af preamp goes to ALC input,
then ALC output goes to lm386 input ??
# I need to put this ALC internally in BITX any solution please....Thanks
It really depends on the signal levels that appear at that intermediate point between the preamp and the LM386. If they are very low, you may need to amplify them (further) with the preamp in order to get into the range that will be controlled by the circuit.
@@w2aew Ok2... what is the minimal or optimal level need by the input of this ALC circuit sir ?
@@ssmbssmbssmb You need about 100-200mVpp input amplitude for the leveling to happen.
@@w2aew Thanks
Can this circuit be fed 5V?
Yes, it should work with 5V too.
@@w2aew Thanks a lot for sharing this one!
Will this work with Ham Radio, 144 and 440 mhz?
it will work on any audio signal, but will need an audio amplifier to follow it.
I didn't know this circuit existed. I kept planning to look for it for ages, but for some reason I had been forgetting to actually do so.
Finally, I did a search for auto volume control regulation or amplifier regulation and this came up. The reason being, I have issues with various recordings and social media in particular not having any standard recording level. So one viewing will be alright then when I go to another, I'll get blasted by higher recording level or conversely cannot hear and have to turn up.
Latter is even worse if I have to increase volume for a presentation then go to another that has an unexpected very high recording level. Each time, I'm having to quickly adjust which can be quite annoying. That is especially so if sound has disturbing content which blasts you.
Otherwise, I maybe listening to music that has an initial quiet, introductory period that progresses toward becoming excessively loud for its ending. That happens a lot with modern classical music. Pink Martini's Bolero is an example.
My concern was how could it be done without clipping the sound each time amplitude would attempt to go beyond a certain desired maximum level. Of course, I'm pleasantly surprised to learn now that clipping can be avoided by use of capacitors.
Now I know this amp regulation circuit exists, why does it not form part of hi-fi amplifier circuits as standard (all you'd need is an optional toggle switch to facilitate its use by the listener)?
Does it severely degrade sound quality why audiophile equipment doesn't have it?
This simple circuit does degrade the signal (adds distortion)
Capacitor