TDA1543 is a miniature and economic DAC which is the only vintage multibit DAC to use single-rail supply, make it simple to use in the portable circuit. It is stereo 16 bit DAC with popular I2s input format. The nominal voltage supply is 5 volt, but with the tolerance can be supply up to 9 volt maximum, makes this DAC can use passive IV with up to 1.5 K ohm resistor to generate undistorted high voltage line output. With this possibility, no wonder this IC never vanished from the DIY audio popularity.
From of my previous TDA1543 DAC project, unfortunately this DAC never sound good for me. I am so curious and never stop experimenting to make this DAC sound better. Finally, I can stay with this TDA1543 DAC with few points that need to be addressed.
In this post, I will share the steps that I have tried, which makes this TDA1543 sound good, having its own sound signature which can compete with others high performance DAC.
The TDA1543 DAC that I was built featured on my post here and the latest post is the improvement here.
Let's start from the first section is the digital input. I was using USB as the data input, deliver I2s data from PCM2706 module. This digital input section actually can be using various input option available such as SPDIF or optical input that goes to CS8412 or DIR9001 with the I2s data output (BCK, WS and Data) to TDA1543 input pin 1, 2, and 3 respectively.
What need to improve in this section?
Put 100 ohm up to 500 ohm series resistor between the I2s signal, it is in between digital receiver to TDA1543 input. This resistor act as digital filter that reduce the peak in the digital signal, make it smooth transient between 0 to 1.
In this TDA1543 DAC project, I was using 2x 18650 lithium batteries to supply various voltage (depends from the batteries capacity) from 7.4 volt to 8.2 volt. I thought when using the batteries, the voltage will clean enough for this DAC circuit, but instead, I should add C-L-C filter to improve it. They are 1000 uF - 47uH - 1000uF before goes to the circuit. This filter gives much cleaner voltage and effect to the sound quality.
For the IV resistor, I was using 1 K ohm to get the target output 2 volt. Although this number is match to standard CD output voltage, but in reality, the output from this DAC might feel very low, especially when connecting with long RCA cable. This is because the current output after this conversion is very weak. So, we need to put a buffer circuit to crank it up.
Before goes to the buffer circuit, remember to add film capacitor for -3 dB LPF circuit in parallel with IV resistor. The target LPF frequency is 22 kHz which translate to the capacitor value is about 6.8 nF. Eliminate this LPF will cause high frequency noises that many listener assume the music details.
The various buffer circuit can be use. It is basically an unity-gain using op-amp or discrete transistor such as B1 buffer designed by Nelson Pass. In this DAC, I was using 2 pcs NJM4556 in parallel to get more than 100 mA output per channel, similar to the O2 headphone amplifier schematic. It is enough to drive any headphone directly from its output.
Remember to put high quality coupling capacitors after IV resistor. TDA1543 output contain DC which harm to the speakers. I put 4.7 uF Elna Silmic just because its small size that can fit inside the case. If size not become an obstacle, large film capacitors will do and sound better.
If you like me, want to have this DAC to drive headphone directly at the output, then we need a volume control. This volume control is a potentiometer put in between the output to the buffer circuit. The potentiometer value is 10 K ohm, up to 50 K ohm. If the output function is only as the line output, we need to terminate the output with 100 k ohm resistor to ground to bleed the excessive voltage from the coupling capacitor when its off.
At these stages, I can truly understand on how well this TDA1543 DAC produce the musical sound. The sound that probably I wish to have many years ago, when I starting my DAC journey, build a DAC from this little but mighty DAC IC.
Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.
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