New Kinds of Tube Guitar Amplifiers

How GAGA will help you sound and perform your best

Light-weight, powerful, elegant, and unusually flexible, GAGA intensifies nuances, enhances "feel", increases dynamics, maximizes purity, heightens musical ecstasy, and brings musicians closer to tonal truth. Smart features fresh to the guitar world yield real world advantages. Berning and Milbert have teamed up again in GAGA. Using patented ZOTL (Zero-Hysteresis Output-Transformerless) Technology™, an award-winning technology renowned in esoteric high-end audio, GAGA provides excellent amplification for discerning musicians. Here's how it will help you sound and perform your best:

• Ultimate in versatile: Completely control "the sound" — GAGA accepts and auto-biases any common octal audio output tubes, in any combination. Forget "matched" pairs (and types!), metering, tedious adjustments, bias drift, mismatch and aging —just plug and play, literally, with unprecedented control over the louder part of your instrument. Tweak the tone: Change a tube. Get a whole new sound: Change all four. Various input tubes may be swapped for an even larger palette of tone and feel. "The...technology is both complex and elegant. The auto-bias circuit alone is a technical tour de force." »
• Lighter tube power — Bring GAGA anywhere...arrive without cramps or one arm longer than the other...enjoy invaluably dependable performance...jam, shine, smile...and then actually leave the gig on time.
• No more batteries — Because GAGA includes a complete system of P3 Technology® (and Power-Chain™ cables), you don't need batteries or hazardous and noisy AC power for a "DC" brick up at your pedalboard. P3 works with all standard 9-volt pedals. It is the end to power problems — and talk about "green" technology: Never land-fill another 9-volt battery.
• Start with purity — No other tube amp provides this kind of faithful, phase coherent, all-tube, pure power amplification across the audible spectrum. Why is this desirable? Many quotes uniformly implore 'start with purity':   Clean Tone = Wide Spectrum = Musically Rich. This is exactly the same old obvious truth that great meals are best made from pure ingredients. What's less intuitive, yet scientifically demonstrated, is that limited amplifier bandwidth results in reduced musical ecstasy and brain activity. GAGA's wide-bandwidth, accurate and full pure tube tone is intense, musical, natural and emotionally involving.

Taken from Berning's White Paper, the following oscilloscope photos demonstrate the audible and measurable superiority of GAGA using ZOTL Technology:

• Tremendous, taught lows — Coherent low frequencies give solid impact and powerful slam that extends all the way down without flub or muddiness due to core saturation and magnetizing current.
  
• Luscious tube warmth — Mids are warm and tubey but resolve without clutter for great tone all the time, without need for "scoop" or constant control twiddling. Extended highs — Highs are wickedly fast, airy, natural, lively.
  

Playing is believing. Measuring is proof.

From Berning's White paper, "Electronic Devices and the Amplification Process":

Left photo (below) shows response curves of 6L6 tubes played through an audiophile-grade audio output transformer. Visible magnetic bloat manifests audibly as lost power, muffled attack, dulled nuance, skewed timbre, or "munge", "flub", "smear".

Right photo (below) shows how response curves of the same 6L6 tubes as used in GAGA match their ideals shown in tube data sheets and technical literature. The resulting faithful tube amplification gives clarity of tone, leaping dynamics, immediacy, impact, body, warmth, and three-dimensional naturalness. Toward the goal of maximizing musical ecstasy, GAGA audibly and measurably provides the purest possible tube tone.

"... B [X-axis] is the notation for magnetic flux density and H [y-axis] is magnetic force. Plotted together, they graphically illustrate hysteresis ["magnetic lag"]. A large separation between the magnetizing and demagnetizing curves (a "fat" loop) shows much hysteresis and a small separation (a "narrow" loop) approaches the ideal of no hysteresis." [With no loop at all, power tube performance in GAGA measurably meets its ideal.] — Line-level transformers in High-End Audio, Mark J. Medrud, Design Engineer, Jeff Rowland Design Group, Inc., 17 March 1995 »


• No "loose ends" that are unterminated windings electrically flopping around, causing sonic mayhem inside traditional audio output transformers. See Luke Manley's comments: "Multiple output taps [present in audio output transformers as the ubiquitous 4, 8 and 16 Ohms] are inherently a serious compromise in performance. Inactive winding-segments are inevitable in a tapped transformer and result in additional leakage inductance that affects high-frequency response." GAGA completely avoids this.
• Elegant — Great tone and reliability. Few, large, single-purpose knobs. Auto-Everything. One output that optimally matches any speaker load, not 4-, 8-, or 16-Ohm taps that are always imperfect compromises. Literal plug and play. No nonsense, nothing to goof up or set wrong.
• Blow-Proof™ Auto Output — Drive any common cabinet or speaker combination, just plug it in. Blow-proof output sustains direct shorts or total opens. GAGA is robust and will drive any cable without damage: In a pinch, a "speaker" cable is not required.
• No distortion hangover — Instant, per-note response amidst any amount of overload, even the most severe output tube crunch. When you stop pushing GAGA it immediately stops being pushed - the sound never becomes bewildered, stalls out, blunders on, or "folds back over on itself". GAGA is made to provide continuously solid response and power, with smooth, rich overload and distortion when so driven, without fading off or collapsing: "lightning fast power without inertia, as responsive as no amp at all." Why is this important?
• Bottomless, pristine energy reserves — Supersonically recharged and regulated internal energy reserves provide for unsurpassed sensitivity, solid slam and lasting sustain. Typical amps store meager energy, loosely regulate if at all, and recharge based on 60Hz line frequency, which is audible as hum; GAGA literally blows all that away and recharges its deep energy reserves at a totally inaudible 500,000Hz rate. One manifestation is dramatic headroom and rich tone across audible spectrum, including bottomless bass. "[GAGA] is the first amp I've heard with headroom up top and down below." — Gary Smyers, audiophile, bassist, NAMM Jan 2011

Quality Parts Vanquish Compromise

Auto-Everything™ — Use Any Tube, Auto-Bias, Auto-Impedance, Auto-Power, Auto-Standby

• Any-Tube™ - Easily and completely change "the sound". Plug in any number or combination of octal output tubes for tone and power. Escape from "matched pairs" or even same types and choose your own voicing and tonality with whatever tubes you like. Insert 2, 3 or 4 tubes. Every tube inserted can be completely different. Any octal output tube (pentode, beam tetrode or kinkless triode) having RETMA standard 7AC style base and pinout will work.   "...a perfect studio amp."

  The output tubes operate in full-power, class AB1, linear push-pull manner at impedance higher than is possible with even the very best traditional audio output transformers, and without any of their attendant saturations, roll-offs, phase effects and hysteresis lags. GAGA delivers purest possible tube tone.

  6L6 family:	6L6, KT66, EL37, 5881, 7581, 6P1P-EV, 6P3S-E, 6P6S 6146
  EL-34 family: (power pentodes)	EL34, KT77, 6CA7 6K6
  6550 family:	6550, KT88, KT90, KT120 » » »
  6V6 family:	6V6, 6EY6, 6EZ5, 6P6S, 6AY5, 587, 5871, 7184, 7408, 7EY6
  STR family:	STR- 417, 420, 425, 427, 430, 442, 447, 450, 454

  Members of the EL-34 family are true Power Pentodes. Many other types are "kinkless" tetrodes.

  

• Use any compatible pre-amp tube to tweak tone further. Plug in any compatible input tubes into any position in the pre-amp section. Combined with Any-Tube™, the available tonal palette presents what some have called an amplification instrument. GAGA ships with a standard tube complement; any of its tubes may be easily changed to attain any desired tone or feel. Compatible pre-amp tubes:

  12AX7 type:	12AX7, 12AX7A, 12AX7LPS, 12AX7WA, 12AX7WB, 12AX7WC, 12AX7EH, 12AX7C9, 5751, 5751WA, 6057, 6681, 7025, 7058, 7729, ECC83, ECC803, ECC803S, E83CC, 12AD7, 12DF7, 12DM7, 12DT7, B339, M8137, 12AK7, E283CC   »
  12AT7 type:	12AT7, 12AT7WA, 6201, 6679, 7728, ECC801, ECC801S   »
  12AU7 type:	12AU7, 12AU7A, 5814, 5814A, 5963, 6189, 6680, 7316, 7730, ECC82, ECC802, ECC802S, E80CC   »
  12AV7 type:	12AV7, 5965, 7062, E180CC
  12AY7 type:	12AY7, 6072, 6072A
  12AZ7 type:	12AZ7

  Generally, the AX and AY variants are higher gain, and the others are medium or lower gain but higher current. Higher gain tubes are geared for amplification; higher current tubes are useful as drivers. See wikipedia for more information and also Frank Philipse's Tube Data Archive.

  GAGA comes with one 12AX7 tube (input), three 12AT7 tubes (tone, loop, driver) and four 6L6 tubes; substitutions are welcome.

  "Everybody else sets a 'sound' and sells it to you; we figured you should be able to set your own sound, and change it whenever you wish by simply changing controls and tubes. Flexibility and individuality largely defines musicians, so why should your amp dictate your sound?" -- Michael Milbert

• Auto-Active-Bias™ - Never worry or adjust bias again. GAGA automatically actively biases any combination of output tubes for full performance. Insert four output tubes, in whatever flavor of tonal variety, for maximum power. Remove one or two output tubes and the sound continues, albeit at reduced power output; GAGA will continue playing.

"The ... technology is both complex and elegant. The auto-bias circuit alone is a technical tour de force." —Charles Hansen, describing Berning's ZH270 amplifier, which lends technologies to GAGA, Glass Audio Magazine, February, 2000, page 38 »

• Auto-Standby™ - The ubiquitous "standby" switch is obviated by GAGA, which handles tube operation and idle automatically. When playing resumes the output tubes instantly fly seamlessly from standby to full power demand at the moment of the first note. There is no lag or delay. Merlin Blencowe offers this interesting information regarding standby switches:

  "The standby switch usually allows the HT to be turned off while the heater and bias supplies are always on. Contrary to popular belief, the standby switch is not there to prolong valve life-span. The theory is that if the HT is applied while the cathodes are cold they will be 'stripped' by ions crashing into the unprotected cathode. However, this simply does not happen. It is an urban myth borrowed from transmitter and cathode-ray tube technology NOT ordinary 'receiving' valves. The only valve which might ever be at risk of failure is a rectifier valve, because it has to supply inrush current to the reservoir capacitor, and some guitar amps fail to use enough limiting resistance to protect against this...

  "On the other hand, leaving a cathode hot without any anode current flowing does lead to the very real effect of cathode poisoning, which reduces the gain (transconductance) of valves. Fortunately this phenomenon really only becomes significant if the valves are left on standby for hours on end.

  "If you're wondering why all those old amps use a standby switch, it's because Fender was designing complicated amps on the cheap. In the bigger versions of the Bassman, money was saved by using power supply caps that were rated only for the working voltage, not the peak voltage which occurred before the valves start drawing current. As everyone knows, Marshall simply copied the Bassman...complete with standby switch, so now we have the two biggest names in the industry using standby switches, and the rest is history. The other big players, Vox and Gibson, never used standby switches since they didn't need them. Only very recently have they started adding them, [presuambly] because too many guitarists want their amp to look just like a Fender/Marshall, even though nowadays no designer (who values his reputation) uses underrated capacitors. But the average amp tech doesn't know this.

  "Note that even the RCA Transmitting Tubes Technical Manual No. 4, p65, states: 'Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature.' In a properly designed amp, a standby switch is nothing more than an expensive, oversized mute switch.

  GAGA, incidentally, includes muting as the middle position of its front-panel INPUT / MUTE / LOOP switch, which has nothing to do with high voltage or proper tube operation.

  Also, the advanced power supplies in GAGA slowly ramp-up voltages at start-up, preventing cathode stripping, inrush stress, and other issues.

Tube lifetimes vs operating temperature — Sometimes in traditional tube amps, tube bias and operating currents are elevated, presumably in attempt to reduce unpleasant crossover notch distortion and shorten overload recovery » Rarely if ever is bias turned down (and now it's clear why not). While examining several major brand tube amps we measured some tube temperatures consequently in blistering excess of 500 degrees Farenheit. None of this afflicts GAGA, whose tube temperatures do not exceed 275 degrees F at full power, conservative by any standard. Tube lifetimes in GAGA are expected to exceed several years, possibly a decade or more, similar to our other products.

• Universal Mains / World-Power-Ready™ - Plug in anywhere on Earth — no settings, no jumpers. Standards compliance 90-240VAC @ 50/60Hz, RoHS, CE. Hum practically vanishes; GAGA is eerily quiet at idle.
• Drive-Anything™ - Nothing to set, match, mismatch, or confuse: Single 1/4-inch output jack drives any reasonable combination of speakers or cabinets over any type of cable.
• Blow-Proof™ - Output sustains dead-shorts or no-load total-opens without self-destructing. No more fear (or awful reality) of blown output transformers. The days of shorted output transformers and problems due to complex reactive loads are gone.

GAGA Headroom Control

Headroom "H" sets power tube overload versus volume and allows power tube overload distortion to be fully realized at less than full volume levels without abusing output tubes or heating big resistors. Headroom and Volume interact smoothly to intuitively yield wonderful and repeatable control over complex tonal colorations.

Headroom changes operating points of the power tubes, a feature made possible by the Active Auto-Bias, and does not directly attenuate the audio signal, nor is it a 'power soak' or 'hot plate'. Headroom is also not merely a "brown" technique of plate (voltage) or heater (current) starvation.

GAGA Tone Stack

GAGA's tone stack is tube-buffered, maintains great tone over wide, independent adjustment of bass and treble. GAGA allows variable 16dB of boost or cut with both bass and treble controls. Midrange Scoop or Boost — Bass and Treble controls are "center flat" and offer 16dB of boost or cut. If desired midrange may be indirectly adjusted via the bass and treble controls: Turning both down gives a relative midrange boost, turning both up gives a relative midrange scoop.

Does an audio transformer affect "the sound" ?

Of course, and with complex, detrimental effects.

"...while many manufacturers wind great transformers, there's no transformer like no transformer at all...The difference is not subtle."

An audio transformer is a big, homogenizing filter. Ongoing research reveals serious measurable and audible drawbacks with what has, until now, been a necessary evil in tube amps. Custom-wound and/or heavier magnetics may arguably improve low-end power handling, but usually at the expense of high-end phase angle (manifesting as impact, "air" or "edge"), frequency roll-off and other factors, not least of which are cost and weight. Regarded as a kind of black art, even superb audio transformers always present complex, inescapable trade-offs, explored below. Let's start with common knowledge:

"Output transformers also have a reputation for coloring the sound..." —Howard Davis, Electro-Harmonix, Pigtronix »

"...transformers can distort and color the sound...a change in the output transformer...can make a huge difference in tone..." »

"...it is the output transformer that can dramatically affect the tone of your amplifier since audio signal is actually passing through it." —John Chappell, et al., "Guitar All-In-One For Dummies" »

It's known that an audio output transformer largely (and often individually and uniquely) sets a characteristic 'sound' — a filter that can never be turned off. How desirable an inescapable effect may or may not be ultimately plays out in ears and minds. Some people may play an amp for its "sound", but not all "identical" amps sound the same because not all "identical" transformers sound the same because not all transformers (with their hundreds of laminations and tens of thousands of windings) end up being made the same. The situation parallels that of cymbals. Or guitar bodies. Or diamonds. Uniqueness at every level (in metal alloys and hammer blows, or grain orientation and crystal cuts) ensures unlimited, unique (and confounding) variety. This is no doubt also true of vacuum tubes, although vacuum tubes are easier to change for tone and feel than are output transformers!

"...I was amazed at how different [transformers] sounded, even [those having identical] specifications..." »

"...it is not the tubes alone that account for the 'tube sound.' The large, heavy output transformer...introduces harmonic distortion, particularly at low frequencies...like the many pounds of transformer weight, this distortion cannot be eliminated when it is NOT desired." — Howard Davis, Electro-Harmonix, Pigtronix »

"I didn't realize that tone was so much a part of the amp." — Paul Reed Smith, Vintage Guitar Magazine, November 2011, pg. 26

Technically, parasitics skew phase and mangle impact », magnetizing current and core saturation rob power », and detail evaporates ». Inescapable magnetic bloat inherent to audio output transformers audibly and measurably manifests as distortion » : munge, flub, smear ».

GAGA unveils and intensifies the character of whatever tubes are inserted by eliminating the audio transformer along with all of its magnetic peculiarities. The goal is to start with tube purity and let musicians select their sound by selecting which tubes they prefer to play. While four 6L6s may sound more "jangly" and "unruly" than four comparatively "smooth" and "warm" EL34s, the choice, mix and intensity of flavor GAGA now avails to each musician individually. In so doing GAGA not only clarifies and intensifies tube tone, but it also allows every player unlimited customization.

GAGA circumvents the magnetic roulette and instead maximizes pure tube tone while eliminating weight, bulk and other traditional limitations.

"...'the sound' of the amp is no longer coupled to the transformers." »

Advanced power supplies and patented ZOTL Technology in GAGA provide idealized impedance matching and power conversion (specifically not power amplification), without all the weight and limitations of traditional audio frequency output transformers and big, low-frequency power magnetics.

"... pure tube tone with no Iron to lug around." »

Freed from driving an homogenizing iron bulk, the output tubes really shine. It's shocking how different EL-34s and 6L6s actually sound, and the sonic benefits don't end with audibly unveiled nuance.

"Like inferior speakers, tube amp output transformers distort the low bass, muddying it and cutting the fundamental." — Howard Davis, Electro-Harmonix, Pigtronix »

"Transformers tend to smear the sound and limit the frequency response, and while many manufacturers wind great transformers, there's no transformer like no transformer at all -- something that becomes clear when you hear...bass as deep as that from a solid-state design, but with levels of detail and tunefulness that most solid-state amps miss. The difference is not subtle." »

"A preamp stage driven nonlinear produces clipping behavior with substantial asymmetry, meaning higher levels of even-order harmonics. Depending on the gain structure of the amp, it is possible that multiple preamp stages will clip. Because the common-cathode gain stages used in tube amps are inverting, a signal that is clipped in two successive stages may appear more symmetrical as a result of the clipping in the second stage. In that case, odd harmonics will be added to the signal. Power amp stages have much more complex reactions when driven into nonlinearity. Because the signal is coupled through a transformer, there is the possibility of core saturation. Additionally the power supply ("B+") DC voltage may begin to sag, causing a type of compression. The onset of nonlinearity is affected by the amount of negative feedback in the design. Zero-feedback designs enter nonlinearity earlier and more gradually, whereas designs with negative feedback tend to stay clean longer but clip more abruptly. A power stage driven into nonlinearity will often lose high frequency bandwidth as it is driven further into clipping, then recover the bandwidth as it comes out of clipping. This has a profound effect on the tonality and dynamics of single notes vs. chords." »

"... transformers epitomize...obstacles to high fidelity: Abruptly limited bandwidth [short-changes] both the ends of the frequency spectrum [with] smeared transients. Limited power bandwidth in particular [hampers] output transformers, resulting in compressed dynamics, masses of harmonic distortions from hysteresis(1), low-frequency saturation(2), phase distortions and more. ...the gross distortions of power output transformers... (1) Hysteresis, in this case, refers to the tendency of the magnetic flux in a transformer's core to not respond precisely to the magnetizing force of the current in primary coil. For instance, the predilection of the core to stay slightly magnetized even when the current in the primary coil has ceased. [In other words, "magnetic inertia."] (2) The upper limit of a transformer's core to contain magnetic flux is called saturation. Above saturation, additional magnetic force causes little increase in flux density. The flux density in a transformer's core is inversely proportional to frequency of the signa1 applied to the primary coil: Halve the frequency and the flux density doubles. [In other words, "magnetic compression."] ... (5) B is the notation for magnetic flux density and H is magnetic force. Plotted together, they graphically illustrate hysteresis. A large separation between the magnetizing and demagnetizing curves (a "fat" loop) shows much hysteresis and a small separation (a "narrow" loop) approaches the ideal of no hysteresis." [GAGA has no magnetic audio loop at all.] — Line-level transformers in High-End Audio, Mark J Medrud, Design Engineer, Jeff Rowland Design Group, Inc., 17 March 1995 »

It's pretty clear what's been going on with audio power magnetics.

Let's next examine some research directed precisely at audio output transformers.

At the 118th convention of the Audio Engineering Society, Menno Van der Veen presented his paper ( PDF | archive ) detailing a universal audio output transformer system that "includes all possible [90+] variations in topologies." [excepting GAGA's ZOTL Technology, which was not included in the study] With good technical discussion it demonstrates how audio output transformers inescapably impose compromises. Compare that situation with GAGA's demonstrably picture perfect performance.

Summarily paraphrasing Menno van der Veen's Low Level Details in Output Transformers research paper (presented at AES 122, May 2007): Failing to accurately transfer fine details at low levels, audio output transformers inherently smear details and obscure natural fidelity. While the research shows this primarily involves fine details at low power levels some effect is always present, and it is equally true that fine details are where finest musicians and best performances really shine.Transformers, according to this research, impede excellence.

M. Hawksford wrote, in May 1986 (Hi-Fi News & Record Review, p.53): "Low-level threshold phenomena ... set bounds upon the ultimate transparency of an audio system." Reasoning and dogged research consistently support what ears can already hear.

"Ideally, a transformer stores no energy - all energy is transferred instantaneously from input to output. In practice, all transformers do store some undesired energy: Leakage inductance represents energy stored in the non-magnetic regions between windings, caused by imperfect flux coupling. Leakage inductance delays the transfer of [energy]...the main cause of...problems... Mutual inductance represents energy stored in the finite permeability of the magnetic core and in small gaps...Mutual inductance and leakage inductance energy causes [arcing] voltage spikes...resulting in...damage or destruction..." — Texas Instruments »

The professional audio people know this, too.

"Phase distortion not only alters musical timbre, but it has potentially serious system headroom implications as well. ... Even ultrasonic phase distortions caused by undamped resonances can excite complex audible cross-modulation products in subsequent nonlinear (any real world) amplifier stages. Low-frequency phase distortions are often described as 'muddy' bass and high-frequency phase distortions as 'harshness' or mid-range 'smear'. The complex cross-modulation products are usually described as 'dirty' sounding and often are the cause of 'listener fatigue'." — Glen Ballou, Handbook for Sound Engineers, p. 605

"The downside with iron [audio transformers], and there is always a downside, is ... time smear ... with sounds that have lots of energy (and tightness)..." — Manley Labs

It may all boil down to this: Were audio output transformers somehow beneficial wouldn't at least one manufacturer by now, after so many decades of expertise, be using two, three, or even ten transformers all at once for "killer" tone thereby totally out of this world? That zero do so tells all.

GAGA's ZOTL Technology vs Audio Output Transformer

A major purpose of GAGA is to maximize the tone and response of tubes. With no physically and electromagnetically bulky, limiting and homogenizing audio output transformer, the purity of output tubes is unleashed.

"Previously, truly changing 'the sound' of an amp meant changing the amp. Now, GAGA gives a remarkable palette of tone by just changing a tube. In other words, the pure sound and response of the tubes is revealed."

GAGA does not attempt to clone or mimic but instead provides a solid foundation for any tone desired with the idea that starting from purity is musically advantageous.

"To sound musically rich, go for wide range, low distortion at high volume, and desirable tone qualities." —Howard Davis, long-time engineer at Electro-Harmonix, » »

"...before you attempt to use any effects or tone-shaping devices, you must dial in a flat-response clean tone on the amplifier...it's crucial to attain a pure, clean tone prior to adding other effects to your signal for better overall tonality. If you can find a clean-sounding amplifier...then anything that you add to the signal path...should accentuate what your natural [guitar] tone sounds like." — David M. Brewster, "Introduction to Guitar Tone and Effects", p. 14, »

Sometimes confusion arises regarding the importance of wide and accurate frequency response in guitar amplification. Malcolm Moore's extensive research into the magnetics and realities of guitar strings and electric pickups provides technical evidence and explanation.

"For a guitar, the audio spectrum needs are wide. ...The lower open E string has a fundamental of about 128 Hz, and significant harmonics are the second, fourth, sixth and eighth meaning the spectrum here extends to 1024 Hz. On the twelfth fret on the upper E string the fundamental is about 1,024 Hz, and the spectrum extends to about 8.192 kHz. On the 21st fret the fundamental at C#'' is about 1,722 Hz, and the spectrum extends to almost 14 kHz! The...frequency response needs to be virtually flat from less than 100 Hz to greater than 14 kHz to faithfully reproduce the vibrations from the guitar strings - before anybody starts to play with the audio spectrum, develop distortion, or introduce echo and / or reverberation." —Malcolm Moore »

As Rupert Neve and others have pointed out, many people can hear the difference between a sine and square wave at 15 kHz which means they are hearing at least the first harmonic of the square wave; at 30kHz, that's well above what is commonly considered the upper limit of hearing.

Famed recording engineer Tim de Paravicini notes the importance of frequencies outside the conventional 20Hz-20kHz range. He points out that one can sense the standing wave of a large cathedral which is below 5Hz. A body senses sound through more than the ears - and we love this: "Likewise, the high frequency notion of 20kHz is also rubbish..."

"This traditional notion of the hearing stopping below 20Hz is absolutely rubbish. We detect sound down to the resonant frequency of the body, about 3Hz. Deaf people certainly seem to hear through the body.

"Likewise, the high frequency notion of 20kHz is also rubbish. We detect audio up to about 45kHz, not as a tone but a certainty that something is going on. My method of demonstrating this was several years doing work on ultrasonic bath cleaners. Everybody in the room suffered the after-effects of tinnitus, aware of something going on. Moreover, playing a 20kHz tone through suitable speakers puts listeners in discomfort. So traditional myths have to be thrown out the window."

Noted amplifier designer Nelson Pass explains how ultrasonic anomalies carry audible effect:

"Although human hearing is generally very poor above 20,000 Hertz, ultrasonic frequency roll-offs produce phase and amplitude effects in the audible region; for example, a single pole (6dB/octave) roll-off at 30 kHz produces about 9 degrees of phase lag and 0.5 dB loss at 10 kHz."

Therefore, amplifiers that fail to reproduce accurately for any reason by definition come between musicians and their true tone. Moreover, such amplifiers lacking in high frequency reproduction have been demonstrated to result in lesser brain activity and lesser perceived sound quality.

More evidence supporting the importance of wideband amplification: Reproduction of high frequencies measurably and dramatically stimulates increased brain activity and "...[listeners] felt the sound containing [ultra sonic high frequencies] to be more pleasant than the same sound lacking... These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the 'hypersonic effect.'"

In other words, limited amplifier bandwidth results in limited musical ecstasy.

Transformer: High-frequency loss

Fig 1: Given a 5 kHz square wave and driven into no-load open-circuit, this test reveals dramatic high-frequency loss (triangular, not sharp rising edge) due to the audio output transformer's capacitance caused by its necessarily large number of windings. Even in superb transformers, this loss generally begins below 5 kHz and gets worse at higher frequencies. See Luke Manley's comments on audio output transformers concerning this loss and other complex factors degrading accurate reproduction in audio transformers. Supersonic roll-off (top leading edges) with ZOTL is due to capacitance inside the output tubes themselves and is above audio frequencies. Accurate high frequencies reproduced by GAGA translate into harshless airiness, presence, naturalness. See Berning's White Paper.

Transformer: Low frequency saturation, power loss

Fig 2: Given a 30 Hz square wave and driven into an 8 Ohm load, this test reveals transformer core saturation evidenced by variably sloping waveform levels. This loss begins well above 30 Hz and gets worse at lower frequencies. Deviation from perfect flatness with ZOTL is due entirely to lack of stiffness in the test power supply. Though GAGA can (optionally) suppress subsonic frequencies, ZOTL Technology amplifies all the way down to and including DC ( 0 Hz ), a technical feat formerly impossible with output tubes. The result is full power bandwidth phase accuracy that keeps all frequencies synchronized in time, for astounding impact and vivid naturalness. "Low frequencies don't turn to mush and muddy everything up. The bottom end maintains phase to deliver a thick, rock-solid feel...not thinned, collapsed or bent out, it remains true to what was played." See Berning's White Paper.

Transformer: High frequency slow response

Fig 3: Given a 10 kHz square wave and driven into an 8 Ohm load, this test reveals a significantly slower rise time caused by the transformer (soft rising edge) which also adds a low-frequency component to its overshoot. This is one way in which the "flub" or "munge" often experienced with traditional tube amps as tones which were never played are nevertheless created and injected into the music signal. "GAGA is extremely fast and faithful to any leading edge however sharp, full body however sustained, and trailing edge of every note however delicate, giving unprecedented feel, immediacy and impact, without audible overshoot or intermodulation." See Berning's White Paper.

These claims are supported by measurements and numerous technology/product reviews noting, among other experiences, sustained periods bordering "on the spiritual". »

GAGA Lightning Response Without Collapse

GAGA is fast, always responsive, and does not mire in overload. Recovery from any amount of power tube overload is instantaneous, on a per-note basis. There is no bias collapse or consequent overload hangover. You can literally fly from the most overloaded scream to the most delicately nuanced pluck in a wink. Play a note and it's there, full-spectrum from head to toe, with an unsurpassed immediacy that audibly melds GAGA as an integral part of your instrument. GAGA's speed may be one of its most understated advantages.

Someone asked:

"By not having either the transformer losses, nor the bias shifts resultant from overdriving capacitively coupled stages are you not removing part of the very features that give some amps their classic sound? The brief sudden loss of all sound (even background hiss) as the electroncs scramble to recover after you've played that ultimate power chord is very much part and parcel of the sound." »

To which we responded:

"... people who've played GAGA haven't [noted absence of] this. I suppose it comes down to if you want to hear amplified music from the guitar or an amp that falls apart when pushed."

"It's apparently somewhat common to turn up tube bias in an AB output stage. This would directly affect bias upset (and also crossover notch) by reducing it. Who turns down their bias (to presumably increase the amount and length of bias upset)? [No one; it's practically unheard of, at least to us.] Also, R. G. Keen notes '...[amps] that sound good...recover from overdrive gracefully.' Both of these facts point favorably to minimal bias upset and faithfulness to what's played, not to how an amp might (mis)interpret it."

"Another thought: imagine if that ultimate power chord never ended or even faltered because of the amp."

Interesting and relevant, an innate drive to subdue awful crossover notch distortion may be the cause behind the general tendency to increase bias in traditional tube guitar amps. Of course this isn't good for the life of any tubes, pushing them to and even beyond their intended applications. GAGA operates power tubes at high impedances and proper bias, automatically maintaining optimum balance, reducing heat, and greatly extending tube lifetimes. GAGA essentially treats power tubes as the valuable, expensive (and sometimes irreplaceable) sonic gems they are. "The...technology is both complex and elegant. The auto-bias circuit alone is a technical tour de force." »

"Crossover distortion is a particularly onerous-sounding animal, and I've never met a guitarist who likes the sound of it. The biasing technique I use with tube amp output stages involves watching the output of the amp with a sine wave input on a scope and increasing the bias just past the point at which the crossover distortion cleans up. This gives you the lowest bias current - and therefore the greatest linear voltage swing and lowest idle power - consistent with no crossover distortion." »

One way to audibly demonstrate this might be to progressively turn down the bias on a conventional tube amp, as doing so would likely increase the unpleasant crossover notch distortion resulting from bias upset or collapse and widen the gap between push and pull. But who does this? Crossover notch distortion has never been prized. That any amps succumb to it is unfortunate.

Not made to clone or mimic specific peculiarities, GAGA provides the purest possible performance of tubes and faithfully amplifies what's played, towards the goal of true tone and musical ecstasy. Particular colorations of tone and feel in unlimited variety may be easily achieved by plugging in various combinations of power tubes. Ultrasonically recharged and tightly regulated, GAGA does not collapse, droop or fade out on its own; it will sustain notes as long as they are held on the instrument.

Is GAGA existing technology ?

No. GAGA uses a new kind of technology that is not solid state, hybrid, OTL, class D or "digital" anything. Compared to traditional audio output transformers, GAGA almost perfectly mates power tubes with speakers. This has been measured, patented and demonstrated in commercial use. GAGA uses new technology called ZOTL to achieve this light-weight magic. Old terms and loaded generalizations such as "hybrid", "switching" and "MOSFET" inadequately describe and mislead.

GAGA uses only vacuum tubes (in preamp and power output stages) to perform 100% of audio power amplification, in analog, not digital manner, coupled with advanced power supply and conversion techniques and patented ZOTL™ Technology — a new name, for a new technology, in a new kind of amplifier.

"I just read their patents and tech descriptions...This really is fresh..." »

ZOTL Technology lets tubes operate more like tubes -- that is, at higher impedances and voltages, and with lower currents. Using advanced, patented radio-frequency power conversion techniques, ZOTL Technology provides automatic, ideal, bi-directional matching and power conversion between any power tubes and speakers, without any of the bulk, weight, compromises, or serious limitations of traditional audio output transformers.

Freed from the measurably and audibly degrading homogenizations of driving any bulky, traditional audio output transformer, the power output tubes really shine and convey their desirable tonality and characteristic response. Audible differences among tube types are magnified, naturalness and emotional appeal is heightened, and musicality is maximized.

New technology can be challenging and sometimes individuals assert ZOTL must be something which it isn't, such as class D, digital, hybrid, OTL or whatever. If any of that were true, the USPTO would have refused patent, citing prior art. Yet, although solid state, class D, hybrid, digital switching, OTL and myriad other techniques existed long before ZOTL, the USPTO affirmed ZOTL's novelty and granted patent. Examination of this page and all of its links reveals no references to ZOTL Technology, further confirming by absence its novelty. It is therefore accurate to describe GAGA as a new kind of amplifier and not as hybrid, solid state, OTL, class-D or other existing term or technique.

Why isn't GAGA a "hybrid" ?

Just as a transformer matches impedances and is not an amplifier, ZOTL Technology also matches impedances and also is not an amplifier (ZOTL patent: column 3, line 20). By definition » » » "hybrid" describes circuits in which some or all audio power amplification is performed by solid-state semiconductors with a tube or tubes present primarily for filtering, feedback or other control. GAGA performs all audio power amplification with only vacuum tubes in pre-amp and output stages, and GAGA performs no analog signal processing of any kind in any way with any solid-state devices (ZOTL patent: column 2, line 29). Therefore, by definition, GAGA is not "hybrid".

In The Absolute Sound Magazine (Feb, 2011), David Berning further clarified one technology used in GAGA: ZOTL emulates an ideal output transformer. It matches impedance just like a transformer, and it is a two-way communication between tubes and speaker as is a conventional transformer. However, ZOTL does not suffer from the frequency-dependence issues of [an audio] transformer that must handle orders of magnitude of frequencies. Its two-way communication separates ZOTL from a hybrid amplifier:

ZOTL "is not a tube amp followed by some other kind of output buffer. By having the two-way communication, the speaker is fully controlled by the output characteristics of the tubes, and that includes all-important damping. This is not the case with the hybrid amplifier that is simply tubes with an output buffer."

Why isn't GAGA "digital" or "Class D" ?

GAGA applies new technology not fully described by old terms: Its ultrasonics are entirely for power conversion and impedance matching (and specifically not power amplification). In contrast, by definition, digital or "class D" amps use the "switching mode of transistors to regulate power delivery" » (or, are those in which "all power devices...are operated as binary switches...the high-frequency [serving] no purpose other than to make the wave-form binary so it can be amplified by switching the power devices." »). GAGA does not do this. In fact, GAGA's tube output stage incorporates linear, class AB ("push-pull") operation (ZOTL patent: first line of abstract and colum 3, line 25), and GAGA uses only vacuum tubes for all audio power amplification in 100% analog fashion (ZOTL patent: column 5, line 54, and all diagrams). Therefore, by all definitions, GAGA is not "digital" or "class D".

Why isn't GAGA an "OTL" ?

"OTL" ( Output TransformerLess ) refers to a technique developed by Julius Futterman in the 1950s that applies numerous output tubes connected in parallel to drive speakers, attempting to overcome fundamental incompatibilities with brute force and purportedly suffering shortcomings including tube noise, unreliability, rather severe impedance mismatch, excessive heat, and inefficiency. GAGA uses patented ZOTL Technology which is entirely different from the Futterman OTL technique. Therefore, GAGA is not "OTL".

About "switchmode impedance conversion" and tube transfer function

"The invention appears to be a tube stage followed by a switchmode impedance converter that eliminates the output transformer. But isn't the transformer vital to the magic of tube sound? If all's you want is the transfer function of the tubes, you could just feed the output of a flea-powered tube amp into a Class-D power amp."

That would seem to describe a digital hybrid type amplifier, in which tubes perform some function, and then the signal is forwarded to a class-D power output stage which then provides audio power amplification to the speaker. There seems to be limited sonic zen in this method, as many have discovered, possibly because the "transfer function" of the tubes is buffered and almost if not totally removed / insulated / distanced / obscured / overpowered by the class-D power amplification, and so what the speaker actually "sees" (or "hears", rather) and responds to is in fact largely or completely the transfer function of the class-D audio power amplification.

In GAGA, however, the power tubes perform 100% of the audio power amplification in linear, push-pull manner WHILE the patented ZOTL impedance converter bidirectionally transfers that power (without losses or limitations normal to traditional audio frequency magnetics) between the low impedance of speakers and the high impedance of the power tubes. Some magic in GAGA is that the necessary impedance conversion that otherwise must be performed by a bulk of iron is now instead performed in a (measurably) nearly perfect manner: Masking by the audio output transformer is eliminated, essentially unleashing the true performance of the power tubes.

Most persons have never played power tubes this way, without audio output transformers; it is exquisite and exhilarating.

Were ZOTL merely some pre-existent technology then it would not have been granted patent. And if it had been erroneously granted patent without technical merit then it would not sustain scrutiny. In fact, ZOTL was patented and remains patented because it is something genuinely unique. Attempting to describe ZOTL in old terms and old paradigms is confusing - which is why it has a new name and why there are sometimes honest misunderstandings.

Ultimately, it's the tone and feel and emotion that matter most, not any particular technique of achieving or amplifying it. After all, many great-sounding amps employ semiconductors (GAGA employs some in new places), and had the digital hybrid scheme of 'tubes buffered by class-D power amplification' actually sounded 'great enough' then anything after would have likely been obviated. Feedback from musicians who play GAGA includes praise for clarity, richness, faithfulness, purity, impact, dimensionality, depth, speed, musicality.

Our conclusion, based on experience and research which details inescapably detrimental effects of audio output transformers, is that GAGA using ZOTL technology unleashes power tubes to amplify in a fresh, tactile, audible, measurable, and musically important way. And it conveys all kinds of additional benefits.

The 1972 AES paper "Tubes vs. Transistors - Is There An Audible Difference?" shows that tubes used in amplifiers seem to matter most at the input and output stages. GAGA of course uses tubes at the input/preamp stages, and ZOTL in GAGA practically perfectly connects power tubes at the output stage, including the crucial bidirectional conversion of impedance between power tubes and speaker.

GAGA Phantom Power for Pedals and Active Pickups

GAGA is the first amplifier to include patented P3 Technology® as a standard feature.

Via any standard stereo (TRS) cable, when switched on P3 provides phantom power for effects pedals and/or active pickups: 9 Volts (supplied by GAGA) flows out to the pedals/pickups while the music signal flows back to GAGA over the same cable. Musicians aurally confirm its laboratory measurements: P3 has no negative effect on tone and in fact improves tone because supply voltage is regulated and no longer droops or fails as do batteries.

On the pedalboard, P3 redefines flexibility. P3 power may be distributed by a break-out box (via standard DC barrel connectors). Also, because any P3 pedal is also a break-out for P3 power, one P3 pedal in the chain (closest to GAGA) may send power out from its DC input jack. Moreover, this power is then daisy-chainable (or Power-Chainable) to all stock pedals. P3 is the end to dead batteries, power cables, ground loop hum, and power problems.

P3's many advantages:

• no more batteries
• no more ground loops
• no more power cables - number of cables cut by up to half — dramatically cleaner pedalboard
• no more AC power required
• no more wall warts
• no more droop or vanishing headroom
• no more D.O.A.
• no hassle setup and teardown
• no more land-filling spent batteries
• no more scrounging or running out for batteries before or during a gig
• high current — 1,500mA continuous, 4,000mA burst
• ultrasonically maintained, linearly-regulated, pristine power

GAGA's licensed and improved implementation of P3 Technology® includes overcurrent, overheat and custom short-circuit protection, pushbutton power on/off, and 1.5 amperes (13.5 Watts) continuous (4 amperes (36 Watts) burst) current of ultrasonically maintained, linearly-regulated, pristine power for all 9-volt pedals and active pickups. A converter is available for other voltages.

GAGA Power, Weight, Tone and Feel

In its final, production form GAGA is six pounds of amp in about six pounds of chassis; powerful, flexible, and oozing pure tube tone.

The first (proof-of-concept) prototype GAGA weighed about three pounds and produced about 50 Watts of power. That prototype was without universal power and required a practical, sturdy chassis.

Now, in a strong but lightweight aircraft-aluminum chassis with all features, GAGA can provide 50 Watts of clean (RMS) output power and (depending on power tube complement) up to 90 Watts of (highly distorted) output power. The maximum power output we've measured is 128 Watts into 8 Ohms using four 6CA7 power tubes. For reference, a typical power tube complement (four 6L6's) provides about 50 Watts (RMS) of clean, undistorted output power, and about 90 Watts of highly distorted output power.

GAGA will operate with four, three or two power tubes, with consequently diminshing output power. The onset of power tube overload can be adjusted (via the Headroom control) with any tube combination.

World Power Ready™ — Universal Power

GAGA may be plugged in anywhere on Earth without adjustment. Proper power design is intrinsic and was not an afterthought. GAGA is an efficient global power citizen.

Last updated 12 May 2012