If you are looking for an authentic tube-amp guitar sound from a DI recording system, then maybe the Dark Blue's all-tube preamp and speaker simulation is just what you need.
Modelling guitar-amp solutions can work well for some styles of music, but there are occasions when only a real tube amp will deliver the sound and feel you want. Obviously there are plenty of good tube guitar amps and combos out there, but it is not always practical or desirable to use one. With their Dark Blue model, Emerson Williams have entered the market with a dedicated tube preamplifier that aims to deliver a genuine tube sound for DI guitar recording.
The Dark Blue uses tubes for the main audio path with solid state support circuitry where necessary and it also includes a speaker simulator circuit allowing the output to be DI'd in such a way that it sounds similar to a miked amplifier. It is not intended to emulate or replicate the sound of any particular amplifier but has enough flexibility of control to cover a wide range of tones, from clean to moderately overdriven.
While the tube circuitry of the Dark Blue is steeped in tradition, the physical presentation is much more outgoing. Perspex windows are set into the thick, aluminium front panel, and give a wide-screen view of the circuitry inside. The circuitry itself is mainly located on one large PCB and uses silver-plated relay contacts for switching, and gold-plated valve bases and valve pins in order to eliminate corrosion. The control legending is engraved on the inside of this window, and when the amplifier is powered up this is illuminated in blue via hidden LEDs — giving an impressively pimped-up appearance! When an amplifier stage is bypassed, its section of the panel goes dark. The marker-lines on the knobs are also picked out by blue illumination, which looks very stylish The only issue I have with this is that it isn't always easy to see at some angles.
The Dark Blue preamp is housed within a 2U rack format with lifting handles at either end of the front panel. These afford some protection for the controls if the unit is put down carelessly, though the rear panel knobs are somewhat more vulnerable in this respect unless the unit is flight-cased.
The input stage of the preamp is based around the less commonly used ECC88 double triode (in this case made by Tesla in Slovakia) in order to both maximise bandwidth and keep front-end noise to a minimum. This is followed by four ECC83 tubes, made by Svetlana, with the high gain version fitted as standard. Of course, all valves bring their own particular flavour to a sound, and the manual suggests that any users who feel the Dark Blue sounds too bright can fit an alternative, softer sounding tube such as Watford Valves' ECC83/5751.
The control panel is divided into three distinct sections. The Input Stage comprises the standard quarter-inch jack input for guitar and rotary controls for Dynamic and Gain. There's also a switch labelled 'Edge'. This produces a brighter tone and the manual recommends this is turned on for humbucking style guitars, and off for single-coil pickups. The Dynamic control is used to adjust the input impedance from 10kOhm to 1MOhm and tends towards a brighter, springier tone in the high impedance position. The Gain control sets the input stage gain but isn't intended to create serious overdrive effects — it is more about matching the input gain to the type of pickup being used.
Next comes the Tone section. This can be bypassed if it is not required, although I found all the best sounds were available with it in. When bypassed, the blue illumination LEDs for that section fade and the panel goes dark. Unlike most guitar amplifiers that have passive bass, middle, treble and presence controls, Dark Blue's EQ section is active and offers Low, Low/Mid, High/Mid and Treble. Both cut and boost is available, with the flat position being in the centre, and there's also a Bright/Dark switch that adds a bit more lower-mid warmth in the Dark position. Presence is generally applied in the feedback stage around the power amplifier and the lack of power amplifier in this stage would explain the lack of a presence control.
The third section is Drive and this too may be bypassed if not needed — though I again found the sound was best with this switched in, even if using very low drive levels for clean sounds. A Gain control sets the amount of drive to the following tube stage and can be used to create a moderate degree of overdrive for blues and lighter rock guitar sounds. If you need something really gritty, you can always put a suitable pedal before the input. Master volume does exactly as the name implies, but because the output stages produce a small amount of residual hiss even with the master volume turned all the way down, you get the quietest results by running with the input gain and master volume gain set fairly high.
A Loop switch brings in the rear panel effects loop circuit while Standby switches off the high voltage to the tubes but leaves the heaters running so the tubes can warm up gracefully. With the bypass switches in their up position, the EQ, Drive and Loop stages can be activated remotely via three switch jacks on the rear panel. These accept any standard latching footswitch though Dark Blue also offer an optional cordless remote footswitch.
The effects loop allows for mono-in, mono-out or mono-in, stereo-out effects to be connected via standard quarter inch jacks where the mix control knob varies from 95per cent effect when fully anti-clockwise to 5 per cent effect when fully clockwise. A further control allows the front panel blue lighting to be dimmed. I feel the Mix knob protrudes rather a long way and risks being damaged in transit unless the unit is fitted into some form of case.
The rear panel also plays host to the output connectors, which are stereo to accommodate stereo effects, though if no effects are connected you can just use a single output. For connection to an amplifier, there are standard unbalanced jacks, but for recording, the DI outputs first pass through a speaker simulator circuit and come out on balanced 600 Ohm XLR connectors. Apparently, the character of the speaker simulator was based on the performance of a Celestion Vintage 30 12 inch speaker in an open-backed cabinet, as this has a tight bass response when not fully enclosed and rolls off above 4kHz to clean up the high end.
Even the mains switch is slightly unusual in so much as it has three positions, one of which is Off and the other two On, but with a choice of grounding schemes. The left position is On with full grounding while right grounds only the chassis and may help to eliminate ground loop hum problems in some situations. It is recommended that full grounding be used where possible.
As with most guitar amplifiers, you have to take time to optimise the control settings to suit the instrument, and before you can do that you should leave the amplifier to warm up for half a minute or so before coming out of standby mode as this maximises the tube life. When I first set up the amplifier, using its DI outputs, I felt it sounded rather noisy, even with the master volume turned all the way down, but running with the input and master gains set fairly high made the noise level of the output stage insignificant. At higher Drive settings some amp noise is inevitable but this is no worse than from other guitar amplifiers at similar drive settings. Though I was using a Strat fitted with single coil pickups for most of my tests, I found I got the best results with the Edge switch turned on and the EQ adjusted to suit. I also found I needed to set the Dynamic control to maximum to get a lively feel from the instrument — I'm not sure of the benefits of offering a lower input impedance as, to my ears, it just dulls the tone and makes the guitar feel stiffer.
It's hard to ascribe a particular character to the sound, as there's no power stage to give it a class A or class B flavour and no power amp output transformer to interact with. In general, the tone is nicely warm and responsive, but with plenty of bite available when necessary, according to how you set the controls, though I felt the newly updated speaker simulator made it hard to get a really jangly rhythm tone. This is always a dilemma for designers as a speaker sim that lets through more high end can sound very raspy or 'fizzy' on some overdrive sounds. Perhaps incorporating a two position speaker character switch would have provided the answer? A practical workaround when recording clean sounds with the current model is to mix in some of the jack output signal (which doesn't have a speaker simulator) to add in a bit of high end gloss.
The lack of a power stage and its subsequent interaction with the speaker means you don't get quite the same low-end thump that a tube combo tends to deliver. But in a comparison with a modelling amp set to give a similar tone, the Dark Blue felt more natural and had an organic warmth the modelling amp couldn't match. If I had to be more specific about the sound, I'd say it wasn't too different to my all-tube Fender Champ, recorded via a good speaker similator.
DI'd overdriven guitar came through with no unwanted grit at the high end, and though it sounds unnaturally dry in isolation, you only have to add a little reverb or ambience and it comes alive in a very convincing way. The unit also seems to handle pedals well so if you need more distortion, you can put your favourite stomp box in front of it and have confidence that it will behave correctly.
When you consider the work that goes into designing and building a product like this, the asking price (while not exactly low) doesn't seem unreasonable. Of course, as every guitar player has their own idea of the perfect sound, it certainly makes sense to try any product out before you make up your mind!
My view is that the Dark Blue produces a good quality (albeit somewhat generic) tube-amp sound. In the context of recording this is by no means a bad thing, as you can use pedals before it and plug-ins after it to mould the sound in any way you want. I don't think the playing experience is quite as tactile as playing through a really nice small tube combo, as the speaker interaction of the combo contributes to the tone in a complex way. However, it feels better and sounds more organic than typical modelling or hybrid solutions, and most players should be comfortable with it.
The Mesa Recto Recording Preamp is in the same price bracket, but offers a distinctly different sound. To get a similar sound, the only real alternative is to use a really nice small tube combo, with a separate speaker simulator, but that could end up being more expensive and would certainly take up more space.