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2 x 120W BT 4.0 A2DP Class D Amplifier Review

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  • 2 x 120W BT 4.0 A2DP Class D Amplifier Review

    BT Amp.png

    Right click on the pic and select "open in new window" to see full size detail.

    Here's a nice little amp. Approximately $15 to $20 depending on source (Amazon, eBay, AliExpress, etc.). But it's not without issues:

    The good:

    (1) Dead quiet at full volume with no signal - BT connected or not, even when source music is paused
    (2) No turn on/off pop at all. Unplugging the PS or removing the 5.5mm DC plug it is quiet. There is no power switch.
    (3) Power up/down tone is loud but not abusive.
    (4) Power up auto connects if your device is ready and has been previously paired (pairing was simple).
    (5) Unit powers up to maximum volume. You don't have to push buttons to get maximum output. Just control the volume from the source.
    (6) The << and >> short button push will replay/advance the songs on my PC using Media player (long presses on the same buttons are vol- and vol+)

    The bad:

    (1) PCB antenna range is short - about 12' line of site. Walking through the line of site will interrupt the stream.
    Note: my desk top's BT is a little USB "thumb drive" like module also with a internal PCB antenna. You may get better performance with a BT module that has a "rubber duck" antenna with higher gain.

    (2) At 24 V you'll get ~33 W rms into 8 ohm speakers and 66 W rms into 4 ohm speakers.
    Note: The 120 W rating is for 2 ohm speakers. The module purports to have two TPA3116D chis is PTBL mode to support this. I didn't remove the "stick-on" heat sink to verify,

    (3) The BT daughter board seems to have been pre-programmed for those little BT speaker phones. As such, the source device will see extraneous, non-functioning, capabilities such as "hands free" profile (easy to just ignore).
    (4) The two SMD status LEDs are very bright and at least one is always flashing. Five layers of cellophane tape didn't do much to to reduce the light. I'll likely paint them with some nail polish.

    The ugly:

    The CSR8635 BT chip has an on board 5 band graphic equalizer. Measurements between the BT chip and amp input indicate that the equalizer limits bass below 100 Hz (see the graph, above). I presume to limit bass for the tiny speakers in the small BT speaker phones targeted by this version/programming of specific BT daugherboard.

    On the flip side, that bass limitation may come in handing for higher volumes in speakers like the Classix II where the DC160 plays low but runs out of xmax at higher volumes. On my Large Advents, I use Media Players graphic equalizer to compensate for the chips bass reduction.

    This amp would be great for a small garage system where volume needs to be higher but the woofers need some HP (like the Classix II).

    Mine sits on top of a book shelf powered 7x24 with a 24 V 5 amp brick. It's always ready to connect and play from my PC (or other source). I never touch it.

  • #2
    Sounds like a good amp for the right application. Thanks again Mike!

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