Power Amp

While the preamp in V2 Revelation is effectively identical to V1, the power amplifier is markedly different.

We redesigned the power amplifier and power supply from the ground up to make it the most flexible power amp on the market.

To start with, the power and output transformers are a completely new design. Both transformer were designed in house and custom made to our spec. They are double shielded toroidal  transformers (yes, even the output!) for ultra low noise, which we have load tested to 400W to ensure longevity.

Secondly, intelligent circuitry reconfigures the operating voltage of the amplifier to suit almost any octal valve type, including KT66, KT77, KT88, KT90, KT100, 6550, EL34, 6CA7, 6L6,  5881, 6V6, and 6K6. Just choose the correct tube class, follow the bias instructions and the amplifier takes care of the rest. Most amplifiers which offer tube swapping are really only designed to work for a particular type of tube. Substituting other types in these amps usually results in the 'under utilisation' of a larger tube's capacity, or pushing smaller tubes way past their spec. The Revelation is different, in that it reconfigures itself to work with the tube. So for example, the Revelation will produce a full 100W from a pair of KT88s, and no more than 20W with a pair of 6V6s. Please refer to the instruction manual in the resources section for a detailed list of tubes and their performance.

Output Power and Tube Configuration

Once you've chosen your power tube, there are a few different ways you can set the power amp's tone and performance. The first of these is the variable output power switch, located on the rear of the amplifier. By varying the internal high voltage applied to the tubes, it is possible to vary the output power of the amplifier between High, Mid and Low (which corresponds to approximately 100%, 60% and 30% for most tube types). This reduction in the high voltage also applied to the preamp tubes, so these settings not only affect the power amp section, but also the preamp. The lower the output power, the quicker the preamp tubes clip, and the more compressed the tone.

For each output power mode, there is an independent bias controls, so your can optimise the bias for each power level.

A further reduction of the output power is possible using the screen configuration Triode/Pentode switch. This not only affects the output power, but also the tone of the amplifier. The transfer characteristics of triodes is very different to pentodes, and the resulting tone is much 'softer'. The open loop gain of the power amplifier is also reduced in triode mode, making the power amp response much looser, and the presence and depth controls less effective. This is a great 'vintage' tone.

Presence, Depth and Feedback

The Revelation features Presence ad Depth controls to adjust the high and low frequency negative feedback of the power amplifier. In addition to this, there is a 3 position feedback switch which controls the amount of negative feedback

When the Feedback Level (F.B) is set to high, a large signal is fed back into the phase inverter. This has three effects. Firstly, it makes the response of the power amp very tight and controlled. Secondly, it makes presence and depth controls extremely active, so that their range is greatly increased. This is great if you intend on using the presence and depth controls for more radical EQing. Thirdly, it reduces the overall gain of the power amplifier, so you will hear a drop in volume. It then follows that when the F.B. is set to low, the response of the power amp will get a little bit looser, the presence and depth controls will have a reduced effect, and the output volume of the amplifier will increase slightly. This setting is the best setting for the vast majority of situations, and should be your first port of call.

Finally, with the Revelation, you have the ability to completely disable power amp feedback. This is done with the F.B. switch in the middle (off) position. In this setting, the power amplifier has no negative feedback, and so the presence and depth controls have no effects. In this mode, the inherent character of different types (and brands) of power tubes becomes very prominent, as well as the open-loop response of the output transformer. The sound is loud, bold and raw. It’s a great compliment to Channel 4’s Mid and High gain modes.

Option: Cathode Configuration

The cathode configuration option is great for people who need an amp that does everything. It nearly triples the number of power amp options, by introducing two new configurations besides the standard fixed bias. These are Cathode Biased and something we call Cathode dynamic.

The standard fixed bias configuration is the pushiest and 'toughest' sounding configuration. The sound is immediate. The tubes run cooler also, running in class A/B, and the amplifier produces the most output power.

The cathode biased configuration, sometimes referred to as push-pull class A greatly reduces the output power of the amplifier, but also changes the feel of the amp. While still punchy, it smooths the response of the amp and makes your tone, especially the clean, more dynamic.

The final cathode dynamic configuration is the quietest of the three, and also produces the least output power. The tone if VERY spongy and the amp has an extremely smooth transition from clean to overdrive. This is Michael's personal favourite for use with clean tones, especially with triode mode. As the amp is driven harder, it almost sounds like you have a compressor on! It also adds a certain complexity, swirl and liveliness to clean tones, with overtones in chords constantly pushing their way forward, then receding. It's something you really have to hear in person.

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