User guide

664 User Guide and Technical Information

v. 1.0 Features and specifications are subject to change. Visit www.sounddevices.com for the latest documentation.

To use a digital input, slide the Input 1 or Input 6 Input Selector Switch to the right to enter the Input

Se ings Screen. Press the Headphone Encoder to display the list of available input sources. Turn

the Headphone Encoder to select AES3 or AES42, and press the Headphone Encoder to conﬁ rm the

selection.

Each connector carries two channels of digital audio. Alternate channels of digital audio sent to Input

1 or Input 6 are available on adjacent inputs, according to the following table.

AES Input Channel: Available to 664 Input:

XLR Input 1, Left Channel Input 1

XLR Input 1, Right Channel Input 2

XLR Input 6, Left Channel Input 5

XLR Input 6, Right Channel Input 6

The 664’s digital inputs are sample rate converted to the internal recorder’s sample rate. To sync the

sample rate of the 664’s internal recorder to external digital audio devices, see Sampling Rate.

Things to consider when using AES digital inputs:

• When using an unbalanced AES3 (SPDIF) input, the other available digital input should not be

used with an AES42 microphone.

• Signal from digital inputs is not available on direct outputs.

Limiters

Limiters prevent clipping by a enuating signals that surpass a set threshold. The amount of a enua-

tion is deﬁ ned by the “ratio” of the limiter and expressed as two numbers. All 664 limiters use a 20:1

compression ratio. This means that signal that exceeds the threshold by 20 dB will exit the limiting

stage at only 1 dB above the threshold.

The time it takes for limiting to begin once signal has exceeded the threshold is referred to as the “at-

tack time” and the time it takes for limiting to cease once signal has fallen back below the threshold is

referred to as “release time”. Signals that exceed the threshold faster than the limiter’s a ack time can

still cause clipping. The 664 limiters have a 1 ms a ack time and a 500 ms release time.

The limiters are globally activated when the Setup Menu item LIMITERS > Limiters is set to On. This

activates both the input and output limiters. Sound Devices recommends using the limiters at all times.

Limiters are present on both mic and line-level inputs as well as the Master L,R tracks and the X1,X2

tracks. The 664 input limiters have a threshold of +16 dBu (4 dB below clipping), while the limiters for