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Saturday, August 16, 2014

Headphone Bass Booster

This is what I've come with this time, the main electronic project this summer.


What we have here is a bass booster device for headphones. It amplifies a range of signals that you can choose with the potentiometer on top. Although you can also boost high frequencies with this, it is intended to amplify low ones which are which mobile phones and MP4 players lacks.

This is the thing out of the box. Each PCB deal with one channel.

The diagram is from somewhere in Makezine, but I modified it to suit my preferences and for improving it a little bit. Mainly, as I didn't want it to be portable, and I hate batteries, I fed it with a wall adapter. I don't want to go too deep into electronic matters, but for this you have to get some adapter rated with more voltage than what you need (I chose 9V), then regulate and filter at the same time with a LM7805 to avoid noises. I made some other changes too.

The thing is based on a LM386. The green wired PCB is right channel.

The result is great. I was worried because when you work with sound stuff you get annoying noises very easily, an as I'm sort of an audiophile, I can't listen to music with a noisy machine. It would have gone straight to the bin if that happened. But fortunately I get absolutely no noise from it!, just pure sound!

Besides it boosts a selected range of frequencies, it also amplifies noticeably the sound in general. Nevertheless, as it's not its purpose, I haven't measured what amount.

I added a nice yellow LED and fitted it into a box with a transparent cover.

I'm very happy with this little thing. I reckon it'll be very useful. For me, it's not about simply using this and there it is. I think the greatness comes when you set up properly an equalizer to manage all the frequencies, then with this extra boost in low ones you'll get a very nice sound.

Testing

I want to show it to you the best I can, so I've made a video where I play with the potentiometer. The audio (courtesy of Evanescence) is recorded through the computer so you can listen better. I promise it's not altered in any way, I've turned off all the equalizers.


Nice project.

18 comments:

  1. can you please provide me with your Circuit Diagram so that i can make it according to how you have made it, it would be of great help :D

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  2. Can you please show me your ckt diagram so that I can build according to your schematic, it wud be of great help

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  3. Can u pls send me the schematic of your modified ckt so that i can build it for myself too.

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    1. Hi Jolton, I have no schematic for this. Modifications are really simple with a minimum electronic knowledge.

      -The wall adapter that I used is connected in the same place as the battery, but between it and the adapter I put a 7805 voltage regulator. It is simple because it only has 3 pins. IN (adapter +), OUT (circuit +) and GND (ground or negative). Check Google on how to connect it if you have difficulties.

      - The LED is in series with a resistor (whose value can't remember), maybe 500 ohm or 1K. It is connected to OUT in the 7805 (which is positive) and ground.

      -The pot in the schematic is R5. I used one double (stereo pot) instead of one simple (mono) for each channel which is stupid.
      - R6 is short-circuited, I mean, it is replaced by a wire. That way you get a better range.

      Pedro.

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    2. Hi Pedro I have some question on the 7805 you said that has three pins and they're cal,l In, Out and GND rite?

      So you also said + side of the adapter goes to In, pin Out goes where you were connect the + of the battery of the pcb, and the GND pin goes to the - side were the battery should be going? Or the - side of the adapter goes were the - side of the battery should be going.

      And last you said to take out the resistor R6 and just put a jumper instead of the resistor?

      Also can you tell me if there any hizz on the amp or just silence when there is no music.

      Well hope you could reply and thank you for the modz.

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    3. Hi,

      "So you also said + side of the adapter goes to In, pin Out goes where you were connect the + of the battery of the pcb"

      That is correct. The GND (GrouND) pin have to be connected to ground, the - of the adapter to ground as well. In this project you can consider negative=ground (GND), because both have 0 volts. Ground is the 0 volt reference, every negative side or ground have to be connected to ground, and grounds of the 2 channels have to be connected together because they are the same 0 volt point of reference.

      "And last you said to take out the resistor R6 and just put a jumper instead of the resistor? "

      Yes I did. I said somewhere, by doing that you get a wider range in the pot. This has no downside at all, but a lot of benefit.

      "Also can you tell me if there any hizz on the amp or just silence when there is no music."

      This is an interesting question. It depends on the audio source you use and the distance to the amp. Generally speaking, the noise is not worrying at all. When using my laptop I get a little bit of it, with my mp4 player you have to be very picky to realise, with my phone just silence. It depends, but don't worry, the result you get of that project is so awesome you won't mind any fuzz.

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    4. Ok thank you so much for your help I would like to have you email if possible, you know so much about electronic and since I just started into this and kind of a noob, also you reply back fast and would like to ask for your help next time im stuck.

      Oh and did you put one pot or still have two pots. If you did put only one pot to control both channels can you please tell me how.

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    5. I put one pot, and I posted exactly how to connect it in the picture I put in some comment. Just look at the numbers for matching pot pins and circuit.

      It's better that if you are in trouble comment here so everyone can check it.

      Pedro.

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    6. Ok thats cool ill check the picture out and ill come back if i need more help thanks.

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    7. Hi Pedro im back I just finish putting everything together like you did and i hear the hizz when I disconnect the power adapter but when I the power adapter on the wall I hear a hmm and its pretty noticeable (loud) and get louder when I put my fingers near the pot. What could it be?

      I still need to try it with other sources.

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    8. Hi man, you don't tell me if despite of the noise it works or not. I guess you hear the noise but not the music you input. In that case, check the circuit joints, make sure what is in the diagram is exactly what you've mounted. I reckon one problematic spot is the LM386 pin numbering. Check if you confused some pin.

      Some noise increase when you touch the circuit or the pot is normal.

      Pedro.

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    9. Well I hear the music but when there is no music thats when you hear the hmm. I checked the board there is no short circuit and I was thinking the lm7805 is 5V do you think that might be the problem that I hear the hmm have you try the lm7809.

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    10. The lm7805 is perfect for the job, but remember 5 volts is the output, the input must be around 8 up to 20 or even 40 DC volts (depending on the manufacturer) so it can work properly. Lower input than that and you'll get malfunction and noise. The lm7809 may be a bit dangerous because it outputs 9 volts, and maybe for your exact lm386 it can be too many. You'd be safe if you connect both channels in series because you'd get 4.5 V for each one. Again, you'd need to feed its input with higher voltage, maybe this time from 12 to max 30 or 40 V...

      Anyway you can always try to feed the circuit directly with battery, avoiding the voltage regulators. Batteries produce no noise at all, they are good for testing. Like that, you can see if the problem is in the circuit or in the power supply. Remember taking care of the voltages, if you connect channels in parallel or just feed one channel, use a 4.5 V battery, if you put them in series, 9 V.

      Pedro.

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    11. Ok I have a 9v power adapter going thru the lm7805, ok ill try three AAA battery and try it on the two channels see if I hear the hmmm or hizz on them separate. If I still do ill just go with the 9v battery. Cause I didnt hear the hmmm before, and thank you.

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  4. Hello Pedro, i tried all possible things i cud do in the ckt, but dont have a result yet, i would want to know how did you connect the terminals of stereo pot into the ckt, maybe the terminal connection is the reason why i am not successful in getting its output.

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    1. Ok mate, don't worry. Check this picture, I wrote some indications on it.

      http://i.imgur.com/W61AU1l.png

      In that, it is powered by a battery. The set up with a wall adapter would need some more wiring. I forgot to add the LED, but that is not complicated. Let me know if you need more help,

      Pedro.

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  5. This a really good project. I’ve seen the video and heard its capabilities, and the boost sounds amazing! Good job on getting rid of those hissing sounds as well, as most gadgets such as these usually have hissing sounds that are really annoying. Anyway, thanks for sharing this with us. Cheers!


    Kellie Taylor @ Aim Dynamics

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