Blackstar HT-20RH MK III 20W Tube Guitar Amplifier Head

Blackstar HT 20R MKII Overview

Experience the next generation of affordable tube tones with the HT-20RH MK III from Blackstar, a 20W amplifier head ideal for home practice, recording, and gigging. Sporting two ECC83 and two EL84 tubes, along with two channels, two voicings per channel, and patented ISF control, you get generations of tube tone at your fingertips.

With power reduction down to 2W via controlled reduction of internal working voltages, you can enjoy more freedom to push your amp without disturbing your neighbors or sacrificing sound quality. The amp includes diverse output options, with XLR, 1/4" headphone, and USB supporting Blackstar's innovative CabRig speaker emulation, as well as a series FX loop, and more. The USB-C port also offers 2x2 interface functionality, allowing you to enjoy a rare marriage of vintage tube tone and modern digital versatility.

HT MK III Series Ethos

When creating a series of amplifiers, the traditional approach would be to start with a preamp design, and then bolt this on to a range of power amplifiers of different power ratings. However, Blackstar acknowledges the interaction between preamp and power amp and the individual requirements that different amps need.

Therefore, although the preamps do share many similarities, each and every model has had the same individual care and attention during sonic testing, and any required tweaking of the circuitry has been applied to ensure each model performs to Blackstar's high tonal expectations.

Clean Channel

The MK III Clean channel is a very sophisticated circuit, albeit deceptively simple looking, that is extremely versatile for producing a range of classic clean and crunch tones. The two different voicings use both parts of an ECC83 (12AX7) tube exclusively for producing any compression or crunch.

Overdrive Channel

The HT MK III overdrive channels are the next in an evolution from Series One, HT MK I through to HT Venue MK III. The topology shares the same basic building blocks in gain structure and tonal shaping and includes the cascaded gain stages of an ECC83 double triode valve. However, each amp has had the overdrive tones specifically tweaked, tuned, and refined during hours of listening tests, to optimize the tone for that model.

An important aspect of the Overdrive channels is how well the tone cleans up when the guitar volume is backed off. In conventional valve-amp designs, the treble response of the overdriven sound is shaped by a series of cascaded first-order low-pass filters placed between each of the valve stages that are being overdriven, which often leads to a droopy filter response and a dull or lifeless backed-off tone. In the HT MK III Overdrive channels, the majority of high-frequency shaping of the distortion is done using a second-order low-pass filter. This has the advantage of removing the unpleasant high-frequency fizz without attenuating the signal below the cut-off frequency.

Patented Infinite-Shape Feature

The conventional three way guitar EQ network, or tone stack, is a key to the characteristic voice of traditional guitar amplifiers. Classic amplifier designs have their own versions of this network which leads to their own tonal voicings.

The passive ISF control allows you to infinitely adjust the response of the tone control network between any of the traditional voicings in a way that has never before been possible, for everything from a classic American to vintage British tonal range. The ISF control is interactive, moves the whole tone stack at once, and is continuously variable.

Clean Voices

The Voice 1 setting (LED off) is based on a classic American clean sound, a mid '60s black-face Fender Twin Reverb. This speaker has high headroom and is bright and clean with a solid low end. On the HT-20RH MK III models, the power amp feedback is automatically adjusted to add presence and sparkle as well as tightness to the full bottom end.

The Voice 2 setting (LED on) has been based on a much loved vintage Class-A British tone (Vox AC-30). The gain structure is reconfigured to put the EQ shaping after both valve stages, and the power amp is set to have no negative feedback. These and other carefully voiced parts of the circuit result in a warm tone with a chimelike top and a relaxed resonant bottom end.

Overdrive Voices

Switching to Voice 2 (LED on) on the Overdrive channel adds more gain for the overdrive and reduces the power amp damping, giving livelier highs and more resonant lows. Overall, this changes the character of the overdrive from a classic tone toward a high-gain, contemporary tone.

Digital Reverb

While a traditional, possibly old fashioned, spring reverb is often the choice for tube amps and can be great for Fender-style clean tones, Blackstar felt this wasn't the best choice for modern overdrive tones. So, they developed their own digital reverbs specifically voiced for both clean and OD tones.

These exclusive Blackstar designs respond well to both the dynamic nature of clean sounds and the more compressed, harmonically rich textures of crunchy and high-gain / overdriven sounds. In addition, the Reverb Time can be adjusted for Clean and OD channels independently using Blackstar's Architect software. This level of choice and flexibility simply would not be possible with a mechanical spring reverb.

CabRig

CabRig is Blackstar's next-generation IR-based DSP speaker simulator, featuring innovative DSP software that reproduces the rich, dynamic characteristics of real-world guitar cabs:

• Boasting zero latency and lower CPU usage than other snapshot technologies, CabRig empowers you to sculpt their sound effortlessly
• The advanced algorithm lets you create new ways of blending mics and cabs without encountering phase issues
• Blackstar's Architect software provides access and in-depth control over every aspect of CabRig, granting a vast collection of gear that in the real world can only be found in professional recording environments
• Over 700 combinations of rooms, cabinets, and microphones allow you to be the sound engineer and get outstanding results every time without any of the hassle
• You have full control over individual EQ and panning for these close mics, exactly as if they were channels on a recording console
• You have the option to choose the room in which you want to place the cab, with complete control over the level of the room sound

Comprehensive I/O

• Balanced XLR direct output (compatible with CabRig)
• Stereo headphone output with improved driver amp for wider compatibility (compatible with CabRig)
• Stereo 3.5mm line input
• USB-C connector for 2x2 recording or Architect software parameter editing (compatible with CabRig)
• Series FX loop with +4 dBu or -10 dBV level switch
• Standard latching 2-way footswitch input for channel and voicing selection
• 8- and 16-ohm speaker outputs for connecting to an external cabinet

Tube Heaters

All HT MK III models have low-noise DC power supplies for the preamplifier tube heaters. This is a feature previously only found in very high-end tube amplifiers.

It eliminates any hum that would be induced from the more commonly seen 6.3 VAC heater power and allows high gain settings to be used without high levels of 50/60 Hz noise or hum being audible.

Quality Construction

All PCBs used in the HT MK III amps are double-sided plated-through types. These provides increased mechanical strength. All tubes are specially tested and graded, removing as many tubes that don't meet Blackstar's standards during the selection process as possible.

All amps are specifically biased to ensure the perfect balance of tone, reliability, and tube longevity. The chassis is fabricated from 1.2 and 1.6mm coated steel plating and incorporates other mechanical design features for maximum absorption of physical shocks.