This article is a brief overview of some basic concepts relating to analog summing, useful for those who are thinking of adding a summing mixer to their setup, or who are simply interested in understanding how it works. Much of this information is scattered online or in the specific technical manuals of each analog device. However, much of this information is poor and incomplete, and do not answer the countless questions and doubts that arise in anyone approaching working in a hybrid environment. Whoever is thinking of spicing up his personal setup with some analogue equipment may find here some useful information.

About analog and digital processing

Nowadays the standard is becoming more and more to work "in the box", where mixing or mastering is done entirely digitally using only software of a personal computer. We often forget how all the processing that is now performed by DAWs and plugins via mathematical algorithms, not so long ago was managed entirely by analog devices. While some of these digital processors show great performances, not all of them measure up to their analog counterparts. This does not mean that digital processing is not of good quality, on the contrary, quality and workflow flexibility have now made digital not only reliable but also extremely practical. However, the growing need for professionals to increasingly simulate the characteristics of specific analog devices has brought attention to the simple question of whether a digital software or plugin truly offers the same characteristics as an analog device. The answer is really simple and it is no, digital models do not have the same characteristics as the devices they are supposed to simulate. The problem itself is very complex, to simplify it just think that for the same model of equipment, analog devices tend to sounds very different from each other, especially if they are devices of complex construction or of old design, It is easy to understand that analog devices are unique.

What is a hybrid environment?

The need for this uniqueness and the different working approach that follows has pushed many to work in a hybrid environment (Digital + Analog), where it is possible to add analog flavor to a mix (or master) without giving up the advantages and flexibility of a DAW and digital processing. One of the device is the summing mixer.

What is a summing mixer?

You can picture an analog summing mixer as the final stage of a mixing console, the stage where all the tracks and groups get summed together to be finalized to stereo track during a mix or a master, where instead the digital sum that our DAWs operate is a mathematical modeling of the very same process operated by mixing consoles. Summing mixers are often fairly smalls (one or two rack unit) while some models can be slight bigger looking like a small mixing console. Both size and the price make summing mixer an interesting compromise for whoever cannot afford a mixing console, either for lacking the space or for budget reasons.

What are some of the benefits with work with an analog summing mixer?

Headroom – you can push harder your analog gear without the risk of unpleasant digital clipping, more headroom translates into a more natural sound and control over distortion and saturation.

Color and saturation – not only your summing mixer, but the entire process of working in a hybrid environment will add color and saturation, giving a certain character to your works. Additionally, adding analog saturation will help translate mix and master on smaller device (like phone, pad...)

Stereo image – the stereo image feels wider, especially great while using modulation such as reverb and delay.

Are there other differences in working in a hybrid environment?

There are things that need to be kept in mind if deciding to move to a hybrid environment:

Workflow – using analog hardware will change your approach to mixing, especially when used in conjunction with other outboard gears such as compressors and equalizers, where proper gain staging is necessary. Although this seems like a disadvantage, many professionals appreciate the commitment of this type of workflow, making it more similar to that of analog studios. For many, the physical contact with an analog gear and the possibility of interaction during mixing or mastering feels more engaging and creative.

Time – Connecting a summing mixer, understanding and getting used to a new workflow It will initially cost some time, which is also true when dealing with any change in your work, such as using a new software, learning a new mixing technique or getting used to a new plugin, this is probably something that every professional is already used to do from time to time. In the long term, hybrid work will save time, the experience of many is that all those small advantages that we have already listed before will translate into less need of processing, less need for plugins that simulate analog gears. A useful function of any DAW's is the capability to “bounce” you mix offline, saving some time, working with a summing will force you to “print” the result of you sum instead. Printing a track is the operation that consist of record back on your DAW the result of your analog processing, this operation needs to be done in real time while playing back your tracks. Although printing, rather than bouncing, takes time and sound a little time consuming, the possibility of creative interaction during printing might result in less need for automation.

Extra gears and costs if you plan to buy a summing mixer

This part of the article is intended to those who work in a small studio or simply own a home studio.

Setting a fairly complex hybrid setup from scratch or modify the one you already work with, it might take some planning in advance. Poor choices can lead to extra cost and the purchase of wrong gears. Here to follows are listed some information and consideration that can help you out while planning to expand (or set up anew) your working environment.   

Summing Mixers - Summing mixer can be expensive, many major brand released different style of summing mixers with different capability and features. SPL MixDream XP Mk2 stand in the market for its very reasonable price and its simplicity. SPL itself already released the MixDream Model 2384 that offers the same quality performance of the smaller XP version but with extra functionality and routing flexibility.

Converters – To use a summing mixer you will need at least one additional digital-to-analog conversion stage (for each track sent out to the summing mixer) and one additional analog-to-digital conversion stage (a stereo pair). Due to these additional conversion operations the quality of the converter is crucial. Cost is obviously not an issue if you already own good quality converters, but purchasing one for this very purpose needs to be taken into account as a cost. The number of outputs is also important to take full advantage of the functionality of a summing mixer. Many summing mixers on the market offer a 16-input to 2-output configuration, you will need 16 outputs in your I/O device to take full advantage of a summing mixer of this type.

Additional converters – If you need extra outputs, purchasing an extra converter might be the easiest solution, especially for those who constantly use extra outputs while working in parallel with a summing mixer. Another solution, for those who only occasionally use some extra outputs, could be to purchase a patch-bay.

Patch-bay – These are devices, usually in rack format with 48 connection points on the rear panel and 48 connection points on the front panel, which functions as a hub. It allows you to connect any input or output of any device in your system, and connect them together with extreme flexibility.  The front and rear panel connectors are wired together with several possible configurations to ensure the most suitable use for each system. The options and selection methods may vary slightly depending on the brand and model. In this way a limited number of inputs and outputs can serve different purposes without the need to purchase expensive extra converters. In this way a limited number of inputs and outputs can serve different purposes without the need to purchase expensive extra converters. Depending on the case, a complex configuration with multiple inputs and outputs can be handled with one larger patch-bay (96 connection points) or several smaller patch-bay units.

Cable – while it may not be worth mentioning, the cost of cables can be quite high in such a setup. The need for a fair amount of cables, especially while using a patch bay, can increase dramatically. Furthermore, a hybrid system, which uses expensive analogue equipment, needs good quality connections. The ideal is to plan in advance the position of each device within your studio, so as to know the type and length of each cable to purchase.

Final words

Every professional who wishes to move towards a hybrid environment and the use of a summing mixer will have to make his own personal considerations. It is important to understand which information contained in this article can be adapted to your personal situations and which should be ignored. After purchasing a summing mixer, the more technical and practical aspects must be evaluated depending on your needs, the devices you want to connect, and your budget. I hope this article has helped you make more informed choices.