SQN-4S IVe User's Handbook
provided with a pair of output peak limiters that may be confidently employed at all times. Coming
into operation just below peak level, theyaccommodate overloads of up to 20dB with an attack time
of half a millisecond and a release time of 100ms.
Peak limiting is an extremely non-linear process that relies on the masking characteristics of the ear
to render the effect essentially inaudible when executed properly and used in moderate amounts. It is
bad practice to make a habit of 'riding' the limiters: the LEDs should only light on the occasional
unexpected peak if the levels are correctly set. Allowing the limiters to be operated by low frequency
or sub-audio rumbles will cause modulation of the more audible midrange and high frequency audio.
In the worst case this may manifest itself as apparently random audible clicks. The bass cuts should
be used to remove dominant low frequency signals so that the limiters are operated only by signals in
the wanted audible range.
The Limiters are actuated by a switch [LIMITER] towards the right of the front panel and in the
[M]ono position each output channel is separately limited, with actual limiting being indicated by an
LED for each channel, placed between the meters. With stereo recording, limiting can introduce a
further problem since, if only one channel of a stereo pair is subjected to limiting, the effect is to shift
the stereo image. The [LIM] switch, therefore, has a third [S]tereo position in which the degree of
limiting is governed by the higher of the two output channel levels. This setting should be used when
the mixer output is stereo, of either type AB or MS.
13. MONITORING HEADPHONES The quarter inch jack [PH] of the SQN-4S will accept any
standard stereo plug. Headphones of any impedance may be employed although impedances of
around 200 Ohms will make best use of battery power. For location work, it is advisable to employ
headphones with good ear sealing even though they can be uncomfortable when worn for long
periods of time. Increasing the headphone level to drown the directly audible sound in noisy
situations could prove fatiguing or even damaging to the hearing in the long term, particularly if the
limiters are not used. The control knob at the bottom left of the front panel allows the headphone
output level to be adjusted - down to zero if desired.
A rotary [PHONES] switch on the front panel allows the operator to select various sources for the
monitored signals, including the output of an MS matrix which will allow an MS signal being output
from the mixer to be monitored as the equivalent AB signal. This switch has the following functions.
• S Stereo
• R Right Channel
• L Left Channel
• MS MS Matrix (MS stereo equivalent)
• L-R Left minus Right (MS stereo equivalent Right)
• L+R Left plus Right (MS stereo equivalent Left or Phase Check).
Below the [PHONES] switch is a pair of three position toggle switches, sprung to their centre
positions which control pre-fade listening to all of the input channels.
14. MIXING & MATRIXING CONTROLS The SQN-4S SERIES IVe mixer is intended to work in
various modes and particularly to accomodate the use of Mid-Side microphones and Mid-Side
recording. The CH1/CH2 pair is treated as a potential Stereo Channel, with or without MS matrixing,
while the CH3/CH4 pair can be routed or panpotted into the stereo image. This is in addition to the
usual routing of individual channels to either output.
The operation of the CH1/CH2 pair is controlled by the [GANG 1-2] and [PHASE] switches as
Page 7 of 10
