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Ampeg Opto Comp Analog Optical Compressor

Whether you play guitar or bass, Ampeg wants to be your main squeeze 


by Phil O'Keefe



Lately Ampeg's really been beefing up their pedal line - you may have read my previous reviews of their Scrambler Bass Overdrive and Classic Analog Bass Preamp pedals. Ampeg has also made more than a few guitar-centric products over the years too, and this time, they are taking a less bass-centric approach to their latest pedals. The two new pedals - the Opto Comp and the Liquifier Analog Chorus (which we'll also be reviewing soon - stay tuned!) are certainly going to be interesting for bass players, but guitarists should also take note too since both of these new pedals are equally suitable for use in guitar rigs. For now, let's concentrate on the Opto Comp and see what it has to offer to both guitarists and bassists.




What You Need To Know

  • The Ampeg Opto Comp Compressor pedal is housed in a zinc die-cast box that measures 4.5" L x 2.6" W x 2.2" H and weighs 0.6 lb.
  • The graphics and overall look of the pedal totally eschew flash; instead the pedal sticks with a very businesslike and utilitarian appearance, with a simple white paint job accompanied by black labels for the controls. The silver Ampeg logo is raised, which adds a touch of class.
  • As you've no doubt guessed based on its name, the Ampeg Opto Comp is an optical compressor. The detector circuits of optical compressors use a light source that gets brighter with louder input signals, and this, coupled with a photocell that senses the changing brightness, is used to control the compressor's gain reduction. Optical compressors have a smooth sonic character, usually with a slower attack time and gentler, more musical release than IC or FET based compressors. 
  • The input and output jacks are side mounted. The Opto Comp was designed to work with a variety of electronic musical instruments - it's not just for bass, so feel free to also use it with guitar or even keyboards. Input impedance is 1MOhm normal, or 166kOhm with the -15dB pad engaged. Output impedance is 200 Ohm.
  • Internally there is a small computer-style three pin jumper (indicated with a red arrow in the photo below). The pad is disengaged in the factory default setting (pins 1-2), but can be repositioned to the -15db setting (pins 2-3) for use with instruments with active electronics and hot outputs.



  • Also inside you'll find the foam-lined battery compartment. Access to the inside is achieved by removing four screws and the bottom plate of the pedal, which comes with four rubber feet pre-attached to it.
  • Power can also be supplied to the top mounted 2.1mm center-negative power receptacle using a user-supplied power supply. The Opto Comp draws around 25mA of power at 9V DC.



  • The Opto Comp features true bypass switching. A purple LED illuminates when the compressor is on. A second green LED acts as a gain reduction meter and shows you what the compressor is actually doing - turning on when the compression kicks in, it gets brighter on louder peaks and with harder playing, and slowly dims and eventually turns off as the compressor runs through its release cycle. The more gain reduction and compression that's occurring at any given moment, the brighter this LED will be.



  • In keeping with the norm for most optical style compressors, the control selection of the Opto Comp is fairly simple - just three knobs. The First is the Compression knob. This controls the compression ratio, and has a range of 1:1 all the way up to 10:1 when it's turned up all the way. When the knob is at the twelve o'clock position, the compression ratio is 3:1.
  • The Release knob sets the amount of time it takes for the compressor to return to a no gain reduction condition after the input signal is no longer hot enough to continue to trigger the compressor. It can be set anywhere from 75 milliseconds (fully counter-clockwise on the knob) to a maximum of 600ms.
  • Since a compressor reduces the signal's overall dynamic range by reducing the volume of the louder peaks, a makeup Gain control is needed to bring the overall volume back up to unity. The Gain control on the Opto Comp takes the output level from muted (when turned down all the way) to +14dB, so it has enough oomph in reserve that it can boost the signal above unity gain, making it useful as a solo boost too.
  • Sound quality is very good, with a natural and musical sound that many other compressor designs can't match. Another plus is that this is a very quiet pedal by compressor standards, with an 80dB signal to noise ratio (100Hz @ 1.0 Vrms).




  • There is no tone control. Like most compressors, the Opto Comp can shave off a bit of the highs and dulls the sound slightly. A tone control would allow you to compensate for this.
  • There is no blend control either, so you can't blend in a bit of your uncompressed signal along with the compression. This is more crucial with "faster" compressors that completely kill the note attacks, and you may not miss it as much with an optical compressor like the Opto Comp.
  • There is no way to adjust the compressor's attack time or threshold.




If you're looking for a compressor with an ultra-fast attack or tons of knobs, you probably want to look elsewhere, but there's a lot to be said for simple, effective controls and the smooth, relatively gentle optical compression that the Ampeg Opto Comp delivers. It's obvious that Ampeg was going for simplicity and ease of use with this compressor pedal, and it's hard to get a truly bad sound out of it. While you can find compressors with more knobs (such as individual attack and threshold controls), Ampeg kept things simple and straightforward, which is an approach many players prefer, yet you still have a reasonable amount of control with the knobs that are included.

The qualities that an optical compressor design bring to the table are on display here - the attack is a bit slower than what you may be used to from many other compressor pedals, giving the pedal a bit gentler character and allowing some of your initial note attack to come through before the compression clamps down on the signal. The release is also very sweet and musical. 

While some players might wish for a tone control, the Opto Comp does its thing with only the slightest hint of dulling to the highs, so while a tone control (and a blend knob, for that matter) is usually nice to have, it's not as essential here as it might be on some other compressors. The Opto Comp is also a relatively quiet pedal for a compressor too, which both guitarists and bassists will appreciate. It works great with both instruments, allowing for not only dynamics control but also adding sustain and fullness. It may not have the most knobs or features when compared to some other compressors, but it does its job very well and at a very attractive price. If you're looking for something a little less brash than your old Ross-style compressor, or if you're an optical compressor fan in general, you should definitely take a close look at the affordable Ampeg Opto Comp. -HC-



Want to discuss the Ampeg Opto Comp or have questions or comments about this review? Then head over to this thread in the Effects forum right here on Harmony Central and join the discussion!




Ampeg Opto Comp Compressor ($139.99 MSRP, $99.99 "street")

Ampeg's product web page     

Ampeg Opto Comp manual (PDF file)     


You can purchase the Ampeg Opto Comp Compressor from:


Guitar Center     

B&H Photo Video   

Musician's Friend     

Full Compass Systems   









Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.  



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