Vacuum Tube Physical Modeling DSPs: Unaudiophile?

Even though it is often done in the electric guitar playing world with varying success, why are there no solid state hi-fi amplifiers that physically model the sound of vacuum tubes? 

By: Ringo Bones 

In the March/April 2000 issue of Stereophile Guide To Home Theater, Lawrence B. Johnson voiced out his disdain over built-in matrix surround modes of surround sound receivers bearing such labels as Hall, Club, Church and Stadium and despite of his conclusion – and so does mine and every true blue audiophile all over the world – that those audio follies are so far removed from the real experience of listening in the kinds of venues they purport to reproduce, manufacturers of these multichannel surround-sound receivers still include them as de-rigueur citing that these silly in-your-face contrivances help in the selling of their product – especially to the nonaudiophile hoi-polloi. Which also got me wondering, why haven’t manufacturers of mass-market hi-fi stereo and/or surround sound gear start adding physical modeling / DSP to their integrated amplifiers / surround sound receivers that will able them to emulate – as close as possible – single-ended triode vacuum tube amplifiers? 

With the help of an audio-buddy, during the past two years I started playing with the idea of making a solid-state preamp with a DSP physical modeling / amplifier emulation input stage that will allow it to mimic – as close as possible – to timbres of some of the most sought after vacuum tube amplifiers since the Golden Age of Stereo. Imagine the ability to be able to make your Pioneer A400 or other well-reviewed budget solid state amplifier to sound like those single ended zero feedback power amplifiers with a Western Electric 300B output tube, a Dynaco Stereo 70 or even a Conrad Johnson Premier Eleven!!! 

As luck would have it, my working musician audio-buddy was also curious to as to whether his Yamaha THR10C physical modeling electric guitar amplifier can be used as a basis for a physical modeling DSP preamplifier for hi-fi / audiophile use. And given my familiarity with the physical modeling chips used in the 1993 era VL1 Synthesizer which also forms the basis of the Yamaha’s physical modeling DSP circuits, we managed to be able to make a working prototype of a DAC with the ability to be able to emulate as close as possible the timbre of 5 different classic electric guitar vacuum tube amplifiers. 

Interestingly, the “sound” produced by our physical modeling DAC is very dependent on the CD that’s playing. My audio-buddy was very disappointed when the HDCD encoded Independence Day soundtrack (09026-68564-2) CD slipped into the CD player resulted in a highly compressed sludge on all of the 5 settings, which is sad given that this is one of his favorite orchestral recordings. Our prototype Yamaha physical modeling DSP DAC did manage to provide really stellar results on some recordings – most of them in the heavy metal rock genre. The CD of Megadeth’s So Far, So Good, So What (CDP 548148) sounds as if the solid-state Pioneer A400 is a Dynaco Stereo 70 equipped with Mullard EL34 tubes. But its mostly a hit-and-miss affair and now I understand why Sony and other mass market hi-fi manufacturers are not making – or won’t be making any time soon – solid state hi-fi integrated amplifiers equipped with physical modeling DSPs priced between 200 to 500 US dollars each that allows them as close as possible to replicate the sound of classic vacuum tube amps like 300B single-ended triode amps and Dynaco Stereo 70 or the famed Conrad Johnson Premier Eleven.