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Hagerman Compressor Review

The COMPRESSOR by Hagerman is a boutique all-analog vacuum tube compressor pedal using a single 12AU7 tube. It was designed to offer transparent compression with low noise while adding great sustain.

Jim Hagerman has been designing analog circuits for over 40 years. All of his tube creations are designed using high quality components including polypropylene capacitors, metal film resistors, and high temperature electrolytics. Even his enclosures are custom designs. All of his pedals are created to be easy to use and he does not copy existing designs. When you visit Hagamps.com you will currently find 7 tube pedal creations ranging from a 12AU7 boost pedal to a 12AX7 tube preamp pedal. Today we will take a look at the Compressor. True to the desire to be straight forward and intuitive there are just two dials on the front of the pedal, one foot switch and one LED that illuminates red when the pedal is activated. The dial labeled Knee could probably have been called Compression or even Ratio. Basically, it sets the amount of gain reduction. I communicated with Jim about why the choice of verbiage labeling this control Knee and Jim shared that at some point, there is a knee in the curve where the signal begins to get attenuated. To learn more about knee on a compression circuit, see this article.


At maximum Knee, with the dial rotated all the way clockwise, you get about 15db compression. At no point in the range of control does the compression feel squishy — it is usable across the entire range. In fact, you might not even feel like it is working, at first. But aggressively pluck guitar or bass strings while rotating the dial and you will realize it is transparently compressing away. I found my preferred sweet spot with the dial between noon and 2:00.


Set the Level dial to compensate for lost gain. There is plenty of gain on tap. Certainly the amount of gain makeup you will require depends on variables like the amount of compression, the pickup types and what is feeding the compressor. Even cranking the gain beyond what I would ever desire to realistically dial in the circuit remained clean with little to no distortion.

If you desire a compressor to dial in more aggressive squashing, or even limiting, look elsewhere.

That's not what the Hagerman Compressor was designed to achieve. Think LA-2A style compression here. The circuit is feed-forward side-chain and custom opto-resistive attenuation produces a soft knee providing a very natural presentation without that dip-and-swell effect. Feed-forward designed compression engines feed the input signal forward to the sidechain, so it can adjust the control signal in advance of the gain reduction element. Hence the name, feed forward. It is an interesting choice here in that feed-forward circuits are often favored for catching fast transients and for hard limiting. However, catching fast transients and hard limiting is not what the Hagerman Tube Compressor is all about.

How does it sound?


This is one of those compressors that if you like it, will be an always on type pedal.

It has plenty of headroom and doesn't really change your tone as much as change the feel. The latter point is important. The Hagerman Compressor does change the way it feels when playing through it. You will probably feel like everything is bigger sounding yet true to the original tone passed through it. In that sense, it isn't a compressor that is highly colored. On the other hand, it is anything but sterile.


Everything just sounds and feel better when it is on.

Interestingly, the Compressor sounds glorious with passive basses where there is no preamp utilized. Maybe something with impedance going on but wow, I really like the sound and feel when switching off my onboard bass preamps. It's great with basses with preamps too. Notable comparable devices would include the Effectrode PC-2A and Effectrode LA-1A. If you've got your eye on the either one of those compressors you should take a serious look at the Hagerman Compressor. It is less expensive and introduces much of the same sound and feel. The PC-2A might be a little warmer sounding and the LA-1A is probably a bit more lively but the Hagerman is definitely in the same ballpark. Also worth noting are differences in power requirements. The Hagerman requires 9 volts and at least 500ma and center positive plug. The PC-2A requires 12 volts and 600ma and center negative plug. The LA-1A requires 12 volts and at least 1 amp and center negative plug. There are certainly differences in the design of the circuits and the Effectrode products are more versatile. For example, the PC-2A has just 2 dials on the face of the pedal (like the Hagerman Compressor) but also has a switch allowing the compressor to serve more in a limiting capacity. The LA-1A ha variable control of knee in addition to variable control of Attack as well as an EQ toggle and DI out. Another comparable might be the Markbass Compressore but the Markbass actually uses the tube for compression. Overall it is a bit darker sounding and can get more squashy. The highs are more subdued. To my ears, the Hagerman Compressor handles lows well — actually, lows and highs remain quite natural. I had no complaints using the Compressor with the low B with a 5-string bass guitar. In the context of tube compressors, it remains articulate and refined.


It is wonderful with bass and guitar.

My Compressor came stocked with a new issue Russian made Mullard tube. I did roll a few other tubes including an old 50's GE gray plates, 50's Baldwin organ branded Raytheon black pages, and an old Siemens silver plates. All 12AU7 of course. There were subtle differences between them all but at the end of the day, the original tube sounded just fine. The exposed tube socket makes it easy to swap tubes to your hearts content though. I must admit, it is fun.



I have really enjoyed running the Hagerman Compressor in front of my Neural Quad Cortex. While I love how the Quad Cortex is able to digitally capture devices like fuzz and distortion pedals and amps and preamps, the dynamic nature of compressors can't be captured well. The Hagerman adds a nice feel in front of the Quad Cortex and I never want to turn the Hagerman off. I was also impressed running bass into the Hagerman directly into my mixing console where it served to warm up the signal and add some excitement.


Several of my reviews reference compressors that serve well as an always on type device. It is truly the case with the Hagerman.

It is really all about subtle and transparent compression that fills out your tone while tightening it and adding sustain. It's not going to radically alter your tone but it does, well, make it sound (and feel) better. It's not about squash. It's not about limiting. It's not about dip-and-swell. It's more about studio style warmth and evening out of your signal. The pedal itself is surprisingly light. Though there is an arced metal bar over the top of the 12AU7 valve it really offers little protection of the tube. The entire tube is exposed other than from directly above. In fact, I almost directly kicked the tube once when hitting the stomp switch a little far down with my foot. But, since it will probably end up being an always on pedal for you anyway, well, you might not ever need to touch the foot switch. That said, I would prefer more protection of the tube or at least recessing the valve more in the pedal (like the Effectrode LA-1A for example).

Input and output jacks are top mounted as is the power input jack. The foot switch is true bypass. The knobs are slightly recessed into the pedal which is an interesting design choice. They are still easy enough to turn.


At $239 (at time of this review) the price is right for a tube compressor. 10 year warranty. Yes, you read that right. 10 years.


I like the Hagerman Compressor and I definitely recommend you try it.

Pros: • Transparency • Feel of the compression • Sound — makes everything sound more present and full • Form factor for a tube compressor • Ease of use • Price Cons: • Lack of protection of the 12AU7 tube • Not highly versatile • Relatively limited range of available compression Hagamps.com View all compressor reviews

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