In this article I cover my existing home audio equipment, what parts I want to replace in the near future and how I eventually settled for the HiFimeDIY T1, a DIY class-D power amplifier kit.
Recently I was in pursuit of a power amplifier for my home audio system. I already had an ancient NEC A230E from the 1970-something. The thing is huge, smells of old dust when it runs and doesn't have any connectors for the speakers. Instead the bare speaker cables are inserted into funny looking connectors that are twisted to clamp the wire in place. See the picture below. To make it easier to clean behind my TV desk I want all connectors to be detachable if possible.
I also wanted something smaller and simpler. I am a fan of buying technology in parts and assembling them into the system I want, as opposed to buying an integrated solution. That way I can get the best parts, for my current definition of best, and when I want to change some part I don't have to throw away the rest of the system. The flipside is of course that I have to research and understand every part, but I usually don't see that as a drawback.
I don't consider myself to have "gold plated ears" and I don't have grandiose thoughts about myself to use fancy words like soundstage or high-frequency roll-off. I am more sensitive to awful sounding audio than most people I know in person though. The things I've seen in PA systems during the years as a social dance course and event organiser would give an audiophile nightmares. Pre-amp gain turned up to 11, line level devices connected to phono inputs and VU meters blinking red on every beat of the music... next to an oblivious audio technician.
In short: If it sounds well I am happy. If it sounds poorly I get grumpy quickly.
In the past five years or so a couple of class-D amplifier designs (see wikipedia) have become very popular. The most well known is probably the Lepai LP-2020 (A) which is based on integrated circuits by Tripath. This is a very cheap amplifier that has received mixed reviews. It is rated at 20 W / channel RMS, but that's with 4 Ω speakers and at 10 % THD. At 10 % THD a sine wave input looks basically like a square wave on the output and does not sound very harmonic at all. With 8 Ω speakers the amplifier can output about 5 W / channel at a more reasonable maximum 0.1 % THD (see references in the end of the article). 5 W per channel is probably enough for a living room setup, but I wanted some margin if I ever want to use the speakers somewhere else. People on the internet have also noted inconsistent build quality and amplifiers failing prematurely. So no Lepai for me.
I don't remember where I first read about HiFimeDIY and their Tripath based amps, but from what I've read they are very good and have excellent value for their price. ValueHifi.net has some information on their amplifiers and also build instructions and videos. If you want to buy a HiFimeDIY amp you might want to consider using his affiliate links. I intended to but then I, ah, forgot (sorry).
Their bare-bones amplifier boards can be found in the DIY section. T1 is their basic model that can drive a maximum of 100 W / channel into 8 Ω. T2, T3 and T4 are variations on the same design but with higher output capabilities. Some are optimised for 4 Ω (requiring higher current) and some for 8 Ω speakers (requiring higher voltage). There is also a lower power rated T1-M model which is half the price of the T1. However, it also sacrifices some of the nice features that the T1 has, like a fancy (ridiculously expensive) ALPS volume potentiometer as well as output relays protecting the speakers from pops during power on/off.
As DIY kits you get to complete them with a case, power supply and various connectors. I've never designed a case for an electronics project this big before so I figure this will make a nice exercise project.
A major selling point for me was that HiFimeDIY give away the schematics for all their amplifiers for free. As an open-source geek, this very much appeals to me. They also maintain stock in Europe (among other places) which makes shipping very convenient and quick.
In the end, I went for the T1. In the next article I'll cover initial testing of the amplifier and later I'll describe how I made a case for it.