6 Replies Latest reply on Feb 25, 2019 12:52 AM by mgillett

    Audio out - amplifier for ear buds


      I am nearly deaf, using the computer audio out 3.5 mm plug for earbuds I often can not hear the audio while attempting to watch a youtube video. Many persons do not carefully record their audio nor use closed caption.


      I need to use earbuds rather than playing the sound through a speaker because I have to have the volume up so loud no-one can stand to be in the house. I turn the computer volume to the max, and the video playback to the max and can barely hear audio. It would be nice to have some range that I can turn up or down.


      I have looked for circuits that will actually amplify the sound without blowing the little earbuds to pieces. I do not know the impedance of the earbuds but figure they are far lower than the 8 ohms for a regular speaker. I do wear blue tooth enabled hearing aids but the computer does not send the audio signal via blue tooth. They use blue tooth for the keyboard or mouse.


      If I did have a device that could connect to my hearing aids through blue tooth, I would still need a way to control the sound level to make up for the wide variation in sound recording levels. I could write a list of ideal specifications like...

      1. Simple

      2. just plug into the 3.5 mm jack on the standard device such as phones, computers, etc.

      3. A volume control knob

      4. An automatic gain control that could level out all signal levels to a standard level so the volume control would simply be for controlling the level.

      5. A bypass connection to go to an external speaker when watching a movie with someone (it would be nice to still have the ability to use my earbuds at the same time.



      1. The quality of the sound does not make much difference to me, I cannot distinguish the high fidelity nuances of music any longer. But the tone level can be very critical. When thinking of an equalizer the higher frequencies are completely gone, as are much of the lower frequencies. My hearing aids are tuned to optimize the level for my hearing. There is still the problem that the audiologist is not able to give enough volume to frequencies I am lacking because of the hearing devices feedback causing a squealing sound. I can't hear the squealing but people run out of the room when it happens. So they set the level as high as they can.

      2. Headphones are uncomfortable to wear for long periods of time. The light ones seem to easily get dislodged, the expensive ones have a pressure that pushes against the head causes an ache in the head.

      3. Blue tooth is wonderful, more than a few times I have gotten up forgetting I have the earbuds in and the cable yanks them out of my head.

      4. I did not lose my hearing until I was an adult and a bit to close to a bomb going off. (A lot of soldiers have this problem)

      5, I know there are commercial devices but I am not certain they will do what I am trying to do.

      6. I originally thought an ic amp that ran on 5 volts with a volume level control that I could pug into the USB to get the power, the audio jack to get the signal, and an output jack to plug in the earbuds. Seems simple but would like some guidance. I am not sure where to find that guidance.


      Appreciate any pointers,


        • Re: Audio out - amplifier for ear buds

          Unfortunately, there's only so much output you can get from earbuds. The drivers are small, and lack the ability to handle high power levels. If your hearing aids already have the proper filters and they support Bluetooth, the best solution may be to get Bluetooth audio output properly configured on your computer.


          Automatic gain control can be done to some extent using DSP, but as the typical approaches are likely to be RMS-based, you'll have to watch out for the varying crest factors of different program content.

            • Re: Audio out - amplifier for ear buds

              Thank you, This is what I figured in terms of earbuds are simply piezoelectric devices. Small input amplitude causing the thin wafer to "buzz" like crazy creating the sound wave. These have limited ability to drive simply due to the nature of their construction. Distortion becomes an issue quickly.


              I do not know if other materials have been used to seek to increase this effect in an earbud configuration. Thinking thin wafer of crystal, limited ability to take much voltage, Different types of plastic bonded to a piezoelectric element? Titanium? Not much value in doing that type of research unless making an ultrasonic cutter, etc.


              I agree with configuring the computer correctly, or a device that does take the audio out and send it into a Bluetooth audio signal (It would be very nice to control it with a simple twist of a knob. Rather than fumbling around for the little slider on a computer screen.


              You are also correct in the concern for the "varying" crest factors of content.


              DSP? Digital Signal Processing? Seems that this would be very difficult to do, the circuit would have to be able to determine some maximum level, it would then clip anything beyond this to that set max level. And possibly just bring all of the signals up to that max level, producing straight garbage.  But without a max level, it would seem to be a mind-blowing experience at times. The hearing aids do have an auto "clipping" circuit that instantly clips things shut as a gunshot. You would not want to amplify that signal from its already 140-190 dB up an additional 100 dB gain if a tiny little piezo device could withstand the signal it would even be "mind-blowing" even if I couldn't hear it. It really is odd to have sound pumping into your ear and fell it through the vibration of your skull with your fingertips but barely be able to hear the sound. I am exceedingly grateful for the researches that have developed these compact, sensitive instruments that I can run on a tiny little battery.


              I believe your answer is absolutely correct, I should focus on getting the computer signal sent directly to the Bluetooth enabled device.


              The follow-up question is then how do I do this? I can do it with my cell phone, and many other devices but not my computer at work, at home, or the TV. (Maybe newer TV's have it built in?) (Maybe some computers have this built in as well?)

              1 of 1 people found this helpful
            • Re: Audio out - amplifier for ear buds

              You may find that an audio compressor will help you. This would allow you to reduce the dynamic range of the audio. Basically you set a threshold and any audio above that threshold starts to get reduced. This will initially make things quieter, but then you apply 'make-up gain' to lift the overall level of the audio back up to where the peaks were. The result is that the loud sounds remain at the same level, but the quieter sounds now are boosted.


              It is normal to find compressors in the preamp stages of AFILS inductive loop systems. They often compress the audio down to about a 30dB dynamic range.


              Combined with some EQ then you can control what gets compressed. You may want to roll off the frequencies that you know you can't hear and concentrate more on the 200Hz - 2kHz range for speech.

              1 of 1 people found this helpful
                • Re: Audio out - amplifier for ear buds

                  I like this idea, the compression makes a lot of sense. Then doing so EQ, it might sound horrible to someone who can hear all the frequencies, but in my situation, it would level out the audio level. Actually, it seems to make sense for everyone. The EQ part, and boosting certain frequencies is different for everyone's hearing for me I would be looking at the 500 hz to 1k at the most, even that would be a broad spectrum for my hearing I could narrow the range even more. Now if I could change the pitch level down at the same time to get it into a range that I still have the ability to distinguish the sound would be great. Everything may seem to be monotonal but that is okay with me if I can just hear what they are saying. My understanding is the compression circuit takes all the audio signals and compresses it into a range of say 30 dB, some higher frequencies would be of lower level yet still at the 30 dB, and the lower frequencies would be at the 30 dB then this signal could be amplified to a range of 60 to 70 dB and thus avoid the overdriving of what is left of my hearing. I looked at some circuits on the internet and found some simple circuits to make an audio compressor using an LT1256 for the compressor, LT1636 attenuation control with an LTC1967.

                • Re: Audio out - amplifier for ear buds

                  I would worry about over amplification possibly causing further hearing damage.  Hearing aids are designed and adjusted to prevent this.  As others have mentioned there are ways to limit the maximum volume, but have you tried speech/voice to text converters?  If you are primarily interested in YouTube videos, I know converters exist for English.  I've never tried one but it might be worth a look while you work on a hardware solution.

                    • Re: Audio out - amplifier for ear buds

                      Yes, I have tried the converter programs, Youtube used to have one built into the program I think, It was 30% gibberish. IT actually only takes understanding about half the words to make sense of what a person is trying to communicate. Accents are very difficult to understand. I appreciate so many people using English (although I speak American, a language similar to English.)


                      I have been concerned about too much sound pressure and use ear protection when using outdoor equipment, power tools and the like.


                      I think the BlueTooth idea is the best one, as you said the hearing aids have high tech programs to limit the loud noise. I do have blue tooth on the cell phone that works very well for me to hear, it is the use of the computer. Primarily persons that record things without any regard to the sound levels.


                      Those that do process their audio are greatly appreciated. It seems that certain kinds of "how to" videos are produced by people speaking too fastly in a second language, i.e. computer programming, java, ruby, SQL, the electronics are a great mix of persons from English (England) speaking countries. The programs may work better with there content.


                      A big shout out to anyone who adds CC (Closed Captioning) to their videos. Thank you!


                      For the home phone, I use something called a CAPTEL (Closed caption phone service). It uses a computer internet connection and a regular phone line. The persons that make that work are typing like crazy. I earned a masters degree from the University of Southern California through the phone and computer. The persons typing that stuff had to learn whole new vocabulary, and keep up with 8 to 12 person's in one sitting. The sessions would be 2 to 3 hours. That has not been automated yet, it is literally a person typing all that stuff. There is no possible way I could have passed those courses without that accommodation.


                      I do appreciate your word on not "over diving" the audio pressure. Without a limiting device, it would be impossible to turn the levels down fast enough. The radio DJ's had something called an optimod that would ake their signal and boost it up to the maximum (I had a friend that was in the radio business that used these kinds of systems. I looked it up Orban still manufactures this type of equipment (OPTIMOD-FM 8700i) audio processing. This is not for audiophiles because there is suppression as well as pushing sound levels (so more noise etc.) These devices try to take the input signal and output a consistent full bandwidth signal.