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Class D Switching Power Amplifiers and Power D/A conversion

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Old 4th April 2014, 01:50 AM   #21
mikey_audiogeek is offline mikey_audiogeek  New Zealand
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Cool!

Yes, I have PurePath Console (PPC) GUI, I also have the PurePath Console Motherboard (as well as the TAS5548EVM).

Don't know if it helps, but the TI "Soundbar Reference Design" EVM includes code for the onboard MSP430 to load parameters/biquads as well as read RC5 IR and handle volume control, source switching etc. link here: PCM3070RHBEVM-K Evaluation Module - PCM3070RHBEVM-K - TI Tool Folder

Cheers,
Mike
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Old 4th April 2014, 01:54 AM   #22
mikey_audiogeek is offline mikey_audiogeek  New Zealand
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Discussion here: TAS5548EVM - device configuration on powerdown/powerup - Audio Amplifiers Forum - Audio Amplifiers - TI E2E Community

Cheers,
Mike
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Old 8th April 2014, 02:51 AM   #23
panson_hk is offline panson_hk  Hong Kong
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Default With miniDSP USBStreamer

Here is my PurePath digital amp with miniDSP USBStreamer.
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File Type: jpg TAS5548_5612 and USBStreamer.jpg (934.3 KB, 482 views)
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Old 9th April 2014, 01:01 AM   #24
mikey_audiogeek is offline mikey_audiogeek  New Zealand
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Nice!
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Old 9th April 2014, 07:15 AM   #25
panson_hk is offline panson_hk  Hong Kong
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Here are measured waveforms of the digital amp. The amp is powered by a regular 12 V SMPS. A 1 kHz of 2 Vrms was driving a 4 R load (USB to I2S done by USBStreamer). The output was connected to AP Portable One. THD+N was about 0.1 % (BW = 22 Hz to 22 kHz). Distortion residual is shown in the left picture below. Right picture shows 100 Hz distortion residual (THD = 0.022 %).

I will use AP-S1 to send digital signal to the board and get more data later including FFT of the output.
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File Type: png TAS5548_5612_12V_1kHz_1W_4R.png (42.6 KB, 401 views)
File Type: png TAS5548_5612_12V_100Hz_1W_4R.png (47.0 KB, 359 views)

Last edited by panson_hk; 9th April 2014 at 07:41 AM.
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Old 11th April 2014, 03:51 AM   #26
panson_hk is offline panson_hk  Hong Kong
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Default distortion residual

Distortion residual of two different output inductors are shown below. The inductors are Wurth high-current shielded SMD parts. For 22 uH, THD is 0.13% (1 W, 4 Ohm). For 10 uH, THD is 0.097 %. THD difference is not much at all. Distortion residual does show different shapes.

Left photo: 10 uH, middle photo: 22 uH
Filter capacitors: C80 = 2.2 uF (film), C82 and C83 = 1000 pF
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File Type: png TAS5548_5612_12V_1kHz_1W_4R_10uH_2p2uF.png (27.8 KB, 342 views)
File Type: png TAS5548_5612_12V_1kHz_1W_4R_22uH_2p2uF.png (28.7 KB, 331 views)
File Type: jpg output filter.jpg (24.3 KB, 105 views)
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Old 11th April 2014, 05:23 AM   #27
panson_hk is offline panson_hk  Hong Kong
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If C80 is 1 uF with 10 uH inductors, THD is improved to 0.083 %. Interesting!
Distortion residual is shown below.
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File Type: png TAS5548_5612_12V_1kHz_1W_4R_10uH_1uF.png (31.9 KB, 99 views)
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Old 11th April 2014, 05:51 AM   #28
abraxalito is offline abraxalito  United Kingdom
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1uF is providing less attenuation of the carrier frequency, but equally means lower HF output current is drawn so I guess less stress on the output stage of the chip. A lower value cap might produce even lower THD... Try 220n?
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Old 11th April 2014, 07:15 AM   #29
panson_hk is offline panson_hk  Hong Kong
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Yes, I will try lower capacitance.

Here is measured data just now. THD = 0.075 % for using two 22 uH in parallel for each output polarity. The cap is still 1 uF.

THD residual is shown below.
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File Type: png TAS5548_5612_12V_1kHz_1W_4R_22uHx2_1uF.png (27.5 KB, 50 views)
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Old 15th April 2014, 09:18 AM   #30
mikey_audiogeek is offline mikey_audiogeek  New Zealand
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I'm running no output filter on my Purepath class D amps

The circuit board arrived today - thanks!

Cheers,
Mike
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