Comparison
UnFairchild vs. the original Fairchild 670
We are obviously not neutral; we build the UnFairchild. So instead of spin, here are the facts of what is the same, what is different, and which unit belongs in which room.
What the original is
The Fairchild 670 is one of the most revered compressors in recording history: a late-1950s stereo vari-mu design with about twenty tubes and fourteen transformers, six switchable time constants, and lateral-vertical operation for vinyl cutting. It shaped decades of records, and surviving units now sell for collector prices and require specialist care: scarce tube types, aging components, and drift between channels.
What the UnFairchild keeps
- The variable-mu tube compression topology and its character
- An all-tube, transformer-rich signal path on the same scale
- The six classic preset time constants
- Stereo operation with the lateral-vertical idea, now full M/S
What the UnFairchild changes
| Capability | Fairchild 670 | UnFairchild 670M II |
|---|---|---|
| Time constants | 6 preset | 6 preset + 4 fully variable |
| Compression mode | Feedback only | Feedback and feed-forward |
| Sidechain | None | External sidechain input |
| Threshold behavior | Fixed | DC threshold control |
| Stereo modes | Lateral-vertical | L/R and full M/S, independent control |
| Serviceability | Scarce parts, specialist repair | Modern components, available JJ tubes, 2-year warranty |
| Price | Collector market | $9,995 new |
The honest verdict
If you are a collector or an institution preserving recording history, nothing replaces an original. If you make records for a living and want this circuit working every day, on sessions, with a warranty, the UnFairchild is the version designed for you. That is exactly why Eric Valentine built it.
Engineers including Shawn Everett, Michael Romanowski, and Kid Harpoon use the UnFairchild 670M II on records today. And if your sessions live in the box, the UnFairchild plug-in is $149 with a 14-day trial.
Quick answers
Is the UnFairchild a clone of the Fairchild 670?
It is a recreation and an extension. The variable-mu compression topology and character follow the original, but the UnFairchild adds four variable time constants, a feed-forward mode, external sidechain access, a DC threshold control, and full M/S operation that the original never had.
How much does an original Fairchild 670 cost?
Surviving originals are collector items that often approach or exceed six figures, before factoring in the specialist maintenance they require. The UnFairchild 670M II is $9,995 new with a two-year warranty.
Does the UnFairchild use the same tube count as the original?
Like the original 670 architecture, the UnFairchild is a large all-tube, transformer-rich design with twenty tubes and fourteen transformers, built with modern, serviceable components and tubes that are still in production.