Analog-to-digital converter for audio: eight-channel A/D units with AES59 DB25 inputs, AES3 or network outputs and word clock sync
Multichannel audio A/D converter units · Input sensitivity at 0 dBFS from +4 to +24 dBu and the SNR it costs, eight balanced channels on AES59 DB25, AES3 and MADI outputs, word clock on BNC with 75 Ω termination, conversion delay in samples
This page covers stand-alone audio A/D converter units: rack or box devices that take eight or more balanced line-level channels and output them as digital audio for recorders, consoles and audio networks. Ask three things first: which input level equals 0 dBFS and what signal-to-noise ratio the unit keeps at the level you will use, which DB25 pinout and digital formats it uses, and how it locks to the studio or venue clock and how many samples of delay it adds.
Stand-alone multichannel audio analog-to-digital converter units for studios, broadcast and live sound, with balanced line inputs and AES3, MADI, ADAT or audio-network outputs. Stand-alone ADC integrated circuits are covered on the Analog-to-digital converter (ADC) chip page, and industrial and test-and-measurement acquisition on the Data acquisition module (analog input module) page. Microphone preamplifiers, audio interfaces built around a computer connection, oscilloscopes and digitizer cards are outside this page.
CNFX editorial research · Sources checked October 12, 2026 · 3 sources
Which input level reaches 0 dBFS, and the SNR each setting keeps
RME's ADI-8 QS manual lists eight servo-balanced line inputs on 6.3 mm TRS and a 25-pin D-sub, 10 kΩ input impedance, and input sensitivity switchable to +24, +19, +13 or +4.2 dBu at 0 dBFS, with an analog limiter that keeps signals up to +30 dBu unclipped. Its 24-bit A/D section is specified at 114.0 dB RMS unweighted and 117 dBA SNR at +24 dBu, 113.6 dB and 116.6 dBA at +13 dBu, and 109.8 dB and 113 dBA at +4.2 dBu, with THD below −110 dB. [1] Focusrite lists its RedNet A8R with 24-bit, 192 kHz conversion, up to 119 dB dynamic range, frequency response flat within ±0.15 dB from 20 Hz to 20 kHz, and inputs configurable for +18 or +24 dBu at 0 dBFS. [2]
Editorial calculation: with 0 dBu = 0.775 V RMS, +24 dBu at full scale is about 12.3 V RMS and +18 dBu about 6.2 V RMS. Choosing +4.2 dBu sensitivity for a quiet source costs about 4 dB of SNR on the RME unit compared with +24 dBu, so set the sensitivity from the peak level of the source, not its nominal level. [1]
Give the supplier the number of channels, the source types and their peak levels, the sample rates, the digital formats or audio network needed, the clock reference in the facility, and the rack space and power redundancy required.
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AES59 DB25 wiring, AES3 over D-sub and word clock on BNC
AES59-2012, published on 18 August 2012, assigns eight pairs of balanced analog or AES3 digital circuits to one 25-way D-type connector, with a female connector on the equipment; TV Technology reports that it adopts the pinout Tascam used on the DA-88 recorder, which gives each signal its own shield contact, and that it is not the same as the other pinout based on Yamaha I/O cards. [3] Focusrite states that the RedNet A8R's analog inputs and outputs are on DB25 connectors wired to AES59. [2]
RME's ADI-8 QS carries four AES/EBU outputs and four inputs on one 25-pin D-sub wired to the Tascam standard, which is 8 channels at 192 kHz, plus ADAT optical and optional MADI on BNC coax. Its word clock input on BNC has a push switch for internal 75 Ω termination, and a separate BNC word clock output. [1] The RedNet A8R takes its clock from internal, word clock or DARS, outputs word clock on BNC, and sends its channels over the Dante network. [2]
RME specifies conversion with less than 12 samples of delay; each MADI-chained unit adds 3 samples at single speed, rising to 6 and 12 samples at double and quad speed, which its delay compensation function evens out across units. [1] Editorial calculation: 12 samples is 0.25 ms at 48 kHz and about 0.06 ms at 192 kHz.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What does +24 dBu at 0 dBFS mean on an audio A/D converter?
It is the analog input level that reaches digital full scale; RME's ADI-8 QS offers +24, +19, +13 and +4.2 dBu, with SNR from 117 dBA at +24 dBu down to 113 dBA at +4.2 dBu. [1]
Are all DB25 audio connectors wired the same?
No. AES59-2012 adopts the Tascam DA-88 pinout; TV Technology notes a second pinout based on Yamaha I/O cards that differs from it. [3]
How much delay does an audio A/D converter add?
RME specifies less than 12 samples for the ADI-8 QS, which is 0.25 ms at 48 kHz (editorial calculation). [1]
Sources and what still needs a direct check
Sources checked 2026-10-12. RME and Focusrite describe their own converters; TV Technology reports on the AES59 standard with comments from the AES standards manager and SSL.
