# Measurement Summary — MENTESH2A v1.0

This document summarises the capture and fitting work behind the
v1.0 release. The full SOP, raw curves, and null-test pack live at
**me-plugins.com/engineering**.

## Reference unit provenance

The unit is a 2014 UA Teletronix LA-2A reissue (1960s Lawrence Silver-era circuit) serial-traced and audited by Mentesh
Engineering. Current operating configuration:

| Component | Spec |
|---|---|
| V1 (input gain stage) | NOS RCA Black-Plate 12AX7 |
| V2 (driver) | NOS RCA Black-Plate 12AX7 |
| Output transformer | Sowter 8940 (stock UA factory) |
| Optocell | T4B (stock UA factory) |
| Bias point | documented; archived in v1.0 capture pack |

## Capture chain

| Stage | Detail |
|---|---|
| Source | Pro Tools 2024 / 96 kHz / 24-bit |
| I/O | Apogee Symphony I/O Mk II, 8×8 analog |
| Cable | balanced TRS, 0.5 m, same cable for hw and plug capture |
| Loopback verification | PR=0, plugin output = unit's loopback path (bit-identical) |

## Capture matrix

11 PR points × 3 sources = **66 raw captures** (33 hw + 33 plug pairs).

| | PR=0 | PR=10 | PR=20 | PR=30 | PR=40 | PR=50 | PR=60 | PR=70 | PR=80 | PR=90 | PR=100 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Vocal  | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Bass   | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Drums  | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |

## Level-matching

Each plugin capture is **RMS-matched** to its hardware pair. The plugin
side then receives a per-source perceptual offset on top of the
RMS-match — the value of the offset is the actual gain the plugin
outputs in a DAW relative to "RMS-equal":

- **Vocal:** +5.5 dB
- **Bass / Drums:** +6.5 dB

This corrects for the well-known fact that compressed program material
with different transient density reads quieter perceptually even when
RMS-equal, and additionally aligns the comparison with what the
production plugin actually outputs in a DAW (not just what a meter says
is "equal"). The offset was set by repeated operator listening tests
on the matched A/B pairs.

## Fitting

The PR-curve was fit using a constrained optimisation over the four
T4B-program-dependent parameters (attack-fast, attack-mid, release-1,
release-2). Constraints:

- Monotonic GR vs PR
- Continuous derivative across PR=30 (where the unit transitions from
  fast to mid attack regime on most program material)
- T4B sub-linear slope above PR=80

**R² fit across all sources:** 0.85–0.97.

## Public null-test pack

The full 33-capture A/B set is browsable at
**me-plugins.com/mentesh2a/listen** with sample-aligned, level-matched,
blind-A/B-able playback in the browser.

The same audio is provided at PR=50 in this press kit's `audio/`
directory for the convenience of reviewers who want to grab one
representative point without scraping the website.

— Mentesh Engineering, v1.0 release
