No matter how fast your computer is, how much RAM and hard-drive space you have, or how good your audio and MIDI interfaces are, you can never have too

No matter how fast your computer is, how much RAM and hard-drive space you have, or how good your audio and MIDI interfaces are, you can never have too much horsepower when it comes to audio. Expanding your plug-in processing power with external hardware has always been an option, but two new products also allow you to unplug and take that solution on the road.

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FIG. 1: Receptor''s front panel features a 2-line, 48-character backlit LCD display; four freely assignable rotary encoders; a guitar input; a headphone output; and buttons for fast access to important functions.

Manifold Labs' Plugzilla and Muse Research's Receptor are the first in a new breed of audio hardware: the standalone software plug-in host. Both machines currently run a variety of virtual-instrument and effects plug-ins in Steinberg's VST format for the PC. As the universe of VST plug-ins grows, the utility of these boxes will therefore grow, making them a rare breed of hardware device that improves with age.

Receptor and Plugzilla do not integrate directly with software running on your computer — they are designed for standalone operation using their own, built-in MIDI and audio interfaces. They can, however, be networked to your computer using Ethernet and TCP/IP for installing and removing plug-ins and presets as well as for updating their internal software. Although networking to a computer is convenient and provides added functionality, it is not strictly necessary. You can connect Plugzilla directly to the Internet for updating, and you can connect a keyboard, mouse, and monitor to Receptor to run its Muse Control software. (You need to network Receptor to a computer to update and add plug-ins.)

Rack ‘Em Up

Although Receptor and Plugzilla are capable of doing many of the same things, they have completely different architectures and different price tags (see the sidebar “Dollar for Dollar”). Receptor is organized like a typical hardware multisynth; it has 16 channels, each of which can hold a virtual-instrument plug-in followed by three insert-effects plug-ins. The effects can be arranged in any order (series, parallel, 1+2, or 2+1), and each Receptor channel can be set to receive on any MIDI channel, which allows virtual instruments to be layered or controlled separately.

Plugzilla, on the other hand, follows the model of a typical multi-effects box, with two effects blocks containing four slots, each of which can hold an instrument or effects plug-in. Flexible signal routing allows you to configure the slots in a variety of ways, including anything from hosting eight separate virtual instruments to creating a single 8-slot effects chain.

Thinking in terms of those models is a good way to appreciate the difference between these two products and to understand how they might fit into your setup. To think of Receptor as a multisynth or Plugzilla as a multi-effects box, however, does not do them full justice. Whereas a multi-synth's or multi-effects box's separate slots hold presets fashioned from the same synthesis, sampling, and effects algorithms, Receptor and Plugzilla slots can hold completely different instruments and effects, selected from the broad and ever-expanding array of VST plug-ins.

Although Receptor, with 143 included VST plug-ins, and Plugzilla, with 233, offer a wide variety from which to choose, they are not completely open systems. For one thing, neither product will accept all off-the-shelf VST plug-ins.

Manifold Labs maintains that Plugzilla will accept the simpler off-the-shelf free and demo PCformat VST plug-ins, but that many free plug-ins (and all plug-ins using copy protection) require modification to work with Plugzilla. Muse Research supports only plug-ins that have been “Receptorized;” however, the company does offer instructions for installing off-the-shelf plug-ins. I tried installing a variety of off-the-shelf freeware and demo plug-ins in both boxes with only moderate success.

Start Here

Hosting VST effects plug-ins wouldn't be of much use without something for the effects to affect. With Receptor and Plugzilla, that can be the output of a virtual-instrument plug-in or live audio input. And in keeping with their individual architectures, each one manages that somewhat differently.

Plugzilla lets you assign any combination of its eight audio inputs to any plug-in slot. If a virtual-instrument plug-in is inserted in the slot, its output is mixed with the assigned audio inputs and passed to the next slot. (The four slots in each of Plugzilla's two effects blocks are always connected in series; however, they can be assigned independent inputs and outputs.)

The input to each of Receptor's 16 audio channels can be set to a virtual-instrument plug-in or one of three audio sources: Line Input (rear jacks), Guitar Input (front-panel jack), or S/PDIF Inputs. To mix virtual-instruments with audio inputs, you need to use two or more channels, and to have them share effects, you need to use one of Receptor's two effects-send buses.

Their flexible signal routing allows each box to simultaneously function as an effects processor and a multi-synth, but Receptor's greater number of slots and 16-channel mixer-style architecture gives it the edge in multifunctionality. Each product lets you load and save complete setups, including signal routing, MIDI settings, and plug-in configuration and settings. That allows you to create a variety of “multis” and quickly move among them during a live performance or a studio session.

Ins and Outs

Receptor and Plugzilla include fully-featured audio and MIDI interfaces, but in keeping with its higher price tag, Plugzilla's audio and MIDI I/O is more extensive.

Receptor has a single MIDI port with input, output, and thru (for daisy chaining with other MIDI devices) and can therefore respond to 16 MIDI channels. Typically, you would assign each virtual instrument to its own MIDI channel; you can, however, assign several virtual instruments to the same MIDI channel for layering. You can also assign a Receptor channel to receive all MIDI channels, thus allowing the incoming MIDI channel to control the sound played by a multitimbral synth.

Receptor is a 2-channel audio device with ¼-inch balanced TRS jacks for each channel of analog I/O, RCA jacks for S/PDIF stereo I/O, and an ADAT output connector, which carries the same stereo signal as the S/PDIF output. (Eight channels of ADAT output are planned for a future software update.) There are also ¼-inch jacks with level controls on the front panel for guitar input and headphones output.

Receptor has five USB 2.0 ports (one in front and four in back), a 10/100Base-T Ethernet port, an SVGA monitor port, and two PS/2 ports for connecting a computer keyboard and mouse. The Ethernet port is for networking to your computer either directly using a crossover cable or through a router using a standard Ethernet cable. The USB ports can be used for computer peripherals such as a hard drive, memory stick, keyboard, or mouse; MIDI devices such as keyboard and control surfaces that feature a USB port; and the Pace iLok copy-protection key that Receptor offers plug-in developers for copy protection. (The front port is conveniently recessed to partially protect the iLok when Receptor is rackmounted.)

Zilla's Plugs

Plugzilla comes with eight channels of analog I/O that is accessible from rear-panel, balanced XLR connectors. Digital-audio I/O includes AES/EBU with word clock, as well as S/PDIF. There is no mic/guitar preamp and no audio I/O on the front panel, presumably because it is assumed Plugzilla will be integrated with a mixing desk.

Plugzilla has two MIDI ports, for a total of 32 MIDI channels, one served by separate In, Out, and Thru connectors and the other served by a single In-Out connector. The second port is especially convenient for connecting an automated MIDI control surface. There are also two ¼-inch TRS footswitch jacks. As with Receptor, Plugzilla's slots can be configured to receive on one or all MIDI channels, and multiple slots can be assigned to the same MIDI channel.

Plugzilla offers five USB 1.1 ports — two type A and one type B on the back, and two type A on the front. The USB ports can be used for computer or MIDI peripherals. Just like Receptor, Plugzilla can be networked to your computer over a 10/100Base-T Ethernet connection.

Hob Knob

Designed for standalone use, Receptor and Plugzilla have extensive front-panel controls (see Figs. 1 and 2). At the heart of each is a 360-degree knob and an associated LCD display for making plug-in settings. Receptor offers four such knobs with a 48-character LCD display. Plugzilla offers eight knobs and two 80-character vacuum fluorescent displays (VFDs), which are clearer and brighter than LCDs. By default, four knobs and one display apply to the selected slot in each Plugzilla effects block, but you can choose to have all eight knobs and both displays apply to a single slot. Receptor's and Plugzilla's knobs incorporate push buttons for confirming choices and making menu selections when appropriate.

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FIG. 2: Plugzilla''s front panel features eight rotary encoders, two 80-character LCD displays, and buttons for access to individual slots and important functions.

Plugzilla's Hot Knobs feature allows eight parameters for each slot to be assigned for quick access from the eight control-panel knobs. Receptor has a similar feature called Soft Knobs. In addition, Receptor, through its Muse Control software, allows you to control which plug-in parameters are editable on the front panel, the order in which they appear, and the name that appears on the LCD. For plug-ins with tons of parameters, it's great to be able to rationalize front-panel editing and to pare down the front-panel parameters to those that are most important.

Separate knobs (Receptor) and buttons (Plugzilla) are used to move through multiple parameter pages. Separate buttons are also provided for changing modes, choosing which plug-in slot is being edited, loading and saving presets, and so on. In short, the controls are what you would expect to find on a sophisticated hardware multisynth or multi-effects box.

Plugzilla and Receptor have extensive MIDI-automation options. Plugzilla allows MIDI Control Change (CC) messages to be freely assigned (including their ranges) to any machine parameter as well as to any plug-in parameter. Receptor has fixed MIDI CC assignments for its mixer parameters and fixed NRPN assignments for plug-in parameters. But the first 16 parameters of each virtual instrument and the first 8 parameters of each effect that are assigned to the front panel can also be controlled by MIDI CC messages.

Soft Landing

Both Plugzilla and Receptor can be networked to your computer using Ethernet TCP/IP. Receptor supports Mac OS 9 through X and Windows 9x through XP. Plugzilla supports Windows 9x through XP, with OS X and Linux versions in the works. Receptor and Plugzilla offer either manual or automatic (DHCP) setup. I used DHCP with Receptor and manual setup with Plugzilla, and the process was quick and easy in both cases.

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FIG. 3: Receptor allows you complete read/write access to its hard drive for updating as well as for adding plug-ins and presets.

Receptor gives you two-way access to its hard drive, allowing you to move plug-ins and their presets back and forth between Receptor and your computer (see Fig. 3). However, some of Receptor's plug-ins are protected from being copied to your computer. Of the 25 freeware plug-ins I tried to move from Receptor to my PC, only 10 were transferable, but those 10 did work in all of my VST hosts.

Plugzilla gives you one-way access. Using its PZView software, you can move plug-ins and presets to Plugzilla, but not vice versa (see Fig. 4). On the other hand, Plugzilla provides PC versions of all its plug-ins on an included CD.

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FIG. 4: PZView software allows write-only access to Plugzilla''s hard drive for adding plug-ins and presets.

Operating system and plug-in updates for Receptor can be downloaded from the Muse Research Web site, then moved to Receptor's hard drive for installation. Plugzilla connects directly to the Web for automatic updating, but it can also be updated manually using a USB memory device.

Good Reception

Receptor includes a software graphic user interface (GUI) called Muse Control for managing its plug-ins. Designed in the form of a mixer with 16 input channels, 2 effects-return channels, and a master output channel, it lets you choose plug-ins and their presets for each slot as well as to program the plug-ins using their own GUIs (see Fig. 5).

Muse Control is run directly on Receptor by attaching a keyboard, mouse, and monitor. Alternatively, you can run companion software Receptor Remote on a networked computer, which gives you access to Muse Control over Ethernet. I did not have a monitor with which to test onboard operation, but the networked version worked quite well. The controls, however, were a bit sticky. Because the GUI is primarily intended for programming presets and setting up Receptor multis rather than for live performance, that sluggishness is not a big issue.

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FIG. 5: Muse Control software provides a graphic user interface for programming Receptor''s mixer as well as individual plug-ins that use their own graphic user interfaces.

Most of the mixer controls can also be set from Receptor's front panel, and, of course, the settings are interactive with the GUI software if it is running. You would, however, most likely set up multis — complete Receptor setups including all plug-ins and their presets together with all mixer settings — with the instruments and effects desired, then use program changes to switch between them during performance. Changing multis does not cause plug-ins to reload if they are already in Receptor's memory, so with a well-thought-out setup, switching between multis can be fast.

Although Plugzilla does not offer a GUI front end, PC users can use the supplied PC versions of the VST plug-ins to program them graphically in another host. The presets can then be transferred to Plugzilla using PZView.

Plug for Plug

As you would expect, Plugzilla and Receptor ship with large complements of VST instrument and effects plug-ins. The version of Receptor I received for this review included 102 free plug-ins (42 instruments and 60 effects) and 41 premium plug-ins (19 instruments and 22 effects) that run in demo mode for 30 days, after which they must be authorized. (Registering Receptor will get you authorization for premium plug-ins worth roughly $400.) Plugzilla came with 233 plug-ins (71 instruments and 162 effects), all free except for PSP Audioware's Prozilla Pack bundle of mastering effects. Interestingly, Receptor and Plugzilla had only 8 instrument and 32 effects plug-ins in common.

Both companies maintain a database of plug-ins on the Web. Plugzilla's database at lists plug-ins that are compatible but not included and plug-ins that are not compatible. It indicates whether the plug-in was created in SynthEdit (a common VST plug-in developers' tool for the PC) and has space for a user rating, although none had been rated at this writing. In addition to sorting and filtering the list by various parameters, you can view the list in annotated form, which gives a detailed description of each plug-in. You can download the plug-ins directly from the site.

Manifold Labs has recently announced Plugzilla support for the Linux Audio Developers Simple Plug-in API (LADSPA), which should significantly expand the company's plug-in offerings.

Receptor's plug-in database is at That's your source for updates, new preset banks, and new plug-ins. Premier plug-ins can be purchased directly from the site and can be downloaded free to use for 30-days in trial mode. As with Plugzilla's Web site, files can be filtered by various criteria, and you can view a detailed description of each plug-in. You can also maintain a wish list for your more generous friends and relatives.

For a Fee

If you're contemplating buying products in this price range, you probably expect them to host an assortment of premium plug-ins. At the time of this writing, both Receptor's and Plugzilla's premium offerings are somewhat limited, and some of your favorites are probably not among them. Receptor is definitely ahead of Plugzilla in premium offerings. One very nice Receptor inclusion is Native Instrument's Kompakt sample player, the only sample-playback virtual-instrument available on either box at the moment. Both companies are working hard to add premium content, and a visit to their Web sites will tell you what's currently available. Definitely look before you leap.

As with native hosting, premium plug-in developers generally require some form of copy protection. Receptor comes with a Pace iLok key that connects to one of its USB ports. All Receptor premium plug-ins use iLok protection.

Plugzilla offers a proprietary scheme tied to their hardware and operating system that does not require a hardware key and that allows a premium demo to run 30 times before being purchased. Manifold Labs plans to add the iLok protection option to Plugzilla.

One from Column A

Both Plugzilla and Receptor are cleverly designed, well-built pieces of hardware. They are rackmountable and roadworthy. The obvious questions are how does one decide between them and why choose to buy either?

Although both products are adept at virtual-instrument hosting and effects processing, Receptor is more adept at the former whereas Plugzilla is designed more for the latter. Receptor's ability to load 16 channels of virtual-instrument plug-ins together with insert effects, then easily toggle channels in and out for layering and splitting those instruments, makes it ideal for the performing musician. Plugzilla's multichannel I/O, flexible I/O routing, and effects-block style architecture, along with its fully-featured audio interface, make it an ideal fit in a rack of effects.

That being said, the question remains, why not just buy a computer and dedicate it to running VST plug-ins. You can buy a desktop or laptop PC with comparable specs for somewhat less than the price tag for either Receptor or Plugzilla, even after adding audio and MIDI interfaces and VST hosting software. And a computer has the advantage of running all VST plug-ins off-the-shelf.

Muse Research and Manifold Labs answer that question in much the same way, with the argument that their systems, being designed exclusively for running VST plug-ins, are more efficient, less likely to crash, and less susceptible to the driver and software conflicts that plague computer users. Furthermore, by virtue of having their audio and MIDI interfaces built-in and of being designed to withstand abuse, they are less accident prone and therefore more roadworthy. Finally, there is the question of latency, which is always a battle on a laptop (see the sidebar “The Time Is Now”). Those are all strong arguments if they apply to your situation.

After having both units in my studio for more than a month, I came to several conclusions. Receptor's multi-channel design, GUI, and flexibility in setting up its front-panel controls make it an excellent live-performance virtual-instrument and DSP-effects host. Plugzilla's eight channels of audio I/O, dual-effects-block architecture, and more extensive front-panel setup are well suited to pro-audio effects processing in a live or studio environment. They eliminate many of the hassles of doing the same job with a PC, but to be truly competitive, both units need more premium content, and it is likely to be only a matter of time until they have it. Receptor and Plugzilla represent a clear advance in multisynth and multi-effects hardware.

Len Sasso is an associate editor of EM. Contact him through his Web site


With Plugzilla ringing in at roughly twice the price of Receptor, it's natural to wonder what you get for your money. The short answer is that you don't need to look any further than the front and back panels. But before getting into the details, I'll describe how a specific setup might be accomplished with both machines.

Suppose your guitar player wants a little compression and distortion, your lead singer wants some EQ and a reverb of her own, and the keyboard player wants to layer a couple of his favorite synths. You can accomplish that in Receptor by using the front-panel guitar input for the guitar, the rear-panel line input for the singer — each with their own Receptor channel. Then dedicate a few more Receptor channels to the keyboard player for his synths and perhaps a couple of effects. But frankly, I don't want to be there when you tell the lead singer she's on the same output bus as the guitar and synths. (Of course, you could pan one source hard left and the other two hard right to get two mono outputs.)

To accomplish the same task with Plugzilla, you might devote one effects block (four slots) to the guitar and vocal (say, two slots each), with their own two channels of audio output. You could then devote the other effects block to the keyboard player to insert a couple of synths and a couple of effects and arrange the remaining four channels of audio output to suit. Eight channels of audio input and output do make a difference.

Moving around to the front panel, there are four rotary encoders with one 48-character LCD on Receptor, and eight rotary encoders with two 80-character VFDs on Plugzilla. Plugzilla also offers more buttons, which makes accessing specific tasks somewhat easier. For example, there are eight buttons across the top for selecting slots, and they have two levels of illumination: Dim, to indicate that the slot is filled (versus dark for empty), and Bright, to indicate the slot is filled and selected for editing. In fact, all Plugzilla buttons are intelligently illuminated, and each of the rotary encoders is ringed by LEDs to indicate the current parameter setting.

Do you need eight audio output buses with XLR connectors, eight rotary encoders ringed with LEDs, bigger displays, and illuminated buttons? If you do, you'll have to pay a premium.


Latency is the bane of software synthesis, and considerable time can be spent trying to set up a computer to minimize latency while still delivering reasonable performance. Receptor and Plugzilla, being dedicated plug-in hosts with built-in audio and MIDI interfaces, can devote more of their resources to lower latency and come factory tuned for optimal performance. You don't need to deal with setting buffer sizes or disabling other drivers and background processes that interfere with performance.

In an unofficial head-to-head test running the same virtual-instrument plug-in (TickyClav from Big Tick Audio), there was no noticeable sluggishness with either machine. Furthermore, playing them simultaneously from the same MIDI keyboard resulted in no perceptible flamming. Performance with several layered synths was also clean and crisp on both boxes.

To get a rough idea of how they compared with an audio-optimized PC, I loaded TickyClav into Steinberg's V-Stack — a software VST host similar in architecture to Receptor — running on my 3.2 GHz Pentium 4 laptop using an RME Cardbus/Multiface audio and MIDI interface. (Bear in mind that this is not the inexpensive system discussed in the main text.) I used Apple Logic Pro 7 running on another computer to send MIDI to and record audio from Receptor and the PC, then Plugzilla and the PC. The results were nearly identical.

Once optimized for audio, the factor most influencing latency on a PC is the audio buffer size. Smaller buffer sizes result in lower latency at the cost of lower plug-in counts. The RME Cardbus buffer settings range from 64 to 8,192 samples, but in practice settings higher than 512 samples are unacceptable for performance.

With a buffer setting of 512 samples, Receptor and Plugzilla had an edge of roughly 6 ms over the PC. With a buffer setting of 256 samples, the performance was nearly identical, with roughly a 1 ms edge for the hardware boxes. With a buffer setting of 128 ms, the PC had roughly a 4 ms edge. Your mileage may differ.



hardware VST plug-in host $2,995

OVERALL EM RATING [1 through 5]: 3

PROS:Built-in MIDI and audio make for no-hassle, high-efficiency performance. Eight audio inputs and outputs for parallel effects processing. Roadworthy.

CONS:Limited selection of premium plug-ins. No graphic user interface software for setup and plug-in preset programming.




Audio Inputs analog stereo (¼" balanced +4/-10)
S/PDIF stereo (RCA)
mic/guitar (¼" unbalanced on front panel) 8 analog (XLR balanced)
S/PDIF stereo (RCA)
AES/EBU (gold plated XLR) Audio Outputs analog stereo (¼" balanced +4/-10)
S/PDIF stereo (RCA)
ADAT stereo (8 channels planned)
headphone (¼" on front panel) 8 analog (XLR balanced)
S/PDIF stereo (RCA)
AES/EBU (gold plated XLR) MIDI Ports In, Out, Thru In, Out, Thru
In/Out 2 (for control surface) Sampling Rates 44.1-, 48-, 96 kHz 32-, 44.1-, 48-, 88.2-, 96 kHz Footswitch Inputs no 2 PS/2 Inputs 2 (for keyboard and mouse) no USB Ports 1 USB 2.0 (front)
4 USB 2.0 (rear) 2 USB 1.1A (front)
2 USB 1.1A (rear)
1 USB 1.1B (rear) Word Clock S/PDIF BNC in and out Ethernet 10/100Base-T 10/100Base-T Monitor Out SVGA output for 1024 5 768 monitor n/a LCD Display 48 character (2 rows of 24) 2 5 80 character (2 rows of 40 in each) Presets/Multis 16,384/16,384 999/999 RAM 256 MB expandable to 2 GB 256 MB expandable to 2 GB Hard Drive 40 GB 20 GB Processor Athlon Barton-core XP2500+ Celeron 2.0 GHz Computer OS Win 9x-XP, Mac OS 9-X Win 9x-XP Dimensions 17.0" (W) 5 3.5" (H) 5 11.37" (D) 19.0" (W) 5 3.5" (H) 5 15.0" (D) Weight 13.25 lbs. 15 lbs.



hardware VST plug-in host $1,599


PROS: Built-in graphic user interface makes setting up a breeze. Built-in MIDI and audio make for no-hassle, high-efficiency performance. Easy and fast front-panel reboot in case of lock-ups during performance. Roadworthy.

CONS: Limited selection of premium plug-ins. Front USB jack only partially protects iLok hardware key. Audio output limited to two channels.