The PastFX Gallstone is an analog phaser pedal that recreates the vintage Electro-Harmonix Small Stone V2, then extends it with controls the original never had. PastFX calls it "our recreation of the vintage EHX Small Stone V2 loaded with extra features to expand its palette while retaining the le[gacy]"1. It keeps the same circuit family as the original, an Operational Transconductance Amplifier (OTA) phaser, and adds a Level control, a Feedback control, a Mix control, an Expand switch and a 2/4 stage mode switch, all in a compact 1590B enclosure1.
Guitar Pedal X's reviewer, writing in October 2025, called it "a warm, expansive EHX Small Stone V2 Phase Shifter" and said of the maker's modulation pedals generally that they are "typified by a warm and lush output profile"2.
The controls
The Gallstone keeps the Small Stone's core phasing but breaks the original's simple "Color" switch apart into several dedicated controls. Delicious Audio describes the result as a pedal that "deconstruct[s] the original's simple 'Color' switch" into an 8-position Width rotary switch and a separate Feedback control5.
| Control | What it does |
|---|---|
| Rate | Sets the speed of the phase sweep1 |
| Mix | Blends the phased signal with the dry signal1 |
| Feedback | Sets regeneration of the phased signal; a separate control replacing part of the original's Color switch15 |
| Level | Corrects the volume drop of the original Small Stone1 |
| Width (8-position rotary) | Offers a wider range of sweep intensities5 |
| Voice (switch) | Toggles between different feedback networks for tonal variation5 |
| Expand (button) | Switches in extra circuitry: a tuned 2 stage high "Q" all pass filter, for more resonant textures15 |
| Range (switch) | Enables super-slow LFO sweeps5 |
| 2/4 stage switch | Pushbutton selecting 4 stage mode (the stock original, red LED) or 2 stage phasing (blue LED)1 |
There is also an internal control: a Max Feedback Trimmer, reported by Guitar Pedal X at the pedal's release4. An LED LFO indicator on the face of the pedal shows the sweep in motion1.
The 2/4 stage switch is worth a note for anyone who knows the original. Pressing the button in selects 4 stage mode, which PastFX identifies as the stock original configuration; 2 stage phasing is indicated by a blue LED1. Guitar Pedal X's reviewer wrote, "I really love both the 2 Stage and 4 Stage Mode options"2.
Power and connections
The Gallstone runs on 9V DC through a 2.1mm Boss style negative tip jack, drawing 80mA1. That is a standard pedalboard supply, but the 80mA draw is on the higher side for a simple analog phaser, so it is worth budgeting for on a compact isolated supply. There is one TS input and one TS output2.
The 2.1mm Boss style negative tip jack means the Gallstone runs from the same 9V DC center-negative supplies as most pedals, and it cannot run from a battery.
How it differs from an Electro-Harmonix Small Stone
The vintage Small Stone V2 is the circuit the Gallstone recreates, and PastFX says it retains the authentic OTA-based phasing of the original15. The differences are all in what surrounds that core:
- Volume drop fixed: the original Small Stone's notorious volume drop is addressed by the Level control15.
- More sweep options: the original's simple Color switch is replaced by the 8-position Width rotary and a separate Feedback control5.
- More modes: 2 and 4 stage modes, where the original offered a fixed stage count5.
- Extra textures: the Expand button injects a tuned, high-Q filter the original never had15.
- Slower sweeps: a Range switch enables super-slow LFO sweeps5.
Delicious Audio summarized the pedal as "a faithful recreation of that classic circuit, loaded with modern enhancements that expand its palette"5.
History and release
PastFX released the Gallstone on 19 September 20254. The maker credits Scruffie with assistance on the project: "Big Thanks to Scruffie for his assistance in this project"1.
Guitar Pedal X's reviewer noted the designer behind it: "Verlie does it again! This is the 4th of her vintage inspired phasers"2. PastFX's phaser range also includes the Phase V, the Rotary Phaser, the Foot Phaser Deluxe, the Nick James Foot Phaser and the PX99 Classic Phase.
What reviewers said
Guitar Pedal X reviewed the Gallstone in October 2025 and was positive about it:
"I think the Gallstone may be my favourite of the PastFX Phasers"
The same reviewer found the pedal warm and expansive in character, consistent with the maker's other modulation pedals2. Later, in Guitar Pedal X's December 2025 round-up of the year's best new modulation pedals, the Gallstone was listed among the year's notable releases at $2073.
Price and availability
The listed price has moved since release. At launch in September 2025 the Gallstone was listed at $2094; in October 2025 Guitar Pedal X reported it typically going for $203 on PastFX's Webstore and its Reverb.com store2; and a December 2025 buying guide listed it at $2073.
Videos
Leon Todd
Foolish Pride
News
Questions
Is the PastFX Gallstone true bypass?
Yes. PastFX describes the Gallstone as a true bypass Operational Transconductance Amplifier (OTA) phaser, so with the pedal off your signal passes through without active buffering or processing1.
What does the Expand button do on the Gallstone?
The Expand control switches an extra piece of circuitry into the signal path: a tuned 2 stage high "Q" all pass filter. Delicious Audio describes it as injecting a tuned, high-Q filter for more resonant phaser textures15.
How is the Gallstone different from an Electro-Harmonix Small Stone?
It is a recreation of the vintage Small Stone V2 circuit, keeping the OTA-based phasing, but it replaces the original's simple Color switch with an 8-position Width rotary switch and a separate Feedback control, and adds Level, Mix, Voice, Expand and Range controls plus 2 or 4 stage modes15.
Does the Gallstone fix the Small Stone volume drop?
Yes. PastFX says the Level control corrects the volume drop of the original, and Delicious Audio calls it a correction of the vintage circuit's notorious volume drop15.
Where can I buy a PastFX Gallstone?
Guitar Pedal X reported in October 2025 that the Gallstone typically goes for $203 on PastFX's Webstore and its Reverb.com store; a December 2025 buying guide listed it at $20723.
Sources (5)
- Gallstone, PastFX, 2026
- Guitar Pedal X, Guitar Pedal X, 2025-10-16
- Guitar Pedal X, Guitar Pedal X, 2025-12-09
- Guitar Pedal X, Guitar Pedal X, 2025-09-19
- New Pedal: PastFX Gallstone Phaser, Delicious Audio, 2025-10-22
