PCM vs DSD: A Technical Look at Digital Audio Formats

/3 September 2025

In the world of high-resolution digital audio, two fundamentally different encoding systems dominate the conversation: Pulse Code Modulation (PCM) and Direct Stream Digital (DSD). Both formats are capable of delivering exceptional sound quality, but they achieve this through entirely different approaches to sampling and encoding an analogue waveform. Understanding the core differences between the two is essential for appreciating their respective strengths, limitations, and the engineering trade-offs involved in recording, mastering, and playback.

Pulse Code Modulation (PCM)

PCM is the most widely used digital audio format, underpinning everything from CD audio to modern high-resolution recording and streaming. It works by sampling the amplitude of an analogue waveform at evenly spaced intervals, with each sample represented as a numerical value corresponding to the instantaneous voltage at that point in time.

The two key parameters defining PCM are sample rate and bit depth. The sample rate, measured in kilohertz (kHz), defines how many times per second the signal is measured. The CD standard of 44.1 kHz means the signal is sampled 44,100 times per second, while professional high-resolution formats might use 96 kHz, 192 kHz, or even higher. Bit depth determines the resolution of each sample. A 16-bit sample, for example, can represent 65,536 discrete amplitude values, whereas a 24-bit sample can represent over 16 million.

Higher sample rates extend the frequency range that can be captured (up to just below half the sample rate, as defined by the Nyquist–Shannon sampling theorem), while higher bit depths improve dynamic range and reduce quantisation noise. PCM audio requires the use of anti-aliasing filters during recording and reconstruction filters during playback to prevent high-frequency artefacts.

One of PCM’s key advantages is its compatibility and flexibility. It is an industry standard, supported by virtually all digital audio workstations (DAWs), audio interfaces, and playback devices. Editing PCM is straightforward: because the audio is represented as discrete numerical samples, processes like cut, copy, paste, crossfade, and DSP-based processing can be performed without special conversion steps.

PCM Specifications

Encoding method: Multi-bit amplitude samples at fixed intervals
Common sample rates: 44.1 kHz, 48 kHz, 96 kHz, 192 kHz
Bit depth: 16-bit, 24-bit (and higher)
Editing and processing: Fully supported in native form
Filtering: Requires anti-aliasing and reconstruction filters
Data rate: Varies; 24-bit/96 kHz ≈ 4.6 Mbps per channel
Main uses: Universal in recording, mixing, mastering, streaming
Key advantage: Flexible and widely supported
Key limitation: Filter design can affect sound quality

Direct Stream Digital (DSD)

DSD takes a fundamentally different approach. Instead of sampling amplitude at fixed bit depths, DSD uses a 1-bit system running at an extremely high sampling rate, 2.8224 MHz for the standard DSD64 format, which is 64 times the CD rate of 44.1 kHz. At each sample point, the bit indicates whether the signal is going up or down compared to the previous sample.

This data is produced using sigma-delta modulation, where the incoming analogue signal is oversampled, noise-shaped, and converted into a high-frequency stream of single-bit values. Because the sampling rate is so high, DSD can represent audio frequencies well beyond the human hearing range without the need for steep anti-aliasing filters. However, the noise-shaping process pushes most of the quantisation noise into ultrasonic frequencies, requiring low-pass filtering during playback to remove it.

The main attraction of DSD is its simplicity in theory: the bitstream can be fed directly to a DAC without complex interpolation, which some advocates claim results in a more natural and analogue-like sound. However, the format has practical limitations.

Because it is a 1-bit system, direct DSP processing, such as EQ, compression, or mixing, cannot be performed without first converting the signal to a multi-bit PCM format (commonly referred to as DXD when working at high PCM rates like 352.8 kHz). This means that most DSD recordings produced in professional environments are edited and processed in PCM at some stage, before being converted back to DSD for distribution.

DSD Specifications

Encoding method: 1-bit stream indicating waveform rise or fall
Common sample rates: 2.8224 MHz (DSD64), 5.6448 MHz (DSD128), 11.2896 MHz (DSD256)
Bit depth: 1-bit
Editing and processing: Requires conversion to PCM for DSP
Filtering: Requires low-pass filter to remove ultrasonic noise
Data rate: DSD64 ≈ 5.6 Mbps per channel
Main uses: Audiophile releases, SACD, archival transfers
Key advantage: Minimal processing stages in playback chain
Key limitation: Impractical for complex editing

A number of recorders were released in the wake of DSD being introduced to the professional recording world, primarily from TASCAM. However there were also excellent models from the likes of the now defiunct Genex with both optical disc and hard drive recorders, as well as Korg with their MR-2000S.

Engineering Trade-Offs

From a technical perspective, PCM and DSD represent different solutions to the same problem: accurately capturing and reproducing analogue waveforms in a digital form.

PCM offers a direct, precise representation of amplitude values, with easy editing and a mature production ecosystem. Its limitations are tied to the quality of the anti-aliasing and reconstruction filters, as well as the achievable resolution within the chosen bit depth and sample rate.
DSD uses extreme oversampling and noise shaping to avoid steep anti-aliasing filters in the audible band, potentially preserving phase integrity at the highest frequencies. However, its 1-bit nature makes it less practical for complex production workflows, as almost all editing requires conversion to PCM.

In storage terms, DSD64 (2.8224 MHz, 1-bit) has a data rate of about 5.6 Mbps per channel, which is roughly comparable to 24-bit/88.2 kHz PCM. Higher-rate DSD formats, such as DSD128 or DSD256, scale this data rate proportionally, increasing storage and bandwidth requirements.

PCM remains the universal standard for recording, editing, mixing, and mastering. High-resolution PCM formats (24-bit, 96 kHz or higher) are common in professional studios and are the basis of nearly all modern digital production workflows. DSD, while more niche, retains a devoted following in the audiophile community and in certain archival and mastering contexts. It is the format behind SACD (Super Audio CD) and is sometimes chosen for archival transfers of analogue masters because of its high sampling rate and perceived sonic transparency. Modern DSD-capable converters and playback systems can handle DSD64 through DSD512, with the higher rates aiming to reduce ultrasonic noise and bring the practical noise floor down further into the ultrasonic region. Both formats are capable of superb sound quality when i mplemented well. In practice, the choice often comes down to workflow: PCM dominates in situations where editing flexibility is paramount, while DSD is favoured where the priority is minimal conversion stages and a purist recording chain.