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The Digitech 2101 guitar multiprocessor has everything -- except for the very most crucial thing: a saturating POWER tube, placed before the time-based effects.

This article contains the ideas that will fuel the next revolution in guitar processing. It's really easy to picture trends in this direction. There are about 10 *great*, sure-fire product ideas here, all based on using low-wattage power tubes.

A year from now, I hope to be able to buy a Digitech rack unit containing not only a speaker simulator, but also a power tube, output transformer, and inductive load in what is now the "effects loop" between the preamp stage and the time-based effects stage. Please, Digitech and others, provide this effectively, and business will boom like never before -- we will have the perfect marriage of tone, effects, flexibility, and convenience -- and in fact, a new, vastly richer form of guitar music.

BUILDING BLOCKS FOR LINE-LEVEL POWER TUBE SATURATION
o Low-wattage power tubes and transformer (the power stage of a low-powered tube amp, such as 5 watts)
o Inductive loads (Power Brake is step-down of power, THD Hot Plate is step-down or even line-level to elim. spkr)
o Speaker simulators (2101 has one -- these are usually just a brick wall filter for high treble)
o Speaker isolation cabinets (large, for 12" speaker [Demeter], or small, for 5" speaker)
o Low-powered guitar speakers (e.g. 25W Greenback, or 5" 5 watt specially selected)
o Microphones (dynamic and/or condenser)

There are many combinations of these building blocks. But there is one item that is absolutely necessary: the power tubes.
Possible building blocks for a low-room-noise or even line-level power saturation: you can put any of these into a revolutionary footpedal, or into the effects loop of the 2101. These are truly "amp in a box" units (again, I'm not referring to the preamp stages, which are already established technology, but rather, the power tubes, speaker, and microphone).

It has become ironic and ridiculous the way power tubes step the wattage up to 100 watts, and then we slam all of that power against an inductive load to bring it back down to where we often want it: less than 1 watt. Why not just develop a family of processing gear based around a 1 watt power tube in the first place?

15 watt all-tube amps are now available from Soldano, Fender, and many other companies. www.torresengineering.com has instructions to build a 5-watt 6V6 amp. Let's not stop there, but instead, squeeze a single power tube into a footpedal.

THE 3 BASIC APPROACHES TO LOW-VOLUME POWER-TUBE SATURATION

A. Somewhat quiet, but is totally authentic: 5 watt power tube and transformer --> low-powered guitar speaker in a speaker isolation cabinet --> microphone

B. Very quiet, may sound a little fake: 5 watt power tube and transformer --> step-down inductive load --> 5" speaker in small speaker isolation cabinet --> microphone

C. Completely silent, but may sound fake: 5 watt power tube and transformer --> inductive load --> speaker simulator

The goal is to approach headphone level while preserving the tone of power tubes pushing speakers against air through a transformer, feeding a microphone. There is no question you must involve real power tubes. The crucial question is whether those power tubes must be directly connected to a genuine speaker (A), or whether you can drain some of the power and volume away (B), or whether you can drain *all* the power and room noise away and completely eliminate the speaker and microphone (C). Clearly, C is radically convenient and deserves dedicated research. For the reference point of this research, set up rig A, and attempt to make C match it. A is the benchmark -- it is literally a saturating tube amp, directly connected to a speaker.

Approach A is expensive to manufacture, cumbersome, and inelegant. Speakers and microphones are expensive. It's also loud. The low bass of muted, percussive power chords penetrates right through the walls of even a sturdy speaker isolation cabinet. I constructed a sturdy box-within-a-box using 3/4" fiberboard, and the low bass from the 15 watt power tubes still came through too loud. Approach B may well be the best compromise. This 5" speaker cabinet is only a cubic foot.

There is a little company in the southeast states that makes an innovative speaker isolation box. It contains a scaled-down, 5" guitar speaker and a dynamic microphone such as the Shure SM-57. It has an inductive load before the speaker to step down the power to an appropriate level for the 5", 5 watt speaker.

There is a little company in the northeast that makes low-powered full-featured all-tube studio amps.

The Marshall Power Brake is an inductive load that lets some power through to the speakers.

Harry Kolbe makes some inductive loads. I bought one of his first units but the pot levels were badly designed and the output sounded fizzy no matter how it was equalized. It also squealed at low saturation levels.

Before I built my speaker isolation cabinet, I tried the Fender Pro Jr amp into the Kolbe inductive load. Putting the power tubes and the soak in the effects loop was a great placement for mind-blowing post-amp echo and other time-based effects. But the Kolbe unit squealed badly and sounded fizzy. It did *not* sound like there was power tubes, a real guitar speaker, and a microphone in the effects loop.

Remember to think of the 2101 not as one monolithic box, but rather, two parts: pre-amplifier processing, and post-amplifier processing. All that is missing for a complete traditional studio setup is the amplifier -- that is, power tubes, a speaker, and a microphone.

Digitech and other companies should make a large footpedal containing a power tube, output transformer, and inductive load. Perhaps it's *not* possible to make this sound just like the post-preamp parts of a tube amp, but many struggling inductive load Edisons are out there trying their hardest to make this happen.

o Can you *really* put an inductive load across the power stage without ruining the tone?
o Can you *really* use a low-pass filter to perfectly emulate a guitar speaker?

A real speaker is a complex system, and should be connected directly to the output transformer. If you interrupt this interplay between the speaker and power tubes, you might ruin the tone. Then, to make things worse, if you get rid of the guitar speaker pushing air, and use a low-pass filter instead, you again might ruin the tone further. All of us who want line-level power amp tone are hoping that you *can* fool the power tubes with an inductive load, and you *can* "simulate" a speaker using a low-pass filter.

INSOFAR AS YOU CAN fool the power tubes with an inductive load, and simulate a speaker using a low-pass filter, a revolutionary new product awaits: the power tube and speaker simulator in a footpedal! *Truly* worthy of being called "amp in a box", unlike all the *preamp*-oriented distortion boxes such as SansAmp and rack-mount preamps with speaker simulators.

Once we have isolated the power tubes and speaker simulator into a module, then we have the greatest power of the studio: the power of putting the time-based effects where they normally belong, *after* the saturating power tubes. The question of "what order should I put my effects in" takes on a whole new meaning.

THE PROFESSIONAL STUDIO SEQUENCE OF PROCESSING AND SATURATION STAGES
1. pre-distortion processing and eq (wah, phaser, envelope filter)
2. distortion stage
3. post-distortion processing and eq (phaser, no intense time-based effects)
4. "tube guitar amp" -- now, use a power tube and inductive load in a footpedal (includes optional speaker simulator)
5. post-amp processing and eq (heavy time-based effects)

The *sequence* is as important as using tubes. If you put the time-based effects before the power tubes, the tubes will be so confused they will sound like mush, with unmusical beats as you bend a note, and distortion from an old echo clashing against the new notes and they both try to squeeze through the saturating power tubes. The Digitech 2101 is fatally flawed because it has stages 4 and 5 backwards. It cannot be emphasized enough: stage 4 *must* be before 5, or there is no hope for your basic tone produced by saturating power tubes.

If you are going to place time-based effects before saturating power tubes, you are committing tonal suicide and all your design work is ruined by being distorted in an unmusical way -- the exact opposite of the intended effect. You include power tube saturation to purify the tone, but when you place this saturation *after* time-based effects, the saturation *corrupts* the tone and turns it into sludge. These are simple, basic principles of saturation and frequency spectra: time-based effects before a saturation stage cause dissonant, unmusical beats because the input signal has too many residues from the detuned notes.

These devices should be packaged both as footpedals and as integrated units, to allow hybrid rigs.

The speaker simulator could be broken off as a separate, eq-type footpedal.

You could still market speaker isolation cabinet systems of various sizes and power capacities, with or without a step-down load for 100-watt amps.

But all the *new* power-tube oriented products will be geared toward miniaturized, low-volume, low-wattage power tubes and speakers -- 5 watts and less, not 15. These are not meant to be played against live, loud drums, but rather, for studio work, apartments, bedrooms, jams with friends, electronic drums, sequencers, parties, and practicing.

Also, there will be an increased need for a variety of ergonomic full-range amps and monitors to amplify the final signal.

You cannot use a single 2-channel traditional all-tube guitar amplifier to switch between a loud clean tone and a quieter but heavily *power*-tube saturated tone. You have to have two amps and/or a sound man running two channels of a mixing board. There is no master volume after the speakers. But if you put a "silent guitar amp" into the 2101's effects loop, you then have a master volume control over the whole "guitar amp" level (where the "guitar amp" in this case is a power tube and either an inductive load or a mic'd speaker in an isolation cabinet).

I am planning another article about the developments in the Fretlight concept, which will mesh very well with computer-control of the Digitech processor. Sequencing software will drive program changes in the guitar processor, LED changes on the fretboard of one or more guitars, and LED changes on a keyboard. Electronic drums could be patched in too. The technology is all here to make this happen, and at line levels with great tone. Software, LEDs, guitar processors, and line-level power tubes are about to be brought together. We'll be able to improvise with truly far-out and dynamic scales and tones, with little musical knowledge required. Instead of wrestling with music theory and with mediocre tone, we'll be able to casually enjoy jamming with friends at a level that currently requires years of effort, mastery of the black art of tone, and loud performance spaces.

These are my original combinations of ideas based on my 16 years of trying to get authentic tone at low room levels.

-- Michael, theorist of self-control cybernetics

cc list:
Harry Kolbe (re: inductive load)
Craig Anderton (re: effects pedals)
Tom Scholtz (re: resistive load)
Torres Engineering (re: 5-watt tube power amp)
THD (re: Hot Plate inductive load)
Marshall (re: Power Brake inductive load)
Fender (re: 15 watt Pro Jr. amp)
Digitech (re: 2101)
alt.guitar.amps (re: low-watt power tube product proposals)
Demeter (re: speaker isolation cabinet)
Hi-Mu (re: 7-watt tube guitar amps)
The cubic-foot 5" speaker isolation cabinet manufacturer (re: scaled-down guitar speaker systems)
harmony.com (re: new processing gear concepts)