Boss AD-8 Acoustic Preamp Guitar Processor Pedal (Discontinued)

94 out of 100. Incorporating 90+ ratings and reviews.

Gearank High Notes

Boss has a tendency of going for the extreme when it comes to adding features into their guitar processors, and this rings true with the AD-8.

This preamp packs quite a lot of sounds, equipped with COSM acoustic guitar modeling technology which morphs your guitar sound to be similar to the miked sound of an expensive and sought after acoustic guitar specimen. In addition, it has built-in reverb and a 4-band EQ which gives you even more room to tweak your amplified acoustic sound.

Check out the LR Baggs Para DI which is the most highly rated acoustic preamp!


  • Boss COSM Acoustic Guitar Modeling technology
  • Six acoustic models
  • Simulates warm, miked acoustic sounds
  • Built-in reverb tailored for acoustic guitar
  • 4-band EQ
  • Anti-Feedback
  • Onboard chromatic tuner with Mute function
  • Input Impedance 4.7 M Ohm
  • 4 Preset memory locations for switching acoustic sounds instantly
  • Balanced XLR outputs allow direct connection to PA systems
  • Weight: 4.25 lbs.


The majority of users are happy with how the Boss AD-8 made their guitar sing, adding upper harmonic sparkle and dynamics that would normally only be available when an acoustic guitar is miked. There was even one who reported using the AD-8 for years, with various guitars and pickups, to his satisfaction, made possible by the wealth of tone shaping features that the unit has. There were some guitarists who play nylon strings who also provided their 5-star approval, saying that with some tweaking, they got their instrument to sound organic. Another commonly mentioned positive feature of the AD-8 is its reverb, which works well regardless of the instrument you’re using.


Of the few low ratings, their main point of contention is the addition of COSM guitar modeling feature. But other users have pointed out that with some patience, it can give desirable results. Another complaint that was raised is its lack of chorus, which the older and cheaper versions had. Some experienced users also mentioned the lack of attenuation setting, which can help better balance out the sound when connecting direct to PA.


Having weighed all the pros and cons, this is still a great acoustic guitar preamp that many recommend, so if you have the patience to tweak and you’re looking for a reliable preamp then this is definitely worth checking out.

Unfortunately the Boss AD-8 is no longer available in stores so if you want to buy new rather than second hand then take a look at our recommendations in our guide to The Best Acoustic Preamps.

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