Parts selection.Ever sat in your living room watching a movie and thought to yourself, "I need more POWER"?
Well, I have, and to remedy that I decided to build an amplifier with power enough to make my ears bleed...
After doing some research I ended up with a Truepath kit from 41hz.com.
OK now, this is by no means a beginner's project, but yet I decided to go forth...
This project is divided into phases due to its complexity and is by no means meant to be a definitive guide, it is merely a description of how I did it...
This is the heart of the project and will be the grounds for most decisions taken from here on! Why did I decide on the Truepath? Well, I thought I needed a power efficient amplifier with enough power to drive my speakers at high volume and with plenty of headroom. The Truepath kit can be purchased from 41hz.com
In order to feed 5VDC and 10VDC to the Truepath I opted for the Tbrick solution from Audiophool as it is ideal for the Truepath. Also it has a speaker protection circuit.
For powering the amp I needed a big-ass toroid transformer able to handle the needs of the Truepath (or alternatively you could opt for an SMPS (switch mode power supply), but I will not deal with those here).
A capacity of 1000VA is recommended for the Truepath. This can be achieved in two ways... either you just buy one toroid of above specifications or you buy several smaller and connect them in parallel to achieve a sum of 1000VA or more. There are several things to consider here:
Several smaller toroids:
+ Could have a smaller footprint than a single large toroid.
+ Might be cheaper or more easily available
- Load balancing might be a problem if toroids are not identical
One big toroid:
+ Size and weight (bigger is better)
+ No load balancing problems
- May be harder to find
- Size and weight
Next thing to decide on is the voltage rating of the toroid. The Truepath can handle up to +/-60Vdc and this will get you the highest output. It will also give you the most stressed components and shortest-lived Truepath (this might actually not be a problem at all, but the higher the voltage, the hotter the components will run and heat will shorten the lifespan of your amp). The +/-60Vdc can be achieved with a toroid with 2x42Vac on the secondary side. To be a bit on the safe side I went for +/-50Vdc and that meant I would need a toroid with 2x35Vac on the secondary side.
As I chose to go for the Tbrick for the "household" voltages of 5Vdc and 10Vdc I would also need a supply of 2x12Vac and this left me with another choice. I could either have a transformer custom-wound to provide BOTH 2x35Vac and 2x12Vac or I could go with TWO toroids (one providing 2x35Vac and one providing 2x12Vac). I chose the custom-wound toroid! You can actually buy a toroid providing 2x35Vac and then add your own windings to provide 2x12Vac, but again, I shall not go into the details of that in this article.
I found a company called Toroidy - Transformatory Lachowski based in Poland and asked for a quote for a custom-wound toroid with the following specifications:
AUDIO GRADE TOROID
SEC: 2x 35V (max. current) & 2x 12V (1A)
"WHOA there!" you might think, "What is with that "audio grade" stuff?" Well, I was offered the option of ordering an "Audio Grade" version which was explained to me as being:
"In audio grade, noiseless transformer price You'll get transformer wound on high inductive, selected and measured core. Core and all the windings will be impregnated. Transformer will also has electric and electromagnetic shields, epoxy filled interior and mounting pads in price."
This sounded quite appealing to me, since shielding is quite welcome in audio applications, and also the epoxy-filling might reduce mechanical noise from the toroid. To make a long story short, I bought the damn thing!
A toroid the size of the one I decided on might cause problems if connected directly to mains power since inrush current might cause your relay to break (or blow a fuse). To remedy this I needed a softstart module, and since I was already making an order at 41hz.com I quickly decided to order their PSU1-SS. In addition to its softstart function it also features a mains filter which will remove noise. Quite ideal for the task so I bought it without further ado.
So, now we have an amp, we have a big-ass toroid just waiting to feed power to said amp, we have a softstart module allowing us too connect mains voltage without blowing fuses and we have the "household" voltages power supplies all figured out. We now need to actually transform the 2x35Vac from the toroid into the 2x50Vdc I decided the amp should be operating at. Enter the PSU1-PS from 41hz.com. This, like the softstart module, should also work like a charm with the Truepath so I added that to my basket
CasingYep, that is right, no pictures for the base case since there will be plenty of pictures of the case later...
This is one important aspect since you need to have enought space for everything to go inside, but also you will not be wanting a gargantuan goliath of a case that will not fit into your rack. Finding a suited case can prove difficult, but I found an online shop for an italian company and ordered the 1NPS03PN from modushop.biz.
Behind those numbers hide a case from the "Pesante" series, 120mm high inside, 300mm deep and with a black 10mm aluminum front. I found this case to be a good compromise between looks and cost. Also, the Pesante has holes for mounting an IEC mains socket and 5x20 fuse holder already in the backplate!
IEC mains socket
I was lucky on this one as the softstart module already features filtering I would not need a mains socket with filtering and so I chose a very basic one, quite suitable to my needs that would fit nicely in the casings pre-cut hole.
Fuse holder (and fuse)
This is just a basic fuse holder that will fit the hole in the back of the case. It accepts 20x5mm fuses and please remember to buy those also, otherwise you will have to troubleshoot why nothing happens when you turn your amp on later! The fuse should be able to handle the maximum operating current of your finished amp!
Yeah, this is actually also a thing to consider... A lot of cool switches can be found, but remember that it must be specified to run 250Vac and must also be able to handle the current you will draw! I found this one which has several advantages, it is 250Vac, 10A capable and it is mounted in a circular hole. "Why is that important?" you might ask. Well, because I will be doing this project without the help of external workshops and since I will be working with limited machines at my disposal, drilling a hole is much easier than grinding a square hole with my multitool.
This is where music goes in... I could have opted for some cheap-ass rca sockets from eBay, but instead I decided to go for some brand ones from Neutrik (though the ones from eBay which can be had for a faction of the price will most likely have done the job just as good).
Speaker terminals (binding posts)
...and this is where music comes out (if I do not screw something up). These are in fact some cheap ones bought off of eBay and they did not cost me much, but they should get the job done just as fine as brand name terminals. The picture is not of the actual terminals I used, but they are quite similar. It should be noted that the more massive terminals you choose the harder it will be for you to solder your cables to the terminals since you will have quite a lot of metal to dissipate your soldering irons heat!