The JAM Pedals "Celestial Window" Tubedreamer is the mk.2 version of the company's 808-style overdrive, dressed in one of JAM's one-of-a-kind hand-painted custom artworks. JAM describes it as "a warm, rich and articulate 808-style overdrive built to cut through a mix without ever sounding congested or harsh"1. It is an overdrive pedal in the Tube Screamer family, and if you want to see how that circuit compares with its closest relatives, our Boss SD-1 vs Ibanez TS9 Tube Screamer comparison covers the two pedals the 808 design is usually measured against.
An 808-style overdrive with a no-diode mode
At its core is the JRC4558D chip, the op-amp long associated with the 808-style circuit, paired with three-diode asymmetrical clipping that JAM says gives "natural response to picking and fretting nuances"1. The mk.2's headline addition is the Clipping toggle: in no-diode mode the pedal removes diode clipping altogether, which JAM says gives "a more open, dynamic and amp-like response with greater headroom and clarity"1. JAM also notes that the mk.2 offers finer resolution at lower Gain settings, expanding the range of usable clean push and edge-of-breakup tones1.
The Tubedreamer mk.2 is an 808-style overdrive built around the JRC4558D chip, which JAM describes as warm, rich and articulate, made to cut through a mix without sounding congested or harsh1. Its no-diode mode removes the diode clipping entirely for a more open, dynamic and amp-like response with greater headroom and clarity1.
The controls
| Control | What it does |
|---|---|
| Level | Controls output1 |
| Tone | Adjusts tonal balance1 |
| Gain | Sets drive1 |
| Clipping toggle | Selects asymmetrical or no-diode operation1 |
| HIGH GAIN footswitch | Activates an additional gain stage1 |
| Two internal trimmers | Set output independently for asymmetrical and no-diode modes, allowing matched levels or a deliberate boost1 |
The two internal trimmers are worth knowing about before you buy secondhand: they let you match the output of the two clipping modes, or set the high gain stage as a deliberate level boost1.
The effect and the HIGH GAIN stage can each power up on or off. To set the startup state, disconnect power, hold the relevant footswitch or footswitches while reconnecting power, and the pedal saves it1.
Power and specifications
The Tubedreamer runs on 9V DC center-negative power and draws 60 mA1. Input impedance is 500 kΩ and output impedance is under 5 kΩ1. It measures 7.5 x 12 x 5.6 cm (2.9 x 4.7 x 2.2 in) including jacks and controls and weighs 280 g (0.6 lb)1.
The artwork versions
The Celestial Window is one of several custom artwork versions of the same pedal. JAM's line on them is "Same sound, different artwork"1, and each is a one-of-a-kind hand-painted piece, so the pedal you receive will differ in painted detail from the product photos1. Other artwork versions include the "Astronaut-y", "Blood Spatter", "Butteskull" and "Monterey" Tubedreamers1. The standard-circuit predecessor is covered on our TubeDreamer page, and JAM's dual-overdrive take on the format is the Double Dreamer. For more circuits in the same family, see our Overdrive Pedals page.
JAM offers a money-back guarantee: if within 30 days of receiving the product you are not satisfied and wish to return it, you get a refund, no questions asked1.
Sources (1)
- “Celestial Window” Tubedreamer, JAM Pedals (www.jampedals.com)
