GIC LPF Schematic & TDA1541 USB DAC Updates

My first trial using the GIC LPF is on this TDA1541 USB DAC. The result is surprisingly amazing. You might check the post here for the detail review of this DAC.

I guess it is already few month passes since the built and this TDA1541 USB DAC is still "naked". Not even I think to put it inside a casing. I using this DAC in my test bench, to testing others audio components and I guess this is the time to find a casing for it.

First of all, I don't want fancy aluminum casing. They are expensive. So I take the unused steel box that, a little bit rusty. It is need some cleaning and painting, but at the end it is a nice casing compare if not using any casing at all.

Please continue read this post. At the end of this post, I will share the GIC LPF schematic that I implemented in this TDA1541 USB DAC.

This steel casing dimension is small, only fit to those 2 board which is arranged tightly inside it.

The IEC power socket cannot be fit inside the casing if I am using the six capacitors filters like on my initial build. So I should rearrange the power supply board more minimalistic.

My approach for this power supply board is now only using 2 pieces 1000uF Nichicon Muse. It is should be enough to filtering the DC ripple from the diodes.

I also build another negative 15 volt regulator circuit to separate the digital supply from analog supply which previously shared together.

This power supply board is now finished, then I connecting the power cables from this board to the DAC board.

Unlike the aluminum casing, this steel casing is not rigid. It easily flex and this is should be taken care by adding an isolator on the bottom of the casing to prevent any electrical shortcut.

They fit perfectly inside.

At this point, I make sure this DAC working properly by testing it for a while.

I also testing several op-amps combination to find what I am preferable to the sound quality.

The last step is only put the USB input.

I using USB-A female connector and put it at the front casing. The cables to connect from this USB DAC to source is USB-A to USB-A cable.

The internal connection from PCM2706 board is point-to-point wiring to the USB-A female connector, but without the positive USB power connected. By this approach, I will not worried the USB DAC give the power to the source connected or charge the battery of the source via this USB connection, which might draw additional current and load to the DAC regulators.

Some of you might be wondering about the detail of my GIC LPF schematic. It is came after I compare few articles and paper works such as from:

1. Active low-pass filter design by Jim Karki, September 2002 published by Texas Instrument.

2. GIC based third-order active low pass filter by Nino Stojković, Dražen Jurišić and Neven Mijat.

3. Datasheet PCM1704, PCM63 and others

So here it is.

The schematic above is divided by 3 stages.

The components use here are 1K, 2K2 ohm resistors and 2,2 nF capacitors.

The dual op-amps is NE5532 use 2 pieces per channel

Power supply are dual rail regulated 15 volt.

The cutting frequency in this GIC LPF schematic is approximately third-order 48kHz.

Hope you enjoy this post. Cheers.

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