Pro-quality effects processing in a computer-based package.
By Zack Price
For the record, rack-mount effects processors won't be facing extinction anytime soon. On the other hand, computer-based, real-time effects processing will be increasingly employed in pro and home studios because of its obvious advantages. For one thing, the digital signal-processing hardware can be configured to produce any type of effect you want. All you need to do is run the appropriate effect software to tell the DSP hardware what to do.
In addition, more parameters can be displayed at once on a computer monitor than on the small display found on hardware effects processors. Better still, the relationship between the different parameters can be graphically displayed. This provides a clearer understanding of how each particular parameter changes influence the overall effect.
Power Technology is the latest company to offer computer-based effects processing. DSP/FX is a stand-alone system: it's not part of an integrated production environment such as Digidesign's Pro Tools. The system consists of one or more hardware cards and flexible software for the Windows platform.
THE DSP/FX card employs 32-bit floating-point calculation, whereas most systems use 24-bit fixed-point arithmetic at best. What makes 32-bit floating-point processing so special? According to the people at Power Technology, fixed-point processing processors are unable to transparently handle signals with a wide dynamic range. At the top end of the dynamic range, fixed-point processors have a limited amount of headroom, so they clip the peaks of high-level transients such as percussive hits.
At the low end of the dynamic range, a fixed-point DSP uses fewer and fewer bits to represent the signal as the level decreases. Extremely low-level signals (e.g., reverb tails) might be encoded with an effective resolution of four bits. This low-resolution processing causes graininess in the tails of reverbs, because those tails are created by adding together many low-level signals.
A 32-bit, fixed-point processor theoretically sounds better, thanks to the additional bits, which increase the overall dynamic range. However, a 32-bit floating format offers the additional advantage of always using all 32 bits to represent the signal, regardless of signal level. In theory, this causes 32-bit, floating-point algorithms to sound much cleaner and more natural than fixed-point designs. The end results are transient drum hits that don't clip and extremely low-level reverb tails that sound smoother because they are constructed by summing many low-level signals that are represented with 32-bits.
This sounds good in theory, but how does the DSP/FX sound in practice? It sounds pretty darn impressive to me. During my review, the sound quality remained excellent whether I was running a master mix directly through the system, routing the card's audio through the aux send and returns of my mixer, or patching a guitar, synth, or percussion track directly t hrough it. I'll discuss the types and quality of effects in more detail later. For now, let's talk about what you get for your money.
The basic DSP hardware consists of a half-length ISA card with a pair of unbalanced 1/4 analog jacks for input and another pair for output. Depending on the effect used, you can configure the audio routing in one of three ways. First, you can use the left input as a mono input and use the two outputs for pseudostereo imaging. This is the routing typically used with the mono send and stereo returns found on most mixing boards.
Second, when both sets of I/O's are used, the incoming stereo mix is processed and sent back out in discrete stereo. The card maintains the true stereo image in both the wet (processed) and dry (unprocessed) signal.
Finally, the unit can function in dual mono, with separate left and right input and output channels. Except for the Room Reverb algorithm, which is only configurable in stereo and pseudo stereo, the parameters of all other effects can be set independently for the left and the right channels, and each channel is processed separately.
The DSP/FX card also includes a 9-pin connector that is used in conjunction with a variety of balanced analog and digital audio options. (I didn't test any of these because they weren't available during review. However they should be available by the time you read this.) The first of these options is the AES/EBU Digital Interface, a daughterboard that attaches to the DSP/FX card. The digital audio connectors are supplied in a breakout cable with AES/EBU XLR jacks and S/PDIF RCA connectors.
Another I/O option is the AES Converter, a single-rackspaced unit that provided 20-bit A/D and D/A converters as well as balanced analog I/O's. This unit can also operate as a stand-alone A/D converter. However when the AES Converter is connected to the DSP/FX card via the D connector, it requires the Digital Interface daughterboard to be installed.
The DSP/FX card includes a 128 KB buffer of high-speed (15ns) static RAM, which yields 670 milliseconds of delay time. You can increase the RAM buffer to 512 KB, which provides about 2,680 milliseconds of delay (single tap at 48 kHz).
As an alternative to mouse control, Power Technology offers the DSP/FX Controller, which is a JL Cooper CS-102. In addition to making the system easier to use, the Controller sends MIDI Control Change messages that can be recorded and edited by a sequencer. (A MIDI interface and the DSP/FX MIDI Patcher driver must be installed.) If money is tight, you can control the DSP/FX system with your sequencer's software fader controls.
Installing the DSP/FX card is a breeze: just find an open ISA slot, and pop it in. the card doesn't require IRQ numbers, DMA channels, or excluded upper memory-block areas. All it requires is a port-address assignment. Kudos to the folks at Power Technology for making sure the eight possible port-address settings weren't likely to be used by any other device in your computer.
However I did notice that the card seems to be a little taller than most cards. This could be a problem if the space inside your computer is tight. In my case, the hard-drive and floppy disk cables rested tautly (but without strain) on the DSP/FX card because I had to run the cables over the top of it. My cables weren't exactly short, either.
As you might surmise, eight available port-address settings mean that up to eight cards can be installed. Version 1.2 which is due to be released by the time you read this, provides support for multiple cards. (I tested version 1.0 which does not support multiple cards.) Realistically, though, most computers have four to six available ISA slots at best, and most users need at least two slots for sound cards and MIDI interfaces. The bottom line: unless you dedicate a computer entirely effects processing, you'll be lucky to install more than three DSP/FX cards in your system.
Still, if you simply must have a dedicated system for effects processing, Power Technology offers the DSP/FX Power Pack ($3999.00), an open-ended, turnkey system. the Power Pack is a rack-mountable Windows PC with a custom mini-keyboard, a mouse, and built-in SVGA video-output. (You supply a standard PC monitor.) The base Power Pack system also includes one DSP/FX card (expandable up to six), one AES Converter (also expandable up to six), the Controller, and all five currently available software plug-ins.
Installing the software plug-ins is not as simple as hardware installation due to the copy-protection scheme. The procedure starts easy enough: just install the plug-in and activate it with the password supplied by the company. This password is recorded into the memory of the DSP/FX card, so you never have to type in the password again. you can make backup copies of the plug-in software as you would with any other program.
That seems simple enough if you only have one card. However, what if you have two or more cards? As it stands now, you must assign a plug-in to a specific card. In other words, you must decide ahead of time which plug-in will be permanently used with card. This scheme is too inflexible. I'd much prefer to call up the plug-in as I need them without having to remember which card they're assigned to; my brain is tiny and overtaxed as it is.
When I asked the Power Technology people why they had designed the copy-protection this way, they replied that the low cost of the plug-ins ($199.00) justified making the copy-protection card-specific. This also prevents users who have purchased a single copy of the software from installing a plug-in into a multiple system containing DSP/FX cards.
However, they do recognize the inherent inflexibility of the copy-protection scheme as it now stands. Company reps have assured me that they will examine ways to improve flexibility while ensuring that plug-in prices remain low. Perhaps using some form of system specific site licensing would be effective. Plug-ins could be loaded as needed on a single system. However, you wouldn't be able to load identical effects into more than one card from a single copy of software. Stay tuned for further developments.
Once you've got the card(s) and plug-ins installed, you adjust each card's settings from the settings dialog box. You can select sampling rates of 44.1 or 48 kHz for all the plug-ins. When using the delay plug-in, you can also select sampling rates of 8, 24, or 32 kHz. These lower rates provide more delay time if you need it, but lowering the rate compromises the fidelity of the wet signal.
You can also select the MIDI channel and device to which a card will respond. The default channel is 16 (which corresponds to the controller), and each card works with its own driver. In addition, you specify whether the effects patch will use a mono or stereo input. I encountered only one problem with the settings dialog box; it closes immediately after changing a single parameter change. If you want to change several parameters at once you must reopen the dialog box for each parameter you want to change. I would prefer that the dialog box remain open until you close it explicitly.
Editing a preset is as easy as falling off the proverbial log. Just select the desired effect and select a preset patch as a starting point, or create a patch from scratch. Whenever you adjust a patch parameter, you not only see its numerical change, but also you see a cool graphic representation of how that parameter fits in the overall context of the effect.
To see what I mean look at the Graphic Reverb screen. The room being simulated by the effect is represented by a rectangular box in the upper right portion of the screen. When this screen shot was taken, I was adjusting the room's high-frequency absorption. The active parameter and its setting are displayed in the upper left hand corner of the screen. The current setting is also shown beneath its onscreen knob. Finally, the high-frequency absorption parameter is graphically represented by the color of the top and right side of the room. In this case, the lighter the color, the higher the setting.
Once you are familiar with how the effects parameters are graphically displayed, you can easily imagine how the effect will sound just by sight. The size of the box indicates that the room is huge. The color depth of the top and right indicates that only higher frequencies are absorbed, and overall color of the box indicates that it's a fairly live room. The distance between the two arrows indicates that the stereo separation is wide. In addition, the arrows point outward, which indicates that the normal stereo balance is maintained. (If they point inward, the stereo field is reversed compared to the dry signal.)
The height of the white bar above the room represents density or diffusion, which is moderate in this case, and the two vertical bars on the right corners of the box indicate early reflection and late reflection intensities, respectively. In this case, the display reveals that the intensity of early reflections are pretty dense. Given these parameters, I do not think we can accurately call this preset "Small Room Bright" as it appears under the graphic display. It's time to save it under a new much more accurate name.
You might notice that some of the reverb parameters mentioned in the previous paragraph (e.g. Density and Early and Late Reflection) do not appear with the on-screen controls on the left side of the screen on the left hand side of the screen. In fact, these parameters are hidden under the basic parameters. To view and change them, you would need to push the edit button.
This is easily illustrated in the Multi-Tap Delay screen. In this particular example, I was editing the fifth delay tap's parameter. You can tell I was editing the fifth this particular tap because the number "5" appears in the upper left hand corner next to the word "Gain". In addition, button 5 in the slider section is depressed. Furthermore, the knobs change to match the color of the selected tap button. Finally the appropriate color-coordinated ball in the display area changes size, color density, and vertical and horizontal positions as its on screen parameters are altered. Pushing a different delay select button brings up color-coded parameter controls for that particular tap, whereas disengaging the edit button recalls the overall controls for that plug-in.
Overall, the available effects are uniformly excellent. For example Room Reverb is just what the name implies: high quality-room reverb with few bells and whistles. In other words don't look for gated, reverse gate, or plate reverb simulations; you won't find them in this plug-in.
Power Technology "modestly claims" that its Multi-Tap Delay is the best sounding in the world. Now, I don't think you can make a claim like that and be modest about it, but I have to agree that it does indeed sound superb. I used it to fatten up a vocal track, which it did with such subtlety and finesse that no one would have known it was a processed track unless they had heard the original.
In addition, the Multi-Element Chorus is excellent. I particularly like how thick (but not muddy) my guitar sounds through it. I love the Analog Tape Flanger for much the same reason. Unfortunately I don't think I'll be able to tolerate running my own effects processor after I have to return the DSP/FX to the manufacture.
Finally, although I'm not usually enthusiastic about pitch shifters in general, I do like the DSP/FX Full Stereo Pitch Shifter. It sounds good and clean when used with guitar leads, and it works well as a small-interval pitch corrector and lead vocal fattener. Its capabilities are more than adequate for my usual applications for pitch shifters, in which I use them as a drum-kit tuner and psycho percussion monster-maker. I don't usually associate "mean" and "clean" with seriously warped percussion, but the stereo pitch shifter has forced me to alter my perceptions in this matter.
Obviously, I really like this product. I am impressed with how it sounds, even though I was limited to using the unbalanced jacks. All of the plug-ins are highly useful, and working with the is a piece of cake. My only major complaint about the system is its inflexible copy-protection scheme that seems to make life harder for users with multiple cards in a single computer.
Power Technology Note: Prices have changed. Please see current price list.
On the other hand, the price is extremely reasonable. You can buy the cards and all five plug-ins for $1,299.00, but if that's too much to shell out at once, you can purchase the card and your choice of one of the plug-ins for $799.00. You can upgrade to the complete set of the current plug-ins for an additional $500.00, which is the difference between the basic and complete package. Not a bad deal, considering that the price for each of the separate plug-ins is $199.00. (Even that price is downright cheap compared to plug-in software prices for other systems.) The money starts to add up quickly, though, when you include some of the hardware options mentioned earlier.
One of the advantages of a computer based effects system is the potential for expansion, and Power Technology is not ignoring this. For one thing, the company has announced the impending release of its new ParaEQ multi-band parametric equalizer plug-in, which is due out in early 1997.
In addition, Power Technology and Innovative Quality Software have announced an agreement to jointly develop a direct interface between SAW PLUS and the DSP/FX system. This interface will allow SAW PLUS users to apply the DSP/FX directly to selected tracks without requiring any external signal patching. This gives Power Technology a ready base for future development, and it gives IQS access to high-quality, real-time effects, which will dramatically improve SAW PLUS' rather Spartan processing capabilities. (See the review of SAW PLUS in the November 1996 EM.)
Even if no other plug-ins are ever developed for it, the entire DSP/FX system package is already a great deal as is. If you're looking to add some great effects processing to your home, project, or pro studio, the DSP/FX system should be on your short list of gear to check out.