REAL-TIME · WINDOWS · FREE-STANDING APP
Four Texar Audio Prisms into an Orban Optimod‑FM 8100A/1 with the XT2 six‑band limiter — the processing stack behind countless legendary CHR and rock signals — recreated as a skeuomorphic virtual rack. Drag the knobs, watch the LED meters dance, and drive a genuine 19 kHz‑pilot composite signal straight out of your sound card.
PRISM → GATED AGC → 2-BAND COMP → 6-BAND LIMITER → PRE-EMPH → CLIPPER → 15 kHz LPF → STEREO GEN
A real knob. Vertical drag, mouse wheel, double‑click to reset — exactly how every one of the 32 knobs works in the app.
Top to bottom, signal left to right — every box in the chain, modelled as its own rack unit.
The famous four-band gated gain platform that kept program density relentless before the Optimod ever saw the signal. Four independent bands with LED gain-reduction columns and output trims, SAFETY BUFFER, DRIVE, RELEASE and EXPAND controls, plus HI BOOST and the aggressive EAGLE mode. Switchable in or out of the chain.
Phase rotator for asymmetry correction, gated dual-speed AGC with adjustable gate threshold and gate lamp, and the classic two-band compressor with RELEASE TIME, CLIPPING, HF LIMITER and band COUPLING controls. Bipolar ±15 dB AGC meter, MASTER, BASS and TOTAL gain-reduction meters, left/right input attenuators, 75/50 µs pre-emphasis selection, and a true OPERATE/BYPASS power switch.
Calibrate it exactly like the manual says: about 10 dB on the TOTAL meter with normal program — AGC on its platform, compressor riding the top.
Six limiter bands with individual output trims and gain-reduction meters, sweepable BASS EQ (frequency, boost, Q), multiband DRIVE, DENSITY, CLIP DEPTH and HF EQ. The SIX‑BAND IN/OUT switch crossfades seamlessly between the XT2 and the 8100A’s internal HF limiter — click-free, just like a relay should have been.
Final 75/50 µs pre-emphasis, a smooth-knee “smart” main clipper, distortion-controlled 15 kHz low-pass filtering, then a full stereo generator: adjustable pilot injection with pilot lamp, 38 kHz DSB stereo subcarrier, and an optional Card‑0-style noise-masked composite clipper with depth control for that extra decoded loudness. MOD% meter reads to 120%, with a FINAL CLIP activity meter and master output level.
Not a simulation of a composite signal. The actual waveform.
Run your audio device at 176.4 or 192 kHz and the generator outputs the genuine composite/MPX waveform — mono sum, 19 kHz pilot, 38 kHz subcarrier and composite clipping — ready to feed an FM exciter, RDS combiner or measurement gear.
At ordinary rates (44.1/48/96 kHz) the same composite processing runs internally oversampled and is decoded back to stereo, so you can audition exactly what the composite clipper does on normal monitors.
MPX BYPASS monitors discrete L/R taken just ahead of the stereo generator.
MONITOR DE-EMPH applies matching 75/50 µs de-emphasis so program audio sounds tonally correct while you work.
Everything in the box. One file, a tkinter front panel, and a lot of late-’80s attitude.
Prism → gated AGC → two-band compressor → six-band limiter → pre-emphasis → clipper → 15 kHz LPF → stereo generator. The whole air chain, in order, in one window.
32 knobs, 12 switches, 16 LED bar meters and 2 indicator lamps across four rack panels — lit, labelled and engraved like the real iron.
Knobs respond to vertical drag (full range over ~150 px), mouse-wheel steps, and double-click-to-default. No fiddly text boxes.
~30 ms parameter smoothing and crossfaded switching mean you can ride any control on air without a single zipper or click.
Smooth AC, Classic CHR Loud, 80s Rock and Clean Classical — plus unlimited save/load of your own settings as JSON.
Live input, band-limited pink noise, or a 1 kHz line-up tone at −12 dBFS for calibration — switchable from the Audio menu.
Input/output selection, sample rate, buffer size and hot rescan. WASAPI, DirectSound and ASIO-capable devices via PortAudio.
Engine state, CPU load, buffer under-runs and the current monitor mode, always visible in the status strip.
Route media players, browsers or playout systems through the rack with a loopback driver such as VB-Audio Virtual Cable — or take a live source straight off your sound card.
Three moves from cold start to a calibrated air chain.
Feed typical program material and set the two INPUT ATTEN knobs so the TOTAL gain-reduction meter shows about 10 dB — the calibration point the 8100A manual prescribes. That puts the AGC on its platform with the compressor riding the top.
RELEASE TIME and CLIPPING trade density against punch. The XT2’s DENSITY and per-band trims shape the multiband texture from gentle to radio-dense.
Card 0 DEPTH raises decoded loudness at the cost of composite clip energy. Watch the MOD% meter — it reads to 120, but your conscience reads further.
Straight from the service sheet.
Free, one Windows file, a tkinter front panel — and the loudest thing your speakers have heard since 1989.
The engine starts automatically on your default devices. Use the Audio menu to pick devices, sample rate, buffer size and program source; the File menu handles presets. To process another application, point it at a loopback driver such as VB-Audio Virtual Cable and select the cable as this program’s input.
Band splits, time constants and curve shapes are documented approximations reconstructed from manuals, service literature and period descriptions. This is a sound-alike instrument built for fun, education and nostalgia — not a circuit simulation, and no null-test equivalence with the hardware is claimed.
Orban, Optimod, Texar and Audio Prism are trademarks of their respective owners; this software is an independent tribute and is not affiliated with, endorsed by, or sponsored by Orban Labs or the Texar estate. Check your local regulations before connecting any composite output to transmission equipment.
Optimod 8100A/XT2 Virtual Rack — by Joel Lagace.