Acoustic Image

CLARUS SL and SL-R instrument amplifier

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The Clarus amp has been a favorite among bassists, jazz and acoustic guitarists, and many other musicians for many years. I've long been a fan of its pristine, transparent sound. And it sure is easy to tote around!

Over the years, there have been several incarnations of the amp; they've been through several panel designs, lots of upgrades to features, improved noise specs, more powerful amplifiers... it's nice that, even when they're at the top of their game, Acoustic Image is always looking to make their products even better.

Includes our exclusive Gollihur Music tipsheet to get the most out of your purchaseWe've often consulted with Rick and the team at Acoustic Image, and some of those discussions have led to improvements and new features. A recent conversation led to the idea that reintroducing an old favorite -- the Clarus SL -- would be a great way to bring the sound and feature set of the amazing Clarus amps to a new, lower price point. And would be a great option for those who needed the smallest amp they could get their hands on, provided that they didn't need more than one channel. So here is the result: the newly reintroduced Clarus SL and Clarus SL-R!

At under 3 pounds, this amp is ridiculously powerful; it uses the same power section as the larger Clarus, and therefore has up to 650w of clean, uncolored power. It's rated at 4 and 8 ohms, but will handle a 2 ohm load.

The Clarus SL amplifier head can be matched with most any speaker cabinet, for use with a huge variety of instruments. Its clean, transparent sound is exceptional for bringing out the best in acoustic instruments like upright or acoustic-electric bass, acoustic or jazz-box guitar, violin, mandolin, cello, harp, ukulele, and more. Unlike the amps of the (not so distant) past, you don't need a roadie to help you move it, either - this 650w preamp/amplifier is under 3 lbs, and fits easily into a small padded carry bag (included) that you carry with one hand.

The Clarus head is the same "front end" featured in Acoustic Image's Contra Combo, with the newest, quietest, most reliable power amp yet.

Couple this amazing head with an Acoustic Image "EX" extension speaker, or with a bass or guitar speaker from another manufacturer. It even sounds great powering a passive PA speaker, like a JBL or Mackie wedge! It provides full-range, uncolored sound for the most realistic reproduction of your acoustic instrument. (Though it works great with keyboards, too!)

I use Acoustic Image gear for almost all of my URB and EUB gigs... what wins me over is -- when teamed with a good pickup or mic -- the amp tends to simply make my bass sound acoustically bigger, rather than giving it a separate electric voice.

— Bob

How can I use this amp?

The Clarus amplifier is an amplifier "head", meaning that it contains a preamplifier and power amplifier; to get sound, you'll need to connect it to a speaker cabinet. We've broken down our description below into sections so that you can understand the various parts of the whole.

The Preamp:

A key ingredient in Acoustic Image gear is the very careful design of the electronics. They have always been engineered to deliver the natural sound of your instrument, no artificial flavorings or colors. Please answer this question... do you want to hear your instrument or the amp??

Me, too. My specifications for an ideal sound is for a pickup and amp to simply make my bass sound bigger than the bass can sound on its own. Don't add or take anything away -- MY bass, only LOUDER.

Besides the amazing transparent sound, useful features have been designed into the Acoustic Image preamps to provide the most flexibility for various playing situations. For instance, you get a parallel effects loop, and a selectable low-cut (aka high pass) filter to help with feedback or “boominess” elimination (see explanation in features list below). You also get a balanced direct out with ground lift, as well as pre/post setting, to allow connection to a mixing board for PA support, or for recording purposes. On the SL-R, you have on/off access to the built-in digital effects.

The front end also features two ¼" input options for either lower impedance (1 megohm) or ultra-high impedance (10 megohm - great for piezo pickups!) Separate Input Level (Gain) and Output Volume Controls (Master) allow for precise tonal vs. volume control, and a Master Mute Switch allows you to cut the output for silent tuning or for breaks.

The preamp features the new, FLEX-Style four-channel equalizer, as follows:

  • Low: Shelving, ±12dB at 30Hz
  • Lo Mid: ±12dB at 250 Hz
  • Hi Mid: ±12dB at 1200 Hz
  • Treble: Shelving, ±15dB at 8 kHz

On the SL-R model only, the built-in Digital Effects can be turned on or off, and the level of the effects blended into your mixed signal can be adjusted with the level knob. The rate setting is now configurable (!) and the effects include the following presets:

  • Reverb
  • Delay
  • Reverb PLUS Delay

Now, most bassists will probably opt to save $100 and choose the SL model without the effects, since reverb and delay are rarely a bassist's friend (they usually just tend to muddy things up.) But AI Clarus amps are full-range, and therefore also very popular with jazz box and acoustic guitarists, mandolin players, violinists, cellists... the list goes on. And a touch of reverb can go a long way to gussy up the sound of those instruments. So if you think you might share the amp with a guitar-playing buddy sometimes, you might consider the SL-R.

One last new feature on the Series 4PLUS amps - illuminated on/off buttons for the front panel controls to indicate whether the button is on (lit) or off (unlit). This is really helpful on a dark stage!

The Power Amplifier:

More Power!! (please insert your own Tim Allen Home Improvement TV show grunts) Yes, it can put out up to 650 watts (at 4 ohms). That said, the Clarus heads are not rock and roll amps — it's clean power, and can get LOUD (depending on the speaker) but it's not designed for creating distorted or overdriven effects (though you could certainly accomplish these sounds with effects pedals or processors).

With so much wattage, this head can get quite loud. But the wattage is there to ensure smooth, clean response. Bass frequencies, in particular, take a great deal more energy to produce that high frequencies, and the somewhat percussive nature of upright bass can be very demanding. The "extra" energy (commonly called "headroom") is available to cleanly handle those peaks and percussive plucks, so you don't get that "squashed" sort of attack many bass amps often deliver when they hit the wall.

Other Fun Facts to Know and Share

The S4 Clarus SL is the newest version of the Acoustic Image Clarus Head, and is equipped with high and low impedance inputs. The SL-R model includes built-in digital effects.

The amps have a low cut filter, which is a variable frequency type that inserts a 12 dB per octave rolloff at frequencies between 30 and 400 Hz, depending on the position of the control. The low cut filter is used to reduce the bass output in cases where room location or instrument/pickup combination results in “boomy” sound. Experiment with the position of the control to give you the sound you like best.


  • 1/4" inputs; input impedances are 1 megohm or 10 megohm based on jack chosen, separately buffered
  • Effects Loop via front-panel 1/4" phone jacks
  • Low Cut Filter: -12 dB/octave sweepable from 30-400 Hz
  • Balanced XLR Line Output with Ground Lift
  • PRE- or POST- switch for XLR output
  • AC Power On/Off switch with LED Indicator
  • 650-Watt (@4 ohms) "Digital" Power Amplifier -- (650w @4 ohms, 350w @8 ohms - 2 ohms minimum load)
  • 2 External Speaker Outputs (Neutrik Speakon)
  • Detachable AC Input Connector with Built-in Fuse
  • Dual voltage operation (115v/230v, 50/60 Hz) via automatic switch (comes with USA Cable; to use in other countries, you can source an IEC-C13 AC Cable, also commonly used for computer power supplies.)


  • Lightweight- less than 3 lbs!
  • Durable Powder-coated Aluminum Enclosure
  • 7.4 x 7.2 x 2.1
  • Padded Carry Bag included


Not 100% Sure? New owners have a fourteen-day trial period during which they may return the amp, in like new condition, for a full refund less actual shipping cost.

14 Day Trial Period on Series 4 Acoustic Image amps and speaker cabinets

New owners have a fourteen day trial period during which they may return the amp in new condition -- NO QUESTIONS ASKED! -- for a full refund, minus our outgoing shipping cost and a small transaction fee to cover credit card or PayPal payment processing. Returns must be preauthorized; a restocking fee applies if the unit is not returned in new condition.


14-Day Trial Period

Your purchase of this Acoustic Image Amplification Equipment is covered by the exclusive Gollihur Music 14-day Trial Period, under the following terms:

You may contact us to return this item, for any reason (or no reason), within the first fourteen days of ownership. The timer starts on the day that you receive the item, not the order date.

Returns are subject to deductions as follows:

  1. Any shipping costs you paid are not refunded, and if the item shipped free, the costs we incurred to ship the item to you will be deducted from your refund or credit.
  2. All shipping costs you incur to return the item are your responsibility.
  3. A small fee is deducted from your refund to cover credit card/PayPal fees which are not refunded to us even if we refund your charge. Note that if you choose to accept a store credit instead of a refund, this deduction does not apply.

Items must be returned in 100% "as new" condition, with all original packaging, shipping materials, and accessories/manuals/bonus items. Deductions are assessed for missing or damaged items.

IMPORTANT: You must contact us for authorization BEFORE shipping the item back.

Product Manual

Need to figure out some of the more in-depth features of this product? Here's a copy of the manual, in PDF format, here.

You may wish to visit the manufacturer's website to see if a more recent version is available.



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Warranty Information

Acoustic Image's Warranty, Simply Stated

We stand behind our products with a full warranty of five years from the date of purchase. Speaker components are warranted for 180 days. Should a problem arise, please call us before returning your amplifier or enclosure. Naturally, our warranty does not cover products that have been damaged through misuse.

Bottom line, we don't say that ours is a "lifetime warranty" or even a "limited lifetime warranty". We do, however, commit to treat you the way we would like to be treated. For good.
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5 Reviews

  • 5
    Acoustic Image Combo

    Posted by Mike B on Dec 16th 2021

    By far the best sounding amp for my upright I've used. I've gone through preamps, house PA's, solid state heads, tube heads, combos - this represents - to my ears - my "true" tone in a way that no others come close to. And Gollihur rocks. Best store for bass needs anywhere

  • 5
    AI Clarus

    Posted by Eric Jackson on Sep 24th 2021

    After five years of living with this amp, there aren't enough stars here to rate it properly. I play acoustic exclusively, with groups of 3-18 players, in venues ranging from small intimate theatres to huge outdoor concerts. I play a 100+ year old Czech bass with a Bass Max pickup, and always manage to achieve a good/ great sound. No goofy "voicings", just wide ranging, easy to use eq and other features. I've had many comments from sound guys on how clean and crisp the direct out signal is. I can't imagine ever needing or wanting another amp. Paired with an EA single twelve cabinet, it's killer. Many thanks to Acoustic Image and the Gollihurs for a great product and great service.

  • 5
    Clarus solved my problem

    Posted by Jim McGiffin on Jan 27th 2021

    I play my upright at blues jams and had trouble competing with the screaming telecasters. This amp is so easy to use and has the power necessary. I switch to the electric and it sounds great for that, too.

  • 5

    Posted by Brian T. on Jul 7th 2019

    Hi Mark, I’d just like to thank you for the excellent advice delivery times and information regarding the Clarus SL 1 Acoustic Image head you sent me here to in Melbourne Australia . My 100 year old German flat back bass and my contra acoustic bass Guitar ( like the Earthwood bass guitar )sound wonderful I have rehearsed with my roots band and they were impressed. Thanks again to Gollihur Music sure I will do more business with you and I will let my musician buddies know of you here in Australia .

  • 5
    Wow! I am amazed at the sound of this thing!

    Posted by Bill S on Apr 2nd 2018

    Hi Mark, I got my Clarus SL yesterday. Transparent and loud if you need it. This is going to make my upright playing life a whole lot better (and lighter). Thanks for your expert advice and great customer service.

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