There has been a lot of debate whether analog summing mixes sound better than the digital summing. This tutorial would serve as an introductory tutorial for beginners in knowing what an analog summing mixer is.
This will not prove whether analog summing mixes sound better than digital or recommend that you switch to analog summing for all of your mixes.
How does it differ from Digital Summing?
Let’s start with a more familiar digital summing. This is done inside your computer and using your DAW software such as Reaper, Protools, Cubase, etc.
In digital summing, binary bits (0’s and 1’s) also known as digital data of every track in your mix are added to produce a stereo “mixdown”. These processes are done “mathematically” inside your DAW that employs complex binary arithmetic or floating point calculation to carry out the operation.
Digital summing illustration
Older DAW uses 32-bit floating point while modern DAW are adopting to 64-bit floating point calculation that improves the “accuracy” of the calculation. The computation that is going on inside your DAW during the stereo mix down process is a complicated one as it also involves a lot plug-in calculations such as reverb, EQ, compression, etc.
In this article on advantages of 64-bit DAW over 32-bit float digital audio workstation, it reveals that even a 64-bit DAW involves rounding off and estimation of calculation results. These errors however are extremely small compared to using a 32-bit bit floating point calculation.
Based on the above diagram, the factors that can affect the digital summing quality are as follows:
1.) Bit-depth and sample rate – the higher the values, the more accurate would be the digital waveform representation of analog signals. Read this pulse code modulation tutorial for details.
2.) The quality of your analog to digital converters – bear in mind that the source audio is analog and being converted to digital during the recording process. The quality of converters can play a great role in having a perfect/high-fidelity digital capture. Quality converters are often found in professional audio interface and not in consumer-grade soundcards.
3.) The digital resolution of your DAW (available in 64-bit floating point, 32-bit floating point, 48-bit fix point, etc).
So what’s analog summing?
In analog world, there are no 0’s and 1’s but only voltages. These are complex sinusoidal voltages that include the harmonics and other elements. Many engineers consider this to add the “warm”, “in-depth” and nice separation sound you get from analog.
analog summing diagram
In the above screenshot, the input to an analog summing device is analog voltage (also known as analog audio). If you use an oscilloscope to view these analog audio signals, it would be sinusoidal in nature and the amplitudes are now in voltages and not in dBFS (digital dB).
Each track that would be rendered for analog mix down is summed in the summing device and their voltages are added. While DAW (digital summing) relies on binary math and floating point calculation to do the mixdown, analog summing relies entirely on electronic circuits to do the job. There is no math involved.
Analog summing mixer example
Credits: Thermionic culture fat bustard
Inside the analog summing device, the entire signals are in analog domain. You can even visualize this if you connect the output of the analog summing mixer to an oscilloscope.
There are two kinds of analog summing devices commonly used in music production:
1.) Passive analog summing mixer
2.) Active analog summing mixer
Passive analog summing does not have any active electronic components on board. Example of these are the transistors, etc. that provide amplification and any other signal manipulation features. Most passive analog summing devices only consist of resistors. Example of this is the RMS216 Folcrom passive summing mixer.
Active analog summing device has complex circuitry that provides additional amplification, signal conditioning features like EQ, panning, etc. An analog mixing console is an example of an active analog summing device.
How to Interface Analog Summing to your DAW (Hybrid)
You can interface analog summing devices to your existing digital audio workstation and come up with a hybrid DAW (utilizing analog and digital technologies). You can try this in your home studio and possibly compare the results of pure digital summing with analog summing from your DAW (also read: “Mixing in the Box vs. Mixing out of the Box“). Here is the extra thing you need:
1.) Analog summing mixer (passive or active) – the number of inputs depends on your usage. In most cases, you should have at least 16 inputs.
High end passive analog mixer can be very expensive; you can use inexpensive analog mixing boards for summing such as Soundcraft. Most home studios may already have an analog mixing console, so you don’t have to buy one if you wish to try analog summing.
2.) Lots of balanced cables.
3.) Audio interface with lots of analog outputs. Go for an audio interface with a reputation of having a great converter as this can influence the quality of the mix.
The process can be done as follows:
Step1.) Mix inside your DAW; assign panning, levels, EQ, compression, etc.
Step2.) Once the mix is done, group your tracks into the number of tracks that match your analog outputs.
Step3.) Configure your DAW tracks output to send to respective analog outputs of your audio interface. This is often done in the routing matrix of your DAW, consult the manual. See below:
DAW analog summing concept
Most modern audio interface includes mix control that manages routing functions such as analog outputs.
Step4.) Use balance cables to connect each of the audio interface analog outputs (which are your tracks) to the analog summing mixer. This will prevent the addition of noise to your analog outputs. For more details, read this post on balanced vs unbalanced audio.
Step5.) You can then get the stereo output of your mix (which is the mixdown in analog). Compare that with mixes done inside the DAW and see the difference.
Best practices on analog and digital summing
1.) Your music production skills and the quality of your music is more important than the summing method. Put more time in improving your production and songwriting skills. At the end of the day, it is still all about the music.
2.) Analog summing from DAW will introduce a lot of conversion that further adds quantization/conversion errors. You might want to consider this tradeoff when deciding to do some analog summing. See the difference below:
Pure digital audio mixing:
Pure digital audio summing
Analog summing from DAW output:
Recording analog source == > A/D conversion == > DAW mixing == > D/A conversion == > Analog summing/mixdown == > A/D conversion ==> Mastering or digital music distribution such as MP3, etc.
As what you can see, you’ll be doing a lot of D/A – A/D conversion (3 stages actually) when you are performing analog summing from your DAW outputs. There is only one conversion stage when summing your mix in digital, and this is an advantage.
Each of these additional conversion stages would introduce errors that accumulate in the later stages; resulting to less accurate digital representation of original recording.
3.) If you want that pure/perfect analog sound, then you need to do everything in analog domain. This implies that the recording and audio mixing are to be done entirely out of the box (no D/A or A/D conversion). There is no loss in signal quality from repeated quantization/digitization and you have that analog sound you need. In this case, you need to build an analog recording studio without computer or DAW.
Content last updated on July 23, 2012