Originally Posted by huub
Does the X32 do this?
(Some yamaha desks do this too, I guess if you built digitally controlled preamps to a certain price you get this phenomenon?)
All digital consoles, (no matter the price point), with recallable mic pre amps, have to deal with this when it comes to digitally-controlled analog gain. The benefit of total recall, including the pre-amp stage, far out weighs this as it is rare to be "sweeping" the preamp knob.
I spoke to our design team and have posted a very detailed description of what you are describing. From our design team:
Some X32 users have detected and reported a slight clicking noise when adjusting the analog preamp gain under certain conditions. The issue is sometimes reported as “zipper noise” and is more noticeable with low frequency signals such as a bass. This article explains the phenomenon and describes how to avoid it.
The X32 uses a digitally controlled precision A/D-Gain stage at the front end of every mic preamp to condition the signal . Just as on a standard analog mixer, the purpose of this A/D-Gain is to attenuate strong or amplify weak signals and thereby provide an optimal match to the preamp. Proper gain staging at this point results in enhanced signal to noise performance and prevents saturation or overdrive of the preamp or subsequent A/D converter. The analog A/D-Gain provides 2 dB of attenuation and 45.5 dB of gain in 2.5 dB steps.
This is further augmented by a digital trim that interpolates and expands the range to -12…+60 dB in steps of 0.5 dB each, for a total of 72 dB across 145 steps. The two attenuators work together to render a smooth and quiet range of gain that has the added benefit of being fully recallable. This is what the Gain control does whenever an analog preamp (of X32 or S16) is patched to an input channel. Compare this to preamps like e.g. the Neve Portico 5015, which has a Gain control with discrete 6 dB steps and 60 dB Range, plus a continuous Trim of +/-6 dB.
In cases where the preamp signal is sent to an outboard soundcard and returned from the DAW the connection between the mic preamp and the attenuator is obviously broken. In such cases the combined Gain is replaced with a purely digital Trim of +/-12 dB, in steps of 0.5 dB. As there is no analog switching involved this will never cause any noise.
As of firmware 1.10 an additional Setup page for Preamps gives back access to the head amps when they are not routed to any of the X32 input channels. Obviously, there is no interpolation and expansion of the gain range and only the 2.5 dB analog steps are in effect. Adjustment of the A/D-Gain under such circumstances may render an audible click, especially at low frequencies.
All digital attenuation in the console has been designed to be completely free of zipper noise and digital gain changes are completely inaudible. While adjustment of the analog input A/D-Gain is also inaudible through the interpolated range, there is a chance that a click can be heard when crossing the 2.5 dB steps. Of course, a rapid change in gain could be interpreted as zipper noise provided that a constant low frequency input signal is present.
This input attenuation scheme is pretty standard for digital consoles, regardless of cost. The digitally controlled analog attenuator is a necessity in the absence of a trimmer potentiometer found on an analog console. This is what makes the mic preamps fully programmable and adds a whole range of functionality to the X32.
I hope it helps!
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