A 1:1 replica of the iconic Sontec 432D9
The Sontec MES-432 was one of the first fully parametric stereo studio equalisers, built in the mid-1970s. Fully stepped switches, surgical precision and extraordinarily musical discrete op-amps put it on virtually every successful record of the 80s and 90s, and it remains the go-to equaliser for mastering engineers around the world.
The MES-432D9D variant, used by some of the most demanding engineers alive, added a two-position high shelf selector (8 kHz and 12 kHz) in place of the fixed 10 kHz of the C variant. Our SA-432D+ carries all three positions — 8 kHz, 10 kHz and 12 kHz — plus an extra 150 Hz position on the low shelf, along with the Iron Mod, Mid/Side and True Bypass.
The op-amps
At the heart of every Sontec MES-432D sit six HS2030 and six HS6000 discrete op-amps. No other op-amp sounds the same, and no other op-amp belongs in this circuit. Stam spent two years measuring, auditioning parts and listening before successfully reverse-engineering amplifiers fully compatible with the originals.
- Six reverse-engineered HS2030 and six HS6000 per unit
- Fully discrete, 13 transistors in each op-amp
- Run at ±28 V for extended headroom, exactly like the original
- Left unpotted for better heat dissipation, stability and longevity — the original DOAs were famously unreliable
The circuit
Respecting the original schematic and DOAs is what brings this legendary unit back to life faithfully. The Q is 100% true to the original. Fully stepped switches with 1% tolerance resistors give perfect stereo matching and effortless recall, and the 0.5 dB steps across the first 3 dB are exactly what mastering work demands. Three parametric bands with wide, overlapping ranges handle musical tone shaping.
The filter design is a bridged-T filter in the feedback loop of an op-amp. Engage bypass and only the filter section drops out — the amp stage with its HS2030s stays in circuit, just as in the original.
Added features
- Mid/Side operation
- Switchable transformers (Iron Mod)
- Additional 150 Hz low shelf frequency selector
- Additional 10 kHz high shelf frequency selector
- True Bypass on the faceplate
Superior components
Every SA-432 ships with a state-of-the-art power supply built around Panasonic capacitors for completely silent operation. Each band uses 1% tolerance resistors and matched WIMA MPK and polystyrene capacitors, with Neutrik XLR connectors and period-correct knobs throughout.
How we use it
Broad tonal shaping first — half a decibel of air, a gentle lift at the bottom of a vocal — before anything dynamic touches the programme. Because every control is stepped, recalls are exact, which matters when eight album tracks have to share one tonal signature. In Mid/Side it widens or tightens without smearing the centre.
Hardware info
Genuine Sontec 432s change hands for the price of a car on the rare occasions they surface. The SA-432D+ puts that circuit, and in several respects an improved version of it, in our rack — still a serious professional outlay.
Hear it on your record
Book a master
This chain is available on every stereo and stem master we deliver from Manchester.