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 half or quarter 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
quarter 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 quarter inch input
does not bypass any internal circuitry and does not change gain or
operating level.
The 5500 carries APIs standard 5 year warranty.
- Classic 550b Equalizer design
- Two range switches to individually alter gain steps
- Usable as a 550b, 550D or 550M
- Peak/shelf switch on Hi and Lo bands
- True hardwire bypass
- Balanced In and Out on XLR
- Unbalanced input on 1/4"
- EQ In/Out switch
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