Do you want to know more about mini compressor pedals? We compiled a Technical Shootout for the most performance and popular mini compressor pedals available. Find out how our CompIQ MINIs stand out.

Originally designed by David Blackmer, the founder of dbx Inc., the dbx 202 “Black Can” Voltage Controlled Amplifiers (VCAs) are still in use in audio consoles today. These pioneering VCAs were the first of their kind suitable for professional audio equipment. They were constructed with a gain cell made up of eight individual transistors. Over time, advancements in integrated circuit technology have surpassed the limitations of earlier designs, leading to significantly improved performance.

For example, the CompIQ series of compressors incorporates THAT Corporation’s Blackmer® VCAs. These VCAs are recognized for their unique exponential control characteristic, where the gain changes directly in decibels. They offer an exceptionally wide dynamic range and maintain low signal distortion. What sets them apart is their neutral tonal character, which means they don’t introduce any significant coloration to audio signals. This makes them an excellent choice for audio professionals seeking high-quality, transparent signal processing.

David Blackmer, the founder of dbx Inc., is known for inventing the RMS-level detector. It calculates the Root Mean Square level of input signals in a way that mimics how our ears perceive sound, which is in a logarithmic format.

This detector’s exact envelope is then used to control the Voltage Controlled Amplifier (VCA) based on user-defined settings like Ratio, Knee, SCF, Threshold, Attack, Release, and Gain.

The CompIQ compressors have a versatile Threshold control that can handle a wide range of input signals, from weak to pro-audio levels, preventing distortion from high-level spikes. The threshold range scale is logarithmic and spans from approximately -40dBu to +10dBu, suitable for various applications. Typically, the optimal threshold for pickup signals falls between -30dBu to -20dBu.

For desired peak compression, set the Threshold knob at around 9 o’clock or slightly higher. Higher compression ratios are unnecessary unless you’re aiming for limiting. If you want more noticeable compression, lower the threshold, but use smaller compression ratios to avoid excessive signal compression, unless you intend to achieve a specific effect, like the “New York compression style,” which blends compressed and unprocessed signals for a balanced dynamic range.

The Side Chain Filter (SCF) is a feature that affects compression based on frequency. It prevents high-amplitude low-frequency content from prematurely triggering compression and dulling the sound. This is achieved by filtering the side-chain downwards from 1kHz, as shown in the graph. By doing this, compression doesn’t affect those specific low frequencies in the VCA that the program sound passes through. As a result, the low frequencies come out louder and less compressed, creating a distinct and fuller, more natural, or punchier sound.

Using the SCF helps reduce unwanted pumping artifacts often seen in “high ratio / low threshold” compression techniques. The compression achieved with the SCF is unique compared to other methods of avoiding pumping, like adjusting the threshold, ratio, using soft-knee compression, or mixing dry and wet signals. Combining the SCF with other controls provides more flexibility for applying compression to different audio content.

Frequency compensation involves adjusting the audio spectrum for the Side Chain Detector. In music, dominant frequencies and harmonics are present in each note. When notes have lower dominant frequencies, like in low guitar strings, they can trigger compression too soon, over-compressing harmonics and higher notes. To tackle this, we use gradual filtering starting at 20KHz and moving downwards with additional high-pass filters at 1KHz. This progressive approach prevents “pumping” and results in a more natural, dynamic processing, especially noticeable in percussive or bass-rich instruments.

Our compressors use a standard side-chain roll-off curve that aligns with human hearing, reducing -12dB at 2KHz compared to 20KHz.

For the CompIQ Stella and CompIQ Twain compressors, we offer three Side Chain Filter options: Normal (based on human perception), Low (-12dB per octave at 90Hz), and Deep (-12dB per octave at 200Hz).

The new variable SCF option on the CompIQ Mini can be adjusted by turning the knob clockwise to free up -12dB per octave at 90Hz, suitable for guitar and bass instruments. At noon, the SCF provides Normal processing, and turning the knob counterclockwise boosts low frequencies below 90Hz with up to +12dB per octave, making it more sensitive to signals from instruments like single coil guitars.

The CompIQ Twain features a variable-range Linkwitz-Riley crossover (70Hz to 1KHz), which splits the input signal into two separate frequency bands processed by dual compression engines. The crossover output also feeds the Dry Line, allowing seamless blending of Dry and Wet signals without phase cancellations, no matter where the crossover is set.

To illustrate, a chart shows matched levels of internal and external circuits with the crossover at 1KHz, output set to buffer level, and Mix at 100% Wet. The chart demonstrates nearly perfect alignment of phase across the audio spectrum.

The input signal’s phase remains a straight line, but the output signal’s phase gradually shifts from 0° at the lows to 400° at the highs. This is a normal result of the signal separation and recombination by the crossover’s band filters and compression engines. When switching from Bypass to Effect, there might be a perceived frequency delay, although no audible frequency loss occurs across the audio spectrum.

The following drawing illustrates the Crossover Knob Frequency Scale and the most suitable setting for utilizing the Saturation feature.

CompIQ Twain Crossover Frequencies & Best Saturation Range

Both the CompIQ Stella and CompIQ Twain compressors offer an analog Tape Saturation circuit that exclusively affects the Dry signal. This lets you add optional saturation to your signal, which can then be blended with the compressed Wet signal to introduce harmonic distortion and warm up the audio while preserving the compressed signal’s dynamics. Note that you might need to dial in some saturation before it becomes audible due to the high headroom of the saturation circuit.

For the CompIQ Stella, you can activate the LPF and HPF by removing the internal jumpers. The CompIQ Twain has variable filters accessible through small trim knobs. The HPF is for the Lows band, and the LPF is for the High band. In both compressors, the HPF is placed before the Saturation engine, while the LPF is positioned after it.

These filters are recommended for use in conjunction with the Tape Saturation feature, as they may affect the clean, dry signal otherwise. The filters were introduced to provide flexibility when processing different audio sources while maintaining musicality and avoiding undesirable artifacts like muddiness in the low end (especially with bass) or harshness with bright guitar pickups.

The X-EQ section comes after the compressor and before the Mix control, affecting only the wet signal. When mixing dry and processed signals, the X-EQ effect gradually diminishes.

In the Stella, the X-EQ has two frequency pivot points for bass (at 330Hz) or guitar (at 1KHz). At extreme knob settings (fully clockwise or counterclockwise), there’s a total 12dB difference between low and high frequencies. When the X-EQ knob is in the central position, no frequency alterations occur. You can bypass the X-EQ section by adjusting a jumper within the pedal.

The CompIQ compressor series can handle input signals ranging from +5dBu to +10dBu without distortion, depending on the model and power voltage. They offer a wide 50dB threshold range from -40dBu to +10dBu, making them suitable for magnetic pickups, line-level signals, line-level FX Loops, and high impedance or line-level inputs on recording interfaces. These compressors provide precise compression thanks to the RMS-level detector, and their LED indication is accurate when the input signal is around the calibrated reference level. The CompIQ series internally sets a “0dB reference input level” at -20dBu (77.5mVrms). The amount of compression (inf:1 Ratio) depends on the input signal level and is typically 20dB for input signals around -20dBu (77.5mVrms) and 36dB for +4dBu (1.23Vrms) input signal levels.

Compressors can introduce noise due to the amplification of make-up gain. As compression increases, more make-up gain is needed, adding noise to the signal. This noise can be further amplified by subsequent pedals or amplifiers in the signal chain. Additionally, any device before the compressor may introduce noise, which gets amplified by the make-up gain circuit.

It’s important to understand that if a compression setting requires a significant amount of make-up gain, noise will become more noticeable during silent parts. The signal-to-noise ratio drops during pauses, where noise may surpass the signal, leading to a negative SNR. Expecting complete silence when applying a +20dB gain is unrealistic. However, compressing at -20dB and then restoring with +20dB results in minimal but still noticeable amplification noise, especially during pauses. If maximum make-up gain is needed, it’s best to use the compressor for peak limiting rather than compressing the entire signal.

To accurately compare compressors for noise, they should be set with the same threshold, ratio, and make-up gain, fed the same reference signal. Some compressors have lower ratio limits, like 3:1 or 7:1, which makes them “quieter” because they require less re-amplification. Note that the term “quiet” is subjective and can be misleading.

In the case of the CompIQ Twain, the Stacked Mode can produce extra noise if not configured properly. The Twain Settings Examples provide guidance on minimizing amplification noise, primarily by adjusting compression and make-up gain in the second (highs) engine more than in the first (lows) engine. You can also manage the frequencies to compress in the second engine by raising the lows threshold, using the Low or Deep side-chain filter, and employing a soft knee to reduce noise or compression feel. Combining these controls in both engines helps find the optimal setting for your specific needs.

Dual-band processing is more complex and requires specialized compression. What works for full-band compression doesn’t directly apply to dual-band compression. The dual-band compressor’s always-on crossover has passive components that inherently generate thermal noise, which is also amplified by make-up gain.

A practical approach is to understand how compression controls (threshold, ratio, knee, timing, blend, side-chain filter, and gain) affect compression and your desired outcome. Adjust these parameters to minimize the need for high make-up gain.

Noise generated by make-up gain is typically lower with higher input signal levels because the signal is larger. When using a limiting setup with a higher threshold, hard knee, and inf:1 ratio that affects only the signal peaks, any noise is usually inaudible.

For weak magnetic pickup signals, using a 4:1 ratio and a low threshold on the CompIQ can provide compression with noise levels similar to studio-grade equipment. You can further reduce noise by blending in dry signal with the MIX control and using a soft knee to minimize the need for make-up gain.

Power sources can introduce noise to electronics. Switching power supplies, in particular, are known for introducing hissing sounds. To minimize this, use well-filtered and regulated power sources. Most pedals aren’t designed for extensive power conditioning and filtering, so it’s essential to use quality power sources separately.

The CompIQ line of compressors features a gain reduction meter to show the amount of compression applied to the input signal in dB. However, the number of LEDs in the meter varies between products and may lead to “invisible” compression between LEDs. To achieve optimal metering, a minimum of 20 LEDs is recommended.

Each product’s metering is designed and calibrated with reference to comparators at 9-12VDC, ensuring an accurate indication of gain reduction. However, the CompIQ Twain can also operate at 18VDC. At 18VDC, some calibrated thresholds for metering may shift, resulting in a metering indication of approximately -3dB less. While running an electronic circuit within a fixed voltage range (plus or minus some tolerance) is proper, operating at 80-100% voltage upshifts may alter certain calibrations within the circuit blocks. While this might have audible advantages, it impacts metering precision and introduces variation.

In rare cases, such as when powering the pedal at a higher voltage and switching the knee, the meter LEDs may appear “locked” and remain lit. This happens due to an electric spike caused by knee switching, briefly activating the LEDs even without an input signal. To prevent this, it’s advisable to switch the knee when no input signal is present but with the input and output plugs inserted into the pedal.

To turn off the remaining lit LEDs, the pedal must be powered off and then on again, or you can play a signal louder than the remaining lit LEDs, resetting the comparators. Alternatively, you can power the pedal with 9-12VDC instead of 18VDC.

The CompIQ pedal line can function within a power range of 9-18VDC. However, for optimal performance and circuit protection, certain components like the gain reduction meter are designed and calibrated conservatively to operate within the 9-12VDC range. It’s crucial to use high-quality, regulated power sources because exceeding the 18VDC maximum can potentially damage active components.

To prevent voltage spikes during pedal connection, it’s advisable to connect the pedals before powering on the power supply. Additionally, it’s a good practice to power your entire pedalboard simultaneously by switching on the AC switch on the power supply or plugging it into the AC wall wart. This helps control current draw and maintain stable voltages at each power output.

While our pedals incorporate reverse polarity protection, there are limits to what these safeguards can handle. Thus, using power supplies within the recommended voltage range is vital to ensure optimal performance and protect the circuits’ long-term durability.

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