SixPac Tube Talk

Dennis Had, the founder and president of Cary Audio Design, speaks about his new SixPac amplifier design.

Dear Audiophile Friend:

Dennis Had - case of sixpacs

I am so excited and pleased with the new AE SixPacs amplifiers. I have spent countless hours designing and refining this very special set of monaural vacuum tube amplifiers.

On numerous occasions, my business partner, Billy Wright, warned me that we did not want to jeopardize the success of the SuperAmp stereo amplifier. "Are you sure you can deliver the same sweet and intoxicating sound of the SuperAmp in these higher powered mono amplifiers?" I must confess that the first renditions of the SixPacs did not come up to the sonic greatness of the SuperAmp stereo amplifier. This was going to be a tough effort to produce a sonic presentation equivalent to the lower powered triode class A SuperAmp. As soon as you gang up a bunch of tubes in parallel to produce more power, the end result many times is more power but at a cost of the sonic merits. In retrospect, I believe this challenge forced me to take a more conservative time frame approach. I mean, when I get excited about a conceptual product, I am flat out day and night designing. I can hardly wait to listen and in turn, get the product in production. The SixPacs actually started life back in November of 2000. I was hearing from the field that the SuperAmp maybe one of the best sounding amplifiers of all time. Some audio magazine reviewers were stumbling over descriptive words for the SuperAmp. At $1200 the SuperAmp is beyond comparison.

Quote from Marc Mickelson in SoundStage magazine June 2000

Now there’s a name that’s a mouthful, and an immodest one at that. Super Amp? Well, "super" can’t refer to power output because the AE-25 Super Amp puts out only 15 triode watts per channel. It can’t refer to the amp’s size because it’s small by high-end standards. And it can’t refer to the price because the amp costs far less than competing designs. No, "super" here comes from the amp’s creator, Dennis Had, the design mind behind AES and, of course, Cary Audio. Super Amp is sort of like Superman, a moniker that heaps respect and hints at special powers, all in one phrase. But can this little amp fly?

My good friend and audio golden ear, Bill Cowen, bought the first SuperAmp off the production line. Bill immediately fell in love with the sonic merits of this little gem. After a few weeks of listening, Bill told me the SuperAmp was creating a bit of frustration for him. "The sound is almost beyond comparison, but I need more power and more bass!" I responded, "Bill you always want more power and bass. In fact you always proclaim you can never have enough bass, give me more BASS man!" Sooooo, I proceeded to take two SuperAmp chassis and turn them into 30 watt mono blocs.

Kirk Owens, Quality Control and customer service manager - looking over one of the first vats of sixpacs

I tested the amps for good engineering parameters and did a brief listening session and into the boxes they went off to Oklahoma to Bill Cowens home. In my mind I thought, these amps don’t sound as good as the stereo version but they sure have more power. I’ll let Bill Cowen give me his thoughts on these quickly conceived mono blocs. Bill called me a few days later. He had gone through a weekend listening session with the SuperAmp mono amplifiers. His opening statement told the tale. "Hey man, these amps have power but they suck!" "You ruined the SuperAmp" "Mr. Had, (when he calls me Mr. Had I know not all is well) you need to spend more time on these, Where is the SuperAmp magic?" I exclaimed "Now Bill, these were only prototypes, I will spend more time on them."

Well more time indeed. In between multiple new Cary Audio products, both digital and analog, combined with a new line of Cary Audio cinema products I did manage to dedicate some time for the new AE mono amplifiers. On March 14, 2001, I completed fresh new drawings for a conceptual six tube mono bloc amplifier measuring close to the size of a six pack of beer, or soda, depending on your choice. Then in the early summer of 2001, I assembled the first prototypes. After a few weeks of refinement off I went to Audio Connection in Verona, New Jersey. John Rutan, the owner of Audio Connection had the opportunity to hear the first rendition. These early amps had a tube line up of six 6V6-output tubes driven by a 6922 driver with an EL-84 current source. John was amazed and attempted to steal my prototypes on the spot. The following day John asked what model number these beauties would carry. I told him I had not given this a lot of thought. He strolled around the amps for a few minutes and proclaimed, "call these guys six packs." "They have six output tubes and you made them about the size of a six pack of beer." Of course after I agreed with John, he wanted to know if his first pair were free for giving me the naming rights. Great fun on that trip to Jersey, for sure.

I am concerned I maybe loosing you. I just seem to get long winded when it comes to the SixPacs. To speed up the process I will bring you up to speed. On December 27, 2002 I did complete all the final drawings. The metal shop was now in high gear to complete the chassis, bottom plates along with the anodized aluminum front panels. I had completed the final circuit topology. Or should I say I thought I had all my parts in a row.

Inserting some NOS 12BZ7 hops tubes

The output tubes were EL-34’s and the input tube was a 6922 sitting on top of an EL-84 current source. With zero feedback in the circuit the SixPac delivered a conservative 30 watts at 1% THD. The sonic presentation was marvelous. Better than the original prototypes. Then along comes our Mr. Gregg Dunn. Gregg is the national sales manager of Cary Audio Design. I have a difficult time keep Gregg out of my lab. He seems to have a propensity for finding last minute changes. Keep in mind the silk screen art had already been completed and the chassis were complete. Gregg wanted me to substitute a 12BZ7 tube in place of the 6922 on the input. I asked Gregg where in the world he came up with that tube. "Oh, years ago I used to use the 12BZ7 in place of 12AX7’s in my audio gear." I rolled my eyes, "Gregg, the 12AX7 is not even similar to a 6922 let alone a 12BZ7." Gregg’s response, "come on now, didn’t I give you the Cary V12 and Rocket 88 ideas?" He always gets to me with his ideas that worked. I dare not mention the hundreds of "Gregg ideas" that were deep in the green trash barrel. I recorded all my test data from the spectrum analyzer on the "final" production SixPacs. It was now about 6:30 PM in the evening. I proceeded to rewire the tube socket filament pins to accommodate this strange, 12BZ7 sync-amplifier television tube. Changes need to be made on all voltage and current passive components to operate this high-mu twin triode. Along about 8:00 PM the same evening up came a SixPac with a 12BZ7 input phase-inverter tube. Did it work? You bet! The SixPac was now producing 30 watts output at .25 % THD and cruising along at 50 watts output, full bandwidth at .55 % THD. The SixPac amplifier was now ready for some serious listening. The following day I configured another SixPac mono-bloc to the 12BZ7 as well, for a stereo pair. The sonic merits were not subtle. This was an elevated presentation above the 6922 front end. The greater power was not as evident as the inner detail and layering of the music. The sound stage had also grown many times greater in width. The SixPacs were now producing absolute "world class" sound.

Billy Wright, CFO of Cary Audio Design -
checking the ingredients for profitable brewing

Gina Wolff, ready to enter your SixPac
order with the brew master

This listening session extended long past the usual business hours. I now had a difficult decision to make. Do I go with a NOS (new old stock) tube in a new product. There is a rule that my partner, Billy Wright, and I follow as a corporate policy.

We will not use NOS tubes unless there is also new production equivalent available. Well, lets just listen with some 12AX7’s. The 12AX7’s sounded great as well. Not as much slam and inner detail but wonderful as well. Then I recalled a sales pitch I received from the good folks at Electro-Harmonix (SovTek) during the CES show in January of 2003. They gave me a few sample 6072A/12AY7 new production tubes. These were mainly targeted to the musical instrument amplifier market. I raced to my lab to recover those high-mu triode samples. Instead of testing them I just plopped them into the socket on the SixPacs input section. Another winner indeed! Through this entire 24 hour period, our "mister 100 idea a week" man, Gregg, was calling tube distributors to check the availability of NOS 12BZ7 tubes. He came into my office about 7:00 PM that second night, with the great news. "Dennis, we can flood the earth with NOS 12BZ7 tubes." "Look at the quantity I have located in the last few hours" This new level of excitement along with Gregg’s persistence got to me. In a matter of 15 minutes we had 500 of the 12 "Blond Zebras" (12BZ7) ordered and in route to the Cary "toy factory". From a technical view point what had occurred with the 12BZ7 verses the 6922 was a much greater voltage swing into the EL-34 output tubes with a lower distortion value in the usable swing. The best of both worlds. A better application of a driver stage for the SixPacs along with new production availability of the 12AX7’s or the new 12AY7 vacuum tubes. GREAT FUN INDEED!

Thank you so much for your interest and support.

Dennis J. Had
Triode Brew Meister