With the Sound Devices Astral® series, gain never needs to be set anywhere on the wireless transmitter or receiver. Instead, control the gain on your mixer, just like you are adjusting the trim for a hard-wired mic. You’ll never lose audio quality in the chain.
We’ve all been there: you’ve set your transmitter gain, wired up the talent under their outfit, and you’re ready to roll. Unfortunately, in the middle of the first take or the first song, the talent begins yelling or singing VERY LOUDLY. This didn’t happen during rehearsal! Now you need to quickly pause production, and approach the talent to make adjustments at the transmitter…
With Astral transmitters, this won’t be a problem. Instead of bothering the talent by changing gain at the transmitter, simply make the gain adjustment right at the trim stage of your mixer, just like you would with a hard-wired mic. This groundbreaking feature is possible with Sound Devices’ GainForward™ Architecture.
So what is GainForward Architecture? Is it remote control? The answer is no. Unlike systems that use some sort of remote-control link to adjust gain at the transmitter, there is zero lag with the GainForward system. And there is never a worry about the transmitter being out of RF range for remote control.
How is it possible that no gain control is needed at the transmitter? Isn’t there a noise or headroom penalty? Again, the answer is no. GainForward architecture differs from systems that require control of gain at the transmitter and that send a limited dynamic range signal over the RF link. Instead, GainForward transmits the entire dynamic range of the microphone input over the RF link, and adjustments to gain are done at the receiving end. By contrast, analog FM wireless systems and most digital systems require gain control at the transmitter. Astral GainForward systems do not.
Though gain control has been moved from the transmitter to the mixer, audio quality is unchanged. The Astral transmitters contain an incredibly low-noise microphone preamplifier with substantial headroom and over 140 dB of dynamic range.
There are three necessary elements that make the GainForward Architecture possible: 1) a very low-noise microphone preamplifier with exceptional dynamic range; 2) patented multi-stage ADC (analog-to-digital converter) topology to capture the entire dynamic range of the analog source; 3) floating-point digital RF transmission.
Shown here is the architecture of a typical RF transmitter and receiver used today.
Shown here is the Sound Devices Astral® architecture illustrating the three main elements of the GainForward Architecture.
Microphone Preamplifier Design
The Astral series of transmitters feature premium high-end microphone preamplifier designs, enabled by using the very latest advances in FET and bipolar circuitry. Equivalent Input Noise (EIN) is the measure of a preamp’s noise floor, the lower the number the better. The preamps in the transmitters feature an EIN of -126 dBV (A-weighted) and are believed to be the quietest transmitter lavalier preamps available. They are on par with high-performance balanced XLR preamps. The lavalier preamplifiers can handle signals in excess of +5 dBV; the Astral HH and Astral TX balanced preamps can handle +11 dBV. In other words, very hot inputs. Extensive listening tests were performed to ensure pristine sound quality, which can meet the most demanding applications.
Multiple-ADC Architecture
Following the microphone preamplifier in the signal path, the microphone’s audio signal needs to be converted from analog audio to a digital bitstream using the analog-to-digital converter (ADC). All Astral transmitters use Sound Devices’ patented (US9654134B2) multi-ADC topology to capture the entire dynamic range of the microphone preamp preceding the ADC stage. The signal is captured with full fidelity, with little added noise, and no loss in headroom. Multiple ADCs are required, since – as of this writing – there are no ADCs on the market with a dynamic range greater than 140 dB that run efficiently off of battery power.
Floating-Point RF Transmission
With GainForward, the signal’s entire dynamic range is preserved and sent digitally via RF over the air to the receiver using floating-point math. Somewhat similar to how 32-bit floating point audio files have increased dynamic range, a related “Floating-Point RF” method is used to send digital audio over the RF link. Audio samples are converted from fixed-point coming out of the ADCs into a floating-point representation. At the receiver, the reverse process takes place and the floating-point signal is converted back into fixed-point audio. This entire RF encoding and transmission topology is proprietary to Sound Devices. It has evolved over many years of work and listening tests, and is the very heart of every Astral system.
FAQ:
Does this mean I don’t need to have low-sensitivity lavs anymore such as the Sanken COS-11 red dot?
No, low-sensitivity microphones are still needed for very loud sounds. Lavalier microphones themselves inherently have a more limited dynamic range than larger diaphragm microphones. Even though the Astral Mini itself can handle the entire acoustical and electrical dynamic range of any lav microphone plugged into it, lavs themselves can saturate with high SPL sources. Therefore there is still a need for different sensitivity lavalier microphones.
Is the Bluetooth or NexLink connection being used to remotely control the gain of the transmitter?
No, there is no remote control of the gain circuitry at all. There are two advantages to this over a system that does perform remote gain control of the transmitter: a) if the transmitter is out of range of Bluetooth/remote control, the gain can still be controlled by the mixer; b) the gain can be controlled as quickly as you can move the trim knob.
Can I use a non-Sound Devices mixer and get the benefits of GainForward?
Yes, the Astral Mini, Astral TX, and Astral receivers can be used with virtually any brand of mixer or mixing console.
Does the AES output of the Astral receivers have enough dynamic range for GainForward?
Yes, AES can transport 144 dB of the audio’s dynamic range, so it is more than sufficient for the >140 dB of dynamic range of the microphones.