The Sure Electronics Tripath TA2024 Board is out of the box a good value for money amplifier module. However with some careful tweaking it can be made to sound better. This article focuses on the power supply to the Tripath chip and shows some improvements that can be made.
Hobbiests that enjoy the sound from Class-D amplifiers tend to favour the sound from SMPS power supplies, though some still extol the virtues of using well filtered traditional transformers. I have not trried both out yet, but chose to go the SMPS route as many were happy with the sound.
In my case I am using a Mean Well S-350-12 SMPS Power supply. This outputs 12v with a potential 29A available. I bought it as I am going to be running 5 amplifier modules simultaneously in my project amplifier. I did not wish to run out of power, and as price wise this and the next size down were not worlds apart price wise I went for the higher powered option.
The Mean Well S-350-12 SMPS power supply comes in an aluminium enclosure. The connections are placed at one end. Rather confusingly two sets of outputs are available. One set labelled +V and the other –V. The –V is on fact the ground line from the power supply. It would appear to be isolated from Earth.
The Mean Well power supply has a voltage adjustment variable resistor that the manufacturer specs will give +/-1.2V adjustment to the 12 volt line. In reality, I am measuring 14.2 volts at the output when the voltage adjustment trimmer is adjusted to the maximum it will go.
On the Tripath TA2024 Datasheet, Tripath recommend 12 volts as being the typical power supply value, a minimum of 8.5 volts and a maximum supply voltage as 13.2 volts. They do specify an absolute maximum of 16 volts is what the chip has been designed to withstand. However over on the forums at DIYAudio.com Bongoman reported that he was running the Sure module using 16 volts from a laptop power supply without disaster and better still he reported some improvements in the sound. Others have also reported sound improvements with Tripath TA2024 based amplifiers when ran on higher voltages.
Now the trouble with using a diode to protect from reversed voltage is that the diode itself drops the voltage slightly as it passes through. Measuring with the multi meter, 14.2 volts drops to 13.9 volts after the diode. I.e. The voltage drop of the diode is 0.3 volts.
Removing the diode therefore and bridging the pads gives another 0.3 volts of headroom in the power supply stage. As I was limited to the maximum headroom of my power supply, I considered this a worthwhile modification to try. It’s a relatively easy modification to the Sure boards. Diode D1 is located at the top left of the board next to the power supply entry points. First of all I removed it using my KADA 852D Smt solder station. I used the hot air gun to heat the component up. With a pair of bent nose tweezers, I gripped the diode and gently twisted it sideways until it became loose and could be picked up off of the board. Once clear I left the heat on the pads for a second or two to allow the solder to flatten to the pads.
Next I used three pins to bridge the gap. These I held in place with the tip of my soldering iron and applied fresh solder to. The solder quickly flowed to cover the pins and melt to the pads. Hey presto a bridge is made.
A note of caution to anyone attempting to bridge the diode. Underneath D1 there is a trace that carries the ground. It is covered in solder mask, but the solder mask is reasonably delicate. Make sure you don’t scratch the mask as you solder, otherwise the solder bridge will create a short circuit. I did this on one of my boards, It was not a hard thing to repair, but worth watching out for. Always check with your multi meter that no short has occurred.
With the diode removed, I was able to use more of the available voltage from my power supply. Listening to the amplifier board, changing the supply voltage from 9.38 volts through to 14.2 volts made a perceptible change to the tone of the amplifier. It’s not a world shattering difference that is made, but it is perceptible. The area where I noticed it most was in low down drum kicks. The drums had more oomph when the amplifier was being supplied the higher voltages.
With more voltage available to the Tripath TA2024 chip, my next set of modifications was to add some more capacitance to the voltage rails. Again this modification was suggested on DIYAudio. Looking again the Tripath Datasheet, Tripath suggest that some capacitance is required on the voltage rails. This is to act to supply transient demands for voltage and to filter out high frequency noise from the power lines. As far as capacitors, Tripath suggest
“ These components must be located as close to the device as possible to minimize supply overshoot and maximize device reliability. Both the high frequency bypassing (0.1uF) and bulk capacitor (180uF) should have good high frequency performance including low ESR and low ESL. Panasonic HFQ or FC capacitors are ideal for the bulk capacitor.”
Sure themselves have supplied 300uf of bulk capacitors on the outside edges of the Tripath TA2024 amplifier module in what looks like surface mount electrolytic (or perhaps solid) capacitors in banks of 3 100uf devices (C26, C27, C28 for the left channel, C29, C30, C31 for the right channel). In addition to this, closer to the chips VDD1 and VDD2 pins there is a 0.1uf ceramic capacitors (C10 and C18) and 22uf capacitors (C9 and C19). At first glance then Sure have exceeded Tripath’s recommendations for the Tripath TA2024 chip.
Others though have reported improvements by supplying in excess of this and I wanted to give it a try. I bought a bundle of Nichicon HZ Capacitors for this purpose. The Nichicon HZ capacitor has a reputation amongst PC motherboard modifiers as being a high quality capacitor and looking at the datasheet it has ultra low ESR and ESL. Pretty much what Tripath are asking for in their datasheet. The Value I opted for was 1500uf and 16v rated voltage. My choice was based on availability and others suggestions as to good values to use. If anything is going to work, my thinking is that this is the capacitor to use. Another advantage is that it is reasonably small in size so be able to fit onto this small PCB.
I ordered quite a few of the capacitors as I plan to try them on my DDAC as well I tend to buy in bulk when I can justify it. Besides I wanted to use 3000uf on both the VDD1 and the VDD2 rails. For 5 boards this was going to use 20 Nichicon HZ capacitors.
When I looked at how I was going to mount the capacitors, several options were available. However I wanted to keep the profile of the boards pretty low. I want to keep my options for layout open in the eventual 10 channel amplifier design. I also decided to keep the capacitors that Sure had provided on the board. They will do no harm and together with the Nichicon HZ capacitors will bring my rail capacitance to 3322.1uf
The first pair of capacitors that I fitted I decided to stack on top of the three 100uf cans at the edges of the sure board. This was a simple fit. To begin with I added 11mm of heat shrink insulation to the legs of the capacitors. This was to prevent the legs shorting against the un-insulated metal case of the 100uf capacitor banks on the edge of the Sure Electronics Tripath TA2024 board.
Next step was to bend the legs down and then back under the capacitor. After this I trimmed the ends and placed the Nichicon HZ capacitor on the bank of 100uf can capacitors. Sure Electronics have thoughtfully left a substantial solder pad to attach the legs of the Nichicon HZ capacitor to. The size of the Nichicon HZ cap is perfect for this position, narrow enough not to exceed the existing height of the board.
For the second pair of Nichicon HZ capacitors took a little more planning to fit. The position that I eventually chose for them was in the gap between the Tripath TA2024 and the Capacitor banks on the edges of the Sure Electronics boards. I have seen others add capacitors which stacked on top of the Tripath TA2024 chip itself and soldered to capacitors C9 and C19 on the board. I did not wish to do this because running the chip at higher than its recommended voltage; I wish to add a small heat sink to the top of the Tripath TA2024.
Scanning the Sure Electronics Schematic, I found several possible power ground points that I could attach to. Most convenient was on the outside edges of the diodes marked D2 and D5. For the positive legs of the Nichicon HZ capacitors I chose to attach them to the 22uf capacitors marked C9 and C19. This is near to the VDD1 and VDD2 inputs.
This meant again adding some heat shrink insulation to the legs of the Nichicon HZ Capacitors as the positive lead was going to be routed close to the ceramic capacitors C10 and C18 and would have shorted the power line to ground. Then I bent the legs to shape and soldered them to the end caps of the diodes and capacitors. I tested everything with my multi meter both to ensure that the Nichicon HZ capacitors had a good electrical connection to their respective power and ground lines and also to ensure that I had not created any shorts inadvertently.
All in place and looking good both to the eye and on the multi meter, I fired up some amp units. I compared three. The first was stock as far as extra capacitance was concerned, the second had one set of 1500uf Nichicon HZ capacitors on each of the power rails and the third had both pairs of Nichicon HZ’s fitted.
Listening to the Sure Electronics TA2024 modules I was to begin with a little disappointed by this modification. I was expecting to hear, based on other hobbyists’ reports an improvement on the bottom end of the sound. I did a fair bit of listening to several different tracks. I have to say that differences that this modification made were subtle in this configuration.
I tested on my old Mission 760i speakers initially and then later on my Mission 753s. On the Mission 760i speakers the difference was as near as undetectable as could be. Certainly I would be pushing it to say that any positive improvements had been made. On the other hand, the addition of the Nichicon HZ capacitors had not had a detrimental effect on the sound either. My Girlfriend could detect no difference at all.
Moving on to my modified Mission 753 speakers I listened again. Theoretically with a wider frequency range the Mission 753s ought to make any differences easier to discern. Again the differences were subtle. I thought I could hear some slight improvement though.
Playing the wonderful Renauld Garcia Fons’s Berimbus album, with its double bass and drums I could here some very small improvement to the bottom end. It was slightly more solid sounding. Other tracks I played in the Rock and folk genres it was less noticeable. In general, I would not get too excited by the difference that this modification has made.
Thinking around this I was puzzled. Why were some people on the DIYAudio forums reporting differences in sound when extra capacitance was added? I decided that one reason may be the power supply units that were being used. I decided to investigate the Mean Well S-350-12 power supply. This beefy SMPS is easy to open. The lid is held on with 6 screws.
Looking in I was interested in the output stage. Here I discovered 3 large CapXon capacitors, each 3300uf/16v. So perhaps this is where the answer lies. With 9900uf of capacitance on the lines already, it is perhaps the case that me adding another 6000uf is not going to make much difference.
On the other hand, the addition of additional capacitors to the Sure Electronics TA2024 based board for me at least has not made much difference. So you would expect perhaps that I would spare the rest of my Nichicon HZ capacitors for other projects? Well no. I have installed the Nichicon HZ capacitors in all but one of my Tripath TA2024 based boards. I intend running several of these boards on the same power supply and as such will be taxing the 9900uf of capacitance present a bit more than when playing just one module. I think that having the extra capacitance cannot have any detrimental effect and may help overall.
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