Aurora Audio GT4-8 User manual

AURORA AUDIO INTERNATIONAL
1520 North Cahuenga Boulevard
Hollywood CA90028
Phone: [phone] ax: 323 462 6137
Email: in[email protected]
Website: www.auroraaudio.net
Aurora Audio 8 Channel, 4 Band, Equalizer
Congratulations on purchasing the new, all discrete transistor
Class A circuitry, four band equalizer.
This unit is designed to normally work with the unbalanced
insertions on the rear of the GTP8, eight channel, microphone
preamplifier. This way, the equalizer uses the transformer
coupled, Class A, circuitry of the GTP8’s input and output
stages.
The equalizer is also available, at extra cost, with the
transformers and amplifiers included as a stand-alone unit.
The equalizers are nominally unity gain and the equalizer
section is engaged by pressing the red switch. The high pass
and low pass filters will only work with the EQ button selected.
The low and high frequency controls can be switched out by
putting their toggle switch in the center position. The two mid
frequency controls are switched out by rotating the knobs
fully clockwise.
The toggle switch on the high and low frequency sections of
the equalizer provide two degrees of boost and cut, a narrow
range on the left provides around 8dB cut and boost while a
coarse range provides around 18dB cut and boost. This enables
delicate adjustments of the controls.
The toggle switches on the two mid frequency sections of the
equalizer provide three degrees of Q adjustment… from a very
broad bell in the left position to a narrow one with the switch to
the right.

The mid frequency controls have a great deal of cut and boost, especially in the broad Q
setting. With the controls fully rotated you can get well over +20dB range… which can
be handy if you want to substantially cut a signal, but in boost mode, you would need to
watch the headroom especially if other EQ controls are boosting. I recommend using
the mid controls very gently until their range and power is fully assimilated! As there is
almost 40dB gain available, with another 36dB in the H /L , it would be easy to
damage speakers with the excessive boost and, at such gains, cause system instability.
There is a substantial overlap of frequency choices between the low frequency and low-
mid (330Hz max L , 100Hz min Lo-Mid), and the same between the high frequency
and high-mid (H starts at 3.3KHz, Hi-Mid starts at 2KHz). This offers a lot of
combinations of frequency compensation in the same frequency bands.
With the high-pass and low-pass filters set to 270Hz and 3.9KHz, a reasonable
representation of a telephone conversation can be set up, especially if the high
frequency control attenuates at 3.3KHz and the low frequency attenuates at 330Hz to
further attenuate the extremes.
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Warranty ONE YEAR PARTS AND LABOR LIMITED WARRANTY
Aurora Audio International warrants this unit against defects in workmanship for a
period of one year and parts for a period of one year from receipt by the original end
user. This warranty shall not apply to damage resulting from misuse including water
damage, in-transit damage, fire damage, improper maintenance, dropping the unit and
operation or storage outside the environmental specification for the product.
Do not try to repair this unit. Only qualified Aurora Audio International technicians are
authorized to repair this unit. WARRANTY VOID I CASE IS OPENED