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Class D Switching Power Amplifiers and Power D/A conversion

Full digital amplifier with chip STA326
Full digital amplifier with chip STA326
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Old 10th December 2018, 05:01 PM   #371
cacio is offline cacio
diyAudio Member
Join Date: Oct 2018
Originally Posted by Nanoloop View Post
After some experimenting, I found for sure the YJ does not have a tone or normal setting.

I tried 3 different psu's - AMB Sigma11 32V 4.5A, LT1083 30V 4A, and a cheap smps brick 24V 5A. They made no difference to the background noise level with signal lock - on 96dB/W Klipsch, the noise vanishes around 30-40cm from the speaker. They do make a direct change to noise level with no signal lock on the YJ 2.1 that does not have auto mute. Similarly, gut punching bass is more gut punchy with the AMB so the main voltage supply benefits from lower impedance. Finally, it seems the 2.1 is more sensitive to its power supply than the 2.0. The AMB is definitely the best partner for the 2.1.

I also tested the roll off created by the 2.1 crossover filter. As per the datasheet, the sub channel seems to have a decent 12dB filter which can be set by one button on the remote - every press is 20Hz higher until 360Hz goes back down to 80Hz.

The satellite channels also have a filter that becomes noticeable at around 200Hz and becomes more significant around 100Hz. This is with the filter set to 80Hz into 4 ohm speakers. I assume this behaviour is because the output of the SE channels goes to ground through a 220uF cap and that forms a filter with a pole at 180Hz and 4 ohms.

Unfortunately, the speakers are more efficient than the sub so the sound is a little too bass light. I will need to set this up when I finalise the speakers I will use with this amp.

I still have more mod plans for the YJ 2.1 - it works well with a Bluetooth APTX-HD spdif source so I will fit one inside the case and dump all the usb stuff which I won't ever use on this amp. Removing the tcxo and PCM270x will reduce current demand to accommodate the CSR8675 so that shouldn't create any issues at all and I can feed the CSR's spdif into the appropriate big blue cap. Piece of cake. :-)
have you succeeded with the Bluetooth mod ?
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Old 21st April 2019, 07:43 AM   #372
SEB120A is offline SEB120A  United States
diyAudio Member
Join Date: Apr 2019
I've been searching but haven't found if anyone has replaced the 3 main power capacitors in the FX audio D802, has anyone found a suitable replacement more like 50v or something?
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