25. Is it a hardware defect or a software problem for invalid EQ under LDAC?

We are so sorry to inform you that after some test of the BTR5 2021 by our engineers, we found that it is impossible to achieve EQ adjustment in LDAC currently.

The main reasons are as follows.
The data stream of LDAC is relatively large yet with a higher sampling rate. The CSR8675's built-in DSP inside the BTR5 2021 has limited processing ability which can only process EQ for audio with a low sampling rate.

Our engineers figured out that we can try to re-sample the LDAC audio, like inputting it to DSP after a down-conversion to enable the EQ function. However, such changes will greatly affect the sound quality of LDAC. Therefore, if you want to experience EQ adjustment while keeping good sound quality, it is suggested to use the aptX HD. You can disable LDAC of the BTR5 2021 through FiiO Control App, so that aptX HD will be the prior codec for connections as default.