[valveman]

Just finished my Headphone amplifier. It's my own design and runs on either a 9V battery or adapter. Not really for carrying around as can be seen by the way I designed the enclosure, but it is portable.

I built this amp for under $20 (NOT A CMOY) and it sounds fantastic. I mainly made it to power my Koss R/200 headphones since my Ipod does not have enough output for them.

 

[SONGsanmanwah]

it looks neat valveman! what does the middle button do?

 

[valveman]

Power is on the left and volume on the right. The middle selects 2 input impedance ranges so this amp can be used with practically any set of headphones regardless of impedance. The amp is absolutely quiet. With no signal, I can crank the volume to max and there is no noise at all. Add music and the amp cleanly amplifies the signal without any detectable distortion even at full volume. It is however dangerous to play at full volume since each side will output a full watt at max.

 

[phergus_25]

any info on the internals?

 

[TzeYang]

any schematics?

 

[valveman]

I'm using a fairly wide bandwidth op amp as the main component in this amplifier TDA2822. I chose this Op Amp for it's excellent specs and high output. I also made some high tolerence component selections to ensure linearity. I am planning to do more R&D with this amp. I think what is unique about my amp is the impedance matching network I designed to handle headphones up to 600 ohms and as low as 20 ohms.
So far I really like the way the amp has turned out. I need to run it through it's paces and get some plots done to see how good it really is. Sound wise I'm very happy with it. As for a basic schematic, I have not made one on the computer as yet. All done by hand. If you look at the data sheet for the Op Amp, you will get an idea of how it is connected. I did however modify things a bit so the Op Amp would be more linear. The impedance matching network is fairly straight forward and involves adding proper resistances at the load so there is maximum power transfer between the amp and the headphones.

 

[fuzzy fuzzbucket]

i have two similar headphone amps utilizing TDA2822 also... detailed but hissings...........

 

[scompton]

Is the phone jack on the headphone standard or is it something you did?

 

[philodox]

Quote:

Originally Posted by scompton /img/forum/go_quote.gif Is the phone jack on the headphone standard or is it something you did?

I just noticed that too, looks like an RJ11 [phone jack]! Weird, but cool.

 

[scompton]

Quote:

Originally Posted by philodox /img/forum/go_quote.gif I just noticed that too, looks like an RJ11 [phone jack]! Weird, but cool.

Yeah, I couldn't remember the name.

It's not something I have to know, so I'm always forgetting.

 

[valveman]

The jack on the phones is standard for the Koss R/200. Any hiss is removed with proper engineering.