Discrete HP/LP Sweep Filter
Features
- Wide range 6 dB per octave LOPASS control
- Wide range 12 dB per octave HIPASS control
- Balanced input stage
- Passive filter design for smooth tone
- Unity gain throughout
- Hard Wire BYPASS switch
- Transformer Coupled Output to +28 dBu
- All Discrete Design
The API 215L is a unique passive, sweepable filter, designed
specifically to contour the sound in such a way that it sounds natural
and seems as if it "always sounded that way". Its extreme
flexibility, repeatable settings and superb sound make it ideal for all
studio, live sound and broadcast applications.
The 215L design is a passive low pass filter with a slope of only 6
dB per octave, and a passive dual hgh pass filter with a slope of 12 dB
per octave. The filters are isolated from each other with the same
discrete transistor buffer used in the famous 550 series equalizers.
This minimizes interaction between the filters, as well as providing a
low impedance source for the filter following the buffer.
The input section is a balanced circuit using the API 2510 all
discrete op-amp, minimizing the loading effect on any device plugged
into it. The output stage is a transformer balanced output, driven by
the all discrete API 2520 op-amp.
The filters are both continuously adjustable, with a range from 20
Hz to 20 kHz in two bands. The low pass filter has a range from 500 Hz
to 20 kHz, and the high pass filter has a range from 20 Hz to 600 Hz.
This covers a broad range of frequencies throughout the eintire audio
spectrum.
Because of the subtle nature of the 215L filter, it finds a home
with uses like rolling off the low end of a hi-hat, where a natural
sound is desired, not the usual "phase-shifter" sound of a 18 to 24 dB
per octave filter found on most consoles. It can also be used to thin
out room mics, without a complete loss of low end, again, resulting
from steep filter circuits.
The 215L can be used in the Legacy Series Consoles or in the L200 Rack. The
215L Filter makes use of the 2520 and 2510 op-amps and therefore exhibits the
reliability, long life and uniformity which are characteristic of API products.
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