SMc Audio: DNA-1 Power Amplifier Upgrades
Tip #101
Dick Olsher (August 2023)

Introduced in 1992, the DNA-1 became almost an instant hit. DNA stands for Distributed Node Amplifier, a unique circuit topology that replaces the ubiquitous large power supply filter caps with clusters of smaller caps placed directly next to each output device, essentially giving each power transistor a dedicated power reservoir. The result was said to be “faster, cleaner music at a lower price.”

Robert Harley had this to say about the DNA-1 Deluxe in the March 1995 issue of Stereophile Magazine: “The amplifier combined uncommon musicality with the ability to drive any loudspeaker load with ease. Specifically, the DNA-1 had a smooth, grain-free treble, a liquid midrange, articulate bass, and a spectral and rhythmic coherence many more-expensive amplifiers lack. In addition, the DNA-1 had excellent bench performance, particularly the ability to increase its output power as the load impedance dropped—meaning that the DNA-1 wouldn't lose its cool when asked to drive low-impedance loudspeakers.”

My interest in the DNA-1 peaked in 2021 while searching for the ideal power amp to drive my reference loudspeaker, the Analysis Audio Omega planar, a 4-Ohm nominal impedance load that dips as low as 3 Ohm. And since my lifestyle is that of the not so rich and famous, I was looking for an affordable option. There is absolutely no reason (except for greed) why a power amp should cost as much as a luxury automobile. Of course, the DNA-1 was long out of production by now, but Steve McCormack at SMc Audio is still offering a series of upgrades for the DNA-1 – quite logical for a man who initially put his imprint on the audio industry with the Mod Squad.

And so, I bought a used DNA-1 and sent if off to California for modification. There were several modification tiers available, which I discussed with Steve and Pat at SMc Audio. They strongly nudged me toward the GTA-21 Ultra Plus design because it includes the full gravity base system which is said to improve sonic performance across the board. Steve famously said that “my design philosophy is design by ear and build by hand. Use the best designs and parts you have access to. But designing by ear is the key criterion.” That is the art of good sound in a nutshell and it’s the design approach that I trust implicitly.

It would be misleading to think of the GTA-21 Ultra merely as a modification – it is in fact a complete rebuild of the original. The only parts reused are the chassis and power transformer.

The upgrade included the following:

§ R3 High Performance Main Driver Board PCB

§ Complete Rebuild of Output Modules

§ All Connectors Input, Output, AC Inlet

§ Complete Re-Wire

§ Bridge Rectifier Upgrade

§ Full Size Panzerholz Gravity Base System

I also opted for an AC mains Synergistic Research Purple fuse.

The finished GTA-21 Ultra Plus amplifier is heavier now and is also approximately 1" taller. There is no true power switch. When the amplifier is plugged in, the amplifier is on. The switch on the front panel only turns the blue LED on and off. It is recommended to leave the amp on continuously for best sound.

Robert Harley’s sonic assessment from some 25 years ago still holds true in spades. This amp is capable of superb soundstage transparency, detail resolution, and suave harmonic textures. It is neutral in character and readily takes on the sonic flavor of the associated front end. It excels in generating compelling rhythmic drive. And it is able to generate a stupendous macrodynamic range. Orchestral tutti never sounded any better. It easily beats all other high-power amps I’ve auditioned in this context. The Omega’s ribbon line-source tweeter covers the range above about 500 Hz and is very revealing of a power amp’s distortion spectrum and dynamic limitations; it became obvious that this was a marriage made in heaven capable of sublime purity and explosive power. This is indeed a combo I could happily live with till the end of time. For a total investment of about $4K I now own a power amp that competes with any cost-no-object design out there.