Is the gain in the inukes actually adjustable, or is it just an attenuator? I ask because he still risks overloading the input stage if the volume dials are actually just attenuators and the gain is fixed. Some amps have adjustable gains, but most "gain knobs" are actually just attenuators slapped onto a fixed gain amplifier architecture.
Most mixing consoles output +24 dBU and so do many pro audio audio devices (RME, MOTU, SSL, Lynx Studios, etc.). A lot of pro amps can handle +24 dBu (12.28) volts on the input due the requirement to work with these mixing consoles and audio devices. As an example, the QSC GX series has a Maximum Input Level of +24 dBU and the Powersoft K20 has a Max Input Level of +27 dBU.
A QSC engineer (Bob Lee) once described it similar to below. I just found one of his
old articles.
An amp multiplies voltage and the gain control determines how much the voltage is multiplied.
{Gain control gain} × {Output stage gain} = Overall channel gain
Gain control gain varies from 0-1 and output stage gain is fixed. If the output stage gain is fixed at 32x, then the amp will increase the input voltage by 0-32x. The gain control gain is adjusted by using the knob. The knob is called a gain knob by most manufacturers, but some also call them attenuators. They are also called input sensitivity controls. They aren't really attenuators because they never reduce the maximum voltage the amp can output.
An amp has a set limit to how much voltage it can output. If the total gain causes the amp to try to output a higher voltage, then clipping occurs.
{input voltage} x {gain control} x {output stage gain} = attempted output voltage
Examples:
DAC output = 2V
Gain knob at full = 1
Amplfier fixed gain = 32x
Total output Voltage = 2 x 1 x 32 = 64V
DAC output = 4V
Gain knob at half = .5
Amplfier fixed gain = 32x
Total output Voltage = 4 x .5 x 32 = 64V
DAC output = 12V
Gain knob at 1/4th = .25
Amplfier fixed gain = 32x
Total output Voltage = 12 x .25 x 32 = 96V
Rane has a good explanation of the gain controls:
First, let's establish that power amplifier "level/volume/gain" controls are input sensitivity controls. (no matter how they are calibrated.) They are not power controls. They have absolutely nothing to do with output power. They are sensitivity controls, i.e., these controls determine exactly what input level will cause the amplifier to produce full power. Or, if you prefer, they determine just how sensitive the amplifier is. For example, they might be set such that an input level of +4 dBu causes full power, or such that an input level of +20 dBu causes full power, or whatever-input-level-your-system-may-require, causes full power.
Amplifier input sensitivity controls do not change the available output power. They only change the input level required to produce full output power. Clearly understanding the above, makes setting these controls elementary. You want the maximum system signal to cause full power at the amplifier.
There are amps that have actual attenuators, but these are more in the consumer realm than pro usage.
Have you got any hands/ears on with the FCA1616?
Nope. I've only used the Behringer iNuke amps and the DCX2496. Yesterday I ordered the
Motu 2496 for some testing.
Motu has a whole new lineup of cool products.