### Network

#### Neptune82

Sep 8, 2017
13
Hello everyone. I'm new here and I hope that this is the correct place to post. So I purchased these radio ear defenders for my work at a not too cheap price of 100euro and I have to say the build quality is great I'm really happy with that part . My main problem is the volume of the radio and the aux output when I plug in my phone is extremely low. I understand this is how they are made because of the db exposure limits .basicly there's 1 button in the middle and that controlles the volume and there are 4 levels after pressing it the 4th time the volume then resets back to the lowest level. I mean u can hear the radio ok but if u want to listen to music from your phone the volume is even lower. Is there anything one could do to perhaps modify them somehow to get the volume a couple of notches higher? I have no idea with this kind of thing but perhaps one of u guys can help. I will post a pic and if more info is needed I can post a link . Many thanks guys and girls

#### Audioguru

Sep 24, 2016
3,642
When they designed the headphones they did not know that you phone has a low output level.
To modify them we need to know if they have an internal amplifier then we need a schematic of it. Then you need an electronic expert to do the modification because the parts are tiny.

#### Neptune82

Sep 8, 2017
13
Thank u so much for the reply
The link I posted was the only info I have .would u have a suggestion how I would find it out if they have a amp? Or maybe I could somehow increase the output on my phone? Many thanks

Feb 18, 2016
236

#### Neptune82

Sep 8, 2017
13
I think they are made to have a lower volume because in the end they are ear defenders but the radio is not loud and when I plug my Samsung phone in it's much quieter!! So I plugged them into my pc and I was able to increase the volume considerably more

#### Braeden Hamson

Feb 18, 2016
236
Screw the $40 stuff, here's an$8 bit from eatafruit:

If you bought that you could get a very small enclosure for it and, a small lithium cell & charge/protector circuit, as well as a potentiometer to adjust the volume. You could also just use 2 or 3 1.5 AA or AAA (this would all depend on how long you want it to run for and how big you want the final product to be.)

Last edited:

#### Neptune82

Sep 8, 2017
13
Screw the $40 stuff, heres a$4 job from eatafruit:

If you bought that you could get a very small enclosure for it and, a small lithium cell & charge/protector circuit, as well as a potentiometer to adjust the volume.

EDIT: keep in mind it's a mono amp. Adafruit also has stereo amps.
I wish I had the skill to do that however I have no clue ! Would this item work ?
Neoteck Headphone Amplifier Portable 3.5mm Audio Rechargeble HiFi Earphone Headphone Amplifier with Lithium Battery and Aluminum Matte Surface Ideal for MP3 MP4 Phones Digital Players and Computers https://www.amazon.co.uk/dp/B01IHGWGDM/ref=cm_sw_r_cp_apa_pjTSzbA463R4R

#### Braeden Hamson

Feb 18, 2016
236
I wish I had the skill to do that however I have no clue ! Would this item work ?
Neoteck Headphone Amplifier Portable 3.5mm Audio Rechargeble HiFi Earphone Headphone Amplifier with Lithium Battery and Aluminum Matte Surface Ideal for MP3 MP4 Phones Digital Players and Computers https://www.amazon.co.uk/dp/B01IHGWGDM/ref=cm_sw_r_cp_apa_pjTSzbA463R4R

Yeah that's what you're after, and a good price too! I doubt you could get a cheaper one if you DIY.

#### Neptune82

Sep 8, 2017
13
Yeah that's what you're after, and a good price too! I doubt you could get a cheaper one if you DIY.
Beanden do u think that would increase the volume somewhat ? Thanks

#### Audioguru

Sep 24, 2016
3,642
The Adafruit speaker amplifier will not work with headphones unless you replace the entire cable of the headphones because each amplifier is BTL. The headphones cable has a common ground for each channel.

The Neoteck headphones amplifier produces fairly low 40mW into 16 ohms but if your headphones are 32 ohms then the power will be only about 20mW. The headphones spec's do not say the impedance so the volume might not be loud enough. The headphones reduce but do not eliminate the loud background noise so you probably need them to be fairly loud.

#### Braeden Hamson

Feb 18, 2016
236
That's interesting, you can't connect the common ground to the amp ground? Why not?

#### Neptune82

Sep 8, 2017
13
Please can I just add that the volume does not have to be so loud that you can't hear the outside world, But just that you can clearly hear .perhaps a 20% increase. I know the headphones can go louder because I plugged them into my pc,s Logitech system and was able to turn up the volume significantly.. But for some reason when connecting my phone the max level is verry low. However the built in radio volume is better than when plugged in to my phone.

When I plug a normal pair of headphones into my phone the volume is more than loud enough

#### Braeden Hamson

Feb 18, 2016
236
I really don't see why an external amp, like the one you showed, wouldn't work. IMO buy it, if it doesn't work return it. (Although from my understanding modifying the external amp, if it were too quiet, wouldn't be extremely difficult.)

#### Neptune82

Sep 8, 2017
13
I really don't see why an external amp, like the one you showed, wouldn't work. IMO buy it, if it doesn't work return it. (Although from my understanding modifying the external amp, if it were too quiet, wouldn't be extremely difficult.)
Well I ordered the one from link and it comes today so I will update

#### Audioguru

Sep 24, 2016
3,642
That's interesting, you can't connect the common ground to the amp ground? Why not?
Headphones are wired with a left signal wire, a right signal wire and a ground wire that is common to both left and right. But the Adafruit amplifier and many more amplifiers that operate from a low supply voltage including most car radios have both wires of each speaker driven with signals called BTL. It effectively doubles the signal voltage and doubles signal current producing almost 4 times the power.

You would need to pick left and right outputs that are in phase (the other two speaker outputs have reversed phase and are outputs so they must never be grounded), add coupling capacitors to block DC and find a ground on the amplifier somewhere to connect to the headphones.

#### Neptune82

Sep 8, 2017
13
Hi guys amp arrived works perfect. Increase of volume 10fold

#### Neptune82

Sep 8, 2017
13
But the built in radio volume is not affected

Sep 8, 2017
13

#### Audioguru

Sep 24, 2016
3,642
Which amplifier works well? Adafruit or Neoteck?

#### Neptune82

Sep 8, 2017
13
The neoteck works super .But as I said it has no effect at all on the built in radio volume

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