Last week my beloved Great American Sound Ampzilla amplifier overheated. The lounge began to smell of hot linen. At first, I thought my sense of smell had gone wonky again. My sinus allergies can cause strange smells from time to time. So I took some antihistamine and started the air-con fan to filter out any particulate that might be about. A half hour later, the smell was still about unabated so I started checking for overheated electrical things in the lounge. I found Ampzilla with a high case temperature and no air flow up the chimney. Very odd since the fan is a Rotron Boxer powered off the line. What to do, have Ampzilla refurbished or purchase a modern replacement? More after the break.
First some history then some market survey and reviews.
Great American Sound
Ampzilla was born as an article for Popular Science Magazine that I read back in the day. I heard one in 1974 or was it 1975 at Stereo Lab in New London, Connecticut. With deployment pay backed up in the bank account I bought one after many hours of listening in the lounge at Stereo Lab. With GAS Thaedra Preamp and KLH Model 9 Electrostatics or Magneplanar Tympani loudspeakers, the sound was glorious so I bought one. I wish I had also bought the Thaedra matching preamp at the time. Together the two produced a rich midrange and wonderfully detailed sense of space. And a working Thaedra is also collectable.
Ampzilla has served me for over 40 years and has run continuously for the last 20 or so. I was always too lazy to turn it off and the inrush current is wicked. In 1997 or so, I shipped the amp to GAS Works out on the northern prairie where it was repaired (drivers oscillating on startup) and refurbished (new caps, culled transistors, resistors replaced where needed, etc.) and returned to me.
Ampzilla is one of several storied amplifiers designed by James Bongiorno  and built by SAE, GAS, or Sumo. The GAS product line was magical at the time and holds up well today.
Ampzilla is collectable. An operable one in good condition sells for $4000 on E-Bay. Mike Bettinger near me here in Virginia is perhaps the best tech working on GAS and SUMO products and Dave  recommends him for GAS service. Given Ampzilla’s collectable status, I’ll probably keep it for eventual restoration. Mike’s fee is $1400 prix fixee. Whatever it needs. Mike understands the circuit, maintains replacement transistors, and has the skills and test equipment needed to do circuit level repair of these amplifiers.
When I took the amp out of the rack, I discovered that the fan was free to turn and not frozen by bearing failure as I had suspected. The amp has a mains fuse on the back and speaker protection fuses on the front should the output stage fail off balance. It may also have fuses for the fan internal to the amplifier. I suspect that a fuse may have opened causing the fan to stop. The amplifier has 40 watts of standing bias allowing it to operate Class A at sane listening levels and Class AB to rock out. The standing bias overheated the amplifier.
Once long ago, I accidentally blocked the chimney by sitting the operating amp on a shag rug for a while. It got warm but not smelly warm. I’m suspicious that the power transformer has failed. If so, this is something I can’t fix and the amp must go off to Mike for repair as he has them or can order modern replacements. The amp weighs 60 pounds of which over 50 are the power transformer. James was serious about 200 watts per channel both channels driven into 8 ohms.
Suspecting the transformer and knowing that the amp would need a through check out by an experienced tech, I decided its revival was not a DIY project. So I elected to purchase a modern replacement for use in the interim or perhaps permanently.
Schiit Happens 
Along the way, I had seen mention of Schiit Audio on YouTube and the Interwebs. I got curious and Google led me to Reference 3 at Head-fi.org. Schiit does what little it does in the way of marketing via Head-fi. And Jason Stoddard, one of the owner-partners, had written a memoir which he distributes there and sells on Amazon. Jason is a SF author with award winning stories and several novels in print so I snagged his memoir and gave it a read. Interestingly Jason began his career in aerospace electronics, got bored, and jumped to Sumo where he earned his audio spurs. He was there after James Bongiorno had moved on and is unfamiliar with Ampzilla. James was a gifted audio design engineer but a miserable corporate partner and manager. Bongiorno’s companies were always a bit rough at the business part. Sumo designs were hard to manufacture with a low yield of working units off the line and high warranty service costs. Jason set out to fix these problems by verifying the circuits, simplifying the product line, organizing parts stocking, simplifying the in shop work flow, and doing proper receiving and construction QA making the business profitable.
After a while, this thing called the Internet came to be and Jason left audio for several years to start a marketing and web design company. Some years later, he and Mike Moffat (Theta and Theta Digital) crossed paths and talked each other into returning to audio as partners in a new company that would start out in quality yet affordable personal audio and go where the market took them. Schiit came to be. Their first products were designed to sell at $99 to catch those entering the market and those wanting good sound at work. Today, these two products still produce one-half of the company’s revenue.
Why the Schiit Audio Vidar
The company started with an entry-priced DAC and headphone amp that quickly developed a following. With discipline, the company was building $99 kit in California that it could sell direct to the end user at a profit. It built a following at the Can Jam personal audio shows and word of mouth. The partners reinvested the profits to make more refined personal audio.
After a while, Jason was jonesing to make a speaker amp and came up with Vidar, a modern interpretation of the fully differential complementary symmetry Class AB amps like the GAS and SUMO designs but with microprocessor thermal protection and bias control.
And it was good. Steve Guttenburg, The Audiophilliac, has reviewed Vidar favorably in print and on YouTube and particularly likes they way the pair with the Magnepan LRS, a speaker I lust after.
John Darko has also reviewed both the Aegir and Vidar amplifiers favorably. He likes Aegir with Klipsch horn loaded stand mounted speakers. To John’s ears, the Aegir is a little more detailed and refined with the Klipsch horn tweeter than Vidar.
Vidar is a better mate for inefficient speakers like my Dhalquist DQ-10s and my objective speaker, LRS or Maggie 0.7’s. John keeps both Aegir and Vidar in his inventory of reference kit and one or the other can be seen in one of the lounge systems.
Based primarily on the Steve Guttenberg reviews, I ordered Vidar having heard Maggie SMGs and knowing that the Maggie LRS had similar efficiency, imaging, and voicing to my current Dhalquists. And knowing that Maggies were on my bucket list. Either speaker is quite revealing of amplifier voicing and imaging.