|Sure TA2024 Tripath, A first look|
The Sure Tripath amplifiers offer a Tripath 2024 chip Class T amplifier for $22 plus shipping from Najing, Jiangsu, China. So what do you get for roughly £15 of amp?
i have to admit at this point that i did not buy this amplifier on a whim. I was alerted to it by a forum on www.DiyAudio.com. The forum there has a section dedicated to T class amplifiers.
For those unfamiliar with T class amplifiers, let me introduce them. "T class" is a little nit of a mis-nomer. Really what we are talking about is a D class amplifier. The D stands for digital and describes the method that the amplifier generates its sound.
"T" class amplifiers are so called, because they use an IC made by a now out of business company named Tripath.
The most famous of the Tripath based amplifiers has to be the Sonic Impact T-Amp. These little battery powered amplifiers created a storm. Made of plastic, and cheap components, they retailed at $39. Why the storm then. Well they started to get a name for themselves in quality HiFi Circles as a giant killer. As reviewers started to get hold of them and test them out against expensive gear, it turned out that this novelty product could turn the ear of many a jaded reviewer. TNT Audio reviewed them in an article in January 05 which is well worth a look. Soon, many DIYers were snapping up these stereo amps and turning hot soldering irons to them with glee!
Various companies took advantage of the T-amp phenomenon and started producing their own upgraded versions, based on the Tripath 2024 Chip or it's siblings. In the links section here there are a few of the suppliers.
Despite the demise of the Tripath company in February, 2007, plenty of the Tripath chips are still in circulation and several companies make DIY kits. Sure Electronics are one of them.
Based in China, Sure retail their Tripath 2024 based amplifier kit for $22 plus shipping. That is one cheap amplifier. Not only that Sure are pretty genererous with the packager they supply. Lets have a look at the package.
The Sure amplifiers arrived in a cardboard box alongside some of the other parts I had ordered. Sure supply SMPS power supplies as well as loose components. China is mega cheap right now, so I purchased a few other bits and pieces that I thought I might need for this and other projects. Opening the box each amp was packaged in a polystyrene box and thick plastic bag.
You can see the catchy product title that Sure electroincs opted for!
Well marketing departments swallow money, so perhaps its for the best that they did not go to town on the packaging and corporate image. The product number, sequence number and packaging date (in US format) are printed neatly.
Its worth noting that there has been at least two revisions of the amplifier. Between revisions even some of the resistor values differ. I saw variations amongst the 5 units I purchased.
Opening up the package, you are greeted with more than just the board. The contents included give you most of the cabling that you need to get a Tripath 2024 power amplifier up and running
You can see here the contents of the package:
Really a lot more than you have the right to expect. The extras lets face it are not Audiophile quality accessories. But they are of sufficient quality for testing purposes.
Missing from the bundle, and I would be cheeky to complain, are the mechanical fixing to mount the boards, a 12v DC power supply and possible a volume pot. But lets not quibble.
Taking a closer look at the board initial impressions are good. I have always been a fan of black solder mask, particularly as the white silkscreen is very easy to read.
The board has multiple inputs including:
That really is a lot of inputs, making the mounting of this amplifier in your project as flexible as it could possibly be. Clearly quite a bit of thought has gone into the design of this amplifier. The binding post holes for the output are a gift to the DIY tinkerer, allowing you to try out various modifications to the amplifier.
With the DIYer clearly in mind, Sure also supply a digital manual which can be downloaded from their site. Asides from giving the expected connection diagrams, Sure also supply a schematic of the amplifier as well. This matches the screen print on the board itself, making it easy to identify parts you may wish to swap or alter. Sure really are friendly to the DIYer.
Downsides to the package? Well if I am going to be picky, the construction quality is a little inconsistent. I had 5 boards, all of them had flux residue on the boards.
It is not really a big deal to clean this up, the main residue is around the chip itself.
There was also a few crookedly soldered in resistors on my amps.
Lastly I noticed that on some of the boards, 20k resistors were used in some places and 22k on others. It was almost as if they had run short of the 22k (the value on the schematic) and used the next value.
Time to test out these amplifiers. For testing purposes, I used a meanwhile 12v SMPS power supply also bought from Sure at a more than reasonable price. Wiring was very easy. However before getting started, I attached a high power 10ohm resistor to the amps output to test for DC offset.
This was not me being a super careful individual. I had read on the DIY forums that these Sure amplifiers were a little random in the DC offset that they put out. The design that Sure has opted for appears to have designed in some extra circuitry in an attempt to eliminate DC offset.
It most definitely has not worked! Members of forums are reporting high DC offsets. I wanted to test my amps before attaching speakers to them.
This proved to be a wise precaution. The DC offsets that I measured are in some cases on the very high side for an amplifier.
The greatest I measured was a whopping -1267mv. That's more than a full volt of DC, enough to park the speaker cones noticeably aware from their natural resting point.
Fortunately, as well as expecting their to be a high DC offset on the amplifier, I was also aware that there was a relatively easy solution to the offset issue. I will cover this modification in a separate article.
The variation of DC voltages can be seen in this Table. It would appear that pot luck dictates the offset you get. One of my sample measured very low DC offset, though most had very high.
i have built several Gain-clone amplifiers, and always have achieved DC offsets of less than 50mv. DC offset means that the coils of your speakers are always passing current and subsequently converting that current to heat. Probably the values we are talking here are not high enough to cause damage, but it seems sloppy that the results are so inconsistent between boards.
Getting past this, I couldn't resist my first listen!
Plugging in my Mission 760i speakers (I like them for testing purposes) and using my laptop as a source. I powered up the amp. The initial movement of the speaker cone gave a visual indication of the DC offset. The amp however started with very little power up noise. A faint click from the speakers was all that could be heard. No hum or other unpleasantness could be heard.
I then tried them with some music. I was in a REM mood, well not really, it was the first disk that came to hand. Automatic for the People has some nice tracks.
Initial impressions were favourable, though not enough to dance about in the streets over. The imaging was clear, even though I did not have my baby speakers mounted in an optimum position. Mid tones were clear and had good presence. Bass tones are punchy in the mid range, though I have heard the Mission 760i speakers give out deeper bass than I was hearing.
On the negative side, the top end is a little rolled off and soft with these amplifiers. Again, thanks to pioneers on DIYAudio, there is already solutions available to the high end roll off of the Sure amplifier board. I will detail these modifications as I get the articles written up. I'll give a hint though, there is more goodness to be unlocked from this amplifier, with some very simple modifications.