Specifications

1331916226-isa-two-front-elevated

Two channel classic Focusrite ISA transformer-based preamps

Front panel, per channel:

  • 1/4″ instrument input
  • Variable input impedance – Low, ISA 110, Medium, High
  • Input selection – Mic, Line, Instrument
  • 0 – 30 dB/30 – 60 dB gain switch
  • Phantom power switch
  • Phase invert switch
  • 0 – 60 dB gain in 10 dB steps
  • 0 – +20 dB continuously variable trim
  • Variable high-pass filter with on/off switch
  • Insert point on/off switch
  • Eight-LED user-calibrated level meters
  • Single power switch

Rear panel, per channel:

  • XLR-F mic inputs
  • 1/4″ TRS line inputs
  • 1/4″ TRS Sends
  • 1/4″ TRS Returns
  • XLR-M line output
  • Single peak meter calibration dial
  • Single IEC power socket

Measured Performance

Maximum Input and Output Levels

Maximum Output Level +24 dBu with a THD+N < 0.01% at 1kHz measured with 150 Ω source impedance and 22Hz/22kHz band-pass filter
Maximum Microphone Transformer Input Level +7 dBu with a THD+N < 0.7% at 1kHz measured at 0 dB of gain with 150 Ω source impedance and 22Hz/22kHz band-pass filter

Mic Input Response

Gain range 0 dB to +60 dB in 10 dB steps, plus 0 dB to +20 dB continuously variable trim
Input Impedance Switched Impedance setting
Equivalent Input Impedance at 1 kHz
Low = 600 Ω
ISA 110 = 1.4 kΩ
Med = 2.4 kΩ
High = 6.8 kΩ
EIN
(Equivalent Input Noise)
Measured at 60 dB of gain with 150 Ω
source impedance and 22 Hz-22 kHz band pass filter
-127 dB
Noise Noise at output with unity gain (0 dB) and 22 Hz-22 kHz band pass filter -97 dBu
Signal-to-Noise Ratio Measured with 150 Ω source impedance and 22 Hz-22 kHz band pass filter 121 dB relative to max output +24 dBu
Total Harmonic Distortion + Noise Measured with a -20 dBu input signal at +30 dB of gain and with a 22 Hz-22 kHz band pass filter < 0.0007% at 1 kHz
Frequency Response At minimum gain (0 dB) -0.5 dB at 10 Hz,
-1 dB at 135 kHz, relative to 1 kHz
At +60 dB gain -6 dB at 10 Hz,
-1 dB at 115 kHz, relative to 1 kHz
CMRR (Common Mode Rejection Ratio) -94 dB for mic input at 60 Hz for max. output = +24 dBu
-91 dB for mic input at 10 kHz for max. output = +24 dBu
Crosstalk Channel to Channel Mic input, with I/P = 0 dBu, gain = 0 dB @ 1 kHz input to channel A, channel B output = -85 dB

Line Input Response

Gain Range -20 dB to +10 dB in 10 dB steps, plus 0 dB to +20 dB continuously variable trim
Input Impedance 10 kΩ from 10 Hz to 200 kHz
Noise Noise at main output with gain at unity (0 dB) measured with 50 Ω source impedance and a 22Hz – 22 kHz band pass filter -97 dBu
Signal-to-Noise Ratio Measured with 50 Ω source impedance and a 22 Hz-22 kHz band pass filter 121 dB relative to max output +24 dBu
Total Harmonic Distortion + Noise Measured with a 0 dBu input signal, +10 dB of gain and a 22 Hz-22 kHz band pass filter < 0.002% at 1 kHz
Frequency Response At unity gain (0 dB) -0.3 dB at 10 Hz,
-1 dB at 80 kHz, relative to 1 kHz
Crosstalk Channel to Channel Line input, with I/P = 0 dBu, gain = 0dB
@ 1 kHz input to channel A
Channel B output
= -91 dB

Instrument Input Response

Gain Range +10 dB to +40 dB continuously variable trim
Input Impedance > 2 MΩ
Noise >Measured with 22 Hz-22 kHz band pass filter Minimum gain (+10 dB) = -95 dBu
Frequency Response At minimum gain (+10 dB) -0.1 dB at 10 Hz,
-1 dB at 115 kHz, relative to 1 kHz
At maximum gain (+40 dB) -2.5 dB at 10 Hz,
-1 dB at 110 kHz, relative to 1 kHz

High-Pass Filter

Roll-Off 18 dB per octave (3 pole filter)
Frequency Range Continuously variable from 16 Hz to 420 Hz (-3 dB)

Weight and Dimensions

W x D x H 480 mm x 280 mm x 44 mm
Weight 3.7 kg