Rivera Amplifiers is a company that has become famous for the legendary reliability and quality of its products. It was founded in August 1979 in Southern California by Paul Rivera, who a few years earlier had been called by Fender to improve its amplifiers that were suffering competition from Mesa Boogie.
My Knucklehead '55, hand-built in 1995, is, along with its 100 watt big brother, the first amplifier in a series that has seen some major modifications over the years.
It is a very versatile amplifier, capable of encapsulating both British and American sounds in two channels.
Driven by two EL34 power tubes for a 3S Industries R002 output transformer and five 12AX7 preamp tubes, it is powered by 3S Industries CO. 109-026 transformer and delivers 55 watts of pure US-made tube sound.
On the front panel the Knucklehead displays power and stand-by buttons, two inputs, one High Gain and one Low Gain, to better adapt to different types of pickups and for each channel, tone (High, Mid and Low) and volume (Gain and Master) controls, while the Presence and Focus controls are common to both channels. The Focus, a Rivera exclusive, allows the sound of the amplifier to be altered by giving the feeling that a closed box is open and vice versa. Compared to other amplifiers, the tone controls are interdependent and have greater sensitivity and range.
By pressing the specific pull-on/off knobs on the tone and volume controls, it is possible to activate the boosts of the two channels or the Bright and Notch switches of the second channel.
On the rear panel is the effects loop with independent controls, the 4, 8 and 16 ohm impedance selector, the output for two speakers, a line out and the FS7 footswitch input with which to control the two channels and the two Rivera boosts.
There are two channels but, unlike traditional two-channel clean-distorted amplifiers, the basic idea of the Knucklehead is more like two switchable single-channel amplifiers, each with a different amount of gain and each characterized by its own timbre: channel 1, of ‘British’ inspiration, which is also the one with the greatest amount of gain, and channel 2, of ‘American’ inspiration, more inclined to clean sounds, but not only.
The new models also have an ultra-saturated third channel and reverb. I have never tried them, but there are those who claim that there has been a drop in quality in these new amplifiers. And actually, considering the saturation levels that the first channel can reach with the boost on, it is not clear why the third channel was added in the new models.
My Knucklehead '55, hand-built in 1995, is, along with its 100 watt big brother, the first amplifier in a series that has seen some major modifications over the years.
It is a very versatile amplifier, capable of encapsulating both British and American sounds in two channels.
Driven by two EL34 power tubes for a 3S Industries R002 output transformer and five 12AX7 preamp tubes, it is powered by 3S Industries CO. 109-026 transformer and delivers 55 watts of pure US-made tube sound.
On the front panel the Knucklehead displays power and stand-by buttons, two inputs, one High Gain and one Low Gain, to better adapt to different types of pickups and for each channel, tone (High, Mid and Low) and volume (Gain and Master) controls, while the Presence and Focus controls are common to both channels. The Focus, a Rivera exclusive, allows the sound of the amplifier to be altered by giving the feeling that a closed box is open and vice versa. Compared to other amplifiers, the tone controls are interdependent and have greater sensitivity and range.
By pressing the specific pull-on/off knobs on the tone and volume controls, it is possible to activate the boosts of the two channels or the Bright and Notch switches of the second channel.
On the rear panel is the effects loop with independent controls, the 4, 8 and 16 ohm impedance selector, the output for two speakers, a line out and the FS7 footswitch input with which to control the two channels and the two Rivera boosts.
There are two channels but, unlike traditional two-channel clean-distorted amplifiers, the basic idea of the Knucklehead is more like two switchable single-channel amplifiers, each with a different amount of gain and each characterized by its own timbre: channel 1, of ‘British’ inspiration, which is also the one with the greatest amount of gain, and channel 2, of ‘American’ inspiration, more inclined to clean sounds, but not only.
The new models also have an ultra-saturated third channel and reverb. I have never tried them, but there are those who claim that there has been a drop in quality in these new amplifiers. And actually, considering the saturation levels that the first channel can reach with the boost on, it is not clear why the third channel was added in the new models.
The sounds
The first channel is British-inspired, some would say JCM-like. The sound texture is indeed comparable to that of 80s-90s Marshalls, with the typical mid-high scratch, but it is more ‘structured’ and ‘full’. It is a modern sound that allows you to go, with the boost switched off, from a good crunch to distortion suitable for rock and hard rock. The first channel's boost, at low initial gain, not only increases saturation, but also boosts the volume and mid-high range a lot, to come out better in solos. At high initial gain levels, the boost, by greatly increasing its compression, changes the sound texture, which becomes more suitable for hard rock or metal.
The second channel is considered by many to be the ‘jewel in the crown’ of the Knucklehead and is often used for clean sounds, but it is not a purely clean channel. It is more like, as the manual says, an ‘American voiced’ channel. In fact, by increasing the gain you can get closer to the typical Fender ‘cranked’ sounds, even though the final tubes are still the EL34s. The different tonal nuances of this channel are further enhanced by its boost (called Ninja boost), which increases its volume and compression, a bright switch and notch switch, which change the reference centre frequency from 550 Hz (typical of Tweed Amps) to 250 Hz (typical of Blackface amps).
The second channel is considered by many to be the ‘jewel in the crown’ of the Knucklehead and is often used for clean sounds, but it is not a purely clean channel. It is more like, as the manual says, an ‘American voiced’ channel. In fact, by increasing the gain you can get closer to the typical Fender ‘cranked’ sounds, even though the final tubes are still the EL34s. The different tonal nuances of this channel are further enhanced by its boost (called Ninja boost), which increases its volume and compression, a bright switch and notch switch, which change the reference centre frequency from 550 Hz (typical of Tweed Amps) to 250 Hz (typical of Blackface amps).