Valve or Tube Amplifiers from Unison Research
Valve or Tube Amplifiers
Valve or Tube amplifiers are a relic from decades ago, using technology that ought to be obsolete, but can have a wonderfully smooth relaxing sound that is rare from a transistor amplifier, even when driven hard and can drive almost any difficult load (e.g. electrostatic speakers) They often have far lower power than similarly priced transistor amplifiers, but they can be turned up without unpleasant distortion.
Many valve/tube amplifiers use the EL34 valve as the main power amplification stage (same valves as used in Marshall stage amplifiers loved by so many rock groups of the 1970s), which are readily available either as "new old stock" or as newly manufactured valves from expensive audiophile companies in America or from the Ukraine. The Unison Simply Four is just such an amplifier that despite it's low power rating is an excellent alternative to a high-end transistor amplifier. It was designed and built in Italy, with beautiful wood features and exposed valves.
Unison Simply Four Valve or Tube Amplifier Review
Unison Simply Four Valve Amplifier Review
Unison Research valve amplifiers look wonderful, which could be justification enough to buy one and the Unison Research Simply Four is no exception. But when you turn it on there is more reason with a faint glow of orange from the valves and the fantastic smooth sound - actually you have to wait for it to warm up before it starts sounding good. If you like vinyl you probably won't mind the slight delay (a few minutes to sound good and half an hour to sound excellent) because vinyl is hardly the most immediate of music formats, but I also use my Simply Four for my home cinema system, powering the front speakers and when listening to CD or even MP3.
Unison amps are visually striking, designed in Italy and extremely well made. The Simply Four has huge heavy transformers across the back and making up most of the bulk. The four EL34 power valves protrude vertically in front, through a metal plate, with the three valves that form the pre-amp stage in front of those. Wooden trim in front and on top of the front section add to the visual effect.
Tube Amplifier Books
Unison Simply Four Valve (Tube) Amplifier Specification
There is also a Simply Two with just two EL34 valves and a Simply Six with six.
Maximum Output Power: 12 watts RMS
Maximum Power consumption: 200 watts
Configuration: Triode Pure Class A
Input Impedance: 47 Kohm/100uF
Output Impedance: 4 ohm or 8 ohm (choice of outputs)
Valves (Power): 4 x EL34(6CA7)
Valves (Pre-amp):3 x ECC82 (12au7)
Weight: 22 kg
What does The Unison Simply Four Sound Like?
From my many auditions of tube/valve amplifiers versus transistors I certainly prefer the sound of valves, but would probably admit that you have to pay a little more to get the same measurable sound quality i.e. clarity, stereo image, detail etc. and certainly a lot more to get the same power, but this is perhaps the beauty of valves: When driven hard, close to full power, they do not distort in a harsh way. Transistors "clip" if a transient pushes the capabilities of the power-supply to the limit whereas a valve distorts nicely so a transistor amp needs to be far more powerful. Valves can also drive difficult loads such as speakers that have variable input resistance. I use mine with Martin Logan Electrostatic hybrid speakers with no problems at all.
The Unison Simply Four has a smooth sound, as you might expect from valves, but still manages to handle transients well and gives a good deep bass, detailed treble and a very good soundstage (with appropriate speakers) The stereo image can be quite stunning, with individual instruments and voices isolated. Valves are often described as giving a "warm" sound, which might just be a nice way of saying that they don't have a very flat frequency response, but in the case of the Unison Simply Four the output seems like it has a pretty flat response and yet still gives a pleasant relaxing sound with most music. Obviously this will depend on the speakers and the source too. Matching my amplifier with electrostatic speakers may help: the "warm" nature of the amp. perhaps offset by the slightly clinical nature of the Martin Logan Electrostatic speakers.
Where to Get Tubes/Valves
Valves (Power): 4 x EL34 or 6CA7
Where to Get Valves (Pre Amp Stage)
Valves (Pre-amp):3 x ECC82 (12au7)