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Sushi Box FX Single Slice Compressor Review

Here we have the latest compressor from Sushi Box FX and it is an OTA (operational-transconductance amplifier) compressor design. Sushi Box FX is known for designing circuits integrating valves and that is true of the Single Slice compressor. In this design, the tube (12AU7) is part of the input stage to add a little special something to the input also to feed the sidechain. The sidechain is the part of the circuit that informs compression engine how to adjust the signal output in relation to the incoming signal. The tube definitely imparts an audible flavor that could be characterized as subtle tubey goodness or warmth.



On the Single Slice Compressor product page at the Sushi Box FX website the pedal is described as having been designed to "provide a gentler squeeze to fatten the sound and control dynamics." I find that to be a good way of saying what my ear is hearing.


Single Slice isn't a highly versatile compressor. It is definitely not a limiting type of device. It is more about sustain and tone characterization.

More about the inherent tonal qualities later. There are five dials on the face of the pedal and one footswitch.


First the COMP dial. The Sushi Box FX website says the comp dial effectively controls the sustain or release time of the signal. To my ear, that is in fact what his happening. As you rotate the dial more clockwise the squish (compression) is dramatized and has the effect of clamping down longer to increase sustain by compressing the signal longer. The word "Comp" is misleading for what the control is actually doing. Why? It seems to me that the Single Slice is essentially a fixed ratio circuit. Increasing the Comp dial (rotating it more clockwise) is not increasing the ratio. I.E. 2:1 going to 4:1 or 10:1, etc. Think of the Comp control similar to the Release control found on other compressors. Below the COMP dial on my pedal is the dial labeled THRESH. Looking at the Sushi Box FX website I see this dial has been labeled differently now. It is called SENS and sets the sensitivity threshold level for the compression. Regardless of how the dial is named, as you rotate the dial more clockwise you are decreasing the sensitivity meaning telling the compressor to react less to the incoming signal. Rotating it more counterclockwise increases the sensitivity to get the compression to kick in faster. With bass guitar, I found the sweet spot between 9:00 and 11:00 for my taste. To the right of the THRESH or SENS control is the ATTACK dial which sets the attack time of the compression. The Sushi Box FX web site says counterclockwise is faster, clockwise is slower. This is not correct. In reality, it is the other way around. Rotating the dial clockwise increases the speed of the attack meaning as you rotate clockwise the compression engine is clamping down faster on your initial transient. The BLEND control blends the dry/unaffected signal with the compressed/affected signal. Full counterclockwise is 100% unaffected, full clockwise is 100% affected. Finally, to the right of the COMP control is the OUTPUT dial. Think of it as a master volume or makeup gain control. There is plenty of gain on tap. All of the controls are highly interactive. There is no LED indicating the amount of gain reduction (a feature I really appreciate on compressors and one that is becoming more common) so you need to use your ear to dial in the right amount of compression for your taste. At first, the controls each seem like they are making subtle differences as you rotate them. For example, rotating the Attack dial clockwise is increasing the speed of how fast the compression engine is claming down. If you have the Threshold too high you aren't going to notice the impact as dramatically. Turn down (counterclockwise) the THRES/SENS control so that the threshold is lower and you will notice the Attack control having more impact. This isn't unique to the Single Slice compressor but it isn't the case here where a little change goes a long way.


I typically appreciate having a dry/web blend control on a compressor because it allows you to dial in more aggressive levels of compression (lower threshold, faster attack, higher ratio, etc.) but then recover some of your natural playing dynamic by allowing some of your unaffected (dry) signal into the mix. Honestly though, the Single Slice probably doesn't really need the Blend control as it overall leans more to the subtle side of response. It's not that it isn't useful, it is. But you are starting with a fixed ratio and essentially increasing or decreasing legitimate sustain and subtle smoothing.


This isn't a compressor that is designed to deliver extreme levels of compression.

One exception to this is if you rotate the Thresh/Sens control all the way counterclockwise. By doing so you have essentially eliminated any threshold and the compressor will work pretty much immediately on any incoming signal which is the best way to get maximum squash out of this compressor.


For my taste I pretty much leave the Blend control 60% to 75% affected. The pedal can be operated at 9 volts or 12 volts. Note that pedal runs at high voltage so you must use a power supply that delivers at least 400ma. I like running the Single Slice at 12 volts. To my ear it sounds and feels more open and maybe a bit less congested and with less sag. There seems to be plenty of headroom at either 9 volts or 12 volts. We are talking subtleties here though.


The footswitch is the soft switching relay type. Input and output jacks are top mounted as is the power input.


The inherent tonal landscape is fairly neutral and seemingly flat EQ.

There does not seem to be a dramatic loss of highs or lows. It doesn't bolster the lows either. Rather it adds a general girth to the overall tonal balance. Moreso than many other compressors the midrange quality of an instrument seems to pop out more when playing through the Single Slice compressor. I suppose that could be a good or bad thing depending on your preference. With a couple of instruments I used to test the Single Slice I found that my ear preferred turning down the onboard midrange control when playing through the Single Slice. On the other hand, that mid presence can be useful in cutting through a dense mix. On that note, to me, the Single Slice is one of those devices that sounds better in a mix than when hearing it in isolation or in your "bedroom" practice setup. It reminds me of listening to my Sadowsky basses alone versus with the band. There's something about that preamp that just works in a live mix but can sound jarring or fatiguing sometimes on its own. I had that same feeling about the Single Slice. In the IEM stage mix though, the Single Slice brought the right punch and warmth and fullness that is pleasing.

It's a compressor that will add a bit of fatness without having to deal with intensive squash.

The tone is rich with a definite inherent character. Not distortion or obvious harmonics. Not intensely wooly either. Just a little special something. A bit like the effect of playing through a cabinet. It doesn't offer the sparkle up top or sheen of tube compressors like the Effectrode LA-1A. It's not dark sounding per se but not as open and lively as some of the FET compressor designs. While it does add a bit of fatness to the tone it does so in a way that adds weight to the notes as opposed to what I would describe as a wider or 3D type of way that the Markbass Compressore or Retrospec Squeezebox or Doc Lloyd DLA-2A does. It does a great job of smoothing out your signal which is exactly what we all want in a compressor. You will hear your softer notes louder and your louder notes subdued with a good bit of added sustain. It's also worth noting that there is no pumping action here either, even with the Comp/Release control dialed up. This Single Slice Compressor on its own is pretty quiet. However, I did find it highly influenced by what was in front of it, including whether an instrument had any type of gain staging built in (like an onboard preamp) which tended to increase the noisefloor the Single Slice picked up. Increasing the Comp/Release control past 2:00 definintely increases the noise floor. To be expected, the more Output gain you add, the more downline noisefloor increase will result. It's not unmanageable though and definintley not something you would notice in a mix.


Build quality is great. Dials all turn with authority and have a very nice level of resistance. My pedal was delivered with an intense pink LED that illuminates behind the 12AU7 tube. I think the pedal has a nice look and the colorful swirly graphic adds flair without being over the top. I've been through 120 or so pedal compressors now in this shootout. I've seen a lot of different designs and implementations. The Single Slice is one of those devices that is enough different and unique that it could find its way into my regular rotation. Pros: • Punch and fullness • Unique implementation • Plenty of sustain Cons: • Not all that versatile • Confusing control naming • Possibly too dark sounding for some Retail price: $250 SushiBoxFX.com Read all compressor reviews.



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