Which is “better”, an Analogue or Digital Synthesizer?

“Dummkopf.. digital is better”!

There is a  lot of great information on the internet. There is also a lot nonsense and the topic of synthesizers is no different. Many detractors and naysayers don’t actually understand electronics and the difference between digital, analogue, integrated or discrete, and yet they formulate opinions about why synth ‘X’ is better than synth ‘Y’, or analogue is better for ‘This’ and digital is better for ‘That’. So let’s just get this out of the way. This explanation will be an over simplified version so anyone new to synthesizers or audio, should be able to wrap their head around the concepts and formulate their own opinion when buying one.

Analogue (Analog) Design.

Analogue design is creating electrical circuits that operate with signals on a continuous basis. An example is me talking to someone directly. Sound waves travelling through the air, from my mouth to the person’s ears is an analogue signal. They travel continuously from the moment I start talking until I stop. In an analogue device, those sound waves are converted into an electrical signal that travel down a wire. Without any modification, that signal travelling in the wire should look exactly like the sound wave signal travelling through the air. Everything we see, hear and even feel in the natural world is through an analogue signal.

Good Points:

  • Everything that forms the sound, is in the signal. All the little harmonics, noise and nuances are in the signal. It is a reproduction.
  • The signal can be infinite, going below or above your hearing range.
  • Analog signals deteriorate as the distance increases. They are absorbed by the medium in which they travel.
  • Analogue, like human hearing, can naturally taper off in the high and lower ends, and we can easily mimic distance and movement by how loud sounds are and taper off.

Negative points:

  • Analog signals are susceptible to noise and interference. Radio waves, poor electrical grounding, leaky components, cell phones can interrupt, block or change the original signal.
  • It is, what it is. Everything the originating sounds provide is in the signal, we can only subtract elements from it through filtering. (but we can add things to it using other signals).
  • Analogue designs (especially synthesizers) are less stable and can change sound quality due to variances in temperature, humidity and age.
  • New features and functions require new hardware.

Digital Design.

Digital design is creating electrical circuits that convert continuous signals into discrete or integer values. An example is me talking to someone directly. Sound waves travel through the air, from my mouth to the person’s ears as an analogue signal. We capture the analogue signal and convert it a numerical approximation. They do this by sampling a series of small pieces of the signal, and applying a value from 0 to 1028 (or higher).

Analogue sine wave converted to Digital slices

Good Points:

  • Noise and interference can be eliminated through error correction of the slices
  • Wave forms and sounds can be created that can’t be easily achieved in analogue designs.
  • Requires less power consumption, minimizes heat.
  • Highly stable as sound quality is always maintained (tuning drift is eliminated).
  • Less expensive to manufacture, generally digital synthesizers have more options available.
  • New features and functions can be added through updating firmware.

Negative points

  • Unwanted artifacts (aliasing) can appear in the signal, natural transitions (tapering) can be lost and clipping can occur as conversion takes place.
  • Requires complicated, highly integrated components that are susceptible to electrical sources
  • Can sound too perfect, but modern digital processing can also add randomization and even warmth to the sound, but this is not always implemented.

Discrete design.

In discrete electrical designs, circuits are made of the individual base components: The passive resistors, capacitors, inductors and the active diodes, vacuum tubes and transistors. Complicated synthesizer designs are bigger as circuits are larger, require more power and give off more heat. Discrete designs are usually analog, but digital computers can also be made from discrete designs. In fact, all of the early computers up until the 1970s were all discrete in nature. Some of the most famous synthesizer VCO & filter designs (Moog) were built with discrete components.

Integrated Design.

Integrated electrical designs place commonly used circuit elements into small packages called Integrated Circuits or ICs. Using various materials and printing/etching techniques, manufacturers are able to miniaturize the passive component circuits. Integrated designs can be analogue or digital or both. Almost all synthesizers utilized common amplifier circuits to provide integration, buffering, differentiation, summing and amplification for signals. These circuits are so common in fact, that some of the first ICs invented were for the purposes of providing the Operational Amplifier (OpAmp)  circuit. Almost every analog synthesizer made since the early 1970s utilizes these ICs.

So, with that in mind:

  • Analog vs Digital is how the signals are processed
  • Integrated vs Discrete is how the circuits are made.
  • Many would consider the use of an OpAmp ICs as a discrete components. They are relatively simply circuits using miniaturized resistors, capacitors, diodes and transistors.

Why does this matter?

There is a lot of misinformation about synthesizers and electronics, whereby some people believe that because a synthesizer circuit looks like the two below, they are digital. They are both in fact fully analog voicing cards but use many specialized integrated circuits to make them smaller.

Highly integrated analog voice card using older through-hole technology

Highly integrated circuit card. 5 analogue voices using modern SMD (surface mount device) technology

Although it looks like it has components very similar to the circuit above, the circuit board below is a digitally implemented synthesizer. All of the control, voicing, filters, effects, etc are implemented in software. In fact, there is no real difference between this synthesizer’s software and any other Virtual Software synthesizer. Conversion to analogue happens at the very end, at the audio output. Developers use DACs, or digital to analogue converter devices to accomplish this. These can be the most expensive device in the entire circuit for many things with higher end audio output.

PCB from a digital synthesizer.

All digital and many analogue synthesizers utilize a microprocessor. Every analogue synthesizer that saves patches or presets, uses some sort of digital circuit to store the settings for later use. Some designs copy the analogue control signals from the sliders, switches and knobs, convert it to a digital signal and then store it, in either temporary or permanent memory. The originating analog control signals are then used to change the parameters of voicing, filters, envelopes, etc.

Other implementations of analogue synthesizers, first store the converted digital signal for patches and presets, but then reconvert it back to into an analog signal for the control the parameters. This is usually done in polyphonic synthesizers as it maintains consistency across all voices for timing and control signals. Analogue “purists” however, will argue that there is a sound difference between a fully analogue synthesizer and one that incorporates digital techniques in the control signals. There is some truth to this, but it is also extremely hard and stupid expensive to build multi-voice synthesizers without some sort of digital control.

The Detriment of Age.

All electronic components are affected by age and temperature. Older through-hole technology is generally more robust than SMT, and handles shock better as the component bond the the circuit boards are mechanically stronger. Older through-hole circuits are easier to repair and generally age better as well. Alternatively, modern SMD circuits utilize less power and handle temperature changes much better. Unfortunately they also require a multitude of disparate metals and minerals to be used in their soldering and manufacturing which can cause unwanted chemical reactions and the bonding tends to break down. In less expensive consumer products many surface mount components will fall off the circuit board after only 5 years.

Over time, integrated circuits will generally fail causing functions to stop working. Discrete components can also fail, however some will just change their values over time, especially passives. A change in resistor and capacitor values can cause both positive or negative effects. It could make it impossible to keep voicing and filter circuits in tune but it could also add character to the overall sound of a synthesizer. Many older, yet identical synthesizers can have distinct sound characteristics.

It is not uncommon to find working analog synthesizers that are approaching 50 years of age. Many of them can be repaired or brought back into the working specifications of the designers. Even early digital synthesizers like the Yamaha DX7 can be repaired. However, the caveat here is that many older Roland and Yamaha synthesizers used customized ICs in most of their designs, and obtaining replacements usually involves cannibalizing from other broken machines.

In reality, arguing over the superiority of “Analog vs Digital” is a waste of time, and really not a viable argument. The advent of digital technologies has definitely made meaningful contributions to electronic synthesis. For example, It has made polyphonic synthesizers more affordable and enabled them to have a tremendous amount of features. It has allowed new sounds to be made and discovered, It has also brought FM synthesis out of the research closets and into many commercial synthesizers. I never covered FM synthesis in this article, but it is responsible for all those wonderful metallic, glass and bell sounds.

Here is something to ponder. Many people make their composition on an analogue synthesizer (because they prefer analog), yet record it and upload to Soundcloud, or YouTube which are digital mediums. In the end, it is just a digitally sampled analog synthesizer.

In my own studio, I use analog, digital and hybrid (a bit of both) synthesizers. My goal is to get that sound in my head onto a recording.