Hughes & Kettner Tubeman Preamp
This dedicated guitar preamp benefits from hybrid tube circuitry, an integral speaker simulator and the ability to impersonate four quite different styles of amplifier.
This has to be one of the most versatile guitar preamps around, its tube circuitry offering a choice of Rock, Blues, Funk and Jazz voicings with comprehensive EQ and speaker simulation facilities. Paul White tunes in and turns on.
Over the past couple of years, there has been a spate of guitar preamps that include speaker simulator circuitry, making them ideal for DI recording, but like the guitar amplifiers they emulate, each one has its own character. It isn't always easy to put your finger on exactly what parameters are responsible for the differences in sound between various guitar amplifiers. In hi-fi or PA, an amplifier is simply supposed to make the input signal larger without changing it in any way, but when it comes to the electric guitar, the amplifier plays just as important a part in shaping the sound as the instrument itself. This is especially true of overdriven rock sounds. You might think that amplifier overdrive is simply a matter of driving too much signal into a circuit so that it distorts, but different circuit designs distort in quite different ways, and valve circuits seem to do so more gracefully than transistors or ICs. To further complicate matters, the distortion isn't all added at one stage in the signal path; in a guitar combo, there are various places in the preamplifier where distortion can be created, while the amount and type of EQ applied before the signal is distorted makes a huge subjective difference to the sound.
Once the sound has passed through the preamp, further overdrive can take place in the power amplifier stage, and in traditional valve amps, the output transformer and the way in which it is electrically coupled to the speaker has a significant influence.
And then there's the speaker itself, which not only acts as a low-pass filter, removing the buzzy high-frequency harmonics, but also adds distortion at high levels as the cone vibrates, bends and rocks in its mountings.
With so many variables, it becomes easier to understand the complexity of simulating all these subtle effects in a recording preamp. Not only must the preamp and power amplifier distortions be emulated, the way in which the loudspeaker and cabinet colour the sound must be taken into account too. The speaker simulation circuitry in most recording preamps is based on active electronic filters which provide the correct degree of high frequency roll-off, though few seem to go so far as to try to simulate the speaker distortion. A well-implemented design can come surprisingly close to the sound of a miked-up stack or combo — all that's needed is a little reverb to complete the illusion of space. And while the purists may still prefer to mic up their favourite amp in their favourite room using their favourite, esoteric studio microphone, there's no arguing with the convenience of a recording preamp, especially if you have restless neighbours!
Hughes and Kettner have just launched the Tubeman, a stomp-box style preamp that can be used on stage in conjunction with just about any amplifier and speaker system, or can be plugged straight into a studio console via its speaker simulator output.
Unusually for a valve processor, the Tubeman runs from an external power adaptor, which suggests that the valve is being run at a lower than usual voltage. The remaining circuitry is solid state. Constructionally, the Tubeman is very solid, being fabricated from heavy sheet steel; the circuitry is mounted on two glassfibre PCBs and is very we supported. Four jack sockets and the power adaptor input adorn the rear panel, while the control section comprises four rotary pots, a four-position rotary switch and a pushbutton. A footswitch is provided to switch the unit in and out of circuit when used in conjunction with a regular guitar amp.
The concept behind the Tubeman is both simple and ingenious; the rotary switch selects between four basic sound characters and the remaining Gain, Mid boost and three-band EQ controls can be used to shape the sound. A master level control allows the level coming out of the Tubeman to be balanced against the bypassed sound.
For recording, the unit has a separate output processed via the same circuitry as used in the H&K Red Box speaker simulator. This output is muted if the bypass switch is operated. For use with a guitar amplifier, there's an unfiltered line output and a line level output for use with conventional power amplifiers.
The key to the Tubeman's versatility is the selector switch, which offers a choice of Rock, Blues, Funk and Jazz tones. The Rock and Blues tones permit varying degrees of overdrive to be added, while the Funk and Jazz settings are essentially clean with just a hint of ragged edge as the gain is turned right up. As I was mainly interested in how the unit performed in the studio, I used the recording output and tried the machine straight into the mixing desk most of the time, though it does sound just as good plugged into a guitar combo.
The Rock setting is very versatile and can be varied from almost clean to very dirty indeed using only the Gain control; the sound is nicely aggressive without being too edgy, and with a little reverb, it really does sound like a miked-up combo or stack. Using the Mid Boost button produces a warmer, more powerful sound, while the EQ section behaves in a similar way to those found in typical valve amps and has plenty of range.
Switching to Blues gives a less distorted sound with a degree of valve compression and a nice, harmonic sustain. Even on maximum Gain, the level of distortion is relatively mild, producing a clear, singing tone. If you're a fan of those half-dirty, half clean blues sounds that really react to picking intensity, then you'll love this setting.
"The Rock setting is very versatile and can be varied from almost clean to very dirty indeed using only the Gain control; the sound is nicely aggressive without being too edgy."
Moving round to the Funk position produces a rich, percussive clean sound with what appears to be a degree of tube compression. As the title suggests, this is fine for funk music, but with a few careful EQ adjustments, it can form the basis of a number of rather nice clean tones ranging from warm to biting. If you're in search of a classic Dire Straits or Dave Gilmour clean tone, then this is a good setting to try.
Finally, Jazz. Yes, it does produce that warm, articulate sound you associate with semi-acoustic guitars, but it isn't limited to George Benson impressions by any means. The sound has a wonderful tube warmth to it and again feels compressed so that it sustains nicely. Once again, EQ lends the basic tone a fair amount of flexibility and you could squeeze anything from Shadows to mellow Pink Floyd out of this voicing.
My only criticism of the Tubeman, other than the fact that it makes me want to spend more money, is that I can imagine settings that fall between the blues and Rock voicings that can't be achieved with the limited pickup output from my Strat. Being an old hippy, the Blues setting feels the most comfortable to me but there isn't quite enough gain available without digging out one of my trusty humbucker guitars. Trying to achieve the same thing using the Rock setting doesn't give quite such a sweet tone. Other than that minor and admittedly personal whinge, the Tubeman performs beautifully, with an acceptably low level of background noise.
The clean sounds are also very authentic, without that sterile hardness that solid-state amps too often produce. What you get is a warm, yielding sound that responds as you play into it — very natural. In fact all the settings are so appealing that you find yourself saying things like "Wouldn't it be nice if you could switch from one setting to another", or "If only they'd made it programmable!" But that would be another product altogether.
For instant electric guitar sounds, regardless of style, this little box comes out as one of the best, and while setting up the sounds on stage could take a little knob twiddling between songs, in the studio it's no problem at all. If you need something that will suit 99% of the guitarists who use your studio, then this has to come close. Simply add a touch of reverb and voila: instant rock guitar — or blues — or funk — or jazz!
Hughes & Kettner Tubeman £269 including VAT.
John Hornby Skewes & Co, (Contact Details).
Review by Paul White
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