The Rooster is a valve based design mic/line & DI pre-amp with EQ and a distortion section based around the same 5725 valve used in the ever-popular Culture Vulture Mastering Plus.
INPUT STAGE
The input is balanced, via an attenuator in Line In mode, with a custom Sowter transformer. There is 48v phantom power selected by a locking toggle, and phase reverse. A DI jack input (unbalanced) comes between the transformer and the Input Level control. Gain is provide by a twin triode 12AT7/ECC81 valve which also powers the active boost controls in the EQ section.
EQ SECTION
The neatly laid out EQ section has all the active boost controls on the left, with our unique “Varislope” bass lift control, peaking at 60 Hz, and a selectable mid/high lift peaking at 2.5k/4k (“bell” shaped) and 7K (“Varislope”). The Cut controls are in the centre. The mid operates at 700Hz, the 6 position Bass Cut is combines a high pass filter with shelving, depending on the setting (see curves in manual). There is also a switchable low pass filter (labelled LPF) to remove unwanted harsh high frequencies.
'ATTITUDE' DISTORTION SECTION
The same 5725-distortion tube which is employed in the Culture Vulture is used in the new Rooster. It offers a subtle distortion characteristic in the triode position, more so than a Culture Vulture due to the higher HT voltage, plus the use of negative feedback, and so has a very low (about 0.01%) distortion when the 'Attitude' control is set to 1. In the pentode mode it generates more 3rd harmonic distortion. Distortion can be pretty radical when the Attitude control is to 'Max' and the input is high.
OUTPUT STAGE
The output valves are 2 triode/pentode PCF80s which combine high output with low impedance, controlled by the Output Level control. The output is transformer balanced. The Output level is indicated by 3 LEDs.
Rooster Specifications
Measurements are made at typical ‘Attitude’ setting ‘2’. in Pentode mode with an output of +4dBu. Measurements made with AC mains input 236V 50Hz. Load resistance is 10k?.
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Available gain (dB)
Mic
Line
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50 (77 with Attitude at max.)
14.5
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Frequency response
+0dB, -1dB
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14.5Hz to 45kHz (balanced version)
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Distortion (THD @ 1kHz)
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?0.06%
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Noise (unweighted, 30kHz filter)
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?97dB below MOL
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MOL (2% THD @1kHz)
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?+24dBu
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Phase shift
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21º (5.6%) at 10kHz
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Input impedance
Mic
Line
DI
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600?
10k?
47k? unbalanced
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Output impedance
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75?
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10k? is the ideal load impedance. The Rooster will work into a load of 600?, but distortion will increase & MOL will be reduced.
VALVE COMPLEMENT (2ea)
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Input:
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ECC81 / 12AT7
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Attitude:
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5725 / 6AS6W
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Output:
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PCF80 / 9AQ8
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