Single-ended tube amplifiers. Have you ever noticed how controversial this amplifier design is? You've probably heard opinions from both sides of the camp. There are those who focus on the strengths of single-ended designs which include phrases like: finesse, purity, wholeness, a more relaxed and easy presentation, a sense of organic realness to the music. Then of course, there are those people who are quick to point out the weaknesses which tend to be statements like ethereal, anemic, light, no grunt or balls and can't drive the loudspeakers that I want to use.
Having heard a number of low power single-ended amplifier designs, I
can honestly say that there is validity to both arguments. In general, most single ended tube designs are a combination of the above strengths and weaknesses. There seems to be a very easy, relaxed quality to these amplifiers and at the same time these amplifiers just cannot drive most
loudspeakers available in the marketplace. Their lower power ratings, usually between 3.5
to 8 watts or so, for the most part, just cannot provide the iron-fisted control required to "properly" drive most conventional
loudspeakers. This really puts these amplifiers at a great disadvantage because loudspeaker
matching becomes paramount. Not only paramount, but a major problem.
A useful option on this amplifier is the availability of a volume control that allows this amplifier to be used without a conventional pre-amp, as a single source amplifying device.
Design And Construction
This design uses zero feedback and also has high peak current delivery.
There is an automatic biasing circuit that eliminates setting the bias. The construction is dual mono on a single chassis. The Diavolo employs a tube (CV-378/GZ-37) choke regulated power supply preceded by pi filter. The output transformers are a novel split core type not normally associated with single-ended design and custom designed by Art Audio to give a wider band width than most generally available transformers. The tube sockets are ceramic with silver plated pins. The entire amplifier is finished in polished (non magnetic) stainless steel
chassis with gold plated transformer caps and name plate. The total power output is 13 watts per channel of single-ended power. The output
impedance of this amplifier is 6 ohms however special custom impedances from 2 to 8 ohms are available at no extra charge. The tube
compliment is a pair of each: 6DJ8, 12BH7, CV378, and EAT power tubes. This amplifier weighs a very heavy 60 pounds and is very well
The output transformers use thick solid core wire, as opposed to other designs that can be quite thin, and these transformer wires are soldered directly to the loudspeaker output jacks with no flexible end leads. This eliminates another piece of wire as well as another solder joint. This amplifier uses excellent ceramic tube sockets with the best grip of the tube pins I've ever encountered. The tube socket pins that hold the power tubes have extra thick metal to provide a better grip on the pins of the EAT power tubes. On the rear panel, there are two transistor heat fins that are most likely for cooling of the power tube heater voltage regulators.
How It Sounds
Art Audio wanted to produce a single-ended amplifier with some power, grunt and drive; an amplifier that would drive most real world
loudspeakers. They have succeeded. Let me first say that, this amplifier sounds fantastic. It has mass, drive and oomph. It certainly does not sound like a wimpy single-ended triode amplifier at all. Our esteemed editor, Steven
R. Rochlin, said of this amplifier in his review several years ago in Ultimate Audio magazine that the Diavolo sounds like a 50 watt amplifier. This is so true. This amplifier has incredible balls for a single-ended triode amplifier and in this regard, it smokes my Audionote Meishu 300B integrated amplifier. The Diavolo strikes an almost perfect balance between the light, airy and ethereal type of sound and the warm, dense more massive solid type. This is an extremely difficult trick to accomplish. Traditionally, most of the single-ended amplifiers that I have heard have great strengths in subtlety, finesse and purity. Their sound is very open and relaxed, but they do not have the energy drive to really move the music into the room. It's almost like the music is massless and lacks the solidity that I hear in live music. I'm not talking here about just loudness but a sense of texture and physicality to the music.
Too often amplifiers either produce the leading edge of the transients, the "bite", or they reproduce the roundness, warmth and body of that instrument. Very, very rarely is there an amplifier that can produce both. The Diavolo is such an amplifier. You can hear an example of this when you listen to the 24 carat gold compact disc of Frank Sinatra "Duets" from DCC. The last song on this CD is called "All the Way/One For My Baby (and One More For the Road)". On this track you can hear the attack as well as the phrasing and tempo changes of the piano, and at the same time hear the woody, resonant quality as well. You can also hear on this track a large amount of detail and subtlety. You can hear the warmth of the strings, the brushes striking the snare drum, the deep resonant stand-up base as well as the power and raspiness in the voice that is distinctively Frank Sinatra. Here is a great example that, with the Diavolo, you get the detail as well as the texture of the music.
The bottom line is that this is one fantastic amplifier. If you have reasonably efficient loudspeakers and like the finesse and texture that single-ended amplification provides, but hate the lack of drive and energy that most single-ended amplifiers produce, you're in luck. This could very well be your amplifier. The Diavolo combines the strengths of single-ended with the ability to drive most loudspeakers as well as the ability to give you the drive and "energy" of the music. It gives you, in one amplifier, both the detail and resolution as well as the warmth, texture, and emotion of the music. In short, it combines the resolution with musicality. Well done Art Audio.
Type: Transformer-coupled, zero feedback pure "Class A" triode stereo amplifier
Output Power: 13 watts per channel, two channels
Input Sensitivity: 350mV
Input Impedance: 380 Kohm
Output Impedance: 6 ohm (special custom impedances from 2 to 8 ohm available at no charge)
Frequency Response: 9Hz to 60kHz
Tube Complement Per Channel: 6DJ8, 12BH7, CV 378, EAT 32 or KR VV32B power tubes
Dimensions 18.25 x 13.75 x 10 (WxDxH in inches)
Weight 60 lbs.
Voice: (401) 826-8286
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