DIY TDA1541 USB DAC With GIC Filter

My previous post is the explanation about General Impedance Converter (GIC) filter which have been long forgotten. This could be, first it is because more complicated design compare to common low pass filter and second, the digital oversampling already took the job for smoothing the audible frequency range and it doesn't require too much filter slope at the output anymore.

But I really want to implement this GIC filter on my DAC built. I want to experience the result by my own. So in this post, I will make another DAC. This is the same TDA1541 non-oversampling DAC using PCM2706 as USB input to I2S converter. Then the analog output would be the GIC filter.

This build schematic will be the same just like my previous TDA1541 USB DAC here and here but at that time the analog is the unity gain Sallen-key filter and this new build will be using the GIC filter. They both will be compare directly.

Although the schematic is all the same, but in this new build, I change few components based on what I already had.

The transformer is taken from vintage Sonic Frontier DAC. This high quality transformer is around 30VA and it covered with metal shield to reduce the transformer interference.

I also improved the filtering capacitors, right now is add more capacitance by total 6 x 2.200uF using Nichicon VZ.

This power supply components are put into one single board and connected by point-to-point.

The next board would be the DAC module. This including the power supply regulator using 2 pair of LM317 and LM337. Both polarity output from regulators are connect in series. The first regulator will set to 15 volt to supply the op-amps and the second regulator will be set to 5 volt to supply the DAC IC.

The filter capacitors for this voltage regulator is now using Panasonic FC. The capacitors value are all 220uF and they put on every input and output of the regulators.

Then it comes to the main DAC circuit.

The PCM2706 is a tiny module, really suitable for this simple non-oversampling DAC like this.

The next components after the PCM2706 is the TDA1541 DAC IC.

I have explained how to connect from this PCM1706 USB to I2S module to this TDA1541 before. Those connection are the same when using the TDA1543 DAC IC because they have the same input mode.

The TDA1541 decoupling capacitors for dynamic element matching is all matching 100nF MKP capacitor.

Now comes to the analog stage which is now using the GIC filter circuit. The schematic I use here is taken from PCM1704 datasheet recommendation which originated has the frequency cutting point at 40 kHz. I made slightly different approach by changing the value of the resistors and capacitors to get higher cutting point.

This is my first time designing this circuit in the point-to-point connection, quite difficult but very excited at the same time.

This DAC is all finished. I only need to connect this DAC circuit to the power supply module.

This TDA1541 USB DAC will be test in this condition, without put inside the casing. This is a test board which initially not intended for fully build DAC unit.

So how is this TDA1541 USB DAC with GIC filter sounds like?

TDA1541 DAC will never sound this good.

The difference only at the analog output which is now using the GIC filter, but the sound quality difference with my previous built DAC is huge.

TDA1541 DAC sound great on mid-range. Everyone know it well. The non-oversampling TDA1541 will suffer from detail and larger sound-stage, and this is naturally from the non-oversampling DAC circuit.

But with this GIC filter, those weakness are all vanished.

Again, this TDA1541 non-oversampling DAC will never sound this good. It is very smooth sounding DAC. The layering of the sound, the depth, the sound stage is all open and wide. Especially the detail and micro detail is all pronounce very clear without over-shoot. The sound is very natural and musical without compromised.

I really think this GIC filter very suitable for this non-oversampling DAC circuit. I just spent some time learning this method but when hear the sound quality result, I think I will recommend this GIC design to everyone.

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