The TWA SH9 is a signature distortion pedal from TWA, built in collaboration with fusion guitarist Scott Henderson and circuit designer Susumu Tamura, the creator of the Tube Screamer. Tamura took the basic SD-9 circuit architecture he invented in 1981 and reworked it to meet Henderson's standards, giving the SH9 increased output level, improved bass and lower midrange response, and what TWA describes as a "thick, compressed, amp-like tone"1. Premier Guitar framed the project the same way: TWA took its classic Sonic Distortion circuit and reworked it to Henderson's requirements2.
The SH9 is TWA's first signature model3. It is made in the USA and housed in a die-cast zinc chassis with a metallic purple powder coating chosen by Henderson1.
A thick, compressed SD-9 distortion
The SH9 sits in the lineage of the Maxon SD-9 Sonic Distortion, the circuit Tamura designed in 1981. Maxon notes that Henderson used the stock SD-9 in his live board for many years, at very specific settings71. The SH9 is the custom take on that circuit built to his specifications1.
TWA's changes to the original design add output level and fill out the bass and lower midrange. Delicious Audio describes the result as a thick, compressed, amp-like tone with horn-like lead articulation, noting that the increased note girth combined with the compressed sound lets Henderson articulate his legato lines8.
GuitarPlayer's reviewer Art Thompson tested the pedal with a Gibson Historic '59 Les Paul and a G&L ASAT Classic with Seymour Duncan pickups, through a reissue '65 Fender Deluxe Reverb combo with circuitry by George Alessandro4. His verdict on the sound:
"The SH9 made its case right off the bat in three ways: its thickness, how much distortion it delivers and the amount of output on tap."
The controls and the reworked Tone
The control layout is the classic three-knob SD-9 arrangement49:
| Control | What it does |
|---|---|
| Distortion | Sets the amount of distortion4 |
| Tone | Adjusts tone; center frequency shifted into the lows and lower-mids14 |
| Level | Sets the output level4 |
The biggest change from the original is the Tone control. On the Ibanez SD-9, the Tone control let the player modify the distortion with bass or treble boost10. On the SH9, Tamura shifted the Tone control's center frequency and focused it in the lows and lower-mids, so there is no loss of bass frequencies when the knob is turned up1. Delicious Audio's coverage framed this as fixing the SD-9's Tone control, which it called unusable past 9 o'clock8.
The build uses components TWA lists as high quality: ALPS potentiometers, Marushin jacks, KOA/Speer resistors and WIMA, Nichicon and Kemet capacitors8.
Running at 9V or 18V
The SH9 operates on 9 or 18 volt DC power, through a 9VDC jack with the adapter not included14. TWA says optional 18VDC operation gives increased headroom, less compression and an alternate drive signature1. Delicious Audio echoes this: powering the pedal with 18 VDC allows for increased headroom with less compression and a slightly different character to the distortion8.
The SH9 ships without a power adapter, so plan on a supply that can deliver 9V DC, or 18V DC if you want the higher-headroom configuration41.
From the SD-9 to Scott Henderson's signature
The SH9's story starts with Tamura's 1981 SD-9 circuit and Henderson's long use of the stock pedal on his live board17. TWA calls the SH9 its first collaboration with Tamura and its first signature model13. Delicious Audio covered it as a new release on January 30, 2023, describing TWA, based in New Jersey, as mostly known for its filter and synth pedals8.
The pedal comes in two faceplate versions: one highlights the SH9 logo in the same lime-green as the original SD-9, and the other is an all-white screen with a replication of Henderson's signature18.
Like all TWA pedals, the SH9 is manufactured in limited batches of 50 to 100 units per run. Both of TWA's product pages showed it sold out, with a build-to-order lead time of up to 14 business days when in stock16.
What reviewers and Scott Henderson said
Henderson's own endorsement, quoted on TWA's page and in Guitar World's announcement coverage111:
"The SH9 is the best distortion pedal I've heard for live playing, and sounds equally great on the bridge and neck pickups."
TWA's page adds his reasons: compression and punchiness for legato playing, a versatile tone knob, low clear bass frequency and an overall fat, musical tone1.
Reviewer opinions were largely positive but with caveats:
- GuitarPlayer (Art Thompson): the SH9 delivers thickness, plenty of distortion and lots of output, and its "thick, muscular drive" makes it "a sweet deal for anyone who's ever wished for a 'more' knob on the Ibanez SD-9"4.
- Guitar World (Paul Riario): listed the price as $299 and flagged it as "Expensive"5.
- Guitar Pedal X (Stefan Karlsson): called it honed for upper-fret legato playing, more of a melody and lead style pedal than a rhythm pedal, and noted it is obviously optimized for single-coil pickup guitars, though with clever EQ and a low cut you can get very decent sounds9.
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Questions
How much does the TWA SH9 cost?
Guitar World's review lists the SH9 at $299, and Guitar Pedal X gave the same $299 price in December 2023. When the pedal was announced in April 2022, Guitar World reported a $300 retail price. TWA's own product pages list it at £230.00 GBP, with B-stock units at £191.00 GBP.
Is the TWA SH9 true bypass?
Yes. TWA specifies True Bypass switching for the SH9 on both of its product pages, and Delicious Audio's coverage lists the same. When the pedal is switched off, the signal passes through without the circuit in the path.
What op-amp is in the TWA SH9?
The SH9 uses a JRC4558 op-amp, the same chip family associated with the Tube Screamer lineage its designer, Susumu Tamura, created. TWA lists the JRC4558 among the pedal's specifications, and Delicious Audio's coverage confirms it.
Who designed the TWA SH9?
The circuit was designed by Susumu Tamura, the creator of the Tube Screamer, in collaboration with TWA. Tamura took the basic SD-9 circuit architecture he invented in 1981 and reworked it to meet Scott Henderson's standards, making the SH9 TWA's first signature model.
Is the TWA SH9 a limited run?
Yes. TWA states that, like all its pedals, the SH9 is manufactured in limited batches of 50 to 100 units per run. Both of TWA's product pages showed the pedal sold out, with build-to-order lead times of up to 14 business days when in stock.
Sources (11)
- TWA SH9 - Scott Henderson signature distortion pedal | Godlyke, Inc. - Godlyke Distributing, Inc., Godlyke Distributing, Inc.
- TWA Unveils the Scott Henderson Signature Distortion, Premier Guitar, 2022-05-12
- TWA SH9™ Scott Henderson signature distortion (B-STOCK), Godlyke Distributing, Inc.
- TWA SH9 Scott Henderson Signature Distortion Review, GuitarPlayer (www.guitarplayer.com), 2023-03-28
- TWA SH9 Scott Henderson Signature Distortion review, Guitar World, 2023-05-19
- TWA SH9™, Godlyke, Inc. (maxonfx.com)
- SUPER SONIC DISTORTION (SSD-9), Godlyke, Inc. (maxonfx.com)
- TWA SH9 Distortion (Scott Henderson Signature), Delicious Audio, 2023-01-30
- Guitar Pedal X, Guitar Pedal X, 2023-12-17
- SD-9 Sonic Distortion by Ibanez, RockBoard PedalPedia, 2026
- TWA's first collaboration with Tube Screamer creator Susumu Tamura is a Scott Henderson signature pedal, the SH9, Guitar World, 2022-04-29
Scott Henderson
