The AMP1's GAIN control features a "Treble Bleed" capacitor that boosts the treble when turned back. This can lead to the sound having more treble in your signal than you actually want.

The LOW GAIN MODE (Mercury and Iridium only)

In this case, the AMP1 Mercury Edition and AMP1 Iridium Edition have a special feature: the LOW GAIN MODE. This mode reduces the input sensitivity so you can turn up the GAIN a bit more. The further you turn it up, the less treble the sound has. To enter LOW GAIN MODE, hold down the left footswitch while powering on the AMP1.

Customize your gain: INDIVIDUAL CHANNEL GAIN

You can take this even further with the help of another Expert Feature: INDIVIDUAL CHANNEL GAIN ‍allows you to set and save a separate maximum gain value for each channel of the AMP1. All you need to do this is a REMOTE1.‍

In Academy of Tone, Episode 14, Thomas devotes himself to the topic quite extensively:

The AMP1's Tone Stack

The tone stack of the AMP1 differs quite clearly from a classic tone stack. The AMP1 is an extremely versatile amplifier, which is not least due to the flexible tone control. In contrast to classic "one-sound amps", the AMP1 does not have just one sweet spot, but there are many setting options that can lead to the goal. Therefore, extreme settings (e.g. TREBLE set to zero) are completely legitimate and in many cases absolutely effective!

Here is an example where Thomas Blug compares the AMP1 Mercury Edition to an Ampete TWO tube amp and sets the mids to 8 and the treble to 0 to match the sound:

Underestimated sound component: the guitar cabinet!

The overall sound of a guitar amplifier always consists of the amp and the loudspeaker cabinet. The cab plays a significant part in the overall sound. There are amp/cabinet combinations that just don't go well together. If, for example, an amp has a high proportion of treble and the cab emphasizes this through the choice of loudspeaker and the front covering, this can sound unpleasant. It is therefore highly recommended to experiment with different loudspeaker cabs. The cabinets from BluGuitar are well matched to the AMP1.

The Vintage Premium Speaker Cable

Last but not least, if your sound has too much treble or sounds too hi-fi, it's worth trying the BluGuitar Vintage Premium Speaker Cable as it gives you an audibly fat, warm and transparent tone.