If you look at some of the pedalboards at the feet of Dino Guitarists, especially by players who perform high gain instrumental pieces like Vai, Satch, Johnson, etc., you'll often find more than one gain pedal in the chain. Sometimes one gain pedal runs directly into the next. Sometimes they're divided by the placement of a different effect type inserted between the gain pedals. These type of effect chains works extremely well with very clean voiced amps.
When going for a super saturated Dino tone your looking for excellent sustain like you'd find in a distortion. Your looking for rich harmonics which are most prominent in fuzz pedals and to a somewhat lesser, though still quite audible amount, in distortion. Your looking for the full bodied voice of a midrich overdrive. While a great high gain amp can provide all three in varying amounts, pedals, as a rule, are less encompassing. They tend to be great at reaching one or two of the goals but only rarely provide all three the way a high gain amplifier can. An option that often goes overlooked is combining two gain units in series that, when used together, will produce a rich blend of all three of the tonal goals.
Example #1. You have a distortion unit that offers great sustain, good harmonics, but lacks in mids. It just has a hollow sound you can't seem to fill. An option you could try would be to run an overdrive in front of the distortion pedal. Set the overdrives gain level relatively low. Your using this pedal for its vocal quality. It's an enhancement. Also adjust the overdrives output level so it doesn't increase the signal volume when its engaged. On the distortion pedal move your usual gain setting down a notch to compensate for the added gain from the overdrive. If you position the pedals side by side you can depress their on/off switches separately or at the same time. The overdrive thickens the voicing. The distortion provides the sustain, harmonics, and any additional volume level you might choose for your solo.
Example #2. Much the same as example one, but, in this case your running a fuzz pedal rather than a distortion. The biggest problem associated with fuzz is controlling the amount of gain. The higher you go on the gain setting the greater the amount of harmonics and overtones, as well as sustain. The problem that develops is a lack of balance between these resultant tonal factors. Setting the gain level of a fuzz to achieve the amount of harmonics and sustain your looking for without burying everything under the mass of distorted overtones takes an extremely delicate tweaking process to get what your going for. In some cases you won't ever be totally pleased because adjusting the gain to a level that achieves your desired amount of sustain will just have to much of everything else. Once again, let's place an overdrive pedal in front of the fuzz pedal. This time, though, set the gain level of the fuzz first. Bring the gain setting up to the point that though it's not yet sustaining to the degree you desire it is producing the amount of harmonics and overtones in just the right amount. These are a fuzz pedals strong suits. Now go to the gain level knob on the overdrive and bring it up to increase the amount of sustain. If the fuzz tone gets a bit unruly just tweak its gain setting down slightly. Gain provided by the overdrive will add sustain at a higher ratio to the production of the tonal properties of harmonics and overtones much better than any increase of the fuzz pedals gain setting would.
Example #3. The last example we'll look at has to do with the way gain units affect other pedals in the chain. Some pedals such as univibes, wahs, delays, phasers and flangers produce completely different results with the placement of a gain pedal in the same chain either before or after the effect. Simply put, when the gain comes first the unaffected signal from the guitar itself is overdriven or distorted. Then the overdriven guitar signal goes to the next effect where it is delayed or phased or whatever. Some effects sound better with a stronger input signal and that's what will be achieved when going guitar to gain to effect. When the gain comes after the other effect then the other effect is applied to the guitar signal first and then the affected tone is sent to the gain pedal. Some effects sound better with gain added to their output signal and this setup of guitar to effect to gain achieves that goal. Because of this gain placement relevance to another effect type you may want to add a little gain to the guitar signal before going into the other effect and than add more gain to the affected tone on the output side of the other effect. This was a method used by Eric Johnson on some recordings. Guitar to gain to tape echo to gain to amp. Two gain units in the same chain split from each other by a third pedal that benifits from having gain applied on both its input and output sides.
The bottom line is that sometimes Dinos buy one gain unit, find it lacking in one way or another, buy another gain pedal that sounds better in some ways but lacks in other ways, buy another gain pedal...... and so on and so on. If you've already taken the bait dangled by the gain pedal salesman two or three times and still haven't found one that provides everything you desire in a gain effect try combining two of those you already own. Mix the voice of one with the sustain of the other or the harmonics of one with the overdrive of the other. Place one on each side of an effect that likes to take it both ways. Experiment. You may already have the gain voicing your looking for in your effects arsenal. It might just be stored on two different shelves or in two different boxes.