SarmaysPre 424
Authentic late-80s cassette multitrack preamp emulation. Two-stage op-amp saturation, Baxandall EQ, tape-era HF rolloff, and analog noise floor — inside your DAW.
Authentic Analog Signal Chain
Every stage of the late-80s cassette portastudio preamp meticulously modeled — from op-amp rail clipping to Baxandall shelving EQ and tape-era bandwidth limiting.
Input Trim
Pre-gain attenuator that controls how hard the signal hits the first op-amp stage. From transparent to overdriven.
µPC4570 Saturation
First op-amp stage with asymmetric tanh waveshaping. Produces rich 2nd harmonic content with a soft, elastic knee.
Baxandall EQ
2-band shelving EQ — Low shelf at 100 Hz and High shelf at 10 kHz, each with ±10 dB of boost/cut.
NJM4565 Coloration
Second op-amp stage providing gentle odd-harmonic warmth. Subtle compression without aggressive clipping.
HF Rolloff & Noise
12 kHz lowpass emulating cassette-era bandwidth limiting, plus analog noise floor simulation for authentic character.
Output Volume
Post-saturation master volume with DC blocking to remove any residual offset from the saturation stages.
Dual Op-Amp Saturation
Two distinct saturation characters work in series, just like the original hardware. Not diode clipping — real op-amp rail clipping modeled with tanh-based waveshaping.
First Stage: µPC4570
Primary Saturation- • Asymmetric clipping — positive/negative rails clip at different thresholds, generating rich 2nd harmonic content
- • Soft elastic knee — gradual transition from linear to saturated, described as “rubbery” in character
- • Drive-dependent — light: transparent warmth. Medium: rich mid-forward color. Hard: granular, musical fuzz
- • 4x oversampled — nonlinear processing at 4x sample rate eliminates aliasing artifacts
Second Stage: NJM4565
Gentle Coloration- • Symmetrical saturation — mainly odd-harmonic content (3rd, 5th) for subtle warmth without aggression
- • Dry/wet blend — mixes tanh-shaped signal with linear pass-through, preserving transient detail
- • Gentle compression — acts as a soft limiter on peaks, taming transients naturally
- • Transparent at low drive — 80% linear at minimum, progressively more colored as drive increases
Simple, Purposeful Controls
Six controls. No menu diving. Every knob and fader maps directly to the original hardware’s signal path. Vintage channel-strip layout with a prominent drive fader.
Under the Hood
Engineered for authenticity and performance. Every DSP algorithm is carefully crafted to capture the real analog behavior while running efficiently in your DAW.
Tanh Waveshaping
Core saturation uses tanh() — a smooth S-curve that naturally models op-amp rail clipping. No harsh digital artifacts.
4x Oversampling
Nonlinear stages processed at 4x sample rate using IIR half-band polyphase filters. Pushes aliasing harmonics well above Nyquist.
DC Blocking
Input and output DC blockers (1-pole highpass at 5 Hz) remove DC offset from asymmetric saturation without affecting audible content.
Baxandall Shelving EQ
Second-order biquad filters using Audio EQ Cookbook formulas with bilinear transform. Frequency pre-warped for digital accuracy.
Parameter Smoothing
20ms ramp smoothing on all parameters prevents zipper noise during automation. Butter-smooth knob movements.
Stereo Level Meter
Real-time LED-style output meter with 10ms attack and 300ms release envelope follower. Thread-safe atomic metering.