The Sentimental Bob Electronics Tephra is a compact distortion pedal built around the classic RAT circuit, extended with a blendable analog octave up and an independent clean boost. Pedal of the Day describes it as "a distortion with a blendable analog octave up and a booster, all combined in one compact package"1. Guitar Pedal X calls it "an evolved Life Pedal take on the Rat, with additional Octave Up, Clipping and Boost"2.
The heart of the distortion is the well-known "White Face" distortion unit, built with tantalum and non-polar capacitors and, as Pedal of the Day notes, "without a single electrolytic capacitor in the signal circuit"1. By default the Tephra uses an LM308H IC along with a KR140UD1408A operational amplifier, ICs that Pedal of the Day reports are complete analogues produced at the Kiev military factory in the late 80s1.
What the Tephra does
Guitar Pedal X describes the Tephra as delivering "a wonderfully potent extended range take on the Rat Distortion"3, and in a later roundup as "a compact Life Pedal variant with obscene levels of gain, both on the Distortion and Boost sections"4. The main Distortion control offers up to +60dB of gain3.
Three sections work together in one box:
- Distortion: a White Face-based RAT circuit with six selectable clipping modes13
- Octave Up: a blendable analog octave that Pedal of the Day says adds "the cleanest possible octave with the least amount of noise"1
- Clean Boost: a low-noise MOSFET booster that is fully independent and can drive other pedals in your chain13
The octave section uses a transistor circuit from the 60s with a doubler on matched Schottky diodes, which Pedal of the Day says lets the Blend potentiometer work as smoothly as possible1. The octave is monophonic, so it tracks single notes rather than chords1. The clean Booster, per Pedal of the Day, "gives a large headroom in amplitude and allows you to warm up your amplifier"1.
An additional opamp buffer helps the Tephra match well with other pedals and, according to Pedal of the Day, eliminates potential volume jumps compared to the standard circuit due to different output impedances1.
The controls
Guitar Pedal X lists the full control set as Volume, a six-position Clipping selector, Distortion, Boost, Filter, Octave, a Boost footswitch and a Bypass footswitch, both soft-touch digital3. The Filter is a low-pass control, and the Volume offers plenty of output1.
| Control | What it does |
|---|---|
| Volume | Sets output level, with plenty of output on tap1 |
| Clipping | Six-position selector: OpAmp, Asymmetrical Silicon, Symmetrical Silicon, MOSFET, LED, Germanium3 |
| Distortion | Gain for the RAT-style core3 |
| Boost | Level for the independent clean boost3 |
| Filter | Low-pass tone filter13 |
| Octave | Blends in the analog octave up3 |
| Boost footswitch | Engages the clean boost on its own3 |
| Bypass footswitch | Soft-touch digital bypass3 |
The six clipping modes and their RAT equivalents
Guitar Pedal X maps five of the six clipping modes to known RAT variants3:
| Clipping mode | RAT equivalent |
|---|---|
| OpAmp | Deucetone Rat3 |
| Asymmetrical Silicon | Solo Rat3 |
| Symmetrical Silicon | Standard / White Face Rat3 |
| LED | Turbo Rat3 |
| Germanium | You Dirty Rat3 |
| MOSFET | Additional clipping option13 |
For a player, that means one pedal covers the range of several RAT versions, from the opamp hard clipping of the Deucetone to the looser germanium character of the You Dirty Rat, selectable from a switch rather than by buying separate pedals31.
Where it came from and how to get one
Sentimental Bob Electronics is a Ukrainian maker, and the Tephra is typically made to order. Guitar Pedal X's reviewer notes that his units were made in the week following the order, and describes the realistic wait as around a month from the time an order is submitted and paid for3. The designer, Sentimental Bob's Volodomyr, is credited by Guitar Pedal X "with his clever clipping options and enhanced circuit tuning"3.
The Tephra was listed at $180 in Guitar Pedal X's 2024 distortion roundup2, and the same site noted in August 2024 that it was on sale at $180 on the Sentimental Bob Reverb.com store3.
What reviewers said
Reviews have been consistently positive. Pedal of the Day called it "one of the most versatile distortion pedals we've played"1, and in a follow-up review of the maker's Albert overdrive recalled that the Tephra "was gloriously dirty and loud"5. Guitar Pedal X's full review placed it among the top tier of extended-range RAT pedals3, and its 2024 roundup of 32 compact RAT-style distortions called it "one of the very best"6.
"Very likely my all-time favourite Rat-style distortion - what with +60dB on the Main Distortion, with a further +30dB on the independent Boost."
In Guitar Pedal X's 2024 best distortion pedals of the year roundup, the Tephra took Bronze2.
Videos
shnobel
Pedal of the Day
Anton Hunter
Questions
Which RAT versions do the Tephra clipping modes match?
According to Guitar Pedal X, the six clipping modes map to known RAT variants: OpAmp matches the Deucetone Rat, Asymmetrical Silicon the Solo Rat, Symmetrical Silicon the Standard or White Face Rat, LED the Turbo Rat, and Germanium the You Dirty Rat. The MOSFET mode is an additional clipping option beyond those RAT equivalents.
Can the Tephra boost be used on its own?
Yes. Guitar Pedal X notes that the Clean Boost is fully independent and can be used on other pedals in your signal chain. The boost is based on a low-noise MOSFET circuit, which Pedal of the Day says gives large headroom in amplitude and lets you warm up your amplifier.
Where is the Sentimental Bob Tephra made?
Sentimental Bob Electronics pedals are made in Ukraine and are typically made to order. Guitar Pedal X's reviewer's units were made in the week following the order, but the general guidance is to allow about a month from submitting and paying for an order.
How long does it take to get a Tephra?
Since the pedals are made to order, Guitar Pedal X advises allowing around a month from the time you submit and pay for your order. The reviewer's own pedals were built in the week after ordering, so actual times can be shorter.
Is the Tephra octave up polyphonic?
No. Pedal of the Day states plainly that the octave is monophonic, meaning it tracks single notes rather than chords. It uses a 1960s transistor circuit with a doubler on matched Schottky diodes, chosen to add the cleanest possible octave with the least amount of noise.
Sources (6)
- Sentimental Bob Electronics Tephra Distortion, Pedal of the Day, 2023-02-24
- Guitar Pedal X, Guitar Pedal X, 2024-12-17
- Guitar Pedal X, Guitar Pedal X, 2024-08-28
- Guitar Pedal X, Guitar Pedal X, 2026-06-17
- Sentimental Bob Electronics Albert Overdrive Boost, Pedal of the Day, 2023-04-06
- Guitar Pedal X, Guitar Pedal X, 2024-08-30
