The Disco-MINT Headphone Amplifier
This is my second working MINT headphone amplifier (pics of the first will be online shortly). It had to have a power-on indicator but to make the amp stand out a bit and to save valuable space on the front panel I decided to light the enclosure from within and mill a slot for the LED to shine through. At first, I had planned to go with a simple blue or white LED but then I decided it would be to dull...
Close-up of the front panel with volume control, 3,5 mm. output and power switch. The volume knob is temporary - it was the only one I had in this size :-)
The rear panel is quite straightforward; a 2,5 mm socket for the power and a 3,5 mm socket for the audio inpt. Because the sockets aren't isolated, I had to use a stereo socket for the power supply and use the "tip" and "ring" connections of the plug. The power supply is a 9V plug-in type which actually gives out around 13V because the power consumption of the amplifier is so low.
The above pictures might be deceptive as far as the size of the amp is concerned, because it really is quite small. The PCB measures just -- x -- mm and the case is the size of a credit card. Nice and compact for a cluttered desk ;-)
Close-up of the finished PCB. Mounting this to the front panel was a bit fiddly and took some time but it worked. Not in the pictures are the piece of teflon used to insulate the underside of the amp from the enclosure. The opamp used is the AD8620. With the exception of the gain resistor, all other component values are identical to the schematic.
The reason why this amp is called the "Disco-MINT" is because it uses a special flashing RGB-LED from LSDiodes. The LED flashes multiple colours in a predetermined pattern. It is very bright and actually lights up a dark room. The effect is very "Disco-like" and so choosing a name for the amp was quite straightforward. LSdiodes has an animation of how the LED works (here) which should give an idea of what the finished result looks like.
This little amp sounds very good. It isn't as good as the PPA, but it is a lot smaller - perfect for the desk at home or in the office. As I prefer the sound of Burr Brown opamps to the AD ones, I'll try out the OPA2107 in the next MINT I build.
©Uffe Nisbeth 2004 Last update: Sept. 28, 2004