Analog Input Stage - Klein + Hummel O 300 Operating Manual

Analog Input Stage

The O 300 input stage is a 14 k Ω electronically balanced type on a female XLR socket.
The O 300 D input stage is a 14 k Ω transformer balanced type on a female XLR socket.
If there is a humming or buzzing sound coming from the loudspeaker, first check it is not the loudspeaker by
disconnection the input signal cables. If the noise goes away it is not the loudspeaker itself and so the noises
must be coming from the cabling or the source. There are various ways to increase the loudspeaker's immunity
from these external noises:
•
Use the ground lift switch to disconnect the audio ground from the electronics' chassis ground. For safety
reasons, the electronics chassis ground is always connected to the mains power earth pin.
•
Use an O 300 D which is fitted with a transformer balanced input stage. This is especially effective when
combined with the ground lift switch.
•
If unbalanced cables are used, they can be specially wired – see picture below. Disconnect the cable screen
from the RCA sleeve if there are still humming or buzzing sounds, and/or use the ground lift switch on the
loudspeaker.
Digital Input Stage (O 300 D only)
In the O 300D there is a 16...24-bit, 32...96 kHz digital input stage that can accept AES3-2003 (commonly known
as AES/EBU), AES3id-2001, and S/P-DIF (with a suitable connector converter) signals. De-emphasis is supported
on 32, 44.1, 48, and 96 kHz sample rates. XLR and BNC connectors ensure good interconnectivity options.
O 300 (D) Operating Manual
Pin
1
2
3
Analog connections on the O 300 and O 300 D
Source (RCA)
Unbalanced RCA to Balanced XLR Connections
Cable for connecting unbalanced sources to a balanced XLR input
Signal
Audio Ground
Positive
Negative
Loudspeaker
(XLR-M)
2 1
3
Klein + Hummel
4