The A20 Mini, Love it or leave it?
IT WAS LOVE AT FIRST SIGHT.
We’re in one of those time periods with wireless audio technology where big innovation is split somewhere between what’s here today and what’s hopefully on the horizon. And with V6.0 firmware the A20 mini transmitter is no exception with its breakthrough SpectraBand offering 285 MHz in the US between 470 MHz – 1525 MHz opening up more RF spectrum then ever seen before in any single professional wireless audio transmitter. It also digitally transmits the full dynamic range of any electret body worn microphone with 130db of dynamic range with its multi stage AD converters and full resolution 32 float bit WAV transmit and record eliminating gain adjustments at the transmitter. Also the transmitters gain forward technology works seamlessly with any brand mixer/recorder putting all things gain staging at the fingertips of the mixer eliminating talent adjustments with a profile that every actor will love with it’s ultra slim design that hides easily from camera and fits comfortably in the wardrobe for excellent wearability.
BUT THEN, THERE’S THE FLIP SIDE
But on the other side of the coin we have a lower than average battery life in comparison to the competition and a head scratching power management system that requires some strategy based on your specific requirements and a workflow plan with your sound team. There is also no screen or multifunction controls on the surface of the A20 mini transmitter with the exception of an interior on/off and bluetooth pairing button. So all transmitter controls must be done via Bluetooth with the A20 app which fortunately has been upgraded from the older A10 transmitter app offering 100’ line of site with it’s Bluetooth 5.2 technology. Also after reading the fine print I found out that over 85 mHz of of that roomy advertised Spectra Band frequency space requires an unlock code from Sound Devices who will need to verify that you have those specifically frequencies on your FCC licenses. I’ll dig a little deeper into FCC licensing later on in this article for those who are interested in those bands. So let’s jump right in and see if I’ll love it or leave it by taking a closer look with some more detail out in the field and see if this relationship will last the test of time.
BATTERY TESTING AND RUNTIME RESULTS
If you’re somewhat familiar with the Sound Devices A20 mini let’s start with what’s on the top of most of your minds which is transmitter run times and battery performance. To start things off you’ll find all the battery run time test results I performed on the graph below. Since I’m most interested in using the more eco responsible rechargeable Sony NP-BX1 batteries I tested them in all the power modes continuous runtimes in the LR modulation mode. I was only able to test the AAA Energizer lithium batteries in 10mw and noticed a 20% increase in run times which I’ll assume is across the board. Although I currently recycle all my lithium batteries. I myself really want to move away from one time use lithium batteries because of the negative environmental impact they create but it’s nice to have the option.
POWER MANAGEMENT WORKFLOW EXAMPLES.
Now before you slam the door on these because of battery life, there may be a sliver lining at the end of that grey cloud. That is remote power management via the A20 app. Since the transmitters are fully remote controlled from the A20 mini app via Bluetooth 5.2 LE which can maintain signal 100’ line of sight you don’t have to continuously cook your transmitter battery when talent is not on set. After much thought, let’s look at some example workflows on a typical hour day on a fast pace TV narrative film set.
Sound Utilities Matt Thirey and Jeremey Rock prepare transmitters and wires for cast.
Initially, I see two possible workflows for my crew. When wiring talent once frequency coordination and sound check is complete the sound utility could power down the transmitters as the first step to conserve battery life. A nice feature of the A20 app is that multiple users can pair the A20 transmitter to their own A20 app and when it’s closed by one sound team member another one can then open it and control the A20 mini transmitter. Next I can see the boom op powering up the transmitters when talent arrives to set ready to shoot and possibly power off again before they leave in-between a big lighting set up. Then simply rinse and repeat and adjust as necessary.. Option two would be simply change the batteries every 3 hours and let it cook throughout the day which means two additional battery changes then what we’re typically used to. One thing worth noting in that in 20mw mode, the run time was only decreased only 14 minutes over 10mw for a total run time of 3 hours 34 minutes using the Sony NP-BX1’s . So for double the power I’ll take the 20mw which will be helpful with antenna body absorption and a typical busy RF environment found a film set without having that much of a run time impact. So although the A20 mini battery run times are not ideal, I do think it’s feasible for a sound crew to implement a power management plan into their workflow scenario because It’s definitely not going to be a set it and forget situation by any means.
SIZE, WEIGHT AND WEARABILITY.
Now let’s start talking about where the A20 mini really shines. First up is size and form factor. Most recently I mixed a episodic college drama where high cast counts we’re typical and wardrobes could be quite minimal making hiding transmitters difficult. Although my current transmitters are small, the squared off sides and thickness were not ideal. We were able to make things work but sometimes we had to make adjustments in between camera set ups to keep the transmitters hidden from camera. The size and form factor of the A20 mini may just eliminate some of these adjustments and minimizing the amount of contact with the actors improves our relationship with the cast and the rest of production. This all being said, the A20 mini transmitter has the best weight, size and form factor out of any transmitter I’ve ever used. I’m only afraid If I put it on talent, they’ll refuse to wear anything else ever again!
SPECTRA BAND
One principle that all wireless systems have in common is they need a defined amount of RF signal to noise separation for optimal performance. And being in a major market like Atlanta I can’t even count the times I’ve done a scan on a location in the UHF TV bands only to see the ultra crowded spectrum and had to determine how to fit varying frequency blocks for twelve talent wireless, two booms, IFB in the UHF TV band in a less then optimal RF environment. With this in mind the Sound Devices Spectra Band A20 mini transmitter is welcome addition solving that problem by simply adding additional real estate to our RF offerings. In the US you get the entire UHF TV band (470-608 MHz), The 600 MHz guard band (614-616 MHz), The 600 MHz duplex gap (653-663 MHz), The 900 MHz ISM Band (902-928MHz) & The 950 MHz STL Band (941.5-960 MHz)
However I’m going to leave out the the 1.5 GHz AFTRCC band (1435-1525 MHz) out of that roomy RF real estate conversation for now. That 85 mHz of roomy Spectra Band frequency space requires an unlock code from Sound Devices who are requiring you to verify that you have those specifically frequencies on your FCC license. I am currently a Part 74 license user and was denied an unlock code because Sound Devices is requiring its customers in the US to provide FCC documentation granting you or your company permission to utilize the AFTRCC band.. I’ve been doing some research and consulting some FCC & RF experts over at Local 695 and there are two types of licenses you can apply for. One is a Special Temporary Authority or STA or Experimental license directly with the FCC. Both licenses don’t seem to fit in any production sound mixers model and we’re still determining the best path forward. But even without this 85 mHz, the A20 mini trumps them all RF real estate wise with it’s ISM band, UHF TV Band and the STL band in a single transmitter even without the 1.5 GHz AFTRCC band!
GAIN FORWARDING
If you’ve been mixing for a while your’e well aware of the importance of signal to noise performance in your system for both RF performance and audio capture. And at the forefront of your wireless system is proper gain staging of your wireless transmitters . My current wireless system requires a manual gain setting as most professional audio transmitters do on the market. On my last show, we first had your typical private director rehearsals and then a marking rehearsal for crew where the actors wouldn’t perform their dialogue and would only walk through the blocking for camera marks. So unfortunately we had to take our best guess on where to set transmitters based on the script and what we know about how the actor typically performs. The A20 mini transmitter eliminates all that guess work. You only need to choose and appropriate lav mic for the actor performance and since the dynamic range of most professional lav mic’s is around 110db and the A20 easily transmits the full dynamic range of the microphone via it’s 32 bit float dual ADC converter with a 144db dynamic range. All the gain controls are available on your A10/A20 receiver and easily passed to your analog or digital inputs on your mixer/recorder. It’s a common misconception that this technology is limited to the 8 series recorders, this is simply not true. You can use the gain forwarding technology with the A10/A20 receiver or directly on a digital input on any recorder making gain adjustments at the mixers fingertips where it belongs!
INTERNAL RECORDING AND TC
The A20-Mini records 32-bit float Broadcast WAV (under 4 GB) or RF64 WAV (over 4 GB) files at 48 kHz sampling rates. 32-bit float files are recorded such that gain decisions can be made after recording with built in TC with a 0.2 ppm accuracy. It will work in all standard frame rates including 23.98, 24, 25, 29.97 DF, 29.97 ND, 30 DF, 30 ND and can be jammed with an optimal specialized Sound Devices USB-C cable from any professional TC source. It also has a built in 64gb drive eliminating the need to manage external media. Also to my surprise I was able to keep the unit powered on continuously and TC locked for just over 8 hours when not in transmit mode which is a big leap over RF transmit run times and one clear advantage over simultaneous transmit and record since we’re not able to do that currently in the US. I’m a big proponent of 32 bit float record workflows and I can clearly see its advantages for the future but for today’s industry standard workflows you can manage and convert these files via the free Sound Devices utility app to deliver to post. I can see deploying the TC Locked recording only feature it in a scenario on a film set where reliable RF transmission is simply not possible. Regardless of how you use it it’s a welcome feature. However it’s important to note that although the connector is a USB-C the transfer speed is only around 100 Mbps which a USB 2.0 equivalent and since it doesn’t have removable media you’ll need to hand off the transmitter to off load, which is a bit awkward and not ideal in a typical workflow. I think the built in record feature and it’s current implementation is an amazing option for self shooters, and a special case uses for larger scale workflows. If your outside the US you’ll have the advantage of both simultaneous transmit and record which opens up many new workflow scenario in which I could write a whole separate article about!
SO WILL I LOVE IT OR LEAVE IT?
So the question remains will I love and hold on to the A20 mini transmitters and implement more of them into my sound carts and workflow on larger scale narrative sets? Overall I’m very impressed with what Sound Devices has created with the A20 mini transmitters but there is still a lot to be desired for my type of workflow in regards to battery life and local controls on the transmitter. Only time will tell if these A20 mini transmitters are up to the task to take the long term physical abuse and RF hellscape we call a film set. At the top of my mind is how is on set Bluetooth reliability, power management, moisture resistance and the over all physical sturdiness of the unit. Some of my current wireless systems have been put through hell and back, are over ten years old and are still in service. Sometimes it simply comes down to return on investment and if it can still do the job. But with its Spectra Band RF large real-estate landscape, gain forwarding and small size checks many boxes that can solve some of my existing problems. In the mean time I’ll be holding on two what I have and will put then on a trail basis for my upcoming show so I can see how we like them and how they perform keeping a close eye on what our friends over at Sound Devices come up with next!