Panda HeadAmp for Dummies - Assembly

Ouch, I went ahead and did it... I bought myself a little something for the holidays to entertain myself...
Having been the proud owner of a Fiat Panda and having read a lot of good reviews on the Panda HeadAmp I thought to myself "why not" and went ahead and bought myself a kit...
The kit is offered from Well I got my kit and after a week or so decided to finally start assembling the damn thing.
For any of you out there who would like to know a little more, please visit the links below (that is where I learned most of what is presented here):
--> Do a Google search of "Rockgrotto Panda amp", the links I once provided stopped working!

As always, I will not take ANY responsibility for whatever anyone does with the information I provide. Actually I won't even guarantee you it is correct, so please do not send me whine-mails after you have made a major fuckup and burned down your home... Please...

Some might wonder what exactly is required for this project tool-wise.
For the raw assembly of the kit I managed to get by with this:

That yellow thing to the left is called a Digital MultiMeter (or DMM by geeks). You use this to check for shorts and measure your resistors and match you components and throwing after your girlfriend if she does not fetch you cold beers fast enough!
Next we have a plyer and a clipper which you will use for bending the legs on your components and cutting them after soldering.
Lastly you see solder wire, something to clean your soldering irons tip (in lack of better words) and my trusted 25W soldering iron.
With these few tools you are ready to proceed!

OK, so this is pretty much what I got in the mail, two bags with components and the PCB (oh, PCB means "Print Circuit Board" for you newcomers out there.

This is the PCB by itself... Unfortunately it got scratched during transport and it bugs me everytime I look upon it, but I chose not to whine to get another one as it should not affect sound quality.

Before starting up you soldering iron (or during its heat-up) I measured all the resistors and sorted them out. This will make the assembly easier in my opinion. Some of you might wonder why I start with the resistors... Well I do that since those are the lowest profile components in the kit. I usually start with the lowest components (height-wise) and work my way up as it is easier to hold the components in place when you do not have to fiddle between some higher components whilst you PCB is turned upside down for soldering.

This is a picture taken after I started soldering the resistors on. Please DO note those NASTY SCRATCHES on the PCB (sigh).

This is the backside, I am the kind of guy who lets those legs be until all has been done, but worry not, that is only ONE of my weird habits. You could cut the legs off after each soldering if you like though (but it MIGHT affect sound quality).

Hmm, and this is where THAT gets us...

Now clip off those legs to get that smooth look you all want. To the right you can see the pile of cut-off legs. I usually save those for other prototype builds to use as interconnections.

Now you should have something like this. Note that I made ALL resistor values point upwards to make them easier to read AND, of course, improve sound quality.

So, got some more components onto the PCB and now things will get a little more tricky...
Now we are going to mount the diodes and "LO AND BEHOLD", the values do NOT match the print on the PCB!
Fear not, the diodes go here:

IN4746 A.K.A. "Erm, the silver ones with the black text on them" go in the holes for "18V".

IN4007 A.K.A. "those black ones with the silver text on them" go in the spot labeled "IN4001".
"The ridiculously small glassy orange-with-nano-text-on-them diodes" should be put in the holes marked "3.9V" and "IN4148".

Next in line are the small capacitors (or "caps" as they are usually called), you should have 8 of them (those small yellow buggers). Carefully solder them into place.

Coming in next is this component that I rightfully do not know exactly what is, I am happy knowing what way to orient it and that most likely I will get no sound out of my amp without it...
Hmm, OK so actually SOMEONE is reading through this... Some helpful soul named "Tvättbjörn" wrote me that this baby is an integrated circuit that will monitor the DC offset and cut off the relay in case it gets harmfully high! Thanks "Tvættbjørn".
Alright you primitive Screwheads, you got this?

Moving on to the transistors, this is where it gets technical. Match them if you want to though there are diverging opinions as to whether or not you will be able to tell. I matched mine since I was sent some spare ones, but since this is the FOR DUMMIES article I will not be telling you how to do this (actually I might just do that if anyone requests it!
The transistors characteristics vary with temperature and since the two positioned close to eachother are linked (like siamese twins, you know?) I believe the general consensus is to hold them together so that they will both have the same temperature during use.
One way of going about this is to put your (matched) transistors in place BUT NOT SOLDER THEM YET!!! Instead yank some heatshrink over the pair as I have done on the transistors to the right, shrink it and THEN solder the transistors in place.

You COULD end up with something looking as nice as this!

Now start populating the PCB with the low-profile capacitors (the red ones) before proceeding to the slightly higher ones as shown above.

This is where I had to stop for a few moments to figure out if I had made a MAJOR FUCKUP, since the green caps did not fit. Oh well, since there were nowhere left to put them I decided that probably the seller had found these caps to perform better than those originally intended and found it to be too much work to redo the PCB layout. In the end I just mounted them slightly skewed.

Here you see what you should now have left (apart from some mounting components), minus the little silver tube of thermal paste that does NOT come with this kit. I have taken the liberty to mount the black heatsinks already.

If you have some thermal paste now would be a good time to apply some to the transistors going onto the heatsinks. Thermal paste has a way of helping transfer heat so I thought that it would not hurt applying some. So should you (though probably not strictly necessary)

Now fasten the transistors to the heatsinks (you remember those heatsinks you soldered on some minutes ago?) with the small black screws and THEN solder them!

All there is left now is soldering on the last few remaining components and TAH-DAAH, you have (successfully) assembled your Panda Headamp.

Next will come the hard part of making a proper enclosure, getting the powersupply working and tuning it in, more on that later!

Of course you will want to get on with your project, so how to proceed after you have assembled your kit?
Well, in order to get a fully functional Panda Head Amp you will need a few more things...
1 x Toroidal transformer capable of outputting 2x18V with a rating of at least 50VA
2 x RCA sockets for your inputs
1 x Jack socket for your headphone out
1 x Fuse holder 5x20mm
1 x 1A fuse 5x20mm (actually having a couple spare fuses will not be a bad idea)
1 x Mains socket (with optional filter if you feel like being a "BIG SPENDA'")

Usually I just hook everything up with loose wires and have it lying all over the dining table, but recently I decided to try something else. I built myself a couple of panels for this kind of tasks holding inputs and outputs. since I figured that some day having everything loose would cause a short ruining a potentially expensive project. Also, it is quite a lot easier managing this way! Above is the Panda Amp connected and ready for the final adjustments...

First though, we have to make sure the toroid is right for the task, so I hooked it up. Please spare me your griefs about this being potentially lethal and just refrain from doing such a stupid hookup yourselves. In brief it is just a wire with a fuse holder attached in series and then hooked up to the toroid.

A toroid such as the one above will have two wires for the mains and 4 wires for the secondaries. The one I used had these specifications:
Primary side:
RED - 230V
BLUE - 0
Secondary side:
RED - 18V
Black - 0V
On the secondary side red and black are "paired" and Yellow and Orange is "paired".
The Panda Amp is designed for a toroid outputting 2x16V but since that is not standard 2x18V will do just fine.The nominal rating is under load, so idle measurements will be higher. Since the Panda Amp will series connect the secondary side "pairs" I have done the same by connecting the black and yellow wires.

SUCCES! Nothing blew up and I am left alive after turning on mains power to the toroid. Measurement says ~40V which is fine, so lets try juicing up the Panda Amp for the first time!

...and here we are, still no equipment has been connected as we have to trim the voltage across the "1k5" resistors as per the instructions found [sorry, the link I once provided stopped working, search google for the rockgrotto forums and find it in there somewhere]
As you can see I decided to go for 1,35V across the resistors.

After probing across the "1k5" resistors we will have to trim the DC offset, also as per the instructions [sorry, the link I once provided stopped working, search google for the rockgrotto forums and find it in there somewhere] I probed at the jack socket since it was easiest.

This is my measurement, I managed to get it a bit lower yet, but it was hard.
When you are satisfied, remove your probes and connect something to feed music to the amp and something to output it (preferrably something you will not miss too much if it blows up)!

Admitted, my phone was not the first thing hooked up to the amp, but all went well and I had sound, so on with the phone to get some more music!
Initial impressions are very promising, I will tell you that much!

All that remains now for you is get it all crammed into a nice box!