The Tone City COMP ENGINE is a compact compressor pedal from Tone City Audio. Tone City Audio describes it as "designed based on the Classic OTA technology like the Ross," placing it in the family of OTA (operational transconductance amplifier) compressors that traces back to the Ross compressor design1. The maker says it delivers "a very pure and low-noise sound" with "wide dynamics range and suitable for a variety of styles of tone"2.
Controls and design
Tone City keeps the control layout simple. The maker describes the pedal as having "3 essential controls" that "can let you run your compression exactly the way you want perfect"2. The company also says the controls all use high-quality components2.
For players used to the Ross-style compressor approach, a three-knob layout is the traditional format: the essential compression parameters without extra secondary functions.
Specifications
| Specification | Value |
|---|---|
| Circuit | Classic OTA technology like the Ross2 |
| Controls | 32 |
| Bypass | True bypass2 |
| Power | DC 9V power supply2 |
| Current draw | 8 mA2 |
| Input impedance | 500K2 |
| Output impedance | 10K2 |
| Dimensions | 9.4(L) x 4.5(W) x 4.8(H) cm2 |
| Weight | 0.26 kg2 |
Bypass and signal path
The Comp Engine is a true bypass pedal2. Tone City states:
"The controls all use high-quality components, and with true bypass switching, your signal will stay as clean and pure as possible."
True bypass means the pedal's circuit is removed from the signal path entirely when off, which matters on a large board where every stage in the chain affects the tone.
Power
The pedal runs on a DC 9V adapter and draws 8 mA2. Tone City states plainly: "This pedal is powered by DC 9V power supply"2. There is no battery option on the maker's specification, so plan on a power supply connection. At 8 mA the draw is light, and it sits comfortably within what most standard pedalboard power supplies provide per output.
The maker specifies a DC 9V power supply only, with no battery option listed. Match the pedal's polarity requirement to the supply you use with it on your board.
Where it sits
As a small, inexpensive-format OTA compressor, the Comp Engine competes in the same space as other Ross-inspired compact pedals. Its three-control layout and true bypass switching are the classic approach; players who want more control over blend, tone shaping or sidechain filtering would look at compressors with larger control sets. For a first compressor, or a board where space and current draw are tight, the simple format and 8 mA draw are the practical points in its favor2.
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Questions
Is the Tone City Comp Engine true bypass?
Yes. Tone City Audio's product page lists the Comp Engine as true bypass, and the maker says that with true bypass switching and high-quality components in the control section, the signal stays as clean and pure as possible when the pedal is switched out.
Does the Tone City Comp Engine take a battery?
No. The maker states that the pedal is powered by a DC 9V power supply, with no battery option mentioned on the product page. Tone City specifies a current draw of 8 mA, which is light enough for most pedalboard power supplies.
What circuit is the Tone City Comp Engine based on?
Tone City Audio says the Comp Engine is designed based on classic OTA technology like the Ross, referring to the operational transconductance amplifier compressor design associated with the Ross compressor.
How many controls does the Tone City Comp Engine have?
Three. Tone City describes the Comp Engine as having 3 essential controls, which the maker says let you run your compression exactly the way you want.
Sources (2)
- COMP ENGINE-Compressor-桂林华声乐器有限公司, Tone City Audio (桂林华声乐器有限公司), 2026
- COMP ENGINE-Compressor-TONE CITY ▏Analog Pedals & Power supplies, Tone City Audio, 2026