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FAQ REVISION HISTORY
- 11.23.94 - version 1.0
11.29.94 - 1.1: line length increase; minor formatting changes; Bulk Dump section added; Program Memory section added; enhanced explanation of "true stereo" operation.
11.29.94 - 1.2: updated Processor / Memory Upgrade section.
12.15.94 - 1.3: added reference to mailing list 1.4.95-
1.4.95: updated PPC-210 upgrade, firmware, foot controller, and Comments/Observations sections; added info on sys-ex document.
6.20.95 - 2.0: updated information per feedback from Digitech (Thanks Randy!) Affected sections: Analog, Global EQ, Foot Controller, Firmware, Limited Edition, Observations, Internet Resources. Also added new "Miscellaneous Questions, Answers, and Tips" section.
9.1.96 - 3.0: Updated David Blevins (blave@almnet.com) version 2.0 FAQ to Fall 1996 standards including the latest 3.00.00 firmware release, formatted in HTML, sectionalized, etc.
OVERVIEW
- The Digitech GSP-2101 (MSRP $1099 US as of Septemeber 1996) is an analog/digital
effects processor for the guitarist. This FAQ (Frequently Asked Questions
document) will address aspects of the 2101 that are either not explained
well or not mentioned at all in the manual. Additionally, it is inteded
as a living document for 2101 users and prospective buyers to reference.
ARCHITECTURE
- The GSP-2101 consists of a digitally-controlled analog preamp section
followed by a true stereo digital effects section. The 2101 utilizes Digitech's
S-Disc, a proprietary Digital Signal Processing chip. Due to its modular
design, the 2101 benefits from the ability to upgrade to a second S-Disc
processor for enhanced capabilities.
- The 2101 has a rear and a front 1/4" monaural input jack. The rear
jack is slaved to the front such that a connection to the front jack disconnects
the rear jack from the input section of the 2101. This signal passes through
the Analog Preamp Section of the 2101.
A single monaural 1/4" output jack is provided for Fx Loop Send. The signal from the output of the Analog Preamp Section is ALWAYS present at this jack regardless of the state of the Fx Loop (Bypassed, Summed, or No-Sum).
Two (left and right) 1/4" monaural jack inputs are provided as Fx Loop Returns. Each input is independantly converted from Analog to Digital, thus making the 2101 a true Stereo Digitial Signal Processor (2 independant inputs, 2 independant outputs).
Two (left and right) 1/4" monaural jack ouputs are provided as Master Outputs. The signals present at these outputs have passed through the Digital Section, the Master Mixer, and the final Output Level Amplifier. The Output Level Amplifier's knob is on the front panel in the upper right-hand corner. This is not digitally controlled, since the Master Mixer has level settings which are digitally controllable. Finally, there is NO Hardware Cabinet Emulation available at these outputs, although a software Cabinet Emulator module has been added to the 3.00.00 firmware.
A 1/4" stereo jack ouput is provided for headphones. This output signal is always present. The level is adjustable via a front panel knob (not digitally contrallable). Finally, this headphone jack includes a Hardware Cabinet Emulator designed to cut some of the high's in the same manner as typical guitar cabinets would. This Hardware Cabinet Emulator is not adjustable in any manner (furthermore, it is always active for the headphone output and cannot be bypassed), although some users have reported success in altering a couple capacitor values to change the brightness of the emulator.
Two (left and right) balanced XLR jack ouputs are provided for mixing board applications. The signals at these outputs are identical to the signals at the 1/4" master outputs. However, note that the 1/4" master outputs are BALANCED, but that typically you will connect them to a device expecitng UNBALANCED 1/4" signals. This is perfectly acceptable, but you will be negating the effect of the balanced circuit. Also, there may be perceived differences in signal strength when comparing balanced vs. unbalanced configurations as a result of the additive input in the balanced configuration. Finally, there is a switchable Hardware Cabinet Emulator available. This is the same emulator that is always used in the headphone circuit, except that it is switchable (on/off) for the XLR outputs. The switch is located in the rear of the unit next to the XLR ouputs.
ANALOG SECTION
- The effect ordering in the analog section is fixed. From the mono guitar
input, the signal passes through a monaural compressor module, a monaural
distortion module, two monaural seven-band graphic EQs (see below), a monaural
Master Volume Control, an Fx Loop switcher/mixer, and finally a Stereo
Noise Gate.
The input levels of the 2101 have been set in such a manner as to optimize its response for as wide a variety of input levels ("hotness" of pickups) as possible.
Note that all paramters of the Analog Preamp Section are Digitally Controlled, are programmable, and can be linked to MIDI CC's and the Control One pedal/switches.
COMPRESSOR:
- The Compressor has typical guitar range settings (Compression Rates
of 1.5:1, 2:1, 3:1, 4:1 5:1, 7:1, 10:1, and infinity:1) as well as adjustable/programmable
threshold, output level etc.
- The distortion module has four parameters:
- Bypass/On
Type (Saturated Tube, Distorted Tube, Clean Tube, Overdrive, Heavy Sustain, and Grunge)
Gain1 (Used for all types - 0.6 to 11.0 in irregular jumps of about 0.3)
Gain2 (used for distortion types Saturated Tube and Distorted Tube only)
- The Analog Preamp Section has two 7-band graphic EQs. One is designed
to be custom tuned to a particular program. The other is Global, meaning
that it's settings apply to every program. Note that the Global EQ is ALWAYS
active in addition to the program's individual EQ. The purpose of the Global
EQ is to allow the user to configure the overall tonality of the 2101 for
different amplification systems and environments (Carnegie Hall sounds
different than your bedroom). This allows you to adjust the EQ settings
for a particular environment for ALL you programs without having to reprogram
each program every time you go to a new gig. Pretty clever. I recommend
that you keep the Global EQ flat at your primary practice location, and
only adjust it to tune things up for different environments/rigs.
I have found that, when I use the headphone output for quiet late-night jamming, I like to adjust the Global EQ a little bit to better approximate the way MY cabinets actually sound. Just remember to set the Global EQ back to flat when you are done.
- The emulator's output is available only at the headphone jack and/or
the balanced XLR outputs; the 1/4" outputs always bypass the emulator and
come directly from the post-digital EQ. The emulator on/off switch is located
on the rear of the unit. There are no parameters associated with the emulator
- it's either on or off.
DIGITAL SECTION
- The S-DISC processor-based digital section is very similar to a Digitech
TSR-24. This portion of the GSP-2101 can be used standalone by bypassing
the analog section. In this mode, it is a true stereo effects processor
- i.e. it can maintain two independent signal paths from input to output.
(As an example, Algorithm #8 is a stereo in / stereo out "Gigaverb" reverb.)
Like the TSR-24, almost complete control over digital effect ordering is
available to the user. Each "ordering" configuration is called an Algorithm.
There are factory Algorithms that cannot be changed; in addition, a User
Algorithm memory space is provided for customer Algorithms. Each of the
100 fixed and 100 User Programs are based on an Algorithm; the rest of
the parameters of a Program pertain to the settings of each parameter of
each effect module that is a part of the Program's Algorithm.
The 2101 in its base configuration has 256 CPU blocks and 256 RAM blocks available; the Owner's Manual includes a table of the _approximate_ number of blocks that each effect module takes. Emphasis should be placed on "approximate". You may think you have enough blocks left over to add, for instance, an MFX Reverb module to an Algorithm (based on adding up blocks used by the existing modules), but it's possible that it won't fit. Sometimes, it is even possible to make things fit by changing the order of effects, although this is not advised, since all Algorithms should, ideally, be created in a logical, ordered manner.
- PROGRAM MEMORY
- Contrary to some early data sheets and mail order catalogs which spec
128 factory presets and 64 User Programs, there are 100 User Programs (1-100)
which can be edited or overwritten as well as 100 factory presets (101-200)
which cannot be overwritten. The unit comes from the factory with the content
of programs 1-100 being copies of 101-200. In some instances, there may
be more than 100 factory presets (the Artist, for example).
It should be noted that a user could create such complex memory-hogging programs that he/she cannot actually acheive 100 User Programs before running out of available RAM in the 2101. In this instance, he would be forced to live with whatever he can fit in his available RAM. Note that factory programs do not require any (at least not much at all) RAM since they are not stored in RAM. Instead, when a factory preset resides in the User Program area (1-100), it is actually just a pointer to the EPROM which has the data on it. Thus no RAM is consumed with a repeat of the factory data. However, if you tweak a factory program, even the slightest bit, it becomes a custom user program, and the entire data structure will occupy RAM. The amount of Program RAM is NOT upgradeable (the PPC-210 upgrade does NOT increase this type of memory).
As with User Programs memory availability, algorithms too have a limited storage space. As Custom Algorithms are created, more RAM is consumed by them. This becomes especially troublesome if they are Dual-S-Disc Algorithms since they are so complex that they effectively require twice as much memory to be stored. While each Algorithm is only stored once, regardless of how many times it is used by programs, there is not alot of Algorithm memory available. Digitech performed some tests and decided there was enough memory for about 7-12 normal-sized custom Algorithms. If you have run out of Algorithm memory with less than 7-12 custom Algorithms, then perhaps you are not normal. The amount of Algorithm RAM is NOT upgradeable (the PPC-210 upgrade does NOT increase this type of memory).
Note that while Program and Algorithm memory utilize the same physical memory chips, they occuppy disticntly separate memory address ranges within the 2101. Furthermore, these memory regions are NOT dynamic. If you eat-up all your Algorithm memory by generating alot of new Algorithms, the 2101 will NOT allow you to utilize some unused Program memory space for new Algorithms. In other words, the Alg/Program space is partitioned from one-another.
The memory inside your 2101 is backed-up with a battery, so that the information is retained in RAM. This is very much like the battery that backs up the CMOS settings in your home PC. The life of this battery is probably between 2and 5 years, although noone has ever mentioned losing their battery. None-the-less, better make sure you back up your data to your computer.
- The PPC-210 is a small circuit board with an S-Disc processor. This
board is plugged into a special socket on your 2101's motherboard. This
upgrade allows your 2101 to perform the following miracles:
- 1. Create algorithms that use BOTH S-Discs simultaneously. This
means that you can now create some pretty big algorithms using more exotic
modules than with a single S-Disc unit.
- OR -
2. Switch Seamlessly between single S-Disc programs. This allows your "Metallica Crunch" program to fade out according to your preprogrammed ramp and hold times while the 2101 is loading up your "Clean Delay" algorithm (because you punched it up on your FC-1). The small amount of time it takes the 2101 to load the second program is covered up with the sound of your previous program fading out, rather than a sharp drop in sound. Furthermore, by allowing slow fade and hold times, you can actually blend the two sounds together for a few seconds to make the transition smoother.
With the PPC-210 installed, four new algorithms are available. Also, fifteen new patches (201-215) show off the dual S-DISC capabilities.
"CONTROL ONE" FOOT CONTROLLER OPTION (list price $299 US as of Sept 1996)
- The footcontroller desingned to work in tandem with the 2101 has undergone
a few name changes. It was first called the 2101-FC. Thus you may see references
to FC-1, FC, C-1, or Control One. All devices are identicle with the exception
of differing paint and decal labels. Don't blow a head gasket over this
trivial difference.
The Control One (C-1) is a dedicated unit - there is only one input/output jack (no MIDI in/out is included). The jack is a 5- pin DIN connector so that a standard MIDI cable can be used to connect the FC to the 2101; both units have large caution labels over the jacks about the bad things that happen when you mistake them for MIDI jacks. The FC receives its power across this dedicated interface. A long MIDI cable is included. A treadle controller (the internal pedal), ten programmable switches, a multi-function Bank/Program/Tuner select switch, a Bypass switch, and a 20 character LED display for program names are provided. A 1/4" input is provided for an additional control pedal (the external pedal). (As a side note, the Control One, formerly known as the GSP-2101 FC, can be used with the Valve FX and Legend II preamps as well.)
All configuration of the FC is done via menus on the GSP-2101 itself. Here, you can do things like set the MIDI Continous Controller assignments of the internal and external footpedals, etc. You can also, for instance, set up the FC so that each footpedal turns on/off individual effects modules (Stomp Box mode). See Configuring the C-1 Footcontroller for more info.
The following items are undocumented in some manual versions:
- Program toggle - once a program has been selected, pressing that program's
switch again will toggle the 2101 to the previous program.
Tuner function - if the 2101 has version 2.00.00 or higher firmware, the tuner can be accessed by pressing the Bank Select switch three times. At this point the tuner "eye" will appear in the FC's fluorescent display. Pressing the Bank Switch again will return you to the current program; pressing another program switch instead will select that new program.
MIDI IMPLEMENTATION
- This section will summarize the contents of the "MIDI System Exclusive
Documentation" manual. This manual covers sys-ex information for the S-DISC
family of products, including the TSR-24, GSP-2101, TSR-12, and RP-10.
It assumes a firmware revision of 2.00.00 or higher. Note that there are
additional MIDI messages handled by firmware versions 3.00.00 and up.
The beginning of the document covers Basic MIDI information such as sys-ex message format, etc. One interesting thing to note is that the Pitch Bend CC is not supported due to the "density of the information and the resources needed to process it properly". The remainder of the document covers the 27 sys-ex commands that are available. Some examples:
- Receive/Request one of the following: One Program / Algorithm / Bulk
Dump / Module Table / Algorithm Link Table / Parameter Value / Error/Status
Flag.
The current version of the SysEx document is 1.23 which now includes data formats for program dumps. It is available from Digitech upon request, but be advised that it won't tell you much about the 2101 other than things you'd need to know if you're writing an Editor/Librarian for it. You can also access this SysEx document on the Internet.
Go to GSP-2101 FAQ Table of Contents
Written by Curtis LeMay Pastor,
CLPastor@aol.com or clpastor@ee.tamu.edu
Last revised as of Feb 3, 1997.