- Classic 550B Equalizer Design
- 2 Range Switches Individually Alter Gain Steps
- Useable as a 550B, 550D or 550M
- Peak/Shelf Switch on HI & Lo bands
- True Hardwire Bypass
- Balanced IN and OUT on XLR
- Unbalanced Input on 1/4"
- EQ In/Out Switch
The lineage of the 5500 circuit can be traced back to the original
550 equalizer designed by Saul Walker, the founder of Automated
Processes Inc. The 550 was designed as a console equalizer which, due
to the architecture of the recording console, uses an unbalanced input.
Because the ergonomics of a console dictate that the controls take up
little space, sometimes the number of included functions can be
limited. The 5500 is specifically designed to address these
limitations. It has a balanced input, a true straight-wire bypass, an
integrated power supply with noiseless muting, and a range control that
expands it versatility to mastering applications.
Like all API products, the 5500 contains no integrated circuits in
its signal path. The gain comes from two hand-built 2520 operational
amplifiers in each channel. The balanced input is handled by a 2510
discrete operational amplifier, which is similar to the 2520, but
without the high current output stage. Besides being a key component of
the API sound, the 2520 coupled with the API 2503 output transformer is
capable of delivering +30dBm before clipping. With this much headroom,
it is unlikely that the 5500 can be driven to distortion unless perhaps
another API unit is driving the input!
A new feature in the 5500 is the range control. The range of the
amplitude controls can be reduced to 1/2 or 1/4 of their stated scale,
providing a means of adjusting the tonal balance with finer resolution
in an even gentler manner. This should be especially useful for complex
program material as contained in stems or submixes, and is ideally
suited for mastering purposes.
Also new on the 5500 is a true hard-wire bypass. In this mode the
output connector is wired directly to the input. Shortly after the
power is first applied, or immediately after it is lost, a special
circuit enables bypass mode so signal is never lost and power thumps
are never heard.
The input XLR is connected to an active balanced circuit. The output
XLR is driven from a transformer coupled output and can drive any load
from 600 ohms or greater to full output capability. The polarity is
such that there is no change from input to output, so it is suitable in
studios using either pin 2 or pin 3 as the "hot" connection. In
addition, there is a 1/4 inch input connector that interrupts any
signal that is present on the input XLR. It is balanced and can be
driven from either balanced or unbalanced sources. A positive signal on
the tip will deliver a positive signal on pin 2 of the output XLR.
Using the 1/4 inch input does not bypass any internal circuitry and
does not change gain or operating level.
The 5500 carries API's standard 5 year warranty.
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