Keep It Simple
Sessionmaster Direct Recording Pre-Amp
The Sessionmaster spurns unnecessary extras best left to other effects units and concentrates on producing a quality DI guitar sound. Dave Lockwood approves.
The Sessionmaster is a 1U, 19" rack-mounting guitar pre-amp, suitable for stage or recording use. A speaker simulator filter is incorporated, enabling the sound of a miked-up amp/cabinet combination to be reproduced when recording DIed into a mixer input. From the same designer as the Session range of guitar amplification, the extremely compact unit is actually built-into a small sub-housing which occupies just the centre section of the rack panel. An external DC power adapter is employed, minimising induced noise, and keeping the chassis extremely light, but probably winning the unit few friends in live performance applications, for the standard DC power-adapter socket is, of course, non-locking.
This is a single-channel processor, with the minimum of controls, and no effects; this is the product of a design philosophy quite the opposite to that espoused by the designers of most guitar DI-recording devices. Essentially, this unit is simply trying to replicate a basic master-volume amp, no more, no less, leaving the effects to devices designed specifically for the purpose, and the choice to the user. Along the way, this concept makes the Sessionmaster simplicity itself to use, and also extremely economically priced.
The absolute minimum of active circuitry appears to have been employed; indeed, peering inside at the single, high-quality, PCB, I could find only two active devices! The simple, and familiar, bass, middle and treble tone control network is entirely passive, and the only other rotary controls are input gain and master volume. Just as in similarly configured amplifiers, you get clean sounds by keeping the input sensitivity kept low, whilst overdrive is achieved by cranking up the input gain and balancing the output with the master setting. In a valve amp, a different kind of distortion can be obtained by working the output stage hard, and there is some merit in keeping the master volume well up, but that does not apply here. The volume setting is merely for correctly matching the output of the Sessionmaster to the following input stage, whether that is a power amp, for a stage rack-system, or a desk mic/line input for recording.
A single 1/4" jack input socket is employed on the front-panel, whilst the rear of the unit offers two outputs, one via the speaker simulation circuitry and the other direct. Output sockets are stereo jacks, and will thus drive both sides of a pair of headphones, but will also work normally when a mono plug is inserted. There is sufficient output to drive high impedance phones to a reasonable level, and enough to directly drive a power amp to its full rated output. The speaker simulator socket, with its steeply-filtered HF replicating the roll-off of typical guitar speakers, is the output to use for headphones or recording. The direct output is there for use with a stage amplification system, where the signal will ultimately receive 'filtering' from the real thing, ie. the inherently limited response of large cone drivers.
Gain Boost, plus Mid and Bass Boost switches are incorporated, interacting with the passive tone control network. In normal operation the EQ appears to be pre-overdrive, for you can affect the degree of distortion quite significantly with the tone control settings. When Gain Boost is selected they take on a subtly different role; fed with a harmonically richer (post-distortion) signal, the treble and mid controls in particular appear to be more active, allowing the sound to be tuned without affecting the overdrive characteristic.
The Bass Boost control I felt to be just nicely voiced to give extra weight to the sound. On clean settings it balances the very bright top-end available; sucking out some middle at the same time gives the classic Strat rhythm sound (using a Strat helps here tool). The Mid Boost sounds like a fairly narrow-band filter, for my taste operating just a little too low in the spectrum. It is at its most useful lending extra fullness to the 'flat-out stack' sound produced with everything on maximum. At lower settings, and on more subtle sounds, I feel it results in an output where the mid range is too forward and a little too thick.
All the controls are usefully and predictably interactive, and the system as a whole also interacts well with the guitar — there are some excellent semi-clean sounds to be found at high sensitivity settings, by under-driving the front-end with a very low output from the guitar (this does require a guitar with no tonal loss at low volume settings to work at its best; mine are all modified with a compensating network across the volume control, as I do this a lot). This sort of gain structure is normally a recipe for excessive noise, but that is one thing noticeably absent on the Sessionmaster; it really is remarkably quiet for this type of device.
"If the Sessionmaster design brief was to provide an easily recorded guitar DI signal with a familiar interface then they have fulfilled it to the letter."
Even at high gain settings, there is less noise to deal with than from most normal guitar amplifiers, certainly less than from any system involving overdrive and distortion pedals feeding a sensitive input-stage.
There is also considerably less 'pick-up' (induced buzz and hum arriving via the guitar itself, subsequently amplified by the system as if it were signal). On many DI systems this is a major noise problem on its own, particularly if you have single-coil (non-hum-cancelling) pick-ups in the electronically hostile environment that most modern control rooms now present, with computers, monitors and digital gear all over the place. A very high level of compression, applied principally to achieve sustain, is normally responsible. The Sessionmaster appears to take a different approach; it seems to me there is no inherent compression at all beyond that applied naturally by the distortion. In DI recording, the unit consequently behaves much like an ordinary guitar amp at moderate volume.
If you want artificially enhanced sustain you will either have to apply compression externally, or better still, if you can, crank up the monitor level until you have some energy feeding back into the guitar, equating to the normal situation standing in front of a loud guitar amp.
Without pre-distortion compression notes do not 'explode off the pick', or hang on forever with unvarying timbre, but then nor do they on most amplifiers without output stage overdrive (valves at high volume), external processing, or both. If the Sessionmaster design brief was to provide an easily recorded guitar DI signal with a familiar interface where all the controls behave exactly as they would on a basic master-volume guitar amp, then they have fulfilled it to the letter.
"Like all good amplifiers The Sessionmaster retains much of the character of the input signal, even with heavy distortion."
The controls may be simple, but there is enough versatility there to make the Sessionmaster a highly flexible unit, the one reservation, particularly in live performance, being that there is no footswitch bypass facility. This is a single-channel unit, and a bypass could have been used to simulate a second channel — you set up a basically clean sound on an amp, and switch in the pre-amp for overdrive. Ganged switching could also be rigged, turning one processor on as another is turned off, from the same switch. Particularly in smaller recording setups, it is often necessary to record more than one type of guitar part to the same track, without necessarily being able to stop to change sounds.
Like all good amplifiers (valve amplifiers in particular) the Sessionmaster retains much of the character of the input signal, even with heavy distortion. The clear distinction between the brittle attack of single coils and the warmer tonality of a humbucker is preserved. Interestingly, a neck-position humbucker, which on many DI devices descends into mush, is still very usable on the Sessionmaster; rich, but with definition. Similarly, the complex waveform of the bridge/middle parallel pairing on a Strat, is faithfully reproduced. This combination, with Gain around 75%, Gain Boost off. Treble well up, and a little bit of middle knocked-out, is, to me, perhaps the best of all the sounds available via this unit.
Distortion quality is a highly subjective area and very personal to guitar players. No-one is likely to buy a unit such as this without trying it out first, but do try to ensure that you audition it in context. Listening to totally dry, unaccompanied distorted guitar is sometimes not all that pleasant, however good the system, and can be highly misleading.
Every DI-recording pre-amp design normally seems to have one area in which it is particularly strong. The Sessionmaster, however, seems to be more of an all-rounder. The deceptively simple control line-up by no means restricts the breadth of usage; the full-range from flat-out distortion to sparkling clean is all there, and able to be found with the minimum of fuss. There is also surely the additional attraction, to many people, of not having to pay for effects that you may already have. This product does precisely what it sets out to do, to a high standard, and at a highly economical price. Sounds like a recipe for success to me.
Sessionmaster Direct Recording Pre-amp £149 inc VAT.
Radius International, (Contact Details).
Review by Dave Lockwood
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