Shin's Music Dumbloid Special

The Shin's Music Dumbloid Special is a Dumble-style overdrive pedal, handmade by Shin Suzuki of Japan's Shin's Music¹. It sits in the family of drives built around the sound of the Dumble Overdrive Special amp, and it is the version of the Dumbloid that adds a Jazz/Rock switch on top of the core circuit². Shin's Music also builds the Dumbloid Standard, which lacks that switch, and the Dumbloid line extends to a version with an added boost and one with two channels³.

What it does

The Dumbloid Special is an overdrive, tagged as such on the tagboardeffects layout page where builders documented their builds⁴. A defining point of the original circuit is its topology: it uses opamp clipping rather than diode clipping, which is why builders experimented with opamp choices, with John K finding the MC33172 sounded best in his build⁴. The circuit can be modified: adding diode clipping makes it "a bit closer to a Tubescreamer," though one builder who got a good tone that way, using a ne5532 and 1n914 diodes, noted it then sounds closer to a TS⁴. Built stock with an OPA2134PA and without the extra diodes, Janne Lummaa reported "no fizzyness at all, sounds rather good"⁴.

The Dumbloid ODS Overdrive Special, a sibling in the line, carries controls for DRV (gain), ACCENT (Cut/Presence), TONE and VOL¹. The Accent control is a feature the circuit family shares: the Guitar FX Layouts technical analysis of the Dumbloid Standard describes that pedal as roughly 95% Tubescreamer with differences in clipping and an added Accent control².

Special versus Standard

The clearest difference between the two is the mode switch. When Guitar FX Layouts published its stripboard layout for the Special in March 2014, the site noted: "No the Special has the Jazz/Rock switch, this is the Standard"². The Special was given its own thread on the site specifically to keep discussion of the two versions separated⁴.

• Dumbloid Standard: the base circuit, no Jazz/Rock switch²
• Dumbloid Special: adds the Jazz/Rock switch, Jazz cleaner and more subtle, Rock with more midrange and gain³
• Other Dumbloid versions: one with an added boost, one with two channels³

The circuit: opamp clipping

The original Dumbloid Special circuit uses opamp clipping rather than diode clipping⁴. That detail matters to players and builders because it separates the Dumbloid from the many Tubescreamer-style drives that clip with diodes; adding a diode-clipping modification to the circuit "does make it a bit closer to a Tubescreamer," according to the Guitar FX Layouts discussion⁴.

For DIY builders, the Guitar FX Layouts stripboard layout for the Special was posted unverified in March 2014 and later verified by builders on the site⁴. A few practical notes from that thread:

• The layout leaves room for wires at the sides if built in a 1590B enclosure⁴.
• The output cap is 220n; one builder changed it to 470n to reduce the low cut⁴.
• A Bitsbox kit for the layout supplies 22k pots instead of a 20k and 25k, and a 1.8k resistor instead of 1.5k⁴.

What builders and reviewers said

Opinions from the Guitar FX Layouts build thread are mixed, and they are worth reading before forming expectations about the circuit's character:

On the critical side, one builder found the fizzy decay ugly and felt the Accent control added to it, judging the pedal too fizzy above about 40% gain for his taste; another builder believed the original pedal has a fizzy decay as well, since that much gain is taken from the opamp decay⁴. The same builder who was critical overall wrote: "Honestly though, found the pedal meh... I'd have been so disappointed to have paid £400ish for an actual new."⁴ A build using a NE5532 and 1N914 diodes did produce a good tone, though the builder noted it sounds closer to a TS sound⁴.

Where it sits

For players placing the Dumbloid Special among overdrive pedals, the key difference is the circuit: the original design takes its gain from opamp clipping rather than diode clipping, and one builder believes the original pedal has a fizzy decay as well, "since the gain is taken from the op"⁴. That topology also explains why the diode-clipping modification pushes it toward Tubescreamer territory, and why builders' results vary so much with opamp choice: John K found the MC33172 sounded best in his build, while chadster, running above about 40% gain, found it "way too fizzy" for his taste⁴. For a closer look at that classic diode-clipping circuit family, see the Boss SD-1 vs Ibanez TS9 Tube Screamer comparison¹.

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