Level References And Gain - RME Audio Micstasy User Manual

18.3 Level References and Gain

The analog output levels of the Micstasy are designed to maintain a problem-free operation with
most other devices. The headroom of the Micstasy reaches 9 to 20 dB, depending on the refer-
ence level.
Reference Micstasy
- +24
Lo Gain +19
+4 dBu +13
With +13 selected, the according headroom of 9 dB meets the latest EBU recommendations for
Broadcast usage. +19 is best suited for professional users who prefer to work balanced and at
high levels. +19 provides 15 dB headroom at +4 dBu nominal level. Set to +24 the Micstasy is
compatible to SMPTE (+24 dBu @ 0 dBFS, +4 dBu with 20 dB of headroom).
The above levels are also found in our ADI-8 series of AD/DA converters, the Multiface, Fire-
face, and even in our Mic-Preamps QuadMic and OctaMic. Therefore all RME devices are fully
compatible to each other.
The definition of gain in a mic preamp proves to be difficult. While many devices claim a gain
range from +10 dB up to +60 dB, the real gain often is somewhat different. The most simple
way to define it is to compare analog input level to analog output level. Unfortunately the flexibil-
ity of the Micstasy (3 different analog reference levels) changes the 'overall' gain already by up
to 11 dB.
And what about devices that don't have an analog output at all? If the mic preamp is connected
directly to an AD-converter, there is no reference for measuring amplification. Often the scale of
the microphone stage of an analog device is simply copied to the digital one. But since every
preamp has a different adaptation to the AD-converter, all mic preamps end up having a differ-
ent sensitivity - in spite of nominally identical gain settings.
Even the Micstasy can not completely solve this problem. To begin with, the analog levels
match the above mentioned professional studio levels, in order to ensure the best possible
compatibility between the AD-conversion and the analog outputs. The triple reference level
further improves compatibility, but also causes the displayed gain level not to be accurate – it
could only be accurate at one of the three settings.
We decided upon +19 dBu, but – after a further market survey – made another compromise.
The displayed gain value refers to an input level of +21 dBu, for compatibility with other popular
high-quality mic preamps. With this, their gain settings can now be simply transferred 1:1 to the
Micstasy. In practice, what this means is as follows:
• At +21 dBu input level, a gain setting of 00 and +19 as analog output reference, the analog
output level is +19 dBu. So the overall gain has an offset of -2 dB compared to the display.
• In this case the AD-converter reaches full scale (0 dBFS). Hence, the relation between the
AD-converter and the analog output level reference is correct.
• With an input level of +19 dBu, the Micstasy must be set to a gain of +2 dB to produce an
output level of +19 dBu, and to reach full scale at the converter stage.
When +13 is selected, the deviation will be -8 dB, while at +24 it is +3 dB.
BTW, taking into account the analog output reference of +24, the Micstasy even features a gain
range of 90 dB.
48
0 dBFS @
+24 dBu
+19 dBu
+13 dBu
User's Guide Micstasy © RME
Headroom
20 dB
15 dB
9 dB