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 |
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| 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 |
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| 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 |
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| Gain range | 0 dB to +60 dB in 10 dB steps, plus 0 dB to +20 dB continuously variable trim | |
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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 |
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Noise |
Noise at output with unity gain (0 dB) and 22 Hz-22 kHz band pass filter | -97 dBu |
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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 |
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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 |
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Frequency Response |
At minimum gain (0 dB) |
-0.5 dB at 10 Hz, |
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At +60 dB gain |
-6 dB at 10 Hz, -1 dB at 115 kHz, relative to 1 kHz |
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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 |
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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 |
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Gain Range |
-20 dB to +10 dB in 10 dB steps, plus 0 dB to +20 dB continuously variable trim | |
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Input Impedance |
10 kΩ from 10 Hz to 200 kHz | |
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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 |
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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 |
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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 |
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Frequency Response |
At unity gain (0 dB) | -0.3 dB at 10 Hz, -1 dB at 80 kHz, relative to 1 kHz |
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Crosstalk Channel to Channel |
Line input, with I/P = 0 dBu, gain = 0dB @ 1 kHz input to channel A |
Channel B output |
Instrument Input Response |
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Gain Range |
+10 dB to +40 dB continuously variable trim | |
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Input Impedance |
> 2 MΩ | |
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Noise |
>Measured with 22 Hz-22 kHz band pass filter | Minimum gain (+10 dB) = -95 dBu |
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Frequency Response |
At minimum gain (+10 dB) |
-0.1 dB at 10 Hz, |
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At maximum gain (+40 dB) |
-2.5 dB at 10 Hz, |
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High-Pass Filter |
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Roll-Off |
18 dB per octave (3 pole filter) | |
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Frequency Range |
Continuously variable from 16 Hz to 420 Hz (-3 dB) | |
Weight and Dimensions |
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W x D x H |
480 mm x 280 mm x 44 mm | |
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Weight |
3.7 kg | |