Pettyjohn Electronics CHIME MKII

The Pettyjohn Electronics CHIME MKII is a boutique low-gain preamp and overdrive pedal, a major update to the company's signature low-to-medium gain overdrive, the CHIME¹. It was announced ahead of the NAMM show in January 2019². Inside, it uses classic TL072 and JRC4558 op-amp stages, with a Burr Brown OPA input and output buffer².

What sets the MKII apart for a player is its power section: a proprietary supply that takes a standard 9V adapter and delivers a full 36 volts of internal headroom, with up to 10 times the current of the previous version². Pettyjohn says this gives the pedal its headroom and dynamic response from a supply of only 9 volts¹.

A low-gain preamp and overdrive on a 4558 chip

The CHIME MKII sits in the low-to-medium gain range, built around carefully implemented TL072 and JRC4558 stages that Pettyjohn says were chosen for warmth and feel². The 4558 chip sits at the heart of the clipping stage, and the pedal's internal mini toggles live around it¹.

The design lineage goes back to the original CHIME, a low to medium gain overdrive in the series²³. The CHIME MKII is a major update to that signature low-medium gain overdrive, built around a 4558 chip². Where the V1 offered its Tubbs setting through internal toggles, the MKII carries the upgrades over from that earlier version.

The original CHIME also carried a Boost control that Pettyjohn described as a pre-boost, increasing gain before the clipping amp in a way the company compared to a "Top Boost" control on some British amplifiers⁴. The maker's own guidance on the V1 was to learn the relationship between the Boost and Drive knobs, saying there is a world of tone locked inside that pairing³.

Power: 36 volts inside from a 9V supply

The MKII's headline change is its high-voltage power section. It runs 36 volts of internal power from a standard 9V adapter drawing 150mA, with up to 10 times the current of the previous version². Pettyjohn describes this as an extremely robust supply that delivers a huge amount of headroom².

The original CHIME took a different route: it ran on 9 to 18V DC, and its dual-rail power section effectively provided 18 to 36 volts of internal voltage swing, which the company translated as extra headroom for a studio-grade feel⁴. The MKII brings that internal voltage range to the pedal full time from a single 9V supply.

From the original CHIME to the MKII

The original CHIME was released nearly three years before the MKII and became Pettyjohn's most popular pedal to date². The MKII update adds several changes over the V1:

• Clipping mix knob: a mini pot that blends between germanium and LED clipping, replacing the V1's internal-toggle approach to clipping²
• Preamp Mode: an internal mini toggle bypasses the clipping stage, making the pedal a clean tone-shaping preamp and boost with no clipping at all²
• 36V internal power: the new proprietary supply described above²
• Direct-coupled stages: internally direct coupled for what the maker calls the purest signal path possible²
• Added frequency range: wide enough that Pettyjohn suggests using it as a bass or acoustic preamp¹

The V1's well-known Tubbs setting was reached through internal toggles; on the MKII, the clipping knob's LED side gets you there, and Pettyjohn notes that players who truly want the original V1 Tubbs setting can open the back panel and set the toggle to the left of the 4558 chip¹.

Four ways to use it

Pettyjohn's own usage guide describes several ways to set up the MKII¹:

• In preamp mode, use it as a first, always-on pedal at the front of your board.
• Thanks to the added frequency range, use it as a bass or acoustic preamp.
• Set the clipping knob to about 9 or 10 o'clock for boost use.
• For the original V1 Tubbs setting, open the back panel and use the toggle to the left of the 4558 chip.

1. Boost: set the clipping knob to about the 9 to 10 o'clock position, where the pedal works as a boost¹.
2. Dirt: full counter-clockwise on the clipping knob is full germanium clipping¹.
3. Tubbs: the LED side of the clipping knob gives the Tubbs setting from the original V1¹.
4. Preamp: with Preamp Mode engaged, use it as a first, always-on pedal at the front of the board¹.

The company positions the pedal as a boutique low-gain preamp/overdrive, crediting designer Stephen with having outdone himself in creating it¹.

Who uses it

Pettyjohn names Shawn, a session guitarist from Nashville, Tennessee, as a CHIME user, saying it is his go-to, always-on pedal¹. The company also recommends the MKII itself as a first always-on pedal at the front of a board in Preamp Mode¹.

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