This is where the mastering process really begins: a good mix produces a great master. Consider the following mix and format guidelines as you prepare your mixes for mastering.
Leave 1 to 2 seconds at the start and end of the mix. Fades can usually be performed with greater precision during mastering.
As de-essing at the mastering stage is normally a compromise, sibilant vocal tracks should be individually de-essed as part of the mixing process. This is especially true if your mix is destined for vinyl, since sibilance can lead to distortion on the cut.
Remove any limiting, clipping, or other loudness processing from the stereo bus prior to exporting the mix. Stereo bus compression is fine if used in moderation for aesthetic purposes and not solely to achieve loudness.
Aim for peak levels of -1 dBFS or below. This is not a strict rule and stray peaks are acceptable as long as they do not exceed 0 dBFS.
Standard PCM and DSD audio formats are accepted.
PCM Audio Formats
File Type: WAV, AIFF
Bit Depth: 16, 24, 32 (float)
Sample Rate (kHz): 44.1, 48, 88.2, 96, 176.4, 192
Submit PCM mixes as stereo interleaved 24-bit or 32-bit (float) WAV or AIFF files at the native sample rate of the project (44.1, 48, 88.2, 96, 176.4, or 192 kHz). 16-bit files are also accepted.
Bit depth (also known as wordlength) is the number of bits required to define a PCM audio sample. In integer (fixed point) formats, the bit depth determines the resolution of the recording. Each bit represents 6 dB (technically 6.02 dB) of dynamic range. Thus, a 24-bit recording has a theoretical dynamic range of 144 dB.
Quantization errors occur whenever converting digital audio from a higher bit depth to a lower one. Dither (also known as wordlength reduction or WLR) is a form of noise which, when applied prior to rounding, randomizes quantization errors, thereby preventing or mostly preventing (depending on the type of dither noise) quantization distortion. Flat TPDF dither eliminates quantization distortion completely.
DAWs typically operate natively at 32-bit (float) or double precision 64-bit (float). The floating point formats provide additional headroom for digital processing and, as a result, theoretically maintain the original noise floor of the recording. There is some debate as to whether dither should be applied when exporting from the DAW's native 32-bit (float) or 64-bit (float) session as a 24-bit file. I believe that the application of dither during such conversions is good digital audio practice and recommend that flat 24-bit TPDF dither (no noise shaping) be applied to the stereo bus prior to or during export. The trade-off is a slight addition of noise which raises the noise floor by about 3 dB.
There are dither types other than TPDF. Some types, such as Izotope MBIT+ and POW-r, utilize noise shaping to move the dither noise to less audible frequencies. However, the use of noise shaping does not translate well if any further processing of the file is performed. And digital audio frequently requires some form of subsequent processing, whether it be further bit depth reduction or lossy file encoding (even CDs are routinely converted to lossy file formats when imported into media players). Flat TPDF dither, on the other hand, distributes the dither noise evenly across the frequency spectrum and, as stated before, eliminates quantization distortion.
Dithering can be avoided altogether by exporting the mix as a 32-bit (float) file.
DSD Audio Formats
File Type: DSF
Bit Depth: 1
Sample Rate (MHz): 2.8224 (DSD64), 5.6448 (DSD128)
Submit DSD64 and DSD128 mixes as stereo interleaved DSF files.
Mixes are submitted for mastering through Mindtree's secure file uploader.
SECURE FILE UPLOADER
M2drive is the front end to Mindtree Mastering's secure file transfer platform. Audio files may be uploaded directly to Mindtree's Dropbox cloud storage by using the M2drive Secure File Uploader (powered by Dropbox) located on the CONNECT page.
Secure File Upload Instructions
1 Enter email address in Email field.
2 Enter upload notes in Comments field (optional).
3 Click on Add file or files button.
4 Click in Password field, enter provided secure file upload password, and click OK.
5 Click on Add file or files button and browse to and select file or files to be uploaded.
6 Click on Add more files button if adding additional files for upload.
7 Click on UPLOAD button to begin file transfer.
8 Click on END button once upload is complete.
The M2drive Secure File Uploader file size limit is 1000 MB (1 GB). Larger projects may be divided into multiple uploads.
The table below specifies the number of stereo minutes source formats will allow with a file size limit of 1000 MB (1 GB).
Source Format Stereo Minutes
2444/2448 WAV/AIFF 1:00:00
2488/2496 WAV/AIFF 30:00
24176/24192 WAV/AIFF 15:00
3244/3248 WAV/AIFF 45:00
3288/3296 WAV/AIFF 22:30
32176/32192 WAV/AIFF 11:15
PCM: Pulse-code Modulation. An encoding method used to digitally represent an analog audio signal. During encoding, the amplitude of the analog signal is sampled at uniform intervals and each step is quantized to the nearest value within a range of digital steps. Linear pulse-code modulation (LPCM) is a type of PCM where the quantization levels are linearly uniform.
WAV: Waveform Audio File Format. Also known as WAVE. An uncompressed linear PCM file format for storing digital audio data. WAV was developed jointly by Microsoft and IBM. The sound quality is identical to that of AIFF files. The file extension is .wav.
AIFF: Audio Interchange File Format. An uncompressed linear PCM file format for storing digital audio data. AIFF was developed by Apple. The sound quality is identical to that of WAV files. The file extension is .aif.
DSD: Direct Stream Digital. An encoding method, technically pulse-density modulation (PDM), used to digitally represent an analog audio signal. During encoding, the analog signal is stored as delta-sigma modulated digital audio, a sequence of 1-bit values at an ultra high sample rate.
A 1-bit digital audio format with a sample rate of 2.8224 MHz (64 times that of the 44.1 kHz CD sample rate). DSD64 was originally conceived for the Sony-Phillips Super Audio CD (SACD) format.
Also known as Double-rate DSD. A 1-bit digital audio format with a sample rate of 5.6448 MHz (128 times that of the 44.1 kHz CD sample rate).