Product Review

Son of Ampzilla 100W Stereo Power Amplifier

May, 2005

Jason Victor Serinus



● Power Output (Per Channel):
    16 Ohms - Minimum 50 watts 20 Hz - 20
    kHz; 8 Ohms - Minimum 100 watts 20 Hz
    - 20kHz; 4 Ohms - Minimum 200 watts
    20 Hz - 20 kHz
● MFR: 20 Hz - 20 kHz
± 0.2 dB
● THD: < 0.05% 20 Hz - 20 kHz
● Noise: - 110 dB
● Input Impedance: 50 kOhms
● Sensitivity: 1 Volt
● Dimensions: 9" H x 12" W x 15" D
● Weight: 52 Pounds
● MSRP: $3,250 USA

Spread Spectrum Technologies, Inc.


Enter Mr. Ampzilla.

My first encounter with the Ampzilla 2000 and its designer James Bongiorno was at CES -  2005. I had entered the VMPS room at T.H.E. Show in hope of hanging with Brian Cheney, whose as yet unheard VMPS RM40 speakers I was scheduled to review. Though Brian was on break, I took the opportunity to listen to three large VMPS RM40s powered by Spread Spectrum Technologies Ampzilla 2000 monoblocks.

The three speakers of larger than Serinus proportions were arranged in a trinaural array (left, center, and right speakers, with the center being a mixture of the left and right), fed by the SST Trinaural Processor. The room was rather small, with the speakers in close proximity to one another positioned fairly close to the rear wall. The bass was strong, but the sound seemed a bit washed out.

Given that every component and wire in the chain was unfamiliar to me, I could not tell what was responsible for what. The tonal deficiencies I perceived could have been caused by inadequate placement, too many absorptive panels, dirty power, inferior cabling, room dimensions, or lack of system synergy rather than by the speakers and/or amplification.

As I was leaving the room, the man in charge directed me to James Bongiorno. James and I spoke briefly in the hallway. Though I knew nothing about the man before we met, the impression he left remains strong.

Dressed all in white – a far cry from the Technicolor outfits he sports on the website page devoted to “The One and Only James Bongiorno” – James was a trip and a half. It was as though I had encountered an aging prizefighter. Or had I instead entered a time warp and encountered someone on break from shooting film noir on the MGM backlot?

Gravely voiced and weathered, Bongiorno began our encounter by proclaiming with absolute certainty that trinaural processing is the only way to listen to music. Although I do not recall his exact words, the gist of his rap was that anyone who did not accept the truth of the trinaural concept was either an idiot or didn't know what they were talking about. Be there or be square.

At the end of our short conversation, I was certain of two things. I still didn't know what was going on in the room, and listening to the Ampzilla 2000 in my own reference system was the only way to find out.

Cut to Oakland

When Brian Cheney brought his RM40s to mi casa, he was kind enough to bring along a spare Son of Ampzilla stereo amp. This enabled me to audition his speakers in my room with the same amplification that he had used at CES.

Because I was in the midst of selling my tubed Jadis Defy 7 Mk. II, I was using the excellent 225W solid state Red Planet Labs STR201 for amplification. Once the VMPS speakers were in place, I invited Brian to take a quick listen to both the 100W Son of Ampzilla amp ($3,250) and the 225W Red Planet STR201 ($2,995). Both were auditioned in balanced configuration.

The differences between the sound of the two products surprised me. When I told Brian that Son of Ampzilla (SoA) sounded lean in comparison to the Red Planet (RP), he countered that SoA was laudably neutral. This I cannot dispute. Son of Ampzilla is a most neutral sounding amp.

I confess that, once the VMPS RM40 review was complete, I deviated from my review-in-the-order received policy to focus on my new reference amp, the Jadis DA-7 Luxe. My gratitude to James and Brian for letting me keep SoA until I could devote sufficient time to evaluation.

The Design

James Bongiorno, designer of the Dynaco 400, came up with the original Ampzila in 1974 as a construction project for Popular Electronics Magazine. It was the first servo-controlled amplifier in existence.

Stopped in his tracks by a rare liver disorder, James returned to the scene a few years ago with the Ampzilla 2000.

To quote from the website: “The new Ampzilla 2000 uses a completely new variation of the Forward Gain topology to achieve unprecedented improvements in linearity. As a matter of fact, the new circuit is so smooth, that it can be actually listened to OPEN LOOP, WITH NO FEEDBACK. Of course, we aren't going to make it that way. The PROPER use of feedback is necessary in order to tie down all of the operating points so there will be no variations in performance from unit to unit. The new Ampzilla 2000 uses 12 250-watt output devices per monobloc. This is 3 times more devices than the original Ampzilla. The B+ and B- supply fuses are EXTERNAL. The entire circuit is totally balanced from input to output although there is a totally and uniquely new un-balanced to balanced converter for single ended inputs. Each monobloc has 100,000 µfd of power supply filtering with dual rectification as pioneered in the original Sumo's [sic].”

There's a lot more on the website that I urge you to read. Of special interest is James' dismissal of single-ended amplification Regardless of your position on the matter, the writing will give you a good sense of the man's personality. You can also find James' performance graphs, seen at, taken from what he terms “the first ‘beat to smithereens' production prototype.”

SoA features four DC power supply fuses with indicators. All fuses are easily accessible from the top of the amp. When a red light signaled which fuse had blown, I had no problem changing it in less than one minute.

Fitted with gold plated input and output jacks, the amp is housed in a 14 gauge steel chassis. The front of the chassis includes an on-off switch, peak-clipping indicator LED, and thermal LED.

James explains that the entire amplifier circuitry (except the power output stage) is contained on one main drive card which also has the input jacks. This means that the amplifier is completely upgradeable with future circuit improvements.

Setup Specifics

Input jacks are located in the middle of amplifier's rear. The Son of Ampzilla comes equipped with balanced inputs and single-ended (RCA) to balanced adapters that allow for use of single-ended interconnects. I listened using Nordost Valhalla balanced interconnects and did not evaluate the adapters.

The four speaker wire terminals, two for each speaker, are lined up vertically on the back side of the amp, with little space in between. Given the wide, flat nature of Nordost Valhalla speaker cable, I found it necessary to loop the right speaker cable back on itself so that there would be sufficient space for the balanced interconnects to pass through.

Nordost Valhalla power cables were used on all components. The latest iteration of SoA allows the use of an extra-market power cable. Mine had a short power cable permanently connected. Using an adapter that Caelin Gabriel of Shunyata graciously gave me some time back, I connected the permanent cord to a Nordost Valhalla power cable.

While I previously plugged all of my components into a PS Audio P600 Power Plant set to P-1, I have recently begun plugging amplification (including the Rocket subwoofer) into the ExactPower EP15A Power Regulator. This ensures that there is no current limiting or compression on the amplifier. While I continue to favor the Power Plant's P-1 MultiWave II setting for transport, DAC, and preamp, I have found it can add an unwanted sharp edge to tube amplification to the point of distorting complex passages. It was only when I began working with a tube amp as extended on top as the Jadis DA-7 Luxe that I became aware of the cause of the problem.

The amplifier is available in either blue or black. My review sample was blue. Some will consider it a fashion faux pas. Judging from photos on the website, I vote for black.


I began with the gorgeous Trio from Richard Strauss' opera Der Rosenkavalier, as performed by Natalie Dessay and company on her recent Amor recital (EMI). As much as I was struck by the goodly amount of air around voices and instruments, I noted a lean orchestral sound and an overall drier and less liquid presentation that I am accustomed to. Some of this, of course, has to do with the difference between tubes and solid state. But as enviably neutral as I deemed the presentation, I also noted a lack of color to voices and instruments. The sound was, if anything, neutral to a fault.

Next came “Let's Face the Music and Dance” and “Devil May Care” from Diana Krall's classic When I Look in Your Eyes (Verve). I quote from my notes:

“Neutral absolutely.

A certain flatness of tone – lack of warmth – neither voluptuous nor offensive.

A prevailing ‘ah' sound – colors a bit muted as though a scrim were present. Listen to the “drm drm” of bass and piano at the beginning of the track – that's the basic coloration or lack thereof.

Note the muted coolness of the vibraphone at the beginning of track 6, “I've Got You Under My Skin.” The shimmering color and chime of the keys is muted.”

Two of my favorite tracks on Karina Gauvin's Songs of the Auvergne (CBC Records) confirmed that bass control was excellent. The bass may not be of the head turning variety, but it was certainly satisfying.

Turning to the extremely live, resonant presentation of Reference Recordings' Rachmaninoff Symphonic Dances again revealed drier than usual sound. The triangle did not ring out in space, the violins were not as silken as I would expect, and cymbals lacked sizzle. I have heard this recording on countless systems, including room after room at CES, and have a good sense of how it should sound.

A favorite test disc amongst audiophiles is Patricia Barber's Modern Cool. C.C. Poon of Monarchy Audio chose this disc to evaluate my system when he last came over. My thanks to Mobile Fidelity for donating their Original Master DSD SACD version of Barber's modern classic.

Barber's “Touch of Trash” features an extended instrumental section where percussionist Mark Walker goes wild. Again, I noted that cymbals sounded somewhat flat and muted. I was reminded of the sound in the VMPS room.

Spark is not a term I would apply to the ultra-cool Ms. Barber, but it's something I expect from Candido & Graciela's Grammy-nominated Inolvidable (Chesky - now available on SACD). Here, percussion sounded tired and plodding, the entire presentation somewhat flat. Yes, the percussionist is a bit mechanical on the first track. But the marvel of the performance is that two musicians in their ‘80s are still filled with life. Some of the zing was missing.

Consider the Context

Are you depressed yet? Don't be. Remember that the common fault of many solid state amps, entry level interconnects and power cables, early digital recordings, first generation CD players, and mass-market equipment in general is that they sound bright and tinny. Those hideous little speakers that pollute the air in gyms and blast away in retail outlets are so sharp and irritating that I am sometimes forced to flee. The reason so many boom boxes have a bass boost adjustment is to compensate for their horrendous treble. The sound of the Ampzilla is a dream by comparison.

I just helped a neighbor set up her rack system. She had recently bought used speakers, which she was convinced were great. They may be quite good, for all I could tell. The problem was, the entire setup, complete with lamp cord speaker cable, stock interconnects, and equipment plugged directly into the wall sounded awful to these ears. No color, no warmth, no midrange; just lots of noise disguised as music. No way.

Had any of my neighbor's components been matched with Son of Ampzilla, she probably would have fallen head over heels at the sheer beauty of sound. SoA would have tamed those highs, granted her a midrange, and extended the bass. She might have cried for joy.

To these ears, SoA's top is somewhat rolled off. I am reminded of the Thule DVD player, and some other components I have reviewed. This is a common design choice, no doubt inspired by reference systems that err toward a bright presentation. It is also characteristic of amplifiers with very low negative feedback.

In other words, system synergy is the key to this amp's performance. I am certain that Son of Ampzilla will sound great in the right system.

Before you sell those bright speakers or that under $1,000 universal player that doesn't sound quite right in your current equipment chain, try a Son of Ampzilla or the Ampzilla 2000 monoblocks. These amps have many good things going for them. SoA may not be an ideal amp for my system, but it will certainly prove perfect for another. Just as with any product, it depends on your preferences. Son of Ampzilla is laid back, and I like a more forward presentation.


Son of Ampzilla is a fine solid state amplifier with good bass, an excellent midrange, and a neutral, air-filled presentation. Leaning somewhat toward the cool and dry side of the spectrum, its laid back treble will prove a fine match for a system that would otherwise sound overly aggressive, brash, or even raucous.

 - Jason Victor Serinus -

Reference System:

Digital Front End:
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen VIII DAC/Preamp
Theta Carmen II transport (on loan from Theta)

Jadis DA-7 Luxe

Talon Khorus X speakers MK. II (with latest modifications and Bybee filters on woofers and tweeters)
Rocket UFW-10 subwoofer

Nordost Valhalla single-ended and balanced interconnects and balanced digital interconnects
Nordost Valhalla bi-wired speaker cable
Nordost Silver Shadow digital interconnect for DVD-V
Nordost Valhalla Power Cables
Elrod EPS-2 Signature

Also on hand and sometimes used:
Interconnects: WireWorld Gold Eclipse 5 and Gold Starlight 5 digital, Harmonic Tech Magic One, Acoustic Zen Silver Reference II balanced, and Nirvana BNC-terminated digital.
Power cables: Elrod EPS Signature 2 and 3 plus EPS 1, 2, and 3; WireWorld Silver Electra 5, PS Audio X-treme Statement, Harmonic Tech, and AudioPrism SuperNatural S2.

PS Audio P600 Power Plant power synthesizer with MultiWave II
ExactPower EP15A
PS Audio Ultimate Outlet; PS Audio Power Ports
Ganymede ball bearing supports under all components and speakers
Michael Green Deluxe Ultrarack, Basic Racks and Corner Tunes

Shakti stones on amp, Theta, and transport
Stillpoints ERS EMI/RFI sheets on most components
Bedini Dual Beam Ultraclarifier, Audioprism CD Stoplight,
Marigo Signature Mat for use atop CDs, Ayre demagnetizing CD and the original Sheffield/XLO demagnetizing and break-in CD.

Room Size:
25.5' deep, 37' wide opposite the speakers, 21.5' wide in the listening area. Ceilings are 9'2” high with heavy wooden cross-beams. Floors hardwood and carpet. Walls are a combination of plaster and wood. There is a large opening to the right of the right speaker



© Copyright 2005 Secrets of Home Theater & High Fidelity

Go to Table of Contents for this Issue

Go to Home Page


About Secrets


Terms and Conditions of Use

Our Vault pages may have some display quirks. Let us know if we need to take a look at this page or fix a bug.
Connect with us
  • Instagram
  • Google+
  • YouTube
  • LinkedIn
  • Pinterest
Secrets "Cave"