Saturday, 20 July 2013

Objective2 headphone amplifier construction guide

Buy your own O2-kit here

Start with measuring all the resistors and labeling them.
Smallest parts first, so solder all the small resistors like this.
Add the diodes, make sure to solder them in the right direction!!! Solder the medium size resistors now too.
The IC-sockets have such short legs to it's a good idea to add them early.
Add the two big resistors at the bottom of the board. Keep 2-3mm distance between the resistors and the board since they can get warm during operation.
Add some of the small capacitors.
Add the slightly bigger capacitors on the bottom right of the board.
Add the blue capacitors.
Solder the LED first, it's important that you get it close to the board and pointing straight forward. Next att the 3.5mm sockets, they snap in to place so they are easy to solder.
Add the power socket. Solder one leg first, reheat the joint and push it in place and then solder the remaining legs.
Add the switches. This can be a bit tricky. Solder only one leg first. Reheat the joint and push the switch into place and make sure it is close to the board and pointing straight forward. If not you will get trouble with the front panel. Solder the rest of the joints when you feel satisfied with the positioning. Add the white square capacitors.
Add the volume potentiometer, try it in the case with front panel on to make sure you put it in the right position.
Volume control soldered to the board. For this kit I had to use the two row in the front.
Now add the two round brown capacitors.
As you can see in the picture there is a bridge between them. Solder the outer legs first, push them in place and then solder the bridge between them. You will need quite a bit of solder here. If you look closely you can see that the on/off switch has only been soldered as one place so far.
Add the four big capacitors. Solder one leg first, push them in place and solder the rest.
Solder the battery connectors. If you are going to mount an ODAC on the board you should only solder the two connectors to the left. If you're not planning on using an ODAC, solder both pairs. Make sure they stand straight! Solder one leg first, push to place and solder the rest.
With battery connectors on board. I will be mounting an ODAC to the board so I only soldered the left pair.
Add the ESD-sensitive parts. Be careful with these and try to avoid touching the legs. Solder smallest first and finish with the biggest. The two big ones to the left must be close to the board, otherwise they will hit the roof of the case.
Reheat ALL joints on the board. This is because when you cut the legs off components the joints may crack and provide bad connection. Reheat all joints and the solder will flow out nice and smooth. Measure all resistances and voltages according to NwAvGuy's guide on his blog. If everything measures as it should, try with a pair of scrappy headphones. Don't forget to add the opamps, and make sure you put them in the right places and in the right directions! This is very very important and triple check this before starting it up for the first time.
Don't use your expensive headphones the first time you are playing it. If something is wrong, you don't want to kill your $300 headphones. 

Thursday, 18 July 2013

Behringer iNuke NU6000 fan-mod

So today I decided to swap the fans of my Behringer iNuke NU6000 amplifier. I had to send the first one back because of some electrical buzzing sound coming from within the amplifier. Picked up the new one a couple of days ago and have been running it without fuss the since then. I had some spare time today, so why not do it and be done with it?

First remove the six screws on the top.
Remove the lid. The fan connectors are in the middle of the amplifier.
Remove the screws, four for each fan. The cover comes off too.
This is a picture of the fan connectors on the board. The cables are glued to the connectors which are in turn glued to the board. I decided to remove all the glue with a dremel.
Since the connectors are 2-pin and the fans are 3-pin you have to do some soldering. Twin the wires like this.
Solder it like this.
Don't forget this! Very important to avoid short circuits.
Fans installed. I decided to use a Zalman fan-controller.
Fastened to the side with a double-adhesive strip that came with it.
The back side. Note that I used rubber "screws" for the top two holes. They came with one of the fans (the fans are identical but I got one from a friend and bought the other).

The fans are Fractal Design Real Silent 80mm ( and they are in fact really silent. I tried hooking it up on the kitchen table with the cover off and the only sound I heard was some faint tapping noise from the fans, probably because they were running at such a low speed. The fan controller was set to maximum speed but I still felt like they were running a bit slow. Might be the amplifier has some sort of voltage reduction on low loads. The amplifier is now completely silent. You can't hear it's on unless you put your ear to the back of it. The fan controller isn't really necessary with these fans but it had been lying in the box unopened for three years now so why not use it?

The mod itself is really easy and all you need to know is how to solder together a pair of wires.

Total time: ~2 hours. Total cost: 80SEK ($12). Would I recommend this mod? YES!