RESEARCH — SYSTEM ALGORITHM
AFB
Phase-Lock Feedback Suppression
AFB breaks feedback by rotating its phase, not by cutting the spectrum. Precision all-pass filters rotate the loop phase 180° at the feedback frequency — the howl stops, the energy stays. Zero coloration, zero added latency.
THE PROBLEM
Forty years of notches
For forty years the industry answer to feedback has been the same: find the frequency, cut it with a notch filter, repeat. Every notch removes energy — after six or eight of them the system sounds thin and lifeless, and the howl simply finds the next frequency.
HOW IT WORKS
How it works
Break the phase, not the spectrum
Feedback needs gain ≥ 1 and phase = n × 360°. Traditional suppressors attack the gain with notches that thin out the sound; AFB attacks the phase and leaves the level untouched.
Fast, parallel detection
Detection runs on a buffered copy — 48 ms at high frequencies — and updates the zero-latency convolution kernel with click-free crossfades. Up to 12 simultaneous modes.
Embedded-ready
Under 1% CPU, 70 KB RAM, portable C library — ready for SHARC, ARM and desktop. A hybrid progressive notch engages only as a safety net.
UNDER THE HOOD
Going deeper
Feedback needs two simultaneous conditions: loop gain at or above unity, and phase equal to n × 360°. AFB attacks the phase: precision all-pass filters rotate it 180° at the feedback frequency, breaking the loop without removing any energy from the spectrum.
The audio path is a pure zero-latency convolution; detection runs in parallel on a buffered copy — 48 ms at high frequencies — and updates the kernel through click-free crossfades. Up to 12 simultaneous modes, under 1% CPU, 70 KB RAM — and a depth-limited progressive notch engages only as a last-resort safety net.
AT A GLANCE
At a glance
| Input | Live microphone / speaker chains |
| Output | Feedback-free program — full spectrum preserved |
| Latency | 0 samples added |
| Implementation | Portable C · < 1% CPU · 70 KB RAM |
| Availability | OEM licensing |
PARAMETERS
Hands on the algorithm
| Simultaneous modes | Up to 12 |
| Detection time | 48 ms at high frequencies |
| Suppression | All-pass phase rotation, 180° at the feedback frequency |
| Safety net | Progressive hybrid notch, depth-limited, auto-release |
| Footprint | < 1% CPU · 70 KB RAM |
POSITIONING
Compared to the alternatives
vs notch suppressors
Every notch removes energy — after 6 or 8 of them the mix is thin and dull. Phase rotation removes none.
vs ringing out by hand
AFB reacts in 48 ms, every show, without an engineer parked on the EQ.
APPLICATIONS
Where it fits
Conference & corporate
Always-on suppression in rooms where mics and speakers coexist.
Live venues & touring
More gain before feedback without thinning the mix.
Houses of worship
Untrained operators, full-time protection, zero coloration.
Embedded mixers & processors
70 KB RAM and under 1% CPU fit inside existing hardware.
INTEGRATION
Built to live inside your product
| Delivery | C · C++ · MATLAB · .dsp — full source code |
| Platforms | SHARC · ARM Cortex · macOS · Windows |
| DSP platforms | Flow DSP · Audio Weaver — solutions in preparation |
| Documentation | Whitepaper — every algorithm explained, in the clear |
OEM LICENSING
- ■ One-time payment per brand
- ■ Full source code — C, C++, MATLAB, .dsp
- ■ Whitepaper — all algorithms explained
- ■ Integration support included
- ■ Free updates
- ■ Volume discounts on multiple licenses
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