Check1.2 - Feedback Checker
Finds the frequency band about to cause feedback, in about 30 seconds, on your iPhone.
Check1.2 uses a 4096-point FFT to scan your stage monitor for feedback-prone frequencies in about 30 seconds, accurate to roughly ±0.2Hz between 100Hz and 8kHz. It also records stereo audio uncompressed — no limiter, no compressor — and includes an ear-training quiz to help you recognize the same bands next time. It's a one-time ¥1,200 purchase after a 7-day free trial, and everything runs on-device: no audio or analysis ever leaves the iPhone.
What holds up
- +One-time ¥1,200 after a 7-day trial — no subscription.
- +Runs everything on-device — no audio, analysis, or voice data is ever sent out.
- +Records stereo audio with no compressor or limiter, so you get the raw signal.
Mind the limits
- −iPhone and iPad only, iOS 17 or later — no Android version.
- −Free tier caps you at 3 saved results and 2 quiz sets a day.
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