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Spread Spectrum Technologies Son of Ampzilla II power amplifier

Spread Spectrum Technologies Son of Ampzilla II power amplifier

High-end audio as we think of it today is about fifty years old. Some brands from the early days are still around and iconic today. Others have faded into fond memories of beautiful musical moments gone by. Few companies have proven successful in maintaining their creativity and innovation after the passing of the visionary founder.

In the case of Spread Spectrum Technologies, a fortuitous introduction between founder James Bongiorno (1943-2013) and EJ Sarmento of Wyred 4 Sound cemented the continuation of the company. Bongiorno had a long design history with brands such as Dynaco, Sumo, SAE, GAS, Constellation, and others. He was looking for someone who had the engineering and manufacturing knowledge to put his innovative ideas into wider production, and EJ was the perfect partner given his extensive industry background and with many of his own product innovations. The goal was to maintain the core of Bongiorno’s circuit designs and his ingenious power supply while ramping up to a true large-scale distribution model.

As Bongiorno’s health failed, EJ acquired the rights to Spread Spectrum Technologies with the plan to offer its well-regarded products as well as future designs he and James had discussed as a separate company from Wyred 4 Sound. The products would all be designed and manufactured in the USA. The first product out of the gate is the rebirth of an SST legend, the Son of Ampzilla II.

The original Ampzilla started as a DIY project for Popular Electronics magazine. The design was so popular that James left SAE and started Great American Sound (GAS) to manufacture the Ampzilla for retail sale. The original Ampzilla offered 200 Watts into 8 Ohms. The Son of Ampzilla at 100 watts into 8 Ohms followed Ampzilla. Today, the new incarnation – Son of Ampzilla II – gives full weight to its progenitor, coming in at 220 watts into 8 Ohms and 350 Watts into 4 Ohms.

I have found in over 30 years of listening that, for a high fidelity amplifier, robust and clean power is a must for quality amplification. James Bongiorno spent years seeking better ways to bring clean and massive power reserves to his designs. The Son of Ampzilla II does this in part by using a massive 2kVA power supply for each channel, with each side benefiting from its own independent windings. Both channels also have a healthy 100,000µF of capacitance. As expected, the front-end voltage power supplies are fully regulated. Finally, there is a thermal protection automatic shutdown circuit to protect in the event of failure.

Output power is doubled from the original SOA, and SOA II delivers 200 watts into 8 Ohms by doubling the number of power transistors per channel. So it has the strength and reserves to manage most any transient peak for nearly anything but concert hall applications.

Given it’s such a plastic term, I often wonder what others would require of an amplifier to have it qualify as ‘High Fidelity’? Recently I was perusing the Harbeth Users Group and I came across an interesting comment from Alan Shaw, lead designer and owner at Harbeth; “A truly high fidelity amplifier should be load insensitive and no matter what sort of speaker by make, concept, size, impedance or power is clamped across its outputs, the amp should perform identically. And that just does not seem to be the case with many so called ‘high-end’ amps (whatever that means). They may well be ‘high-end’ but they cannot meet the elementary definition of ‘high fidelity’ because the signal that leaves them to drive the speaker does not have the same energy/frequency balance as the signal that arrived at the amp input sockets.”

Coming from one the world’s most distinguished speaker designers, this was interesting. So I asked Tony Holt from Spread Spectrum Technologies what he thought of this. His response was; “We agree with Alan on this. Likewise, our amps adhere to his philosophy of ‘high-fidelity’, which is achieved with solid engineering for exemplary amplifier performance and stability. Both the SoA and Ampzilla 2k are very much in this ‘load insensitive’ camp, in that their outputs are consistently more or less flat across the frequency spectrum regardless of load. We spent a lot of time and effort in the design process to ensure this.”

Nice to know I am in good company in thinking this amp is High Fidelity!


To get started I disconnected my Cary SLI-80 Tube integrated with the Ultimate Mod package, which I had been using in amp-only mode, and then went to the robust, double-boxed SST shipping container. I placed the Son of Ampzilla II on my amp stand atop three Stillpoints Ultra 6 isolation devices. I then connected the Son of Ampzilla II to my Moon Neo 430HAD Pre-amp/headphone amplifier for some initial digital files listening. The Simaudio Moon Neo 430 HAD offers many of the refinements of the Simaudio Evolution 740p Preamplifier with the notable exception of it being single ended output only. The optional built in DAC uses the highly regarded ESS9018 Sabre chip and it can handle PCM to 24/384 and DSD256. Files were served from a 2012 MacMini via Roon connected by a Light Harmonic Lightspeed 10G cable. I then connected the Son of Ampzilla II to my Vandersteen 2Ce Signature II speakers using Blue Jeans speaker cables. With all the connections accounted for it was time to queue up some music.

I have owned the Cary for many years and it has been my go-to amplifier when I am simply interested in enjoying a day of music. Putting in the Son of Ampzilla II would be a change in character and specification. The Cary is a valve amp focused around a quad of Golden Lion KT88’s delivering 40 watts into 8 Ohms in the triode mode I favour. The Cary has a seductive midrange without the slow, too-sweet tube character of some tube amps. As expected, placing the SST amp in the mix was quite a change to the listening experience.

First up was Morphine’s ‘A Head with Wings’ from 1993’s A Cure for Pain. [16/44.1 AIFF iTunes] This is a well-recorded album that makes the most of space and location. The baritone sax and bass guitar really plow the low end. Vocals are dead centre and the drum kit is behind and covers both left and right of vocals as you sense the breadth of the entire drum kit throughout the song. My initial impressions were how well the $3,500 solid state amp kept up with the nearly $8,000 Cary tube amp for dimensionality. The sense of front to back was strong and stable. Morphine is an ensemble of saxophones, bass guitar, vocals, drums, and an occasional guitar. The Son of Ampzilla II provided solid and foundational low-end power for the Vandersteens as the baritone sax and two-stringed bass guitar pulled the tune inexorably forward. What I got from the Son of Ampzilla II was stronger, and more solid low-end action without smearing into the low mids and midrange that the Cary presents so sweetly. Overall a great start to this review.

Switching up genres, I moved on to Aleks Sever’s 2012 album Danger Girl and the fabulous jazz/blues tune ‘Silhouette’ [AIFF 16/44.1, iTunes]. Ms Sever is an extremely talented and versatile blues guitarist. With this song, I was able to enjoy the exacting finger work along the fretboard. The drums, bass, rhythm guitar, and Hammond organ flanked her throughout the soundstage at appropriate positions. Her precise playing soared and floated above the supporting cast. When I listen to this type of arrangement I appreciate the sense of being in the club. I want it to be an intimate venue with just a bit of smoke in the darkened room. The Ampzilla brought the front centre table to life. This meant I had the best seat in the house and a presentation that made the time fly by. I ended up listening to the whole album.

Moving on to vinyl, I went to Electric Light Orchestra. Zoom [Big Trilby Records 2013] is an album that does not get its due. One of my favorite cuts is ‘Moment in Paradise’. I placed the record on my VPI Scout 1.1 with its Dynavector 10X5 high output moving coil cartridge. I secured the LP with my Stillpoints LPI Long Spindle record weight. The ALO Audio Phono Stage connects to the first analogue input on the Simaudio Moon Neo 430 HAD. I love the simple presentation of this song. It is slow and sweet, offering gentle melodies with the guitar, bass, and drums anchoring the presentation. The Son of Ampzilla II allowed each note its own space. Each instrument was positioned in its own appropriate three-dimensional spot. The sense of depth was nice and deep. Again, in contrast to the Cary, the bottom end had a firmer grip than with the valve-based midrange champion. It was a nice contrast to have a wider spectrum functioning together. The extra power of the Son of Ampzilla II allowed the Vandersteen’s 100mm bass driver and 150mm passive bass radiator much more to work with and they responded with firm and satisfying bass down into the 29Hz range.

Switching to classical I put on Eiji Oue and the Minnesota Orchestra’s 1996 performance of Stravinsky’s Rite of Spring. [Reference Recordings, 24/88.2 AIFF] I love this particular rendition of this work and I have had the opportunity to hear them live on occasion, as I grew up in the St. Paul, Minnesota area. Classical orchestral works can expose equipment as fast as any other genre. The range of dynamics will lay low amps with insufficient power reserves. Music can build from a single instrument to the full orchestra, potentially smearing the soundstage with indistinct noise. But, a great amp will allow each performer to shine through. Each section can be heard as a cohesive blend within the score. It will paint the notes across the sonic canvas to allow the masterpiece to be seen in all its clarity and colour. There is a point from 5:30 to 8:00 where the intensity builds and layers are added. Tympani strike with power and intensity. It is beautiful. The Son of Ampzilla II allows the crescendo to build without distracting from any of the orchestral components. Well done SST!


For a final listen I was planning on using the the title song from David Bowie’s new album Blackstar [Columbia]. I downloaded the 24/96 AIFF from the minute it came available on January 8th. The news of his passing just two days later had me shift to another track, ‘Lazarus’. Listening to this via the Son of Ampzilla II, I was afforded the opportunity to be one on one with a pinnacle performance of a legend of music. Bowie’s haunting lyrics, which hint at his soon-to-come demise, were accompanied by a tight and intimate performance from his band. The quality of the mastering and the clarity of the recording were a perfect match for the Son of Ampzilla II’s high-end capabilities. The quick snap of the opening snare, the entry of sax and woodwinds with just the right mix of rasp and and tone, and the strong and persistent bass guitar all framed Bowie’s clear and still hopeful voice. The song is a message of joy and vision. SST’s latest effort brought full justice to to the song, to David Bowie’s creation, and–in a satisfying touch of fate–to the full measure of the rebirth and rise of James Bongiorno’s life-long vision as well.

To sum up, my time with the Son of Ampzilla II has been both a revelation and a privilege. I have never found such a high performing solid-state amplifier at this price point. Generally, it would take a big step up in price to reach these sonic heights. It is also my first opportunity to spend significant time with a James Bongiorno design. But there are so many good designers and so little time to sample their work, I suppose! Highly Recommended.

Technical Specifications:

Type: Stereo solid-state power amplifier

Inputs: 2× Balanced XLR, 2× single-ended RCA

Power Output (per channel, into 8Ω): Minimum 220 watts 20Hz–20kHz

Frequency Response: 20Hz–20kHz  ± 0.1 dB

THD (A-weighted): < 0.03% 20Hz–20kHz @ 8 Ω Full power

Noise (A-weighted): 45µV

Input Impedance: 130k Ω balanced, 65k Ω unbalanced

Signal/Noise ratio: 110 dB (20Hz–20kHz)

Gain: 27.5dB, 1.76v RMS for 220 watts 8Ω (either input)

Sensitivity: 1.76 V

Dimensions (W×H×D): 45×14.3×25cm

Weight: 18kg

Price: $3,500

Manufactured by: Spread Spectrum Technologies
4235 Traffic Way, Atascadero, CA 93422, United States

Tel: +1 (805) 466-9973



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