ขออนุญาต ถามคุณ LN Audio และทุกท่านครับ
เกี่ยวกับกำลัง ของหลอด 845 เท่าที่ค้นหาดู PD= 75W เอง แล้ว ทำไมแครี่ ถึงคุยได้ถึง 50W แบบA2 ทั้งๆบอกว่า ประสิทธิภาพดีขึ้นมา (ที่ 50%เท่านั้น)
และ ถ้าไม่เป็นการรบกวน ขอช่วยลงวงจรเฉพาะภาคเอ้าท์พุท ของA2 ให้เป็นวิทยาทานด้วยนะครับ
ขอบคุณครับ
http://www.stereophile.com/amplificationreviews/740/index7.htmlSam Tellig wrote about the CAD-805 in March 1998 (Vol.21 No.3):
It takes courage to buy an amp
the Cary CAD-805Cso retro in its technology and its look.
"You bought those," my friend Pavel said, referring to the CAD-805C monoblocks in my listening room. "Wait till I tell my friends back in Russia. We couldn't wait to get rid of tubes."
Ha-ha-ha.
Or kcha-kcha-kcha, as they say in Russia, there being no h in Russian. It is thus that Handel, Haydn, and Horowitz are transformed into Gandel, Gaydn, and Gorowitz. And Dennis Had, President of Cary Audio Design, becomes Dennis Kchad.
"Audiophiles in Russia know all about Dennis Kchad and the Cary CAD-805C," I assured Pavel. "In fact, Audio Magazine in St. Petersburg said that Cary is real high-end."
As Pavel continued to chuckle, I invited him to take a seat. With the amps well warmed up, I played a recording of Tchaikovsky's Symphony 4, with Gennady Rozhdestvensky conducting the London Symphony (IMP Classics PCD 867). Pavel stopped laughing.
"It's amazing," he said. "You're right there."
This is one of the pleasures of owning a pair of CAD-805Cs: playing them for Pavel. Or Slava, or Lev, or whomever. Hearing is believing, at least for some audiophiles. Audio critics are another mattersome have even taken to ranting against single-ended triodes.
There are just three tubes in the CAD-805C: a 6SL7 input tube, a 300B driver tube, and an 845 output tube. The 845 has a thoriated tungsten cathodethe tube glows white. A pair of them will light up a room enough that you won't stumble around in the dark.
Now supplied with new Western Electric 300B driver tubes as standard, a pair of Cary CAD-805Cs retails for $8995 (footnote 1). Cary claims the 805C will deliver 50W into 4, 8, or 16 ohms, and there are separate sets of speaker terminalsie, output transformer tapsfor each.
The tube complement has changed since the Cary 805C was introduced at the Las Vegas CES in January 1991, a year before the amp actually went into production. Then the output tube was the 805, hence the amp's name. The output tube has changed but the name hasn't. And the driver tube was an EL34 instead of a 300B. By the time Dick Olsher caught up with the amp two years later in the January 1994 Stereophile (Vol.17 No.1, p.104), the driver tube was still an EL34 but the output tube was a 211, as it was until the 805C of January 1997.
Dennis Had, designer of the amp, describes the power as "pure class-A1" up to 28W, and "class-A2" up to 50W.
Class-A2 takes over where class-A1 leaves off. The circuit's efficiency is increased by nearly 50%. Dennis explains:
"With only a capacitor coupling between the 300B and the 845, the output would be limited to 21-25W. The grid of the 845 goes down to a low impedance and you can't drive it any further. Unless..."
"Unless...?"
"Unless you use an interstage transformer. This transforms the impedance of the 300B to drive the grid of the 845 output tube. When you play the amp loud, it will draw positive grid current driven by the interstage transformer. The interstage transformer makes the amplifier circuit very efficient."
In other words, the cathode-based 845 tube draws no grid current in class-A1. Drive the amp harder and the 845's grid goes positive, drawing current via the interstage transformer that couples the 300B and the 845. With class-A2, however, comes increased distortionone reason to avoid highly inefficient, difficult-to-drive speakers with the Cary CAD-805C. Nevertheless, with the CAD-805C, you're far less limited than you are with a single-ended triode amp using a single 300B output tube, where you're limited to around 10-12W max.
But power ratings can be misleading, especially with single-ended triode amps. Compared to a typical 50Wpc stereo tube amp, for instance, the CAD-805C sounds big. Humongous, in fact. As Pavel heard, you do get your $9k worth of sound.
