RME M-16 AD [15/57] Limiter

User’s Guide M-32 AD © RME

8.5 Limiter

For the reference converter ADI-8 QS, RME developed a new fully symmetrical circuit design

with digitally controlled release time. The same circuit has been added to the M-32 AD. While

the analog limiter is constantly within the signal path, it operates fully transparent as long as

there is no control signal generated, so does not cause noise or distortion. This special feature

made it possible to define a threshold of +3 dB in deactivated mode, preventing an overload of

more than 3 dB of the AD-converters. This avoids not only extreme overload effects, but also

prevents the AD-converters from being damaged.

Both the fully symmetrical design and the digitally controlled release time

contribute to the reduction of the unavoidable distortion of a peak limiter

(linearity errors of the control elements, generation of the control voltage).

The distortion value of about 0.3% stays the same at any level and any

frequency.

Another exceptional feature is the ability to handle extremely high levels. At

the level references +24 dBu, +19 dBu and +13 dBu up to +30 dBu can be

fed, the signal is still limited correctly (-3 dBFS), THD is still 0.3%. At the

setting +4.2 dBu the maximum unclipped input level is +24 dBu. So there is

more than 20 dB overload possible!

Note

: As with all such basic designs, increasing dynamic ratio and gain reduction causes audi-

ble pumping effects.

8.6 Clock Section

The source and frequency of the unit's clock is configured in the CLOCK SECTION. The key

CLOCK lets you step through the options external clock (Word, MADI, ADAT) and internal clock

(44.1 kHz or 48 kHz). The button STATE sets internal, but also the external sample rate to dou-

ble or quadruple of the basic sample rate.

WCK, MADI, ADAT (Slave Mode)

Sets the corresponding input to work as clock

reference. A missing or invalid clock source signal

is indicated by flashing of the corresponding LED.

44.1, 48 (Master Mode)

Activates the internal clock with a sample rate of

44.1 kHz or 48 kHz.

DS, QS

With the DS LED additionally lit, the sample rate

will be 88.2 or 96 kHz, with QS lit it will be 176.4

or 192 kHz.

A selection of DS and QS is also possible when using external clock (Slave). If the M-32 AD

should operate at 192 kHz, but receives a synchronous word clock of 48 kHz, the button STATE

activates DS or QS mode. This way, AD-conversion and digital outputs are configured to oper-

ate in the frequency ranges Single Speed, Double Speed or Quad Speed.