Consonance J400 Integrated Tube Amplifier
A very good sounding, well designed 300B amplifier at a bargain price.
Reviewed by John Rivers
The Consonance range of amplifiers are the products of the small Chinese hi-fi company Opera Audio. Opera Audio manufacture a range of valve amplifiers for the hi-fi market and sell their products mainly in China, Taiwan, Germany and the USA. The company, which was founded in 1994, is led by two enterprising and dedicated (or should that be fanatical?) audiophiles, Liu Zhao Hui and Ma Wei, who are both in their early thirties. Liu Zhao Hui and Ma Wei have adopted as the basis of their design principles the classic tube designs and construction methods that were pioneered by Western Electric and others in the 1930s. Occupying pride of place in their product line are several amplifiers based on classic tube circuitry, using the amazing 300B tube in the single ended, parallel single-ended and push-pull pair modes.

The J400 is an integrated amplifier, offering three inputs, CD, Auxiliary and Line, a volume control and 18 watts per channel of parallel single-ended 300B power. It is a hefty unit. Think twice before lifting it. It weighs a solid 30.5 kg, or close to 75 lbs in the old numbers. Most of the weight is in the transformers and most of the transformer weight is in the two output transformers. Opera Audio have obviously taken a lot of trouble over the design and manufacture of these key items. They use selected silicon steel in c-cut form. They wind the primary and secondary coils in the same direction so as to achieve close coupling. Most manufacturers wind one clockwise and the other counter-clockwise. They use traditional paper and varnish for coil insulation and not plastic and apply traditional damp proofing techniques. The transformers are impressive to look at under their steel covers, but even more impressive in their ability to deliver smooth, solid, and musical deep bass sounds.

The J400 is built on a steel and stainless steel chassis. Good quality components are used. Inside electronic components are of high quality and most parts are heavily soldered on to tag boards. A particularly family-friendly feature is the solid state power supply and soft start. The J400 is one of the few 300B amplifiers which is suitable for non-audiophile family use. Switch on uses one switch. After a minute or so of delay, and after the 300B heaters have warmed up, the main high voltage turns on with a soft click. Select your source and go.

On the outside the J400 is quite well styled. The main base of the amplifier is shiny polished steel, the low sides are polished wood, the transformers are housed in a black crackle finish cover and curving over the complement of tubes is a perforated cage, again of black crackle finish steel. On the front are two solid steel knobs, the power switch and an LED, and occupying pride of place in the centre, an ammeter for measuring the bias current for each of the four 300B tubes. The overall look is decidedly retro. The J400 has a solid, dependable look, it's going to be on your hi-fi shelf for a long time, it's an investment. You want to know how a well-heeled hi-fi fanatic felt when he bought a Marantz in the 1950's, buy a J400 today.

The circuitry combines the new classic with the old classic. At the input end is a 6DJ8 tube with the two halves of the double triode arranged as a shunt regulated push-pull pair. This piece of classic tube design only came into use after tube amplifiers had departed from the dealers shelves. It's an innovation that came out of the work of Japanese tube fanatics. From this pair the signal goes to the Alps volume control and on to a 6DJ8 voltage multiplier which drives paralleled 12BH7s (another modern audio classic) which in turn drive the parallel pair of single ended 300B output tubes. The output pair are classically configured, without feedback, and they deliver the classic 300B sound.

The parallel pair of 300Bs gives a healthy 18 watts of output. This is a very nice feature. A single 300B is usually rated at 7 watts. This is mouse power and it makes speaker choice highly restrictive and very problematic. Lifting the output to 18 watts gets the power monkey off your back. In an average size listening room 18 watts will do very well with speakers rated at 89 dB efficiency. These are not too hard to find. I know. I have my own home built single 300B amplifiers and I used Lowther speakers for eight years, committing some criminal acts on my ears and justifying it all by appealing to the mystic virtues of back horn loading. No more. Diatones in reflex boxes will do all that Lowthers do and better.

So how does the J400 integrated 300B amplifier sound. Liu Zhao Hui and Ma Wei have done a very good design and build job. The J400 sound is very sweet and pleasant in the classic neutral 300B way. The whole sound range is very well reproduced. The bass is exceptionally clean and well defined for a single ended amplifier. The impulse response is also good which helps makes the bass sound very realistic with percussion and drum instruments. The bass is °«—

Copyright© The Opera audio Co.,Ltd