Applies to: ISA 828

Mic Input Gain

With the Mic input selected, the user has access to the full gain range in 10dB steps from 0dB to +60dB (yellow legend). The gain range is split between two gain modes depending upon the status of the 30-60 switch.

Mode 1 Mic Gain Range 0-30

With the 30-60 switch off, the stepped gain dial operates over a gain range of 0dB to +30dB, the level of gain chosen being indicated on the front panel by the outer arc of yellow numbers around the gain knob.

Mode 2 Mic Gain Range 30-60

With the 30-60 switch on (illuminated), the stepped gain dial operates over a gain range of 30dB to 60dB, the level of gain chosen being indicated on the front panel by the outer arc of yellow numbers around the gain knob. An additional 20dB of gain can be applied to the signal after the mic/line Gain knob using the Trim knob. (See the ‘Trim’ control text below for a full explanation.)

Line Input Gain

With the line input selected, the user has access to gain settings ranging from –20dB to +10dB, indicated on the front panel by the arc of white numbers around the gain knob. The 30-60 switch is inactive when the line input is selected, as the gain range for Line level inputs is restricted to –20dB to +10dB in 10dB steps. An additional 20dB of gain can be applied to the signal after the mic/line gain knob using the Trim knob. (See the ‘Trim’ control text below for a full explanation.)

Instrument Input Gain

With the instrument input selected (inputs 1-4 only), the gain is applied to the input signal by using the trim control only, which allows +10dB to +40dB of gain range. The level of gain chosen is indicated on the front panel by the outer arc of yellow numbers around the gain knob. This input is suitable for high impedance sources such as guitar or bass pickups (which may be connected directly without the need for an external DI box) or vintage synthesizers with high impedance outputs.

Trim

The Trim control provides an additional variable gain of 0dB to +20dB when a mic or line inputs are selected. The level of gain chosen is indicated on the front panel by the inner arc of white numbers around the gain knob. The additional 20dB of gain that can be applied to the mic or line signal is very useful for two reasons:

When high gain is required:

Using trim in conjunction with the mic gain of 60dB gives a total of up to 80dB of pre-amp gain, making it very useful for getting good digital recording levels from very low output dynamic and ribbon microphones.

Gain adjustment during recording:

When small amounts of gain adjustment are needed to correct performance level variations during recording, use the trim knob rather than the stepped mic/line gain knob, as switching the 10dB gain steps would be much too intrusive. It is therefore good practice to apply some Trim gain before using the 10dB stepped gain knob to find the optimum recording level so that the Trim control can be used to gently add or take away gain later if so required.