500 Series Effect Processors
Introduction
So far on our website, we’ve covered the key points of the 500 series world and highlighted the most important modules you can add to your setup. We’ve already published a complete guide to the chassis—the fundamental and most essential unit where you’ll be installing your modules.
After that, we took a closer look at 500 series preamps, compressors, and equalizers. With those bases covered, the next category includes all the other effect processors that don’t fit into the previous sections. We’re grouping these under one roof—effect processors.
Beyond the basics, these modules are also crucial because they add that sought-after analog character to your audio signals. Plus, there are some real hidden gems among these modules.
In this article, we’ll cover the remaining 500 series effect processors and provide a brief review of each one we mention.
Just a quick note—these best 500 series effect processor reviews are listed in no particular order. We’re keeping things randomized, so they’re not ranked from best to worst.
Listed below are our Top 15 Best 500 Series Effect Processors:
1. Rupert Neve Designs 542 500 Series Tape Emulator
As a 500 Series follow-up to the Portico 5042, the 542 delivers the same thick, musical tape simulation, but with much greater creative control thanks to several new features.
In addition to the “true tape” circuitry—perfect for enhancing third-order harmonics—the 542 includes a soft-clip circuit that tames harsh sources and boosts second-order harmonics. It also features a versatile, variable Silk/Texture circuit for three distinct transformer tones in one unit, plus a wet/dry control so you can blend in just the right amount of saturation.
The Portico 542’s “True Tape” emulation gives you that nostalgic tape rounding and compression, usually only possible with real tape, and it can smooth out the harshness often found in digital recordings. Unlike digital emulations, the “True Tape” drive circuit feeds a tiny magnetic “record head,” which is then connected to a precisely equalized replay amplifier.
As the voltage increases on the “record head,” saturation builds, and at higher levels, a gentle clip circuit kicks in to round off peak transients. You can further shape the tape sound with selectable 15 or 30 IPS modes and a pre/post-tape blend control.
Alongside the tape circuit, the 542 features the variable Silk & Texture controls from the Portico II series, allowing you to fine-tune the harmonic balance and tone of the output transformer.
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Rupert Neve Designs 542 500 Series Tape Emulator |
2. SPL BIG 500 Series Stereo Image Processor
German developer SPL has expanded their 500 series product lineup with BiG—a double-slot module designed for stereo stage processing. According to SPL, BiG enhances the stereo image in a whole new way and introduces creative sound-shaping possibilities using just three intuitive controls:
- Range Control selects the frequency range to be processed.
- Stage Control moves this frequency range forward and backward within the stereo field.
- BIGNESS Control adjusts the depth of the processing.
Another highlight is the BASS function, which many users may recognize from the SPL IRON Mastering Compressor. This bass enhancement uses a passive filter, similar to the AirBass function found in the IRON.
With BiG, SPL focused not only on precise engineering but also on fine-tuning by ear. All components are installed on the circuit boards using through-hole technology, allowing the use of the highest-quality, best-sounding parts. Like all SPL devices, BiG is manufactured in the company’s own factory in Niederkrüchten, on the Lower Rhine in Germany.
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SPL BIG 500 Series Stereo Image Processor |
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3. elysia karacter 500 Series Saturation/Distortion
The karacter 500 is a box overflowing with vibrant colors. It covers the entire spectrum, from mastering-grade saturation to tube-inspired distortion and even wild sonic destruction. Gone are the days when you needed a rack full of outboard gear to achieve these elusive and highly desirable kinds of tonal coloration.
The entire unit is built with discrete class-A topology, so even the most lo-fi sounds benefit from the karacter’s high-end touch. Whether you want to enhance your tracks or completely destroy them, it’s all a matter of karacter.
The karacter 500 offers two individual channels that can be used in dual mono, linked stereo, or Mid/Side configurations, making it an incredibly versatile tool for any studio or live situation.
Its unique Color filter network allows for subtle or extreme tweaks to the harmonic-frequency relationship, while the built-in Mix control for parallel signal processing helps you dial in just the right amount of enhancement or grit. Stepped potentiometers ensure quick and precise recall of previous settings.
The elysia karacter 500 is all about bending sound. You really have to use it yourself to understand just how powerful it can be. Trust us: you need to hear it to believe it.
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elysia karacter 500 Series Saturation/Distortion |
4. Little Labs VOG 500 Series Analog Bass Resonance Processor
The Little Labs VOG analog bass resonance device is a creation from Little Labs and marks their first entry into the popular API 500-Series module format.
The VOG was originally designed to capture the chest resonance of vocalists or voice-over artists, allowing them to achieve a proximity effect without needing to be right up on the mic—hence the name, VOG, or Voice of God. However, once we heard it on kick drum and bass, it quickly became clear that this would be the go-to device for making those instruments sound massive.
The VOG lets users sweep a sharp peak resonance from 20 to 300 Hz, while anything below that peak is rolled off steeply at -24dB per octave. This allows you to focus on the low end you want, while cleaning up unwanted rumble and excessive woofer movement.
You can emphasize a subharmonic, the fundamental, or the higher harmonics. On a kick drum, for example, turning the VOG’s frequency knob can sound like you’re tightening or loosening the drumhead. In a mix, the VOG allows you to carve out space for bass-heavy instruments so they don’t clash with each other.
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Little Labs VOG 500 Series Analog Bass Resonance Processor |
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5. Radial TankDriver 500 Series Reverb
With the Radial Engineering Tank Driver, you can take any balanced line-level signal or prerecorded track and run it through your favorite spring reverb. Think of it as a Reamp system designed specifically for the reverb tank in your amplifier, letting you send vocals, drums, or any audio material through any spring reverb for a whole new range of creative sounds.
The Tank Driver features a transformer-coupled output driver with both regular and high settings to work with both modern and vintage spring reverbs. Separate drive and return controls let you fine-tune the signal to maximize your signal-to-noise ratio. To shape your sound even more, the Tank Driver gives you two tone controls so you can adjust the high end (shimmer) and the low-frequency content (boom).
If you have an old amplifier that no longer works, you can simply remove the spring reverb tank and place it on your desk. Connecting the Tank Driver to and from the spring reverb is easy, and most spring reverb tanks are clearly labeled with input and output.
For even more creative possibilities, try sending a prerecorded stereo track through two Tank Drivers. This preserves the full stereo image and lets you adjust each reverb tank for unique spatial effects. Try it on a drum track and blend it in—you’ll be amazed at the results!
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Radial TankDriver 500 Series Reverb |
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6. Neve RMX16 500-series Digital Reverb
The AMS RMX16 500 Series Digital Reverb module was launched at the 2020 Winter NAMM Show and is a much more compact unit that fits into just three slots of the popular API “Lunchbox” racks. In addition to the original nine well-known programs, the new RMX comes with nine more, carefully selected from the Remote Terminal’s collection, for a total of 18 programs.
The new RMX uses 24-bit, 48 kHz sample-rate audio and 32-bit DSP processing, delivering over 100 dB of dynamic range and +22 dBu of headroom. The A/D and D/A converters, along with the original hardware’s input/output performance specs, have been modeled to sound just like the original unit.
Factory presets include various Room, Hall, and Plate reverbs as you’d expect, along with Echo, Delay, and Chorus effect settings. Fans of the classic 1980s snare drum sound will instantly recognize the Nonlin setting, which offers a short burst of reverb with an abrupt cut-off, much like a gated reverb effect.
Reverse reverb is also available, as well as a unique Freeze setting—which might sound complicated, but is actually simple in use. One of the best things about this unit is how intuitive it is to operate. Choosing basic presets is extremely easy, and tailoring them to fit your needs takes almost no time to master.
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Neve RMX16 500-series Digital Reverb |
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7. Drawmer DS101 500 Series Noise Gate
The DS101 is a primary noise gate designed specifically for the 500 Series rack system, joining the Drawmer family of industry-standard noise gates like the DS201, DS501, and DS404. Anyone familiar with these models will feel right at home with the DS101.
Based mostly on a single channel from the DS201, the DS101 offers a range of features that are important to sound engineers, including variable high- and low-pass filters for frequency-conscious gating.
Other features include complete envelope control—attack, hold, decay, and range—plus a host of additional options, all adding up to an excellent processor.
When placed side by side in a 500 series rack, two or more gates can be linked using the new infrared triggering mechanism found on the DS101. This lets you link any number of gates, each with its own envelope shaping, while the trigger pulse passes through unchanged. This opens up a whole world of envelope follower effects, limited only by your imagination.
The unit can also be switched to accept a key input, allowing the gate to be triggered externally. For example, you could use a snare drum signal to open the gate on a separate ambient microphone, creating a natural alternative to gated reverb.
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Drawmer DS101 500 Series Noise Gate |
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8. Meris Hedra 500 Series 3-Voice Rhythmic Pitch Shifter
Add lush, expansive harmonies to your guitars, keys, vocals, and more with the Meris Hedra 500 Series rhythmic pitch shifter. Layer three independent voices beneath your original signal, setting each to intervals ranging from two octaves down to two octaves up, with the flexibility to choose key and scale.
Hedra’s glide control lets you easily move from modern, hard-tuned pitch shifting to more natural transitions between notes. The Micro Tune control delivers synth-like detuned effects, fattening or warping your sound. Plus, Hedra offers four delay configurations for complex echoes and slapback effects, creating deeply textured harmonies.
Musicians of all kinds have embraced Hedra. For solo singers and songwriters, it adds new dimension to vocal performances. Synth players love it as a creative tool for elevating their patches. Even string and horn players use Hedra to add experimental flair to their sound. A truly innovative pitch shifter, there’s nothing quite like the Meris Hedra.
The streamlined interface puts a range of inspiring features and controls at your fingertips. Select delay intervals for each of Hedra’s three voices to create cascading pitched delays. Use the half-speed and auto-swell functions for morphing, tidal wave-like effects. With Hedra, you have an entire musical ensemble at your command!
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Meris Hedra 500 Series 3-Voice Rhythmic Pitch Shifter |
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9. Radial EXTC 500 Series Guitar Effects Interface
Guitar effects on vocals, drums, and more? Absolutely, it’s been done before. But never quite like this. The Radial EXTC guitar effects interface lets you easily incorporate your favorite pedals into any setup, all while maintaining top-notch sound quality. Want wah on vocals or tremolo on strings? The EXTC makes it possible, unlocking creative possibilities and keeping sound quality front and center—all within the convenient 500 Series format.
With the Radial EXTC, you can effortlessly explore the world of effects pedals at any stage of the recording process, while preserving the signal quality your professional studio demands. Just connect a line-level audio signal and let the EXTC do its magic.
The EXTC converts your signal to hi-Z, so you can patch in any stompboxes you want using the 1/4″ send and return connectors on the front panel. Send and Receive knobs let you set your levels, while the blend control helps you dial in just the right amount of effect.
Radial designed the EXTC with signal integrity as the top priority, opening the door to creative stompbox use far beyond just lo-fi tricks. The EXTC features Radial’s award-winning, fully discrete Class A guitar buffering, plus transformer isolation to eliminate ground loop buzz and hum.
You’ll also find a 180-degree polarity reverse switch to keep your effects and balanced signals in phase. The EXTC is another high-quality example of Radial’s best work, ready to fit into any 500 Series compatible rack.
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Radial EXTC 500 Series Guitar Effects Interface |
10. Heritage Audio BT-500 v2 500 Series Bluetooth Streaming Module
The Heritage Audio BT-500 V2.0 frees you from those dreaded mini-jacks and delivers a professional solution to the everyday problem of streaming audio in a studio environment. As streaming from devices has become more common in modern studios, the BT-500 V2.0 offers a quick and hassle-free answer.
With a range of over 100 meters, you’ll never be out of reach with the BT-500 V2.0. Now you have no excuse not to do a quick reference check with your favorite tracks from Spotify, YouTube, or Apple’s iTunes Store. Need to quickly access a file from an email? No problem!
Audio received over Bluetooth is sent through fully differential Burr Brown balanced outputs, delivering +24 dBu and capable of driving a 600-ohm load. This means you get the high quality you need for direct level comparisons while mastering or mixing. There has simply never been anything like this before. Offered in the convenient 500 series format, the BT-500 V2.0 is accessible to everyone at a very affordable price.
Whether you’re using a smartphone, tablet, smartwatch, or any other device, you can trust the BT-500 V2.0 to find the best connection for seamless integration. It’s truly never been easier to access your iOS or Android device in the studio.
On top of all that, the BT-500 V2.0 is a stylish piece of gear. Its clean and uncluttered design keeps things simple while remaining visually appealing.
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Heritage Audio BT-500 v2 500 Series Bluetooth Streaming Module |
11. Meris Ottobit 500 Series Bitcrusher
Designed and built in the USA, this 500 series module is just a little quirky and ready to take your sound places you probably never imagined.
The Meris Ottobit bitcrusher captures the vibe of classic gaming consoles and transforms it into a versatile 500 Series module for advanced sonic manipulation. At its core are variable sample rate and bitcrushing controls, letting you add subtle down-sampled grit or completely destroy your signal into sputtering, mangled chaos.
But Meris doesn’t stop at traditional bitcrushing. With built-in LFO modifiers and ring modulation, the Ottobit goes further. Its user-friendly controls make it easy to get started, but it also invites deep exploration, delivering a variety of effects like rhythmic tremolo, wild filter modulations, and more.
The Meris Ottobit 500 Series module stands apart from the pedal version with unique features, including an LFO for modulating the sample rate and a ring modulator. You can sync the LFO to a tapped tempo and adjust the depth of the effect.
The ring modulator also offers mix control for blending amplitude and frequency modulation, giving you dynamic tremolo and vibrato effects. Both the LFO and ring modulator feature selectable waveforms, so you can experiment with different textures and uncover endless new sounds.
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Meris Ottobit 500 Series Bitcrusher |
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12. dbx 510 500 Series Subharmonic Synthesizer
For years, dbx’s patented Subharmonic Synthesis has been shaking foundations and boosting bass across a wide range of professional settings—including nightclub and DJ mixing, theater and film sound, music recording, live performances, and broadcasting. The unique Subharmonic Synthesis process from dbx actually creates a new, waveform-modeled bass note exactly one octave below the original audio’s bass.
The dbx 510 500-Series Sub Harmonic Synth is the answer audio professionals have been waiting for, delivering Subharmonic Synthesis in a compact 500 Series module format. The dbx 510 features two separate bands of subharmonic synthesis, giving you the perfect blend of smoothness and control, while its independent low-frequency boost circuit is designed to get the most out of high-performance, low-frequency speaker systems.
While an EQ can only enhance the bass frequencies that already exist in your audio tracks, the dbx 510 subharmonic synthesizer 500 series module actually generates a solid low end an octave below your original audio. Electronic musicians and DJs understand the power of subharmonic synthesis—it adds incredible bass punch and energy without affecting your mids and highs.
Whether you’re adding weight to kick drums or beefing up synth lines, you’ll take command of any subwoofer with the dbx 510 subharmonic synthesizer module in your 500 series rack. Unlike other bass synthesis approaches, the dbx process creates musical low frequencies that don’t interfere with your mids and highs, even when you dial up the synthesis and boost to the max. The result is a low-end punch that people can truly feel!
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dbx 510 500 Series Subharmonic Synthesizer |
13. Meris Mercury7 500 Series Reverb
The Mercury7 module takes up a single rack slot, and its striking faceplate comes in a beautiful shade of blue. This is an “open” style module, leaving the top of the main PCB exposed, while the back is protected by a full-length metal plate. Named after the legendary group of American astronauts, the Mercury7 is a reverb unit built for spacey, swirling, and evocative reverberation, featuring handcrafted algorithms and extensive modulation capabilities.
Multiple Mercury7 modules can be linked together for stereo or surround operation, creating massive and immersive soundscapes. In a linked setup, the left-hand unit typically acts as the master, while the right-hand (slave) module automatically follows the master’s settings.
Audio quality is assured with the use of a Burr Brown INA137 balanced line receiver and DRV135 balanced line driver for the rack’s rear-panel line-level XLR connectors. Digital conversion is handled by a 24-bit AKM AK4621EF converter, boasting a dynamic range of about 116dB.
The Mercury7 features both high- and low-frequency damping controls to shape its tonal character, along with an advanced auto-swell function for dramatic ambient crescendos. To add harmonic complexity to the wet signal, the Mercury7 offers a Pitch Vector control with several interval options, including subtle pitch up and down, a fifth up, octave up and down, and shimmer.
Like all Meris effects, the Mercury7 has a deep feature set accessible via a press-and-hold Alt control. This lets you adjust parameters such as pre-delay, modulation, vibrato speed and depth, attack time for the swell feature, and mix control for the pitch-shifted reflections.
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Meris Mercury7 500 Series Reverb |
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14. Radial X-Amp 500 Series Re-amping Distro Module
The Radial X-Amp is a 500 series module that lets you take a pre-recorded guitar track and send it back out to amplifiers and effects, so you can fine-tune the sound to fit your needs. Reamping offers many benefits: during recording, the guitarist can focus solely on the performance. You can experiment with different sounds and perfect mic placement later on. This saves hours of tedious repetition and gives the producer more control over the track as the production progresses.
Using the X-Amp is simple and straightforward. It features an XLR balanced line-level input on the rear panel of the 500 series rack, which feeds the X-Amp. For the highest fidelity, the X-Amp uses 100% discrete class-A circuitry.
The X-Amp takes the pre-recorded signal, unbalances and buffers it, and then feeds two transformer-isolated hi-Z guitar level outputs. The 1/4″ jacks are conveniently mounted on the front panel for easy access, and include ground lift switches to eliminate hum and buzz caused by ground loops. Independent level controls let you adjust the signal going to each amp for the best tone. If one of the amps is out of phase, pressing the 180º switch quickly brings them back in line.
The X-Amp converts the line-level signal to the correct pedal or guitar amp input impedance, so you can record guitars or other instruments directly and then dial in the perfect amp sound later. With two Class A transformer-isolated outputs, the X-Amp allows you to drive up to 50 feet of hi-Z cable without losing quality.
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Radial X-Amp 500 Series Re-amping Distro Module |
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15. Fredenstein F605 500 Series Headphone Amplifier
The Fredenstein F605 is a high-efficiency, professional headphone amplifier that delivers effective headphone volume management for both live and studio settings when paired with a Fredenstein Bento rack. The Bento racks provide two inputs per slot, making stereo modules possible.
The Fredenstein F605 500-Series Headphone Amp features five toggle switches for convenient monitoring options. The top switch simply swaps the left and right channels. The next two toggles select either the left or right channel and present it as mono to the headphones—ideal for matching two mono sources. The bottom two switches reverse the polarity (phase) of each output.
These switches are especially useful for vocalists, as there may be some phase shift between the voice heard through bone conduction and the full recording path of the microphone, preamp, processing, and possibly converters.
The Fredenstein F605 offers balanced inputs, extensive signal control, and low output impedance to connect headphones ranging from 20 Ohms to 600 Ohms. It’s a unique module compared to typical 500 series options, but it’s incredibly useful in everyday situations. How many times have you needed a pair of headphones at the outboard rack, or a dedicated pair for monitoring a specific source, or a separate feed for the producer or talent?
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Fredenstein F605 500 Series Headphone Amplifier |
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Conclusion
As we mentioned at the start of this article, we’ve put together a list of what we consider to be the top 500 series modules, covering a range of uses and features. These 500 series effect processors are sure to enhance your sound, especially since they’re made by brands known for their quality and expertise.
If you’re interested in trying them out, visit the official websites where they’re sold to see if a demo or try-out option is available. And if you have any questions about any of these modules, feel free to ask in the comment section—we’ll do our best to help!
