Cloud 36 Installation & Operation Manual - Page 11

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Level Control

A maximum gain reduction of 60dB can be achieved with a control voltage of +10V; the rate

of attenuation is approximately 165mV per dB. A control voltage of zero realises unity gain

(full volume), however, with no external connection to pin 2, an internal 4k7 resistor

connected to the +15V power will 'pull up' the control voltage to provide maximum

attenuation. The output impedance of the control voltage source should be low enough to

overcome the influence of this resistor.

Source Select

Here are the details of the music source select control voltages (pin 3) required to switch the

six line input signals:

With no external connection to pin 3, an internal 15k resistor connected to +15V will 'pull up'

the source select control voltage and the 'off' position will be selected. The output impedance

of the control voltage source should be low enough to overcome the influence of this resistor.

If you would like to fix the music signal to a particular line input, wire a fixed resistor from the

table below between pins 1 & 3 on the remote control connector:

If the control voltage source is not isolated from the power earth, there is a small risk of

creating a 'ground loop' by linking the mixer technical ground (0V) to the ground (0V) of the

equipment providing the control voltages. To minimise the risk, we suggest that all pieces of

equipment be positioned in close proximity and supplied from the same power outlet.

Solving problems

25.1

Ground loops (aka Earth loops)

Despite your best efforts, if the completed sound system 'hums' you probably have a 'ground

loop'; the offending signal source can be found by setting the volume control to minimum

then disconnecting the input leads (both left & right channels) on each line input until the

'hum' disappears. This problem is often caused by terminating a screened input cable into a

signal source positioned a significant distance from the mixer. A good way of avoiding this

potential problem is to use signal sources (CD players and the like) that are double insulated

with no connection to the mains supply earth. If a signal feed were derived from a second

mixer (a club or microphone mixer for example) it would be perfectly normal to expect this to

be earthed; we suggest that a transformer be used to isolate the signal and prevent a noisy

loop (See diagram on following page).

25.2

Connecting balanced signals to the unbalanced line inputs.

We recommend the use of a transformer to convert a balanced signal to an unbalanced

signal suitable for direct connection to the mixer line inputs. The transformer should be

mounted close to the Zone Mixer and the unbalanced output lead should be kept as short as

possible. Where both the source unit and destination mixer are earthed, it is important to

isolate the primary and secondary windings to avoid a potential ground loop; if there is any

doubt about this, we suggest that the balanced cable screen is not connected at the

transformer end. Suitable transformers for this application are the RS Components 210-6447

06/12/02 V5.0

Off

>+9.0V

Line 1

+7.5V

Line 2

+6.0V

Line 3

+4.5V

Line 4

+3.0V

Line 5

+1.5V

Line 6