Neumann.Berlin Digital Microphones For High Resolution Audio User Manual

AES 31st International Conference, London, UK, 2007 June 25–27 

 

1

schneidm@neumann.com 

 
 
 
 

Microphones with digital output format have appeared on the market in the last few years. They integrate the functions 

of microphone, preamplifier, and analogue-to-digital converter in one device. Properly designed, the microphone 

dynamic range can thus be optimally adapted to the intended application. The need to adjust gain settings and trim 

levels is reduced to a minimum. Dynamic range issues inside and outside the microphone are discussed. Advantages of 

digital microphones complying with AES 42, with a wide dynamic range and 24-bit resolution are shown. 

 

 

 

 

INTRODUCTION 
One should first define the term “digital microphone” in 
the context of this article. A possible classification 
could comprehend: 

- 

a transducer where the underlying acoustical-
mechanical-eletrical  transduction principle 
contains a quantization, 

- 

a combination of separate transducers, each 
responsible for certain quantization steps,  

- 

a microphone integrating an analog-to-digital 
converter (ADC). 

The first category describes the “purely digital” 
transducer. The first microphone by Philipp Reis [1], a 
single contact transducer, represented such a transducer, 
albeit with very low quality due to the 1-bit resolution. 
This is the only purely digital transducer known to the 
author. 
In the second category we find e.g. an optical 
microphone, where the position-dependant displacement 
of a diaphragm is traced with distinct light rays. The 
reflected rays excite separate sensors, whose outputs are 
combined into a single signal [2]. Another, electrostatic 
transducer experiment shows the diaphragm as part of 
the ADC, as component for the electrical / acoustical 
summation in the feedback loop of a Σ∆-converter [3]. 
To obtain dynamic ranges comparable to the 120-
130 

dB of standard analogue microphones, these 

principles would need to be scaleable over 6 orders of 
magnitude, a feat hardly achievable due to the extreme 
mechanical precision involved. 

Current microphone technology thus focuses on the 
third category: microphones with integrated ADC. Here, 
a purist could further differentiate between 

- 

microphones with ADC output modules, 

- 

microphones with ADC in closest proximity to 
the transducer, 

where the first subcategory would describe a complete 
microphone, just with an added ADC module; the 
second subcategory represents transducers where the 
transducing element itself is closely integrated with the 
analogue-to-digital conversion process. In the context of 
high resolution audio it will be clear that the preferred 
transducer should be of the electrostatic (condenser) 
type, as this principle still yields the highest 
performance regarding parameters like linearity, 
dynamic range and frequency range. 

1  HISTORICAL DEVELOPMENT 
Possibly the first realization, in 1989, incorporating an 
ADC in the same housing with an electro-acoustical 
transducer is mentioned in [4]. The corresponding 
electret condenser microphone by Ariel company was 
intended for use with the now defunct NeXT computer, 
with the then available 16 bit transducers and a stated 
dynamic range of 92 dB. A 1995 prototype by Konrath 
[5] put an ADC circuit inside the housing of a 
commercial microphone. It featured a 7-pin XLR-
connector and dedicated supply, delivering a multitude 
of supply voltages to the circuit. A later commercialised 
version by Beyerdynamic (MCD100) simplified this set-
up with the adoption of phantom power, similar in