FUSION2
Revolutionising guitar sound with vintage tubes and modern op-amps.
The Revolution
Fusion 2 is not just another amp; it's a revolution with its unique approach to tone control, or rather, the absence of it. With 16 volume controls and no tone controls, it lets you shape your sound in ways previously unimaginable, ensuring the guitar, not the amp, takes centre stage.
Fusion 2 - It's Different!
Lately, I’ve come to the realisation that I might not be able to keep firing on all cylinders long enough
to design and market the several designs that I wanted to put out there. Don’t get me wrong, I’m in great
health now, at 82, but who knows in a few years – will I still be making kit at 90? Somehow, the thought
of me drooling onto the soldering iron seems a bit pathetic...
Over the past two years I’ve been looking with new eyes at a preamp I designed in 1975 that I hoped
would revolutionise guitar amplifier design! While everyone agreed that it was unbelievably good, the
general feeling was that with 9 tubes, it was way too expensive to produce! Right... forget it. But with
modern technology “too expensive” is no longer a barrier. Now, we have op-amps, and while these are
solid-state, they are used in a way that controls the sound without affecting the waveforms in any way, so the tube channel remains pure tube – and they cost much less!
Yet Another Guitar Head – What’s So Special About This One?
My successful Kickstarter project two years ago, was intended to get funding to set myself up for small-
batch manufacturing. The reward I offered was a limited edition of a practice amplifier that I had built for
Jimi Hendrix in 1966. At that time components were, to say the least crude, and this version, while
employing exactly the same schematic, was smaller and more efficient than its predecessor. That was
Fusion.
Now I’m back with another unique design from the past. I designed this guitar head amplifier in 1975 and
although my associates generally agreed that while it was probably the future of guitar amps, using 9
tubes (some of them doubles!), it was way too expensive to produce, and nobody would be able to afford
it if I did! But now we have op-amps...
The idea of the Fusion range of amps is that the original circuit is used, and this still applies, as the op-amps do not affect the actual sound fidelity in any way, and so are legitimate.
So what’s it all about? It’s all to do with tone controls. Originally we had tone stacks, which were passive,
and so had to use extra amplification to make up for their losses. This increased noise and distortion.
Next, in 1950, came the “magic” FVM tone stack. Nobody could really say who invented it, so it was
called FVM (Fender, Vox, Marshal!). Then, in 1952, the Baxandall tone control emerged – a brilliant
design, but using feedback caused some unpredictable results, and the range was limited to typically
+15dB to -15dB. Baxendall tone controls were originally intended for hi-fi amplifiers, but were swiftly co-
opted into the guitar amp world. Then in 1975 I designed my own approach, which did not use tone
controls at all!
Fusion2 has 16 volume-controls on the front panel and no tone controls!
Fusion2 houses both tube and solid channels, plus some useful functions. You can use the channels as totally separate 50W amps, or you can join them at the power-amp end to get a thunderous 100W, with tons of mixing and sideline capability.
Fusion 2 has 2 variants:
Fusion 3 - the tube channel only, with 50W output (T suffix, and
Fusion 4 - the solid channel only, with 50W output (S suffix).
All 3 products come in a wooden cabinet for use on the road (G suffix), or
As a rack-mount unit for studio use (R suffix).
I’m just going to make 100 of the new Fusion 2 – no need to tempt fate!
Fusion 3 was meant to be exactly the same as Fusion 2, but all solid-state. The filters do not actually
change the sound, and the mixers, apart from allowing another opportunity for distortion in the tube
channel, also have no effect on the sound quality. So the real comparison is between the tube preamp and
the solid preamp – at last the argument about which is best, tubes or solid, can be answered, as they’ll
both be in the same box!
There will be two separate 50W channels, which can be joined both at the amp end (2 x 50W digital
amps) to deliver 100W rms, and also joined along the signal route. I’ve added a parallel fx side loop to the
usual serial loop - something you rarely get in a reasonably priced head - and some good recording
takeoffs, and that’s the final version of Fusion 2, as shown in the pic.
So now in the Tube channel we’ve got 2 tubes, plus 7 op-amps. What do we get? We get the first guitar amp ever that lets you hear the guitar and not the guitar amp! Magic? Yes, it is! It works like this:
The solid channel uses magic too, but without tubes, it’s simply an extraordinary ‘normal’ guitar amp with the amazing benefits of the way tone control is now achieved.
How it all Works
The first tube isolates the guitar from the rest of the preamp so that the guitar’s own controls are not
suppressed. But the guitar can still overload the first tube, so if we want it, we have our first level of warm
distortion. Otherwise, the pure tones of the guitar are seamlessly passed through the first tube. The two
tubes in the preamp are spy-radio tubes, invented in1940 for the war, just a year before I was born! Being
transmitter tubes, they are quite at home working past the audio band up to where the guitar harmonics
live. These red-spot mini tubes also only take a few seconds to warm-up – ideal for spies! Also, these
tubes are low-noise, as well as being tough enough to survive a musician’s lifestyle!
Then come the op-amps. They do nothing to the guitar’s sound except to divide it into 5 bands – familiar?
Yes, but hese are not tone controls, they are filters – big difference! Now here’s the magic... Suddenly,
every knob on the amp is a volume control. Nothing actually interferes with the guitar sound, the controls
only set how the three channels relate to each other. When you hear it you’ll know what I’m talking about.
It’s never been done before! Get ready to hear the real sound of your guitar!
The filters allow you to build your sound, as they are additive. In effect, this means that if you want just a
little little more bass, without wrecking the general sound balance, you can feed a bit more bass in – or a
lot more! You can increase this until distortion occurs, either across the whole sound, or just in the ‘slice’
you’re increasing. Of course, this is only recommended for the tube channel, as there’s nothing worse than
raw digital distortion! DB figures are meaningless in this system, as the filters are volume driven and so
you can turn any channel down to nothing at all, or up to distortion level. So when all the filters are down
at zero, there is no sound at all! Logical, of course, but strange nevertheless. That’s the effect of driving by
volume to get tone; it makes the sound very flexible, without any effect at all from the filters.
The second tube is simply a perfect mixer for the 5 sound channels, but it also provides a second chance
to get some warm distortion.
And what about the linkable 50W amps that follow this magic preamp? Well we don’t want it to do
anything to the sound except make it loud enough to use on a gig, so the obvious choice is a digital
amplifier that provides clinically perfect sound... OK, but everything that I looked at in the ready-made
world (after all I’m trying to keep the costs down), proved to be disappointing in the top end, where I
needed perfect harmonics. So I had one made to my own specification. It’s clean and adds nothing except
volume to the most amazing amp you will ever have used.
That’s Fusion 2. Look out for the launch on Kickstarter – soon!
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