Headphone amplifier

[Nic]

Ok, so here is my take on the headphone amp. The build was in itself pretty straightforward, but since I try to always put the option to go battery powered, I've decide to replace everything and add some switches. Battery only for now on this baby. I'm actually missing a dpdt for the output selector, but other than this I'm really happy.



Just need some more clear coats.

Right now, my input also has to be rewored as I made the connection on the ring instead of the tip. I had to drill my knob to a quarter inch because I ordered a splined one, the fit is thight I have to align my led also.



As for how it sounds, it's good, amplify the input. At max volume it gets king of glitchy, don't know if it is normal. Alone, it will not go super loud, just loud enough to avoid ear damage. I dit not try any pedal in front of it at this time.

 

[EGRENIER]

That's a good looking box !!!

I plan to build a few of these, but I want to include an aux input and I'm even considered a Bluetooth board I found, the MH-MX8. Goal is that I would be able to play a back track over bluetooth or a physical 1/8in input aux.

About your volume glitch, If what is does is start cutting off when raising the volume to high, I had a similar problem with an OCD/SDHD build. When I was raising the level, the sound would just cut off. It turns out I had a solder bridge that was probably creating an irregular voltage/input of the opamp. So check for that and see if you may find one of the opamp voltage/input to miss behave when rolling the volume up.

In my case, I had the issue, performed a visual inspection and spotted the bridge. A reflow fixed the issue immediately.

 

[Nic]

I had that idea about a bluetooth input also, but am not sure enough about my skills at this point. I may add an aux input eventually.

As for my glitch, I've just reboxed everything after a fresh coat of clear. I have two pair of 386 chips, I may try the other pair for comparison... 386N vs 386L. And then may start audio probing.

I plan on using that one to audio probe future projects, small size will not take as much place on my bench as an amp.

 

[bowanderror]

I had that idea about a bluetooth input also, but am not sure enough about my skills at this point. I may add an aux input eventually.

As for my glitch, I've just reboxed everything after a fresh coat of clear. I have two pair of 386 chips, I may try the other pair for comparison... 386N vs 386L. And then may start audio probing.

I plan on using that one to audio probe future projects, small size will not take as much place on my bench as an amp.

I'm finishing mine up and have the same 386N vs 386L question. Did you end up testing both?

 

[Nic]

No, I'm waiting to reopen it to add the output switching, I'll swap the L in it at that time. Tayda should arrive monday.

 

[Robert]

Lower (or jumper) the two 100R resistors at the L/R pads and you'll have more volume on tap.

 

[Nic]

Lower (or jumper) the two 100R resistors at the L/R pads and you'll have more volume on tap.

I may try that, thank you @Robert

 

[Nic]

I'm finishing mine up and have the same 386N vs 386L question. Did you end up testing both?

I tried the L tonight... to my ears the N produce less distortion at maximum volume and act more stable.

 

[Rpschultz13]

I'm thinking about adding this to the EMU amp sim. But the build doc's aren't listed. How did you build it without the build docs? The PCB only lists numbers, not values.?!?

 

[Nic]

The image on the website shows the references, but the real board has values. I think also the the BOM was posted somewhere after I asked about it.

 

[Nic]

Here...

Headphone Amplifier

Headphone Amplifier Drill Template - Revision 1 Drill Template - Revision 2

forum.pedalpcb.com

Note about the 100R resistors, those can be lowered or jumpered.

 

[Nic]

I'm thinking about adding this to the EMU amp sim. But the build doc's aren't listed. How did you build it without the build docs? The PCB only lists numbers, not values.?!?

Just look at my posts above, sorry I did not reply directly to your comment

 

[yerblues]

That's a good looking box !!!

I plan to build a few of these, but I want to include an aux input and I'm even considered a Bluetooth board I found, the MH-MX8. Goal is that I would be able to play a back track over bluetooth or a physical 1/8in input aux.

About your volume glitch, If what is does is start cutting off when raising the volume to high, I had a similar problem with an OCD/SDHD build. When I was raising the level, the sound would just cut off. It turns out I had a solder bridge that was probably creating an irregular voltage/input of the opamp. So check for that and see if you may find one of the opamp voltage/input to miss behave when rolling the volume up.

In my case, I had the issue, performed a visual inspection and spotted the bridge. A reflow fixed the issue immediately.

I really want a headphone amp with stereo spread and and aux input and this seems like the perfect platform for something like that. How would you add an aux input? Would it be as simple as wiring a stereo jack to the stereo output jack? would any resistors be involved? would you be able to add a passive volume control to the aux input?
Thanks!