This Sanwu HF183 board has attracted my attention because it offers both Bluetooth and remote control at a good price. The sound quality is pretty decent, but the gain is too high, so I decided to mod it, without much success.
Seeing there isn't much information online about this board, and having already removed the heatsink to mod the board, I decided to take some detailed photos of the board circuit for future visitors' reference. (R27 was originally an 100K ohm)
This board came pre-assembled with the heatsink, which was glued with a rubbery substance and very difficult to remove. Once the heatsink was removed, I noticed R28 was a 39K resistor, and assumed it was configured with 32db gain. I am pretty new to modding, so couldn't quite figure out which resistor to remove to drop it to 20db gain. I ended up removing R27 (100K ohm), but that didn't work for me. That's where I stand as of now. 😕
Seeing there isn't much information online about this board, and having already removed the heatsink to mod the board, I decided to take some detailed photos of the board circuit for future visitors' reference. (R27 was originally an 100K ohm)
This board came pre-assembled with the heatsink, which was glued with a rubbery substance and very difficult to remove. Once the heatsink was removed, I noticed R28 was a 39K resistor, and assumed it was configured with 32db gain. I am pretty new to modding, so couldn't quite figure out which resistor to remove to drop it to 20db gain. I ended up removing R27 (100K ohm), but that didn't work for me. That's where I stand as of now. 😕
Attachments
Sorry I haven't had a chance to clean up the board yet. The wire interconnect plugs came in, so I was busy making wire connectors which allowed me to easily swap out amp boards for testing and compare. After proper comparison, looks like the mod of removing R27 did reduce the gain by about 8~10db.
The mod however also introduced a louder pop sound when I initially connect the power supply, so I am looking into that now.
The mod however also introduced a louder pop sound when I initially connect the power supply, so I am looking into that now.
btw, for anybody who has this board and wants to mod it, it was very difficult removing the heatsink, and I dislodged C20 while doing so, which took me hours to solder back on (partially due to lack of skill). I think it might be possible to remove R27 without taking off the heatsink.
Vinegar is acetic acid, a relatively weak acid. But incompatibility of acid with metals e.g. iron and copper is known (induce corrosion). I would avoid touching a PCB filled with components with acid. May be try other solvents first.
Regards,
Regards,
I cleaned up the board as much as I could, and here are the new pictures.
I also noticed the circuit looks the same as:
Reducing the gain is supposed to reduce any start-up pop noise, so the increased pop noise in my mod could be due to me messing up the board in the modding process, such as improperly re-soldering the C20. If I get another board, I might redo the mod again to see if there is any difference.
I also noticed the circuit looks the same as:
- https://www.diyaudio.com/forums/class-d/349145-tpa3118-noise-pop.html#post6072170
- Improving TPA3118 Class D Amplifier | HiFiVision.com
Reducing the gain is supposed to reduce any start-up pop noise, so the increased pop noise in my mod could be due to me messing up the board in the modding process, such as improperly re-soldering the C20. If I get another board, I might redo the mod again to see if there is any difference.
Attachments
For anyone who is interested, I obtained another copy of the same board, and was able to remove R27 without removing the heatsink. The result was the same as before:
It's weird that removing the R27 resistor would introduce the new pop noise. While the pop is not very loud, I worry it might damage my speakers, so will probably stay with unmodded version of this amplifier instead.
- the gain dropped by ~10db
- this also reduced the loud notification sound when powering on the device or connecting Bluetooth
- the speakers now make a pop noise when power supply is is plugged into the amp
It's weird that removing the R27 resistor would introduce the new pop noise. While the pop is not very loud, I worry it might damage my speakers, so will probably stay with unmodded version of this amplifier instead.