Here's an interesting interview of James Bongiorno. I think he speaks pretty well for himself...
https://www.tnt-audio.com/intervis/bongiorno_e.html
I have my own stories to tell about and related to Bongiorno.
I greatly respect James Bongiorno as one of the best and most original audio amplifier designers of the 1970's to his death, in good company with many others like that including Sid Smith, Nelson Pass, John Iverson, Dan D'Agostino, Bob Carver, and Matti Otala. For a fleeting moment or two, Bongiorno may even have been the very top. But sadly his associations and companies never lasted long.
I had the amazing luck to have met him in person 4 times over 30+ years as well as having had some chats on the TunerInfo group in the mid 2000's. He often complained about ego in audio design, but I can't think of any who quite reached his level in that regards. Usually somewhat prickly, he tended to disassemble my honest but limited respect as insincere and unworthy.
Two of my best high school friends worked at Great American Sound (GAS) after graduating high school. They worked at GAS with founder James Bongiorno and also in the post-James epoch. Though Chatsworth was just a few miles from my primary and secondary schooling home, I moved farther and farther away after graduating from high school, but I often or at least sometimes came to visit my friends.
One of these friends, who we always called Bro, was my idea of a geek's geek. Already in high school he'd built his own Black Box for tapping into telephone lines (but not a Blue Box, he was quick to point out). Then he built an amplifier copied from SAE's latest IIIC amplifier.* It was in a big open box where you could see all the parts including huge computer grade electrolytic capacitors. He didn't try to make things look "finished." Instead it seemed he revelled in exposing bent metal and wires, wires everywhere. He used a heavily modified AR turntable, ripped open in the back (tin snips perhaps) to mount an SME arm. Sometime later he used a GAS Sleeping Beauty cartridge, and a preamp based on the Thaedra (but in a small box open on the top and sides so you could see all the tangled wiring). We'd hang out in his bedroom with other friends and listen to stereo, frequently swapping positions for the "hot" seat. He had giant home made speakers including 18 inch woofers. Was anyone else in our high school at this level of audio coolness?
I always remembered it as an SAE copy. However, on one visit another friend once said, "It's actually a Dynakit but he gets a rise by telling people it's an SAE." Just checking now, I see the Dynaco 400 kit was introduced in 1972 and the SAE IIIC having similar design but improved specifications was introduced in 1973. We started hanging out listening to Bro's "SAE" in 1973. Bro insisted he changed it to be just like the SAE:
"So what did you do that makes it like an SAE?"
"I took out the Dynaguard."
"Leave it to Bro to take something out, and call it a feature."
"It's better that way."
"Why? Why couldn't you just turn the Dynaguard off?," I asked.
"Because then I took out the switch and relay too, so it's really direct coupled."
Then Bro showed the speaker wire soldered directly to the wire connecting the output transistors.
"That makes it much better," Bro said.
Bro's "SAE" did indeed always make a noticeable thump when he turned it on. When the thump wasn't there, you knew something was wrong. But many years later, my Dynaco 410 which is basically what Bro had, a Dynaco 400 without Dynaguard, it makes no thump at all. I think the tech in Austin that did the last refurb did a very fine job of adjusting the DC balance.
In a few years Bro had upgraded to an Ampzilla in similarly open chassis with no fan. All 3 of those amplifiers: the Dynaco 400, the SAE Mk XXXc, and the Ampzilla were designed by James Bongiorno, in the course of a few short years, to the accolades of many, including reviews by Bascom King in Audio Magazine who described the Ampzilla as the dawning of a new era in amplifiers.
After starting to work for GAS, Bro always had a TO-3 transistor on his 73 VW Beetle dashboard and liked to paraphrase from a Steely Dan song saying "a transistor and a large sum of money to spend." To which another friend said "You only wish you had the second part."
Then the first time I met Bongiorno was at one of the first GAS factories, in Van Nuys, California. I had been asking Bro if he could get a stepped attenuator for me. I really needed something like that for the experiments in auditory perception I was doing for my senior thesis in college. I was using headphones to present stimuli to test subjects, and normal stereo volume controls weren't tracking well enough to make them precise. Bro invited me over to the GAS factory to see what it was like. He also promised he'd make a small amplifier for me based on GAS Grandson from one of the boards in rework. I said that would be nice but wasn't as necessary as the attenuator. I had been using my Marantz 2270 as an amplifier for the experiments, and I believed it was good enough. (Bro said it wasn't high fidelity. I said "What?" He said "Maybe you wouldn't hear the difference anyway?" "What?" "See what I mean?" Bro wasn't just popping off, we had in fact done a listening test comparing his amp to a real SAE to my Marantz receiver, in Andy Hefley's apartment in Tarzana. Bro claimed to hear a lot of differences. The only difference I was sure of was that the bigger component amplifiers had better woofer control.)
But it would be nice to keep my 2270 in my dorm room, I admitted.
As I arrived, Bro announced my name as Charles. Bongiorno asked me, as "Charley," what I liked to listen to most, and I honestly said I liked FM radio. He then made an inside joke among his staff by asking, "But does FM radio like you?"
I didn't get the joke at all. I figured he was making fun of me because serious audiophiles didn't take FM stereo very seriously (but I had for a long time, and lusted over tuners such as the Marantz 20b).
Bro later explained to me that I wasn't being put down because of liking tuners. Bongiorno had been talking about making a Charlie tuner, named after the figure in StarKist advertisements who says he has good taste, and his friend tells him "But Charlie, StarKist doesn't want tuna with Good Taste, StarKist wants tuna that Tastes Good."
After that Bro came over to the Psychology lab at Pomona College and attempted to get the little grandson amplifier board working. But it was not going well. I made what I thought was a friendly comment but Bro took it badly. He said "Don't disparage me" and then he refused to do any more work on the amp. Fine, I said, it was your idea and I didn't really need it anyway, I just wanted a stepped attenuator.
Some time later, in 1978 when I worked at Audio Dimensions, the parent company of Audio Directions in San Diego, the store carried GAS products. However they were not particularly admired by the owner and staff because we always had something else we liked better, including electronics made by Spatial, Mike Moffat, Threshold, PS Audio, and so on and on. The owner Ike Eisenson was big into modified tube equipment, and technicians like me would do the modifications onsite following his Tu-Be manual. But Ike's well known penchant for modifying every kind of tube equipment meant we didn't care famous tube lines like Audio Research and Conrad Johnson. They, rightfully, didn't trust us. The owner believed his modifications were better than those anyway. Instead we had carried transistorized amps from all the then smaller companies who didn't have onerous contracts and other "requirements." GAS was just another one among many of these companies.
In fact, and though I had never seen him there, James Bongiorno already had a colorful nickname at Audio Directions,. We called him Bongo Jim. I asked "That's because he's a musician, right?" Some senior tech set me straight right away, "And because he constantly beats his own drums." Another senior tech walking down the hall said "And he's more than a bit bonkers from from listening to them too." Ro Pennell, the business manager, popped out of her office and said, "Now get back to work. And quit badmouthing our idiot suppliers."
Meanwhile, Ike gave his top level of respect for Richard Freyer and Damien Martin of Spectral Audio. Ike, who wasn't afraid to tout his Mensa membership, pre-announced their visit to the store staff by saying they were the smartest people he knew. We never carried the Spectral line however, it was too expensive, and they probably did have onerous requirements. In the interview above, Bongiorno disparages Spectral and their 3 Mhz bandwidth as nuts.
Bongiorno had gone to great lengths to eliminate capacitors and transformers from the signal path. I'm not sure if he was the first, but was at least one of the pioneers the use of servo loops in power amplifiers which not only cured any minor DC offset but also eliminated the need for even a coupling capacitor at the input or anywhere else in the signal path. So amplifiers like the Ampzilla and Grandson are Direct Coupled.
On the other hand, Spectral believed that servo loops were not the answer. Spectral did not believe that input coupling capacitors were pure evil, only that input coupling caps had to be high quality caps like polypropylene. They insisted that servo loops introduced their own set of sonic issues which could not be so easily fixed. And properly considered, things like servo loops are in the signal path themselves, so in fact capacitors are not being eliminated by their use.
This is an interesting argument. But I do not believe that servo loops are a significant audio issue when designed and implemented properly. OTOH, nor are good coupling capacitors. All this debate comes to little.
But as it turns out, nearly all of the amplifiers that I have today are direct coupled. This is relatively easy to do in a MOSFET amplifier, like the Hafler 9300, which is fully direct coupled. In an amplifier with Bipolar Transistors as Bongiorno insisted were required for High Fidelity, servo loops are pretty much required for direct coupling, and they are used in all Parasound amplifiers (I have 3 of them IIRC, one in the bedroom now) and Aragon amplifiers (like my 8008BB).
Bongiorno even took his belief in direct coupling to point of making a direct coupled preamplifier, the Thaedra, with servo loops to eliminate any need for capacitors. That is very rare, but hardly anyone builds preamplifiers out of discrete transistors anymore anyway, and I wouldn't be surprised if opamp chips have their own built-in servo loops.
While basically ignoring all the GAS equipment, the Audio Directions staff fell in love with the Nikko Alpha III mosfet power amp. Afterhours we'd just sit in the front room and listen to it. MOSFETs are just like tubes, Ike would explain. Because of MOSFETs, it was a very simple amplifier. It would be over 10 years before MOSFET amps became big in audio, with the ultimate audio genius Nelson Pass himself switching from Bipolars (used in his Threshold amps) to MOSFETs (used in his Adcom, First Watt, and Pass Labs amplifiers). Meanwhile, in the interview above, Bongiorno continues decades later to say MOSFETs are unsuitable for high fidelity amplifiers. BTW my current favorite amp, the James Strickland designed Hafler 9300, is also a MOSFET amplifier. As far as I can tell, Bongiorno never explained why MOSFETs are unsuitable for audio. Sadly I forgot to ask him that when I had the chance on our last encounter.
Once a GAS Grandson amp came into the back room where I worked at Audio Dimensions. Somehow distracted, I first plugged it in, then unplugged, then plugged it in again. That apparently killed it. No one bothered to do anything with it and it just sat there for months like an omen.
I first visited the new GAS factory in Chatsworth to buy a turntable. I hated the Connoisseur turntable I had bought at Audio Directions (the only thing there I could afford). I called it the Con-noisier because I could hear the motor running from across the room. So I bought a Micro Seiki turntable at a special GAS sale, a DD35. I hated it too because the thin wood plinth was so resonant. It was about 12 years before I finally got a turntable I pretty much liked, the Sony PS-X800. That Sony is wonderful until it needs repair, which few techs are willing to mess with. That's how I ended up with a Linn Sondek LP-12 which has been kept in good repair by the same guy who sold it to me, Mark. I now believe that by this time, Bongiorno had already split from GAS.
Then I bought a second hand Son of Ampzilla. I had always believed this was the GAS amp to get because...no fans! Also no problematic servos like the Grandson. (BTW I now have many very robust amplifiers with servos, the Parasound amps and the Aragon. They are indestructible. Also the Krell FPB, which is somewhat finicky, but not so much because of the servos but because the servos are so good they keep everything looking good until the breaking point.) However before long I was plagued by RF noise from this GAS amp. I took the Son apart only to discover the side panels were literally plugged in with giant connectors. That did not look as reliable to me as normal wiring and solder. Though I knew a bit about repairing and modifying tube amps by this time, the Son of Ampzilla was utterly incomprehensible to me.
So I contacted Bro about getting a schematic. He offered me a chance to get it straight from the "horse's mouth."
I drove up from my home in San Diego and of all the amazing experiences I could have possibly had, I visited the GAS factory while Andy Hefley, apparently the new engineer after Bongiorno left, was doing the final design (or re-design?) of the feedback and stabilization networks for the long rumored Godzilla amp. Different parts were clipped in and the square wave response checked. It was not unlike speaker design I've done myself (and seen others, like the late Albert Von Schweikert, do). A memorable example of "Cut and Try" engineering that's more common than many would admit.
I was standing here, wondering when to pop my question about an old amplifier I bought used, while the very future was being re-invented. I was in total awe, as if watching the first open heart surgery. I'd had sessions like that already with senior tweakers at Audio Dimensions. But this seemed more intense and special. Andy, a long time friend of Bro's was clearly seemed in charge, and Bro was helping, and there were others watching and commenting.
*** Update, if I remember correctly, Bongiorno himself showed up to this meeting. However I only remembered this for certain after writing this post. This would make 4 times I met or saw Bongiorno in person. IIRC, at this re-design meeting, there was mumblings about "him." Then finally Bongiorno showed up, and never took his trenchcoat off. He was not particularly helpful to the current situation. He sort of approved the (re-)design Andy was making by not vetoing it. Then, as quickly as he arrived, he vanished, before I had a chance to ask him about the schematic for my Son of Ampzilla. Soon Andy and Bro were loading the Godzilla into Andy's van. I was pissed about missing my opportunity with "the man."
From there, Bro and I hurried off Andy's beachside home near Ventura, California. Andy was replacing the two Ampzilla II's he had running his two pairs of Magneplanar Tympani IV's with the one new Godzilla. I asked whether that was a good idea.* No problem at all, said Andy. One Godzilla has even less impedance than two Ampzilla's. He demonstrated the capability of the Godzilla by welding two copper wires together. As Bro was getting the act together I said "don't bother" but he insisted no problem, and indeed the welding occurred.
(*While making this comment, I also had in mind the other question, about whether it sounded good to a normal person on normal speakers. But perhaps I hadn't considered that the "normal" person who bought the latest 400W amplifier was planning to listen much like this.)
But Andy and Bro played way too loud for me to even enjoy.* I could barely stand it. I was only 24 years old and it felt like my ears were going to explode. After a short while I begged to go outside and smoke a tobacco cigarette. (I managed to quit smoking tobacco in 1991.)
(*So apparently there is a market for amplifiers with fans, among those who listen so loud it wouldn't make a difference.)
In combination with the other drugs, and the long day, and everything, that was it for me. I begged to lie down and Andy showed me to his guest bedroom. I promised myself I'd get up after 5 minutes and beg Andy to turn the level down and give it another listen at a tolerable level, if that were possible. But I was exhausted and had no desire to get up and face the music. Impossibly, Bro and Andy kept playing louder and louder for another half hour or so. Suddenly there was deafening silence, punctuated only by Bro yelling "Fuck!" multiple times. I ran out to see if everyone OK. Andy had gone off to get something. Yeah, Bro said, pointing to some burned out part, "It wasn't supposed to do this." I went back to bed.
I was awakened barely on time to be herded out in the morning. Godzilla was going back for another redesign.
Finally as we were paying the bills at a restaurant where we were having breakfast, I finally popped the question about getting the Son of Ampzilla schematic. (I thought Bro had asked Andy up front, the whole point of the visit I thought.) Andy said he'd be happy to get it next time. But it was the last time I ever bothered to ask about seeing him. I later did buy the set of GAS schematics from a guy on eBay around 2002, but I haven't looked at my Son of Ampzilla since the 80's.
Bongiorno always blamed "poor marketing" for the failure of GAS after he left. However I've always had a different idea based on my own personal experience of two GAS products. I do not believe they were the most reliable. I don't attribute this to poor engineering on the part of Bongiorno himself. We he compares himself (as a "real engineer" compared to Morris Kessler) I think what Bongiorno is talking about is that he designed by the book and also tested things to failure. Most audio products cannot take such abuse, but Bongiorno came not from the likes of audiophiles (whom he often detested) but musicians, who tend to drive amplifiers into oblivion at a sizeable fraction of full power. THIS is why so many GAS and Sumo amps have fans (which I detest) when most other audio products don't. They are designed to be run in problem test cases like 1/3 continuous power. I'd presume you can run a GAS amplifier with fans at 1/3 power all day long, whereas most other audio amps will shut down before one hour under such abuse. I wonder if Bongiorno had anything to do with the FTC audio amplifier power labeling requiring a 1/3 power "preconditioning" for an hour. Most amplifiers will shut down before the hour is finished.
I think the problem stemmed from assembly, not circuit design. I think those very wave soldering machines that Andy was bragging about were the downfall of GAS. Wave soldering is a tricky business to technicians educated on the old fashioned kind of soldering. You may notice now that there are not many GAS amplifiers for sale and many have been repaired many times by now. The Dynaco 410 I have was only refurbed once, and I just did it because I thought it would make it better (it made no difference). If indeed there was a reliability problem at GAS, it might also have stemmed from the cocky attitude of the staff, including Bongiorno himself and my two friends who worked there.
But it's possible that "marketing" was indeed an issue. And it likely was an issue long before Bongiorno left, in large part because of James's own personality. You can see that he didn't get on with audio companies very long, even when he was the head honcho himself.
While Bongiorno is universally praised by audio magazines now as "a genius," that was not necessarily true when he was making the GAS and Sumo amplifiers. Bongiorno was highly praised by his friend (and fellow engineer) Bascom King at Audio Magazine, and to a lesser degree at J Gordon Holt's Stereophile (J Gordon Holt actually preferred the Morris Kessler designed amplifier SAE made before hiring Bongiorno), but he often got a cold shoulder from The Absolute Sound. The sound of one of the GAS amps was described as "Hard as Nails." If you read those early issues of The Absolute Sound, you might find Alan, my other friend who worked at GAS, responding very derisively to these reviews. The reviews probably deserved that, but it didn't help either. Alan was in "marketing" at GAS.
I would not at all be surprised if there were differences between Bongiorno and Harry Pearson that went far beyond audio as such, political. And these would not at all be ameliorated by Bongiorno's tendency to disparage subjectivist audiophiles and reviewers out loud, though perhaps unbeknownst to himself being actually one of them himself, in not founding his requirements in double blind listening tests. But he considered himself an engineer above all the rest except his small set of key friends like Sid Smith and Dick Sequerra. Bongiorno was shooting for objective accuracy, which was after all what is required, into any kind of impedance, because as David Rich says, most loudspeakers are designed by tweeks and have near-impossible load angles.
Sadly when it comes right down to it, GAS products were not the products that audiophiles of the time most wanted. An amplifier of about 100-150W most would be suitable for many, and GAS never built an amplifier in that range. Either the Ampzilla, which was too big, ugly, and noisy because of its fan, or the Son and Grandson which were too small. The Ampzilla may have been a beautiful and inspiring electronic design, with direct coupling, servos, and Complementary Symmetry, but it didn't look like high priced audio gear. It still looked like a kit made from surplus parts, which was famously how the project got started--but it was a kit was never actually delivered, after having been advertised, at some point Bongiorno decided it was too complex for hobbyists to build, which was correct, and he converted kit deposits to deposits on the pre-assembled amplifier, which most accepted.
What might have been a more profitable hit would have been a recasting of the 200W Ampzilla from it's cheap kit-like appearance up to a massive Mark Levinson style chassis, and with no fan!, and hopefully less inflated price than Mark Levinson. Sumo products were generally a step forwards and away from the stereotyped styling of GAS products, but Bongiorno still couldn't get away from those darned fans in his electronically wonderous statement pieces like the Sumo Model Nine.
Why bother to have an amplifier with 130dB dynamic range if the listening room itself can't get 40dB below the level of 1 watt due to fan noise? And generally I want to have my power amplifier in between the two speakers in plain view, polluting the very important phantom center image if it makes any noise at all. (Done properly, nothing is Better than a phantom center image. A speaker there always sounds fake to me... Though I've never heard Bongiorno's trinaural system.) I can't understand why someone as obviously brilliant at amplifier design as Bongiorno couldn't get this basic fact over decades. Musicians are generally more tolerant as they play even louder and already know what the notes are.
Amplifiers like fans, but most amplifier fans don't like amplifiers with fans.
I think the basic problem was, Bongiorno didn't listen to anyone else, and it's not clear he spent much time listening to recorded music either, by his own admission. He was too busy. He knew how amplifiers should be designed, and that good engineering was building an amplifier better in every way every time. Brilliant engineering was being original in finding better solutions every time as well. He was all that. He had no concept of want, need or good enough--which is actually what all good amplifiers are, and not perfect.
This all leads up to the second I met or at least saw Bongiorno in person. That was in the fall of 1981, when the San Diego Audio Society was hosting both Bongiorno (then at Sumo) and Nakamichi (who had just introduced their offset correcting turntables). It was one of the most amazing audio events of my life and I only wish I could remember the details better.
The meeting was held at Audio Directions, had expanded greatly since I left the company in 1979. Ike himself had established the San Diego Audio Society but by 1981 it had become independent, and Ike had left the company, divorced his wife, moved to the east coast, and was no longer working in audio. The store was being run by his former mother-in-law, Ro Pennell, who had put up all the money for Audio Directions and Audio Dimensions in the first place.
In the much enlarged main room, there were more audiophiles than I had ever seen then (and after) in a local audio society meeting. It was packed with GAS fanboys and the curious as well as local audiophile regulars. My friend and I arrived a bit late but found a place in the middle of the packed room.
Bongiorno talked about balanced amplifier design, why it was so much better than unbalanced, in its interactions with both input and output, and also hyping up the specific ideas in the Sumo "Nine" Class A amplifier which he then loved the most, including the 4 quadrant feedback (also touted in his much later Spread Spectrum Ampzilla 2000 and Son of Ampzilla 2000). Back then I really bought into all Bongiorno's hype about how wonderful and important this all was (though over time I've become much more cynical about such things...unbalanced amplifiers can be just fine, and EVERYTHING has trade-offs, for one example I think the unbalanced Hafler 9300 vastly superior to the balanced Hafler 9500--which has nearly 10x more THD+N, possibly from noise, which is one bane of balanced circuits...OTOH I'd love to get my Krell FPB 300 working again with a change to medium bias Class AB, it has incredibly good and fundamentally balanced circuitry and that IS a plus when everything else is right.).
Bongiorno then as always claimed credit for the Complementary Symmetry circuit used in audio power amplifiers. Actually Complementary Symmetry was pushed by the semiconductor manufacturers themselves, after they had made the first reliable NPN/PNP complements. The first Complementary Symmetry audio power amplifier was not the Ampzilla nor the SAE Mk XXXIb but probably the JBL SA600 made in 1966, several years prior to any Bongiorno amplifier design I know of. And like everything else, complementary symmetry is a trade-off. It turns out the silicon PNP and NPN complements are not at all perfect complements. You might do just as well with Quasi-Complementary as used in many famous Marantz amplifiers (including the Marantz Model 15 Bongiorno himself praised as Sid Smith's best design) and amplifiers still being made today. Many designers have made a point of using Quasi Complementary as an inherently superior design. Ultimately here is no "magic" formula which will transport you to a different world, in fact good solid state amplifiers that have less than about 0.1% distortion sound exactly the same, I myself learned in the late 1980's (and reproved to myself in 2018 and again and again). But I digress.
Bongiorno also talked about tuners, why ceramic filters were inferior to the tuned circuits used in Marantz 10 and 20 (which he had some experience with during his short time at Marantz) and which were going to be used in the Sumo Charlie. He didn't think Kenwood was at all on the right track with their Pulse Code detectors, but other "statement" Kenwood tuners were pretty good. Bongiorno specifically praised the newly introduced Kenwood L-02T but not the earlier L-01T which had used a pulse counter design. (He was right, of course.)
(As far as the anti-ceramic filter thing, I believed in that for awhile but ceramic filter based tuners can be incredibly good. Many of my favorite tuners are some kind of mixture or entirely ceramic. I believe my all time favorite L-1000T is a kind of mixture as earlier statement Kenwoods had been. The phase errors of whatever introduced by ceramic filters barely show up in the wash of system phase errors we aren't much sensitive to, anyway. And there's no evidence ceramic filters are especially microphonic. I think the Sony 730ES is all ceramic filter and it's fine sonically. Over time, the "stays aligned" thing becomes more and more important, and ceramic filters are stable in that way, but no more stable than other low impedance circuits. It's the high impedance circuits like in all tube tuners that are fundamentally unstable over time.)
When asked by my friend what speakers he used (something Bongiorno had never discussed), Bongiorno conceded he had had his fill of speakers that didn't account for room acoustics and poorly recorded music, and he himself didn't bother with recorded audio at home anymore. He had just bought himself a grand piano and was playing that instead. I took this as dodging the question. My friend took it as proof that Bongiorno was useless as he didn't use amplifiers on speakers himself, so what did he really know?
While it may have been really cool, the Sumo Nine just didn't have enough power for most audiophiles then, despite the fairly high price (for the time). And the fan killed it for me.
I wanted to go and ask Bongiorno some questions but my friend reminded me about the Nakamichi turntables, which were unusual and should have been groundbreaking, so I went to than presentation next.
Finally the last time I met Bongiorno in the flesh was at T.H.E. Show in Las Vegas in 2009, which was happening at the same time as the January CES show. By this time I'd actually spent a few evenings sparring with Bongiorno online on the FM Tuner List, which had been a serious preoccupation of mine from about 2002-2005. Not that I disagreed with what anything he said in particular, but Bongiorno never responded very well to "questions." He had pat answers to just about everything and stuck with them.
Bongo Jim was also into his own set of things to the exclusion of all others. He raved about how the Marantz 10B and 20 and Sequerra Model One were the best tuners ever made, with his own Charlie following in their footsteps. Well, he had (briefly) worked at Marantz when the 10B was being made and the 20 was being designed, and was an associate of Sid Smith and Dick Sequerra. So this was all like his family. And he was committed to being their street fighter.
Most tuner aficionados don't have very much respect for Bongiorno's Charlie tuner*, and only limited respect for the others despite their ongoing cult-ish followings. They are understood as tuners that might sound "good" (the famous/infamous Marantz Champagne sound) on strong local stations, but are not very good at picking out distant stations or when there is interference. A short example list of tuners that tuner experts would prefer include the Kenwood L-02T, the Sansui TU-X1, the Pioneer F-26, and anything made by Accuphase. Meanwhile Marantz made absolutely unbelievable claims about the performance of tuners like the Marantz 10b, such as 150dB alternate channel selectivity. That's simply impossible, and it would be impossible to measure too. In fact the Marantz 10B is not a highly selective tuner, just somewhat better than the average tube tuner. The tube tuners best at handling urban reception problems might well be the Scott tuners.
(*This is further complicated by the usual story. Bongiorno departed from Sumo at about the same time as the Charlie Tuner had been introduced. Only the first 1000 or so Charlie's got the final alignment by Bongiorno himself, which is just as tricky as with a Marantz 10B, the "official" secrets of which have only ever been revealed to a handful of insiders like Mike in San Diego. Those are the ones with rack handles. Bongiorno claimed that all the rest were never aligned correctly by the Sumo factory. He had given them instructions which they refused to follow. And that was the sort of reason why he left Sumo also. But according to some who have tested both, there isn't actually much difference between the handled and unhandled Charlie's. They are pretty good sounding on local stations and that's it. Many of the Marantz 10B inspired tuners suffer from things like "birdies" on problematic stations, and the Charlie is no exception.)
One of the first articles to pick apart the cult following of the Marantz 10B was the test of tuners by The Absolute Sound in issue number 6 in the mid 1970's, which didn't actually formally test a 10B but compiled a list of anecdotes about them. (Note: this tuner review hyped the Sequerra tuner way up, but was entirely based on audio quality with home transmissions, not real world reception problems, thereby overlooking the limitations of the varistors to be as sensitive as an air capacitor as in old dial tuners. But meanwhile it was the first magazine column to even mention the Marantz 10B cult, only then to immediately pick it apart. I personally have one of each kind of Charlie, with the rack handled version serial number below 500, a collector's item, but I haven't listened to that one much because sadly it had tobacco smell. The unhandled version is "ok" but only "ok.")
The general dislike of early Marantz tuner hype continued on the Tuner discussion list in the 2000's, with the exception of Bongiorno and a San Diego technician named Mike (about whom I have too many personal stories to recount here) and a few others. I myself think the Marants 20B is an incredibly good sounding tuner on clean local signals and worth the refurbing I need to do to mine on that basis. It may well be the best "engineered" of the lot...including even the Sequerra. The 20B stuck to the basic 10B design but basically did it even better with transistors. The ultimate flaw in the Sequerra tuner is the fundamental inferiority of varactors to tuned capacitors.
Well I really wanted to know exactly why Pulse Count detectors were inferior, as Bongiorno and others had long insisted. I had bought a 600T and several people I knew considered the KT-917 as "the best tuner ever." (I regretted selling the one I had in 1989-1991). So I asked Bongiorno what kind of measurement could be done to show the inferiority of Pulse Count Detectors. Bongiorno was not an audio subjectivist (or at least he didn't think he was) but an engineer. So he should have the answer. This time, Bongiorno gave a most memorable answer while trying to duck me as quickly as possible.
"The problem is not in the measurements, it's in the theory."
I've talked about that idea before in this blog, and it's become part of my central audio philosophy. It's really hard to unpack things by measurements sometimes (though I still believe it should be possible somehow). And it's why I adjust my phase corrections "to the model and not the measurements," though, the model itself being informed by the measurements. Neither I nor Bongiorno write off measurements entirely, as many subjectivist audiophiles do. But you can't always tell the important things from simple measurements.
If I remember correctly, Bongiorno also said something like "you'd need an output of 100v to see the difference"). Then it's a question of resolution, and indeed resolution errors can be buried in the noise, as they probably are in tuners. Then, do they matter? Well they represent different things, correlated vs uncorrelated noise. I think in principle it matters, just as Bongiorno said, but maybe not if the resolution is good enough, as with 24 bit digital. Kenwood pulse count tuners are doing something with way less than 24 bit bit resolution. But it's not clear how MUCH this matters when you're only talking about 80dB S/N anyway. It doesn't matter as much as many other things, perhaps.
For the past 2 years, since I removed my most beloved Kenwood L-1000T for chassis modification (vent holes to be done by a machine shop, because the L-1000T runs too hot) I've been using the Kenwood 600T as the kitchen tuner. The 600T is Kenwood's very first tuner with a Pulse Count Detector. It was their top of the line model in the same year the KT-8300 was introduced, the Pulse Count detector gave it about 6dB higher S/N, and was a big marketing thing (never needs alignment). This was just after many of the original Kenwood tuner designers split and formed Accuphase which started making very nice tuners but with conventional detectors. It looks as if some of the senior engineers had been unhappy with the Pulse Count Detector project but Kenwood management insisted on going ahead with it anyway.
What I like most about the 600T is the signal strength meter, which unlike any others (except KT-917) is calibrated in linear increments of 10dB: 10dB, 20dB, 30dB, and so on up to 80dB. The sound is decent, PROVIDED you turn the MPX filter on. Otherwise it has the slightly too bright "classic Kenwood" sound that most "silver box" Kenwoods, including the KT-7500 and highly praised KT-8300 Kenwoods had regardless of whether they used Kenwood's original detector or the Pulse Count detector. Only with the L-02T and L-1000T (and others of that general design) was Kenwood able to get away from the too-bright "Kenwood" sound. The PLL "linear" detector was best. (Note: I am not talking about PLL Multiplex here, as most tuners since 1978 or so have had that, as it's built into nearly all the MPX chips everyone has used since then. A PLL Detector is something very special that only very few high end tuners have).
The fact that the alignment hasn't changed as much as it might have otherwise is also a big plus for the 600T. That's probably why the KT-8300 now sounds notably less nice than the 600T. Mind you, the 600T is a very complex beast with intermediate frequencies! There are in fact a lot of alignment adjustments. But they don't matter as much with a pulse count detector, whose performance is barely affected if everything else is slightly off.
So I've been listening to a Pulse Count Detector tuner for the past two years, and it's "ok." True, I like the L-1000T with it's PLL detector and analog-multiplier MPX (the ultimate best analog technologies for these tasks) best of all, but the 600T is ok. I think I like the 600T about as good as most of my tuners except the very best sounding ones, the L-1000T and the Sony 730ES and Pioneer F-26 and possibly the Marantz 20b (not listened to in awhile). I had intended to use the Pioneer 9500 instead of the Kenwood but it's been too hard to get out of storage. I suspect it's like the F-26 but slightly noisier. Meanwhile I think I may prefer the 600T to the Onkyo 9090 mkII, despite the "inferior" pulse count detector of the 600T. I prefer the 600T with MPX filter engaged to the KT-8300...but I've never tested KT-8300 with it's MPX filter engaged, come to think of it. It may well be that's the trick for getting all of the "Silver Box" Kenwoods to sound good. It wouldn't be surprising if almost everything comes down to the high frequency response--does it tilt up or down?
Highly knowledgeable (and perhaps less egoistic) engineer David Rich positively concurred in the 90's with Bongiorno's assessment that the Kenwood's pulse count detectors were inferior, and that the L-02T PLL Detector was far better (and said on paper the L-1000T had the most promising of all designs except for the digital tuning which is inherently inferior than the analog of the L-02T, he never had one to test though). Then Accuphase in the later 2000's started making much more sophisticated pulse count detectors that did indeed have the required resolution, perhaps.
This came to mind as I'm re-testing my Dynaco 410 for sale. I think I once said something about Bongiorno having designed part of the 410, and Bongiorno himself dressed me down on the FM tuner list. I can't remember whether he wanted credit for all of the 410, or none of the credit. It's basically the same audio circuit as the Dynaco 400, which Bongiorno always takes 100% of the credit for (however, AFAIK Erno Borbely designed the Dynaguard circuit, and somebody else was involved on the 400 too IIRC), but the 410 was released long after Bongiorno left Dynaco. By the time the 410 was released Bongiorno had worked at SAE for several years, then started the GAS company and moved from Van Nuys to the Chatsworth location as GAS had, for a fleeting moment, become a big name. But the Dynaco 410 was Bongiorno's audio amplifier circuit without Borbeley's Dynaguard circuit, so it seemed to me to be even more like a Bongiorno design than the 400. In all his later work Bongiorno stayed away from things like Dynaguard. He wanted maximum linearity.
One thing about the 410 is that it's a very solid piece of metal and weighs a ton. I recall GAS amps being basically made out of bent sheet aluminum. Even the heat sinks. Never cast aluminum. Bongiorno liked the efficiency of that and didn't believe in wasting any money on the casing. However perhaps it would have been better to have more dimensionally stable casing. SAE were a bit more solid too. And Dynaco tended to use rock solid steel. That solidity seems to translate into reliability as well. My 410 has been perfectly reliable for me for 40 years. For some reason, though, I never took it seriously. It never occurred to me until writing this post that this is essentially Bro's amp, the one he wowed us with for several years (until he upgraded to the Ampzilla). It's the Dynaco 400 without the Dynaguard. And for most of the time I owned it, I ran it without the fan without any problems.
I bought this amp with one and only one purpose in mind. To be the poweramp for my subwoofer. I think I used it for a huge "slot-loaded" home made subwoofer I bought at the Bongiorno audio meeting parking lot after the meeting was over.. A year later I bought a pair ML2's to use as a pair of subwoofers. They had some burned out other drivers, but that didn't matter and I was crossing them over with a 24db/octave crossover made by dB systems, which was the second thing I bought at the parking lot sale.
And in 2003 or so I got a Pioneer D 23 four way crossover, sometimes labeled "Series 20" for one of Pioneer's short lived super premium lines (mine is not so labeled, but is exactly the same thing). This replaced the dB systems and gave me total flexibility (and with stepped controls) to set crossover between the subs and my Rogers LS 3/5 A's. But soon I had added a different tweeter (after I burned out the one in the Rogers), the Dynaudio D21AF (one of the best tweeters of all time, I think, and I'm still using them now as my supertweeters) and was then using 3 "ways" of the 4 way D23 crossover.
But without much thanks, the Dynaco powered the ML2 "subs" from the day I got them, and through modifications, until I retired them for a "real" subwoofer, the SVS 16-46, which gives me bass down to 13 Hz in the bedroom, around 2005 or so.
Before then I'd gotten concerned about low level noises. This was in my bedroom after all (where I'd had my main stereo since moving to this house in 1991, since I shared it with my mother) and it wasn't until 2008 that the living room stereo became "high end." Until then it had been mainly used for TV sound at monthly movie parties.
I thought the Dynaco 410 might be a contributing factor so I had it refurbed in 2001. Despite my long time dedication to measuring instruments, I had no way of electrically measuring hum in line level signals. It's tricky and most DVM's don't do a good job with low level signals. I just knew there was hum at the output of the power amp. Refurbing the amp made no noticeable difference IIRC. It still has amazingly low hum and noise. It turned out the hum was being caused by my beloved D23, which itself needs a refurb. It's been sitting in my laboratory skandia shelving since then. I switched to using digital crossovers, first the Behringer DCX 2496. I now have a Meguro Noise Meter which can measure the lowest line level noises you can find in audio equipment with the required "A" rating.
Anyway, as soon as I started using a "real" subwoofer with a built-in plate amplifier, I no longer needed the Dynaco 410, and I always felt my other amplifiers were "better." I had been for some time using a Nikko Alpha III, just like we loved at Audio Directions. (That had been my stand in since selling all my tube equipment in 1991 before moving to Texas). But I decided I didn't totally like the sound of that either, and replaced it with a Parasound HCA-1000A which served as my bedroom amplifier until recently being replaced by a Parasound HCA-1500A which is even better. Dynaco 410 has nothing on either, except somewhat more power than the HCA-1000A.
When the Living Room System got serious in 2008, the first amplifier there was the Krell FPB 300, which went through various repairs. I had originally intended to get something cheaper, an Aragon 8008BB, but it seemed I missed my chance and then had a huge desire to get the Krell. Later, as the Krell needed servicing, an Aragon 8008 BB (and perhaps the very same one) came on the market, so I bought it. The Dynaco 410 has nothing on either of those amplifiers. The Aragon has the same capacity power supply capacitors, except 2 per channel, and somewhat larger transformer capacity. The bias is essentially user adjustable, you can crank it up to high bias Class AB+ like I have done and it then has less than half the distortion of the Dynaco. But at low bias settings, maybe around the official ones Klipsch posted, it is possible the Dynaco has lower distortion. I find it works better with about twice as much bias, and still stays between 120-130F at idle and never gets to 140F in hard use at the heatsinks, which I think is acceptable. It turns out you don't have to think about this too hard, they more bias the distortion, with the heat sinks being the limiting factor. And the Aragon 8008 BB has more heat sink than the Dynaco. I suspect technically the Aragon isn't as well designed as the Dynaco, but it has the advantage of better parts, and is more flexible meaning you can do more tweaking to it w/o completely messing it up. I bought it with aftermarket feet than made it very low, and this pushed the bias up because of self-reinforcing heat effects, to 140F. I put much bigger feet on it hoping to cool it down, but got more than I bargained for as the temperature fell to 100F and in this bias starved condition it had significantly higher distortion. I fixed that by cranking up the bias controls, back up to 120F or higher. I recall meeting one of the founders of Mondial, and he had put something on top of the amplifier to show it was possible AND to make it sound better (because it ran with hotter bias).
Now I use the Hafler 9300, which has essentially the same typical distortion level as the Krell, 0.002%, and with total reliability and simplicity and far less energy cost. I was unable to find a measurement other than power in which the Krell was notably superior. Even in damping factor sometimes the little Hafler edged out the Krell. Both of these amps have about an order of magnitude lower distortion than the Dynaco, and far wider bandwidth out to 300 kHz, which I do think is a good idea (but maybe not 3 Mhz). Things have improved a bit since the Dynaco 400 was introduced in 1972. Engineers know more, and it's not as much a challenge to design great amplifiers anymore either, because the transistors are much better, both bipolars and MOSFETs.
Bongiorno kept his subjectivist faith in every circuit detail being important, and nottesting or proving this faith with double blind testing. So he believed that linearity (and balance, if possible) had to be preserved every step of the way. The truth is, only monotonicity and not linearity is absolutely required in a feedback amplifier. That's why Class AB amplifiers even work, though in principle you could align the two sides for greater linearity than Class A, in reality that would probably take bias levels you wouldn't want to work with anyway. Absolute perfection is not required in every step, but instead good enough. The raved about TIM and SID type distortions in the end turned out to be the same old THD, though there are specific potential problems with intermediate stage clipping or slew limiting that a small number of high feedback amplifiers may have suffered from. So the no-holds-barred ultimate slew rate unlimited design by Matti Otala, the Citation XX, is beautiful but way more engineering than necessary to get decent sound. This fundamental knowledge has now been incorporated in every amp since 1980. Inexpensive Parasound amplifiers have boasted 50 V/us slew rate from the beginning of the company, and up from there.
Actually if you look at the GAS specs, they've been pretty commonplace since the 1980's., like 0.05% distortion (my Hafler 9300 is rated at 0.02%, and typically achieves 0.002%...not unlike CD players). Bongiorno success with Complementary Symmetry attracted many to the idea, but comparable performance was also attained by many other means, including the plain old quasi-complementary Bongiorno broke away from. GAS amps have notably low slew rates by more recent standards because Bongiorno wasn't trying to wow people with such specs. Slew rate is technically meaningless if bandwidth limits are reached first, and GAS amps also tended to have bandwidths less than 100 kHz, less than typical high end bandwidths since then of 300kHz and up. Bongiorno makes fun of Spectral amps with their 3 Mhz bandwidth. That means GAS amps didn't "need" super high slew rate to prevent TIM and/or SID. They weren't going to have it anyway because of the 100kHz bandwidth limit. And Bongiorno used proper termination networks, much like John Iverson, instead of being able to claim "no inductors in the signal path" as with Parasound. Either approach works fine, although Bongiorno and Iverson actually gain stability bragging rights by having extra stuff in the output circuit, which they then also lose because otherwise their amps are so more "bleeding edge" (and ultimate part degradations force frequent refurbs more frequently than other amps).
Now, out around 2000, Bongiorno was back at the top of the heap again for awhile, and perhaps even still, with the Ampzilla 2000, a much more advanced design than before (but still building on the ideas of the Sumo Model 9 that I heard the Bongiorno tout in 1981).
https://www.thefreelibrary.com/Son+of+Ampzilla+2000+Circuit+and+Measurement+Review.-a0133864374
However regarding the amplifier, I like the 100 watt output, the 2kW transformer, and it even looks like the Son of Ampzilla 2000 might not have a fan. Here in it's second incarnation, it even has very nice looking cast aluminum heatsinks on the sides! The price is about right for an amp in the High End category, but not for poor folk as I've become.
David Rich speaks to the Cut and Try amplifier stabilization and loudspeaker optimization techniques I thought I saw being used by Andy Hefley and Albert Von Schweikert. He does not like them, and points out that they won't work with complex balanced amplifiers like the Ampzilla 2000. Anything done to stabilize one servo or feedback loop may well destabilize the others. He believes that amplifier feedback loops, and especially servos, should be designed first on paper and then best verified with a computer simulation. He knows that Bongiorno used to use the pencil and paper method exclusively but started using computer simulation with these 2000 amplifiers. It requires an understanding of Control theory and it's subset Compensation theory specifically for feedback loops. Those that Rich calles Tweak audio designers do not understand such things very well must rely on Cut and Try and sometimes to their downfall. BTW, I'm a fully unqualified Tweak audio designer myself.
In the end, David Rich concludes the Ampzilla 2000 is the most advanced audio amplifier available (at the time). The Son of Ampzilla 2000 is a bit less, sacrificing some of the performance. But he also doesn't think anyone needs such a perfected amplifier.
Reading the description of the Ampzilla 2000, I can't help thinking that it sounds a lot like my old Krell FBP 300, which is also a fully balanced amplifier following the 4 criteria Rich mentions. (Hence the "Full Balanced" in the name.) And like the Ampzilla 2000, the FPB amplifiers are also two stage and have regulated power supplies for everything. And they have the differential servos, plus computer monitoring. I'm not sure if the second amplifier stage is differential, however. Honestly I think even Rich tends to over hype Bongiorno's originality. The downfall of FPB is that the top Class A plateaus should not have been used. FPB amplifiers can burn out their own transistors in an intermittent no-load condition (and some very problematic speakers like Acoustats) because the heatsinks cannot possibly absorb the maximum output of the power transformer (3kW in the case of the FPB 300) and remain below destructive temperatures. And Motorola quit making the transistors with nothing else of the required capability available in the same TO-3 case. I feel a bit guilty about this because I met Dan D'Agostino at a different audio society meeting in the mid 1980's. He had just produced a Class A amplifier with a fan, and I told him I wanted a fanless Class A amplifier that changed the bias level to stay in Class A all the time. Now I see it was a bridge too far. High bias Class AB is just fine.
I've also had the feeling ever since that D'Agostino was a gentleman who listened to his customers, like many of the best audio equipment makers, rather than talking down at them. But we all make mistakes.
One thing I personally don't like about many of Bongiorno's top amplifiers was the use of fans. An actual audiophile would appreciate the silence of having no fan, or fans only switched on only in extreme conditions. Of the GAS products, the only one I liked the looks of was the Son of Ampzilla, which had no fan either. But both the Son and the later Sumo Model 9 are a bit underpowered for speakers like my Acoustat 2+2's. The Model 9 has a fan too which I remember as being too loud for me.
I wish I knew more about the kinds of speakers Bongiorno used when and if he ever used speakers personally. (He admits to designing speakers for Rectilinear, though he hated the company's owner.) I would have placed Bongiorno in the Dick Burwen camp as a believer in loudspeaker and room correction via electronic EQ. And even in 1981 I remember thinking of that and that he probably didn't want to discuss such things in a room full of audio tweaks. He might have mentioned EQ in those talks but didn't dwell on it. Famously he refused to ever design a preamp without tone controls, which had become the standard audiophile thing by the late 1970's.
In his own words Bongiorno often seems to dismiss his audiophile admirers and customers as idiots. He was a musician and an engineer, not an audiophile as such. To him, designing audio amplifiers was a kind of mathematics in which he revelled, but without much touching the ground. And he wasn't that great as an audio consultant, partner or businessman, nor necessarily as an audio scientist either. He frequently become terribly monotonous because of endless and ridiculous self-promotion. He possibly might have had more stable work relations with psychiatric medication, like lithium (though at what cost to his creativity?). However he left us with a few (often slightly rough) gems and applied and pioneered if not invented many good ideas in audio electronics which have been useful and inspiring to many. Few can claim as much.
No comments:
Post a Comment