A few years ago I developed an infatuation with guitar compressors – yes, those subtle and mysterious pedals that often go overlooked in many rigs in favor of flashier and more exciting effects that have a more obvious impact on your overall sound. While the workings of compressors can be elusive to some guitarists, many of you know that a good compressor dialed in right can cohesively bond your guitar with your amp to create a more consistent and smooth response which in turn can enhance the sound and playability of your instrument and your entire rig for that matter. Guitarists who use a compressor often regard them as indispensable and rightfully so.
While there are many types of compressor pedals with subtle differences in how they compress your audio signal, I’d argue that the inherent sound quality or audio fidelity of a compressor should probably be the first consideration made when buying one. Compressors typically have the inherent drawback of raising the noise floor as they level out your volume and increase the clarity and sustain of your notes, so extra consideration should be made to choose a compressor that boasts high quality, low noise operation. In this review we’re going to be taking a look at arguably the quietest and most advanced compressor ever released in pedal form: the Effectrode LA-1A Super High Resolution Leveling Amplifier.
Audiophilia in Pedal Form
Effectrode is a UK based pedal builder that specializes in building what they call “audiophile pedals”. Living up to that moniker (primarily due to an unparalleled expertise in vacuum tube technology) has helped them build a rabid following of dedicated fans who fill up waiting lists for the limited batches of their latest releases. One such Effectrode offering that has garnered praise among tone aficionados is the PC-2A, a photo-optical tube guitar compressor inspired by the legendary Teletronix LA-2A Limiting Amplifier – yes, the same LA-2A that’s widely hailed as the greatest rack compressor of all time and which you’ve heard on the majority of relevant albums released in the past forty or so years. While the PC-2A is a very respectable heir to the LA-2A legacy and remains a formidable compressor that is still in production, the new Effectrode LA-1A Super High Resolution Leveling Amplifier aims to set yet a new standard in stompbox format guitar compressors.
From 2 to 1A
Effectrode started with the topological foundation of the PC-2A and sought new ways to offer even higher fidelity dynamic volume attenuation. To achieve the lowest noise floor possible, Effectrode employed a parallel tube plate design typically only found in high-end phono preamps for turntables. This type of circuit has never before been implemented in a guitar pedal or professional grade studio leveling amplifier/compressor. The results Effectrode achieved even led to their claim that the LA-1A is “technically the quietest pedal or studio leveling amplifier ever made”. While that might be one of the most casually confident and hype inducing statements I’ve ever seen in print, the implementation of the parallel tube preamp in the LA-1A lends credibility to that statement. For the technologically inclined, here’s an entry in the Tube Cad Journal that explains how a circuit using multiple tube stages in parallel lowers effective resistance and resistance noise. We’ll discuss that more in relation to the LA-1A in a moment.
There are other notable design variances between the PC-2A and the new LA-1A. The PC-2A is a reasonably compact compressor that has only 2 knobs (Peak Reduction & Gain), and on the back is a Limit/Compress switch. This completes a simple parameter set-up that mirrors the ease of use of the original LA-2A. The PC-2A also has internal Attack & Knee trimpots which are useful for calibrating the response of the pedal to perform optimally with your guitar or other instrument of choice. The trimpots’ default settings were perfectly functional for most general uses; however, some musicians and engineers wanted to have these controls more easily accessible. David Gilmour of Pink Floyd fame is known for using a modified PC-2A pedal with external Attack & Knee controls. I’ve also used one and can attest to the merits of having external Attack & Knee controls. The larger LA-1A, housed in an Effectrode Blackbird style enclosure, draws upon the PC-2A mod and provides dedicated surface knobs for Attack & Knee. It also adds a foot-switchable Boost and some other handy functions. We’ll discuss these differences and functions in detail as we go along.
Sound & Performance:
While we’re not exactly doing a PC-2A vs LA-1A shootout, this review will contain notable references to both pedals throughout, so it may be a useful resource if you’re deciding whether to get one pedal or the other. The PC-2A is noteworthy for its simplicity. Just set your Peak Reduction to dial in the compression amount and then set your makeup Gain to match unity gain or add a little boost if desired. The LA-2A retains that ease of use while providing more tweaking versatility and a lower noise floor. And wow, is it quiet!
No hype or exaggeration intended, but I’ve been absolutely astounded by how clean and quiet the LA-1A is. The PC-2A is already one of the quietest guitar compressors available, but the LA-1A somehow surpasses it along with every other guitar compressor I’ve heard in terms of low-noise operation. Anyone comparing the two units side-by-side will notice this simply by setting the pedals to a similar compression response and A/Bing the pedals. According to Effectrode the measured self-noise for the LA-1A is -6dB/oct lower across the entire audio spectrum (20Hz to 20KHz) relative to the PC-2A. That provides some measured proof from a scientific standpoint, but I was convinced just by hearing the difference for myself. Compressors often pose the unwanted tradeoff of adding signal noise in exchange for the volume attenuation and audio massaging qualities they provide, but the LA-1A doesn’t suffer from this drawback even when pushing the Peak Reduction into extreme compression territory and having to boost the Gain quite a bit to compensate. It’s bizarre yet refreshing to experience first-hand as you’d generally expect to fight with the noise-floor when adding more compression. The unparalleled low-noise operation of the LA-1A compared to other guitar compressors will easily justify the cost of admission for many musicians.
The LA-1A is relatively easy to dial in. I’d recommend starting by setting the Gain, Attack, and Knee at around noon and then raising up the Peak Reduction from its minimum position until you hear the compression kicking in while you play. As you get it set to where it’s applying a gentle squeeze to your signal that sounds and feels good, you can then tweak the Gain to match your unity signal level.
I want to discuss the Knee before the Attack as this parameter is especially important in altering the response of the compression. If you set the Knee all the way counter-clockwise, you’ll notice that the Peak Reduction knob seems to have less of an effect as you turn it. The Knee control changes the response curve of the compression (re: how quickly it reaches maximum gain reduction), so as low settings it’ll seem to have a less pronounced effect as the compressor releases while played notes are ringing out before ever reaching maximum compression, making for a very subtle effect. As you increase the Knee, the compression will reach maximum gain reduction faster, resulting in a harder compression and seems to take longer to return to baseline. At extreme settings it has a much more pronounced limiting effect as the compressor achieves full Peak Reduction instantaneously (after the Attack, of course).
The Attack knob sets how fast the compression kicks in (with the Knee determining how quickly the compression reaches maximum gain reduction as mentioned before). Generally, you’ll want to have the Attack set slowly enough so that your initial pick attack gets through before the compression starts happening. To set it up, just crank the knob to fully clockwise and start cutting it back while playing until you’re happy with the transient sound of your pick attack. You can generally get away with pushing the Attack as high as around 3 o’clock without killing your pick attack as long as you’re using lower to moderate Knee settings. I often find myself pulling the Attack down to around the 1-2 o’clock area and setting the Knee to around 11-ish o’clock; then I’ll set the Peak Reduction to taste. Different styles of playing may call for a different feel; for example, try a fast Attack with higher Peak Reduction for a sound that blooms in after your initial pick attack when the compressor starts releasing. As always, let your ears guide you to what sounds good.
Perhaps the most controversial change to the LA-1A from the PC-2A is the removal of the classic LA-2A style “Limit/Compress” switch. On the PC-2A this switch would let you take the compression from a smoother, gentler response to a super squished sound. It’s similar to the switch you find on the front panel of an LA-2A rack unit (or any LA-2A emulation in your DAW software). On the LA-1A, the dedicated “Limit/Compress” function is absent.
Before I did my homework (meaning before I simply asked Effectrode engineer, Phil Taylor), I assumed that the Limit/Compress switch functioned by adding elements to the compression circuit to induce the harder compression response the Limit setting is known for. In actuality the switch “adds resistance in series with the photo-optical attenuator to make the limiting effect more subtle (aka compression)”. In other words the circuit’s natural response is more prominent before elements are put in place to reduce the intensity of the compression. Now at this point you may be wondering what the absence of the Limit/Compress switch on the LA-1A means in actual use. Well…
The PC-2A already added elements to the classic LA-2A style of compression courtesy of the pedal’s Attack & Knee trimpots, and the Knee in particular is a parameter that takes the Peak Reduction response from a smoother compression to a harder limiting. In use it sounds and feels like the Knee control is providing a smooth taper between the classic LA-2A style “Limit” and “Compress” settings. With the LA-1A making the PC-2A’s trimpot functions external, thus giving you quicker access to lighter compression or harder limiting, the Limit/Compress switch could be considered a redundancy among the LA-1A’s surface parameter set. After all, the Knee control on the LA-1A is essentially allowing users to dial in a custom “Limit/Compress” response rather than being restricted to only 2 static settings at either extreme.
I’m over-simplifying what’s going here as the PC-2A and LA-1A are both achieving similar styles of compression response by slightly different means because of the removal of the Compress/Limit switch, but essentially what the PC-2A achieves via a switch and 2 trim-pots the LA-1A is achieving with only 2 external knobs. I find the LA-1A a bit more convenient to use in this regard with its Knee parameter being noticeably more effective when setting a compress or limit response compared to the PC-2A’s Knee trimpot and Limit/Compress switch.
Dynamic EQ – “NORM – JANGLE”
In place of the PC-2A’s Limit/Compress switch is another mysterious switch at the far right of the back panel next to the Input jack. (The test prototype unit in my photos is unlabeled, but production units say “NORM – JANGLE”.) This is the LA-1A’s Dynamic EQ switch. When in the active position, the LA-1A boosts the level of audio content in the upper frequency spectrum. Why is this necessary and important? Well, a noteworthy side-effect of many compressors is that when volume peaks are reduced, you’ll tend to notice a perceptual loss of high-end content. Basically, many compressors kill your top-end. Sometimes this effect is desirable, but the perceived alteration of tone can often seem to dull the sound of your source material. This is why you sometimes see additional Tone controls on some compressor pedals – to compensate for any loss of high-end. But Effectrode’s approach to this issue is surprisingly unique and a rather compelling solution. The Dynamic EQ function boosts upper frequencies relative to the setting of the Peak Reduction knob. Basically, the more you compress your signal, the more the Dynamic EQ will compensate by increasing your high-end. It’s incredibly subtle and musical. I consider the Dynamic EQ function to be the LA-1A’s “secret weapon”, and I pretty much leave it on 100% of the time regardless of which guitar I’m using or what style of music I’m playing. As an extra tip when using the Dynamic EQ function, remember to consider how setting the Knee knob affects whether you need more or less Peak Reduction to fine-tune your compression since the amount of Peak Reduction used will affect how much Dynamic EQ compensation you’ll hear. While these shades of subtlety may go unnoticed to some ears, those of you with a keen attention to sonic detail will likely appreciate the nuances you’ll hear.
LA-1A’s Tube Stages
The LA-1A, like the PC-2A, has two tube stages. The first stage is a grounded cathode tube stage. It’s exactly like the first preamp stage of a Fender Twin Reverb or Blackface Deluxe Reverb. The output stage is a cathode follower circuit which also acts as a buffer. The PC-2A uses a single sub-miniature tube for these stages, but the LA-1A has a lot more tube muscle coming into play here… and protruding from its surface.
For the LA-1A’s cathode tube stage, a pair of 12AU7s provide four triode tube stages in parallel and are primarily responsible for the pedal’s incredibly low-noise compression. These stages overlay 4 identical copies of your guitar signal, and without altering your signal tonality, any self-noise from the tubes “is averaged, smoothed, and reduced.” For the cathode follower stage, two triode stages of a 12AT7 are implemented in parallel to enrich the output signal.
While the stock JJ Electronic tubes sounded fine during my testing, Effectrode also suggests trying other N.O.S. tubes for personal customization; Effectrode recommends Philips JAN 6189W or JAN 5814A in the 12AU7 positions and a JAN 12AT7WC for the 12AT7 position if you seek even “sweeter and richer tones”.
Need a Boost?
With the LA-1A populating a larger Effectrode Blackbird style enclosure, the increase in size afforded the possibility of another foot-switch function. A dedicated Boost function seems like a fine pairing with a compressor as a compressor will generally be running into other drive pedals or into an amp if it’s all you’re using. The LA-1A provides up to a modest +6dB of boost. That may not really sound like a lot compared to what you’ll find of some pedals (+20dB? Seriously?), but experienced ears often understand that less can be more when it comes to precise volume level adjustments and listening for the intricacies of tone variation that small adjustments can make. So the LA-1A’s Boost knob gives you a huge sweep to carefully dial in just a bit of extra volume boost, and it will be more than enough for the needs of the musicians that this pedal will most likely appeal to.
On a note worth mentioning here, the Boost isn’t exactly a dedicated “tube boost” as all the pedal’s tube stages are already being used in the circuit; however, since the Boost can only be used when the pedal is engaged for compression, you’re already getting an audio signal that’s harmonically impacted by 6 tube stages before the Boost jolts your signal a little harder into the rest of your audio path. So you are technically boosting a tube flavored audio signal, just not applying any other tube gain stages that could potentially alter or color your sound. Sure, it would be neat if Effectrode could have crammed a subminiature tube under the hood somehow for even more tube-y goodness, but the approach implemented is more respectful to the painstakingly attuned audio signal produced by the compressor.
On a side note, I did originally have minor concerns about the Boost not being able to be used independently from the compression, but then I realized that I’ve really been leaving the LA-1A on all the time. With most “always on” compressors, I still find myself sometimes turning them off on occasion; for example, a particular compressor may always sound great for leads but sound a little off when playing some styles of rhythm. In the past few months I’ve been using the LA-1A, it has become a staple of my sound. So yes, while I’d still argue from a critical standpoint that would have been nice to have at least had a dip-switch toggle option to set the Boost to be used independently (maybe in a future PCB revision?), but it most likely won’t be an issue in actual use if you find yourself leaving the compressor always on.
The EXT. SELECT jack lets you plug in a TRS cable to take remote control of the Bypass and Boost foot-switches. This gives you similar control to that of using a 2-button foot-switch with your Fender Twin Reverb or other similar amp. And the external switching functionality is an indispensable accommodation that users of professional effects switchers will appreciate. If your switcher has at least two “control out” or similarly named output jacks, you have use them to operate the LA-1A. But what if you have limited control outputs and/or want to leave the LA-1A always on and just operated the Boost remotely? Simply make a custom TRS cable and short the “Tip” end of the cable. This will make the pedal be activated by default. Then use the “Ring” side of the cable with your switcher’s control output to toggle the Boost on and off as needed.
Studio Use – Direct Out
For maximum versatility in the recording studio or other professional audio environment, the LA-1A has a few extra nifty features in its arsenal. The “600 OHM BAL. OUT” jack is a ¼” TRS output that lets you connect the pedal (using a TRS to XLR cable) to a mixing console or other destination that has an XLR input. This output is fully balanced and isolated with a Triad Magnetics audio transformer to eliminate ground noise and reduce hum to an absolute minimum. A gain pad switch with +6dB, +12dB, and +18dB options facilitates matching the output level with other line level or instrument level gear.
Stepped Gain vs Variable Gain
A fascinating point of note about using the “Direct Out” option is that it completely bypasses the Gain knob and Boost functionality of the pedal. The idea behind this is that in some audiophile and pro-audio circles, stepped volume attenuation is preferred to variable potentiometers for improved audio fidelity. With the LA-1A this approach shouldn’t be mistaken as a means to simply achieve more transparency (as the Triad Magnetics audio transformer adds its own subtle character and colorization), but instead what’s happening is that the Balanced Output is bypassing the Gain and (switch-able) Boost potentiometers, removing any possible elements that could potentially add signal distortion. The 3-position Pad switch is instead used to select your fixed output level while the input gain on your audio interface or the level sliders on your mixer can be used for precise gain adjustment. The pro-audio crowd will likely appreciate this stepped implementation for how it facilitates integration of the LA-1A in professional audio environments.
For fun I connected the LA-1A to my pedal chain via its Balanced Output using the Tip plug of a TRS cable to feed my other pedals. It’s hard to say if the Triad Magnetics transformer was actually further sweetening my tone or if the pedal was even quieter or more “hi-fi”. It already sounds excellent, and it’s the quietest compressor pedal I’ve ever played, so it’s likely not necessary for guitarists to attempt to “hack” their way into using the Balanced Out in a typical guitar setup. Still, if you must toss conventional wisdom to the wind, you could experiment with running it this way although bypassing the Gain pot may not be ideal considering you’ll still need to use another gain stage (like your amp’s Gain or another pedal with volume control) to precisely set your volume level. Also, giving up the Boost might not be acceptable. While reading the spec-sheet might inspire the imagination to try things like this, for pedalboard use you’ll be better off sticking to recommended use of the normal Output. Save the Balanced Output for recording guitar or bass directly into a DAW (like Logic or Ableton Live) for processing with amp plugins or re-amping your dry guitar.
Still No Gain Reduction Metering?
Aside from all the praise I could continuing heaping upon this pedal, there’s only one other thing I’d like to have seen: gain reduction metering. Sure, it would likely be impossible to fit a real LA-2A style VU meter on the LA-1A’s already packed surface area. And even a row of metering LEDs might have been difficult and costly to implement. But perhaps a single multi-colored LED that indicated Peak Reduction could have been squeezed in somewhere. As with the PC-2A, you’ll just have to use your ears, but hearing can be deceiving and all kinds of factors like listening fatigue and the Fletcher–Munson effect can play tricks on how we think we’re perceiving sound. The LA-1A often performs best by adding very subtle compression, and it would have been nice to get some visual feedback as well as providing a helpful training aid for guitarists who are less experienced dialing in compression or really hearing the difference it’s making to their signal. The lack of gain reduction metering isn’t a deal-breaker and doesn’t really hinder performance or enjoyment of playing the LA-1A, but it’s likely to be the most notable addition that could make this pedal a more perfect guitar compressor.
The Effectrode LA-1A Super High Resolution Limiting Amplifier is a top-shelf photo-optical tube compressor for musicians who place the importance of premium low-noise operation above all else. For all the variations of compressor pedals that exist and countless iterations from various builders, the LA-1A is most likely to objectively be the quietest, reaching a new plateau I don’t expect another builder to match anytime soon. It even somehow manages to top the venerable PC-2A thanks to its external Attack & Knee controls and tone sweetening Dynamic EQ functionality – not to mention the sweet Boost function. (The PC-2A is still an excellent unit, and if board real estate is a concern, that pedal is definitely worth considering.) While my overall impressions are primarily based on how exceptionally well the LA-1A performs as a pedalboard bound guitar compressor, the potential to use it in the studio as an alternative to an LA-2A rack unit may also warrant consideration. Effectrode have spared no attention to sonic detail in designing a compressor that stands tall in all areas of operation and applicability, and in the few months I’ve spent with it, it’s become my new favorite guitar compressor pedal.
That concludes our Effectrode LA-1A review. Thanks for reading.