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Manual-4

Audio Connections

As a safety precaution, turn all devices (especially power 

amplifiers) OFF when making connections. Doing so gives you a 

chance to find and correct wiring mistakes and prevent damage 

to your amplifiers, speakers, ears, etc. 

Analog Inputs and Outputs

The RPM 44 has four balanced analog Inputs and four bal-

anced analog Outputs. 

For each Input or Output Euroblock connector:

• Connect the (positive) audio line to the ‘+’ terminal.

• Connect the (negative) audio line to the ‘–’ terminal.

• Connect the cable shield to the ground terminal.

For those installations where the RPM 44’s internal shield-

to-chassis connection causes interference, connect each shield 

directly to the chassis PEM nut located above each Euroblock 

connector, keeping the shield wrapped around the audio conduc-

tors as much as possible. 

For optimum Electromagnetic Interference (EMI) immunity, 

connect the shields at both ends of the cable. See RaneNote 110 

“Sound System Interconnection” for more information on system 

connections and proper grounding practices.

Analog Input Stage

The analog input uses a two-stage gain approach. The first 

stage contains a software controlled analog line/mic pad and 

switchable-gain preamp. The second stage contains a Digital 

Trim control located immediately after the A/D converter. 

The RPM 44 takes the following approach to input clipping: 

If you’ve set the Analog Gain so the input stage is not clip-

ping, it is not possible to clip the A/D converter, since there is no 

additional gain between the initial input stage and the A/D con-

verter. The Digital Trim control, located after the A/D converter, 

can be set to clip the signal to your heart’s content, so adjusting 

this trim to provide the hottest signal to the DSPs 

without 

clip-

ping is the most important step when setting up gain structure. 

For this reason, a dedicated meter displaying the signal level be-

ing passed to the DSPs is provided in each Analog Input block.

If the DSPs are working with a clipped signal, the audio is (as 

expected) distorted and none too pretty, but it is not a drastic, 

damaging sound. And while it’s technically possible to write a 

DSP algorithm to emulate the glorious clipping distortion of 

vacuum tubes, it’s not particularly useful for an installed sound 

system, where the DSP power could be put to better use remov-

ing that annoying 500 Hz feedback from the Pope’s podium mic. 

Plus, they don’t yet make DSP chips with gold-plated substrates 

for those celestial highs and that moist, supple midrange.

Analog Output Stage

Each analog output also uses a two-stage gain approach, 

which differs slightly from that of the analog input stage. The 

first stage is a Digital Trim control located immediately 

before 

the D/A converter. The second stage is an analog trim control 

located immediately 

after 

the D/A converter. Attenuation is han-

dled in the analog domain, while boosting (when the incoming 

digital signal is low) is handled in the digital domain. Boosting 

and attenuating using this two-stage approach helps maintain 

the RPM 44’s excellent noise performance.

Digital (AES3) Input and Output

AES3 is a popular 2-channel (stereo) digital audio inter-

face commonly found on professional digital audio equipment 

(digital mixers, DAT machines, etc.). Each channel of the AES3 

digital stream is treated independently within the RPM 44.

See the RaneNote “Interfacing AES3 and S/PDIF”, available 

from Rane’s web site (www.rane.com/library.html), for more 

information about interfacing consumer S/PDIF gear to the 

professional AES3 standard.

Use the AES3 I/O to:

•   Connect multiple RPM 88/44/22/26z’s together to create a 

2-channel digital “bus” between devices.

•   Connect directly to the AES3 output of a digital mixing 

console.

•   Connect directly to the AES3 input of a DAT machine for 

recording purposes.

•   Connect to an external A/D or D/A converter, effectively add-

ing two more analog inputs or outputs.

Incoming Sample Rate and Word Length

The AES3 input has a built-in sample rate converter capable 

of accepting incoming sample rates up to 96 kHz. Sample 

rates exceeding the RPM 44’s internal 48 kHz sample rate are 

automatically downsampled. Word lengths up to 24-bits are 

accepted.

 

Outgoing Sample Rate and Word Length

The AES3 output uses a fixed 48 kHz sample rate and 24-bit 

word length.

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