Yes, I decided to shake the old days and take up the tests again. Not so long ago, I bought myself the now popular Xiaomi Redmi Note 5 and today I intend to evaluate its capabilities in terms of high-quality sound reproduction.
I must say right away that from the first minutes the smartphone pleased with a clear, noisy sound (you can hear background noises except in a completely quiet room) and a flat frequency response, which is especially felt by ear in the bass area. before that I had an inexpensive Lenovo A606, and I suddenly I realized that there were simply no low frequencies.
So, we have at our disposal the Chinese version of Xiaomi Redmi Note 5 4 / 64GB (RAM / disk) with the latest for today, the 10th version of MIUI. An important point to make here. When buying from a smartphone, the MIUI version was 9, and the sound in it completely suited me, but after the update I noticed that the playback volume seemed to decrease. At first, I did not attach any importance to this, but now, in preparation for the test, I found information that manufacturers underestimate the volume for some regions (apparently in order to comply with local sanitary standards), and Ukraine and Russia belong to these regions. In order to restore the previous volume level, I needed to set the region of India (Advanced settings. Region). After restarting the player (you need to unload it from memory), the maximum volume becomes almost 16 (!) DB higher.
For recording, I use a PCI-e card ASUS Xonar Essence STX with a signal-to-noise ratio of 118 dB input.
In the Poweramp settings, I selected the Hi-Res output, where the sampling frequency is set in accordance with the signal parameters, 24-bit resolution and all effects are disabled.
To generate and analyze signals, I still use the wonderful program RightMark Audio Analyzer version 6.4.5., And I record a signal using Adobe Audition 2018. for better control of recording and eliminating problems with ASIO.
By the way, it is interesting that both RMAA and Poweramp were created by Russian developers.
First of all, I determined the base frequency of the generator in the phone using the Audio Buffer Size program. It turned out to be a multiple of 48000 Hz:
That is, for high-quality playback of 44.1 kHz audio, a resampler is required.
When playing 1 kHz. 0 dB tones, the RMAA shows the input level. 8.1 dB. Although he says that this is not enough, it is enough for the analyzer to work at this level. In fact, even at the current volume level, listening to music in low-impedance headphones is already uncomfortable.
First of all, I tested the phone in optimal mode. 24/96. This will allow us to see the possibilities of circuitry, and we will not be an overkill in terms of microwave.