Chameleon In SP's Clothing
Peavey SP Sample Playback Synthesizer
Martin Russ takes a close look at Peavey's long-awaited DPM SP dedicated sample player, and its sample input partner the DPM SX.
The Sample + Synthesis (S+S) architecture instruments I have examined usually have a wide selection of ROM source sample sounds, plus comprehensive synthesis facilities to alter those sounds. Many offer memory card expansion of the basic ROM samples, and a few offer RAM for your own samples — the Peavey DPM3SE keyboard and the V3 rack-mount module are the Peavey examples.
But almost invariably there are three missing ingredients: a large RAM capacity; a disk drive for ease of loading new samples; and a way of rapidly accessing large numbers of samples. The Peavey SP has it all: MIDI Sample Dump support for slow transfer but wide compatibility; a high density disk drive (1,44MB) for easy loading of samples; and SCSI bus connectors for connecting the SP to CD-ROM or large hard disk drives. The SP's 1U high front panel is deceptive — this is a powerful and sophisticated piece of technology.
The SP is a 'CD-quality', multi-timbral rack-mount sample player module. Functionally it is actually very much like an Emu Proteus/Roland U220/Yamaha TG55, but with RAM instead of ROM for the sample memory. The synthesis section is similar in many ways to Peavey's DPM series of synthesizers, and offers the depth of controlled dynamic filtering that the Proteus lacks. Almost everything would be very familiar to anyone who has used any other S+S instrument, though names for sound elements may be unfamiliar — see the 'SP-Speak' and 'SP Architecture' boxes.
There are no factory presets here. The sound of the SP is exactly what you create with the samples that you store in RAM, but more than that it is what you then do with those raw samples using the synthesis tools. The SP can be viewed as a simple sample playback machine, as shown by the three factory disks (piano, acoustic guitar and ethereal voices), but this wastes the powerful synthesis capabilities for making the most of the samples. It is certainly nearer to a perfect S+S instrument than any other I have seen: power, sophistication and loads of creative potential.
The SP has a simple user interface, both in hardware and software terms. There are two rotary knobs, 12 buttons, an LCD, disk drive and mains power switch on the front panel. The knobs are particularly notable: they have soft rubber edges which offer an excellent non-slip grip to the sweatiest of fingers. In contrast, the buttons suffer from the usual problem of being small and fiddly, the same colour as the front panel and a neat but unhelpful layout. Of the 12 buttons, seven select the editing and setup pages, four are cursor and increment/decrement controls, whilst the last is the 'Execute/Enter/Proceed/Do it!' button. I would have preferred two separate groupings: a group of 'Page' buttons on the left of the LCD and a group of cursor/editing buttons next to the data knob on the right of the LCD. Even so, the ability of the human body to acclimatise means that your fingers do eventually learn where to go without too much conscious thought.
The LCD shows 2 rows of 20 characters in an easily readable 'green on black background' backlit format, with a control on the rear panel to fine-tune the viewing angle and contrast. The data knob is a 1U panel version of the data wheels that offer rapid tweaking of values and page selection in many of today's instruments. The data knob works in conjunction with the increment and decrement buttons — they offer precise 'nudging' of parameter values or page movements, whilst the data knob lets you zip through the range or values or pages very quickly.
The SP uses a page-oriented software user interface. There are seven 'menu' buttons which lead to a series of related pages: Global and Utility are self-descriptive, whilst the Disk pages also deal with the SCSI functions. The remaining buttons provide the editing for the elements which make up the sounds: Waves, Tones, Maps and Presets. Some pages lead through to further subsets of pages on particular topics, mostly editing and deeper functions. The organisation of the pages is designed so that the most frequently needed pages are near the start or end of the range, so that the data knob can quickly find them.
The organisation of pages can take some getting used to, since there is no map of pages in the manual; you need to spend some time exploring before you can become familiar with the locations. Moving between pages is made much easier by the way that the SP remembers which page you are on under any menu button — when you return to a menu you go back to the same page. The way that parameters are changed is unusual, but very effective once learned — the position of the cursor matters! If you place it over the units digit then changes are made as you might expect, but selecting the tens digit forces changes to the parameter in steps of ten (up to the largest value, of course). This makes rapid changes to parameter values much easier when editing, although it does slow down cursor movement on a page, since you need to move through all the digits of each parameter.
The rear panel of the SP has two 25-way female D-type SCSI ports (one is a Thru for chaining the SCSI bus, much like a MIDI Thru), the filtered IEC mains connector, four audio outputs and strain-relieved MIDI In, Out and Thru sockets. The small rotary contrast control is for the front panel LCD.
Inside the SP you'll find a single, large, double sided, plated through hole, solder resist and silk screen legended PCB (275 x 300 mm), with eight SIMM sockets just behind the LCD display. Two 1MB 100ns SIMM modules were present in the review model, leaving six free for additional RAM. Two Bergstik selectors presumably enable selection of 1 or 4MB SIMMs, giving a maximum memory size of 32MB. The PCB is dominated by a 68000 microprocessor chip running at 12MHz and a Motorola 56000 DSP (Digital Signal Processing) chip running at 33MHz. The SCSI interface uses an AMD 5380C chip, with socketed SCSI termination resistors. A 6850 UART provides the MIDI interface to the main processor, whilst an FDC 37C65 running at 16MHz provides the high density floppy disk controller functions for the well shielded drive. The Operating System EPROMs are two 27C512 and on the review model were clearly marked 'SP 1.1 Jan 92'.
There are a large number of miscellaneous 74 HC/HCT series digital logic chips on the board. I would have expected such random logic to have been replaced with either an ASIC, Gate Array or PLD device. This would save board area, reduce cost and improve reliability and testability. The MIDI opto-isolator is a high quality Hewlett-Packard 6N138 device, and the MIDI sockets had ferrite beads to prevent problems with RF interference or EMI leakage.
An internal 0.25A mains fuse connects the mains power to a low-profile transformer, which provides AC for an inductor-stored switching +5V logic power supply regulator and for the +/-15V analogue power regulators. Local +5V analogue power regulators (78L05) are used in the audio output area. Two Burr-Brown PCM56P DACs provide the digital-to-analogue conversion, with de-multiplexing from two CD4053 switches. Active filtering is provided by op-amps from Texas Instruments: 5532; TL072; and 4558.
The casing is constructed from folded steel, except for the front panel which is an aluminium extrusion. A secondary steel front panel is used to mount all the front panel components — the extrusion is mostly decorative. The overall construction is rugged and well designed. The depth of the unit (335mm) and its weight suggest that additional support at the rear might be needed, rather than just front panel mounting bolts. The top cover can be removed after removing just eight bolts. Overall, an excellent example of Peavey's commitment to high quality workmanship and construction.
Pressing the Preset button allows you to select the Preset which will be played by moving the cursor to the 'p#' parameter. The Global button also accesses the Presets directly on the initial page. It lets you select the Preset which will be played, whilst subsequent pages set the volume, MIDI channel and receive mode (Omni, Poly or Multi). A special MIDI Notes Play option lets you choose how received MIDI note messages are interpreted: you can choose to play as per the MIDI receive settings, as per the current display, or you can 'lock' the sound being played to a Preset, Map, Tone or Wave. The current display option was my favourite, since you always hear what you are editing. It also means you do not need to create special receive settings for editing.
Accessing the 16 Multi settings is next in the page order, and this involves quite a few button presses to recall a Multi setup from memory. You can have 16 Multis per Bank (and thus per floppy disk), and the only editing commands are global ones acting for each MIDI channel separately: Preset Allocation, Volume and Channel Disable. The remaining pages deal with other global parameters: tuning, preset memory status, SCSI settings and note display options (C#3 or 61). The Preset memory is separate from the sample memory, and allows up to 255 sample Waves and Tones, and up to 128 Maps and Presets. In practice, you would be unlikely to use anything like these numbers — the example disks supplied with the SP have less than 10 of anything.
Playing the SP sample discs showcases the high quality that seems to be consistent with the SX sampler expander's over-sampling delta-sigma convertor and the almost 'industry standard' PCM56 digital-to-analogue convertor. The low level of quantisation noise on the decay slope of the piano and guitar sounds was excellent. A large number of commercial SP disks will be available by the time you read this, and some Public Domain discs are in preparation (including one by myself).
Pressing the Preset, Map, Tone or Wave buttons enters the editing pages — you can always directly select the part you are working on by moving the cursor to the 'p#','m#','t#' or 'w#' parameter. The editing pages for the Presets, Maps, Tones and Waves all share some pages with identical functions. The initial page shows the Preset, Map, Tone or Wave name and 16 dots which turn into semiquavers (16th notes) when you send MIDI Note On messages — this neatly shows the dynamic voice allocation working since you can see when all the 16 voices are being played and note stealing is taking place. The next few pages are also common to all the editing pages, and allow the creation, deletion, copying and naming of the Preset, Map, Tone or Wave you are editing.
The remaining pages are specific to the particular part of the SP sound you are working on. Having the house-keeping functions like copy, name and delete available within each set of pages makes it easy to keep track of what you are doing — if there was a separate button it would be very easy to lose track of what you wanted to work on. Unfortunately, the splitting up of the SP sounds into these four component parts means that you do need to do quite a lot of jumping between pages in order to edit a complete sound.
Starting with the Wave pages, you alter the sample start position or the loop points, then change the envelope, filtering and modulation in the Tone Pages. Allocating and transposing Tones to Zones on the keyboard is then done with the Map pages, whilst the layering is dealt with by the Preset pages.
Choosing sensible names also helps: the SP will let you call a Wave, Tone, Map and Preset by the same name — 'Piano', say — but trying to decipher this is hard work. Waves and Tones need descriptive names like 'E-2 Clunk' or 'C2 ff', whilst Maps need some indication of their purpose in the final sound with names like 'Piano pp' or 'Piano ff'. Presets should have the overall sound description: 'Steinway Piano'. Multis should have names which are application driven and should be indexed on paper: 'Hard Rock 1', 'Nu Age 23' etc. I found that little clues like these made putting sounds together much faster, and Peavey certainly get full marks for allowing you to name all the constituent parts of a sound individually.
The most obvious SP 'gotcha' is the dynamic RAM — turn the SP off and you lose all the samples. But this is also a strength, since the SP will automatically load the contents of any disk in the on-board disk drive when you power it up. This means that for a basic 2MB SP, you can mostly fill the memory with just a single disk, whilst for larger capacity SPs (up to 32MB is possible) you will probably fill it via the SCSI bus — neither method takes very long, and the cost reduction of not using static RAM is considerable.
This neatly introduces the second 'gotcha': the price. The SP offers comprehensive 44.1 kHz, 16-bit sample playback facilities at a very affordable price. When I initially read the specifications, I expected it to cost considerably more than it does, and it is very easy to forget that comparably price S+S machines from other manufacturers offer only onboard ROM and memory card expansion.
Compatibility is the one area where the SP loses out on just one count. Although the MIDI SDS and SCSI provision is good, the V1.1 SP does not read Akai disks, which automatically reduces its appeal for users with large sample libraries on disk in what must be the de facto format. The SP also does not allow samples to be 'exported' via MIDI SDS.
The SP's rather limited sample editing functions are designed to enable basic management changes to the samples. Apparently Peavey's intention is that MIDI SDS files would be edited in a graphical environment on a computer, and then transferred back to the SP. The SP's LCD does not suit complex or detailed editing, and so the software overhead of providing facilities like timestretching is probably not viable. Using an external computer certainly seems to make sense, and keeps the SP's cost low.
The last 'gotcha' is the lack of a built-in sample facility — the SP is a sample replay synthesizer. But the low-cost SX sample expander enables the SP to become a complete sampler and replay system, and using the SCSI bus as the transfer mechanism for samples ensures rapid movement of samples between the SX and the SP.
The manual supplied with the review SP was only a preliminary version, produced to enable early release of the SP hardware, although the return of the registration/warranty card guarantees despatch of a full manual. For an early glimpse at the full manual, the preliminary manual does a good job of describing the initial setup and first explorations of the SP. The MIDI and SCSI details are slightly sparse, although you can get further details of the MIDI Implementation free from Peavey. The manual promises further tutorials on editing and applications in the full version.
Based on the upgrade record of the DPM3 (currently featuring the third major version release of its operating system software) the SP will not stand still. Many of the changes to the DPM3 have drawn on user feedback to make it easier to use by providing shortcuts and additional features. Peavey make upgradability a feature and offer reasonably priced hardware and software updates, which promises well for the future of the SP.
The SP has been well worth the wait. I expected simple 'load disk into RAM and replay it' functionality, but instead of taking the easy way out and producing a simple sample replay machine, Peavey have taken their time and produced an outstandingly versatile instrument. Although you could use the SP like a basic sample replayer, the power and sophistication it offers should encourage much more innovation and personalisation. The potential offered by the SP is quite breath-taking, especially at the price: a fraction of the cost of many competing instruments. The more Peavey products I look at, the more impressed I am — the SP definitely gets my vote as the most desirable S+S rack-mount replayer. Recommended.
Peavey DPM SP £899 inc VAT.
Peavey DPM SX £325 inc VAT.
Peavey Electronics UK, (Contact Details).
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