- Variac. This particular function simulates the saturation level reached by the valves of an amplifier when it's connected to a voltage attenuator. The variac is a piece of equipment that connects to an electrical outlet in order to regulate the voltage level of any units that are connected. The best way to use the valves is to connect a valve amplifier and to increase the input voltage. In this way the amplifier increases both in power and in dynamics, giving an otherwise unattainable sound. The problem with using equipment like this is the valves, when they are pushed to the limit they have a short life, and amplifier maintenance can be very expensive. Obviously, the simulation in modern preamplifers doesn't have this type of difficulty.
- Rectfier. This circuit, which replicates the effect of the valve grinder in the preamp, checks the dynamics and the saturation level of the gain. Some manufacturers mount this type of valve in the circuits of their power amps.
Both the controls just described have very good dynamics. For example, varying the touch of the right hand and turning the volume of the guitar off, you can vary the response of the amplifier: with a stronger touch, you get a harder sound, while a lighter touch gives you a cleaner sound. All with extremely superior dynamics with respect to a preamp that doesn't have these types of controls, that therefore gives more faith in the response with regards to personal technique, touch and expressiveness.
Post-Distortion EQ.
The sound obtained in the gain section, can now be refined. Attention! In this stage the sound is retouched slightly instead of extreme changes to the basic sound. With the "post-distortion" equalizer you can work in the area where there are some small sound imperfections. Here are some examples:
- You notice that the sound is poorly defined and slightly closed. In this case we focus on the presence, which helps emphasize the middle-high frequencies, and are very useful for the "impact" (or presence) of the sound.
- The sound is too full-bodied or too weak. The middle frequencies help to sweeten the sound (by cutting the frequency range) or to enlarge it (by emphasizing the frequency).
- Obviously the lows are adjustable in their frequencies. Also in this case a small adjustment might be necessary. A good system is one that regulates the distorted sound and plays it with "palm-muting" (stopped by the right hand) on the bass strings: all of the low frequencies will be out in the open and therefore will operate by cutting (if there are too many lows) or emphasizing.
Intensifying a frequency (especially the middle tones) gives the illusion to increase the volume in the entire range, while in reality it only increases the volume of one frequency. By contrast, if you cut a frequency it seems to decrease the total volume, but really only that frequency decreases. You can obtain more information on this subject in the section devoted to the equalizer.
Another fundamental point is to compare the sounds. When you program a preset (a program number on the equipment), it creates at least two or three similar sounds, each of which can be slightly different in volume, saturation or, as in this case, emphasizing or frequency cutting data.
It would be useful to verify all possible differences in order to understand its characteristics.
After being processed, the sound is directed to the output section, which regulates the volume coming out of the preamp. We usually have the possibility to regulate the entire volume of the equipment and, in regards to the Midi preamp, also to regulate the volume of every single preset. The overall volume should always be kept near half, so when you program the preset you have the possibility to increase or decrease the volume. The overall volume is often called output level; many times we also find an input volume control (input level), which regulates the input signal. This can be adjusted according to the output power of the guitar. In non programmable preamplifers don't have volume problems because it's possible to intervene in real time during a performance: you need to balance the volumes between the various channels of the preamp. This is not the case for Midi preamplifers, although they are more versatile, the errors made in the programming phase are paid for during a live performance.
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