Every time I fly to California, my brain gets stuck on the lyrics of that Arlo Guthrie song: “Coming into Los Angeles / bringing in a couple of keys . . .” Even landing in San Francisco, I’m always smiling, because I’ve never been busted in California.
Which means that I’m a lucky guy. In this life I have acquired nothing of material value, but I did see Howlin’ Wolf and Little Walter in Chicago in 1962, at Theresa’s. I spent the whole Summer of Love (1967) in San Francisco listening to music. And because I lived only a few blocks away, I witnessed the Ramones’ first gig at CBGB, in 1974.
So you see, I’ve frequently been in the right place at the right time, standing on the right corner wearing a hat of the right color. Every time a black car pulled up and the driver said, “Get in!,” I was brave enough to complyno questions asked. To my surprise, audio has sent more than a few (metaphorical) black cars to corners I was loitering on. The latest was an invitation to the 2018 edition of the Burning Amp Festival, “DIY Audio’s Premiere International Festival,” at the Fort Mason Firehouse, under San Francisco’s Golden Gate Bridge. This time, instead of sleeping in the bushes of Golden Gate Park, I stayed in a genuine Fisherman’s Wharf hotel that was conveniently attached to an In-N-Out Burger. My assignment was to look, listen, and learnand walk the beach with Burning Amp supporter and Pass Laboratories founder Nelson Pass; his vivacious wife, Jill; their wolf-eyed dog, Jack; accomplished circuit designer, Wayne Colburn; and PR magician, Bryan Stanton, of J.B. Stanton Communications.
On September 29 it was raining hard. I got in late, but the hotel clerk and an associate at In-N-Out were still up, waiting for me. The next morning I went for a walk and realized I hadn’t been on Fisherman’s Wharf since 1967. I saw some of the same burnt-out hippies I saw back then. But what a beautiful sunny morning it was: Alcatraz to my right, and Fisherman’s Grotto #9 directly in front of me. Burning Amp would open at 11am, and I knew it was somewhere nearby. I typed “2 Marina Boulevard” into Google Maps and began my wonder-filled walking tour of San Francisco Bay.
I spent so much time gawking at fit hipsters and petting hound dogs that I was almost late. Burning Amp Festival’s new manager, Mario R. Yrun, greeted me at the Firehouse door and hooked me up with a T-shirt and a badge. Admission is $20unless you’ve brought along a component you’ve built yourself to be auditioned or simply admired, in which case admission to the one-day event is free. A tasty, healthy lunch is provided, as well as three lectures by distinguished audio designers.
According to Nelson Pass of Pass Labs (footnote1), “Burning Amp was started in 2007 by some of the guys hanging out at diyaudio.comfar as I can make out, they were Mark Cronander, Vladimir Simovich, and Stewart Yaniger. Mark Cronander went on to manage the event until 2017.”
The Burning Amp Festival is a siren call to audio tech heads and DIY audiophiles to come out of their basements and share their discoveries. The beauty of such forums and gatherings is that more experienced builders can mingle with and inspire neophytes. I’ve been a DIY amp builder since the 1980s, and every one of the supercool audio wizards I’ve met, including Amp Master Pass, has entered my life through participation in the worldwide DIY community. Ever think about joining them?
Lectures
Burning Amp’s trio of DIY project descriptions (footnote 2) were MC’d by the erudite Kent English, who works for Pass Labs and is a seasoned amateur audio builder.
The first lecture was by Wayne Colburn, Nelson Pass’s close friend and design partner since the days of Threshold. Colburn described a DIY line stage using four n-channel JFETs. I laughed when he mentioned that the output stage was biased by an LED that, he added, “Lets you know when the unit is turned on.” At the end of his talk, Colburn mentioned that there were free circuit boards of his design for each of us to take home.
Roger A. Modjeski, of Music Reference and RAM Tube Works fame, made a huge shout-out for vintage RCA Tube Manuals and F. Lanford Smith’s venerable Radiotron Designer’s Handbook, Fourth Editionthe Old-Testament Bibles for every builder of tube amps. He explained vacuum-tube plate characteristics (graphs of plate current vs plate voltage) and how best to establish operating points (grid-cathode voltage). I asked Modjeski if he ever went beyond voltage and current and considered transconductance in determining operating points. “No,” he said. “I use my own RAM Labs curve tracer and plot for minimum distortion.”
Not surprisingly, Amp Master Nelson Pass continued the discussion of load lines and operating points in his description of his H2 harmonic generator and LX Mini active crossover. According to Pass, the H2 is designed around some “cheap-ass JFETS that are almost not good enough to carry signal.”
I can hear you thinking: Why would anyone need or want a harmonic distortion generator?
The simple answer: Maybe a little distortion of the right kind could make our recordings more intelligible. Maybe adding just the right amount of second-harmonic “information” will assist our neural sensors and brain in reconstructing a recorded sound event.
In a recent interview, Pass explained something I’d been waiting 45 years to understand:
“Having previously designed with SIT (VFET) single-ended amplifiers and also the Korg Nutubes, I have worked up some performance targets which deliver an effect that is usually well-liked. This effect is described as having negative phase 2nd harmonic at approximately 1% of the amplitude of the original signal . . . but after you invert the output (to get absolute phase correct) you will find that it is now a negative phase 2nd harmonic. I know this might be confusingI have occasionally awakened in the middle of the night and thought ‘That can’t be right.'”
Pay attention now, because here is where it gets really interesting:
“So why is the phase important? Well, it’s a subtle thing. I don’t suppose everyone can hear it, and fewer particularly care, but from listening tests we learn that there is a tendency to interpret negative phase 2nd [harmonic] as giving a deeper soundstage and improved localization [of images] than otherwise. Positive phase seems to put the instruments and vocals closer and a little more in-your-face with enhanced detail.”
You knew this, right?
“Your results may vary, but when I first explored this with the SIT-1 amplifier at First Watt, I had a knob on the front of the amplifier which varied the amount and phase of the 2nd harmonic. It was easy enough to lend the amplifiers to listeners who didn’t know what the knob did and gather their comments. Roughly speaking, they tended to prefer about 1% negative phase 2nd harmonic, so it became my standard setting for that knob.”
Right away, Kent English raised his hand: “Why would we want to add distortion?”
Pass smirked. “Because this is entertainment, not dialysis! . . . and I am giving these things away!”
Pass reminded everyone that “The H2 works best with simple material. With complex material, second harmonic may be more of a burden than an asset. When you turn the knob to the left, which is negative-phase second harmonic, the room gets bigger, more atmospheric, you start to see images of musicians. Turn the knob right, you get positive-phase second harmonic, which brings the musicians closer to you: drier but more intimate, more apparent detail. But of course,” Pass reminded us, grinning hugely,” this is all illusion!”
A man in the audience cleverly explained how the second harmonic is exactly one octave up from the fundamental and is “like a chorus of backup singers. As H2 distortion rises, the backup singers get louder.”
My objectivist friend Mr. O calls H2 “second-harmonic sauce.” I’ve always called it “second-harmonic echo.” I think a little of it makes voices fuller toned and more intelligible, spaces more spacious and tangible. To my ears, modest amounts of H2 fill in some blanks of the illusion and make reproduced music more comprehensible.
Trickster Pass reminded disbelievers: “You are welcome to take my remarks as entertainment.”
Footnote 1: Pass Laboratories Inc., 13395 New Airport Road, Suite G, Auburn, CA 95602. Tel: (530) 878-5350. Fax: (530) 878-5358. Web: www.passlabs.com.
Footnote 2: See videos of all three lectures here.
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