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Antminer S19j Pro Underclock

The honest answer to “S19j Pro undervolt settings”: set a watt target of 1,850 W. That is the best-efficiency point in the preset library — about 76 TH/s at 24.3 J/TH, roughly 60% of the 3,068 W factory rating — and everything from there to 2,000 W stays within 5% of peak. The absolute floor is 1,740 W. There is no frequency or voltage to copy: the autotuner derives both for your unit once you set the target. An extraction quirk worth knowing: the S19j Pro binary carries no profile set of its own — it inherits the S19j Pro-A table at runtime.

Quick answer

The Antminer S19j Pro tunes across a 1,740–7,164 W envelope (Normal mode: 65–199 TH/s). Best catalog efficiency is 24.3 J/TH, and the sweet spot — everything within 5% of it — spans 1,850–2,000 W. The floor is 1,740 W — 57% of the 3,068 W factory rating. There are no frequency/voltage settings to copy: you set a watt target and the firmware autotuner derives the rest for your unit. Status: Verified (extraction).

Best efficiency sits at or near the envelope floor: the lowest watt target your hashrate goal tolerates is also the most efficient point in the catalog.

Antminer S19j Pro — Normal mode Verified (extraction)

1,740 W – 7,164 Wwatt envelope
65 TH/s – 199 TH/shashrate span
24.3 J/THbest efficiency @ 1,850 W
1,850 W – 2,000 Wsweet spot (≤5% off best)
Risingcurve shape
25catalog points

Floor fits a 120 V 20 A continuous-load budget (1,920 W) but not 15 A. Budgets are the NEC 80% continuous-load rule; circuit fit only — stock Bitmain APW-series PSUs require 200–240 V input, so any 120 V build needs a PSU change regardless of watt target. At the floor this mode dissipates about 5,937 BTU/h (watts × 3.412).

Source: Extraction fact: the S19j Pro binary embeds no profile set of its own — it inherits the S19j Pro-A set at runtime. Points above the ~3,068 W factory rating assume upgraded cooling and PSU headroom; they are catalog facts, not recommendations.

How to set a power target on this model

Aftermarket firmware exposes underclocking as a power target (sometimes "power limit" or a preset picker), not as frequency/voltage fields. Pick a watt figure inside the envelope above; the autotuner benchmarks your boards and settles onto it over a tuning period. Braiins OS+, VNish and LuxOS each expose this in their own UI, and DCENT_OS uses watt-target autotuning on its supported models; the undervolting guide walks through the firmware side step by step, and the firmware comparison covers which firmware supports which model. Verify the result at the wall with a meter — the target is an input, the wall draw is the fact.

Frequency and voltage are calculated at runtime by the firmware autotuner — never fixed presets; per-unit silicon quality, ambient temperature and cooling shift real results.

These envelopes are derived aggregates (bounds, bands, counts) — the row-level operating points, the interactive picker and the CSV/JSON of the source data live in the ASIC Power Profiles Database, the single source dataset for every number on this page.

Antminer S19j Pro full specifications → · Row-level operating points (source dataset) → · Overclock headroom by cooling → · All tuning envelopes →

About that “1,850 W / 76 TH” forum number

If you searched this model, you have probably met a single reddit data point: 1,850 W and 76 TH/s. It is real — it is the best-efficiency preset on the curve above, which is why it keeps resurfacing. What the forums could not tell you is the rest of the envelope: the floor below it buys quieter fans but slightly worse J/TH, the band above it holds within 5% of peak up to 2,000 W, and the library runs all the way to targets no air-cooled unit should chase. Cathedra’s engineering write-up on underclocking their S19j Pro fleet found the same shape from live-fleet data — worth reading for the institutional view; this page gives you the preset library’s actual bounds.

Related products, repair, and setup paths

Last reviewed August 13, 2026.