Crazy Tube Circuits Golden Ratio Phi v2 Compressor Review

Crazy Tube Circuits is back with an updated Phi Compressor design. The Phi V1 included two pedals in one with an optical engine and FET engine. This time, you get three separate compressor circuits in one pedal at the flip of a switch.


Despite the name Crazy Tube Circuits, the Phi V2 does not use any tubes. Crazy Tube Circuits is a boutique effects company out of Greece.


In addition to the optical and FET compression engines, the V2 adds an OTA design with a feed-forward detection circuit designed to "squeeze" things harder. Crazy Tube Circuits describes the OTA engine as ideal for catching fast transients and for serving as a limiter. I would concur. There are many guitar compressor designs using an OTA circuit.


Also selectable is a FET compressor with a feed-back detector that relies on a FET transistor for gain reduction. The FET design allows for super-fast response and does add a little color.


Finally, there is an Optical compressor engine with a hand selected photocell combined with a feed-back detector circuit. The result is smooth attack and release characteristics which many describe as organic and musical. I found this to be true with this design and the Optical circuit can be dialed in to be very neutral.


In general, I found the FET engine to feel the most crisp and punchy. The optical circuit feels the most warm and fluid. The OTA design is commonly used in the Ross and Dynacomp type compressor designs.

I liked the OTA engine with guitar but not as much with bass guitar as it didn't handle the low end as naturally as the high end. With bass guitar, the FET and Optical engines were more to my taste.

Having three compression engines in one small form factor is quite unique for sure. I had a lot of fun experimenting with each using various guitars and basses. How different each feels and sounds to you will be dependent on specific nuances of your instrument and your ear.


As a general statement, don't expect a radical difference between each of the compressor types.

It is for this reason that I encourage you to take your time with this pedal and come back to it with fresh ears from time-to-time because differences are there, and you will notice more nuances as you become more familiar with the device. For example, given the choice I preferred the FET circuit with my PJ bass guitar. With a modern style soap bar pickup equipped bass I really liked the Optical circuit. And that is where the Phi V2 wins — the choice it gives you over three compression designs in one pedal. Again, give it time and use your ear before writing off any of the compression engines.

The Crazy Tube Circuits Golden Ratio Phi V2 compressor packs a punch with its comprehensive offering of control. Because of the amount of control available the Phi is extremely versatile.

The Threshold dial allows you to adjust the amount of signal that goes into the compression detector circuit. The more you turn the dial clockwise, the lower the threshold meaning more of your signal is triggering the compression engine. There is a LED directly below the Ratio and Blend dials which illuminates red with varying intensity as compression is engaged. Higher levels of signal will result in more LED brightness. I prefer pedals that have multiple LED's for this purpose but the single LED here is sensitive and works well for the purpose of giving you a visual on the degree of compression happening.


The Attack dial allows you to set the time until the gain reduction (compression) begins. Turning the dial clockwise adds more time before the gain reduction begins and therefore allowing more transient through. However, the range of time differs by compression engine. FET and OTA = 1ms to 30ms; Optical = 3ms to 33ms. In practice, the differences are very small.


The Release dial sets the time until the compression stops and returns to the initial level. Turning more clockwise slows the release time and increases sustain. Like the Attack control, the range of time differs by compression engine. FET and OTA = 50ms to 5s; Optical = 80ms to 4s.


The Ratio controls allows you to adjust the amount of compression. The ratio increases as you turn the dial clockwise. The ratio range varies by compression engine. FET = 1.5:1 to 10:1 which is not really limiting territory. OTA = 1:1 to 20:1 which on the far side is much better for using as a limiter. Optical = 1.5:1 to 15:1.


I like compressors that incorporate a blend control allowing you to blend in as much or little of the compressed (effected) signal as desired. Phi V2 offers such a blend control with 100% dry-uncompressed signal when turned all the way counterclockwise and 100% compressed signal when the dial is all the way clockwise. Blend controls are especially useful with 5 string bass guitars where you might want to maintain some of the original dry signal for low end management. Judicial use of the control can also help with added punch and sustain yet still allowing for playing dynamics to come through.


Use the Volume dial to set the output level of the compressor. There is plenty of gain on tap. You will want to increase the volume as you increase the ratio to makeup lost gain. The toggle switch is a 3-way switch used to select each of the three compression engines: FET, OTA or Optical.


Inside the pedal are three additional controls.


The first is a FET compression circuit trimmer which effects the compression ration range of the FET circuit. It has no effect on the OTA and Optical engines. Sometimes high output instruments can overload a FET design introducing distortion. This trimmer will allow you to hear less distortion and lower compression ratio as you turn the trimmer clockwise. You will need a small long screwdriver to adjust. I noticed a small amount of distortion with my Sadowsky basses with active preamp when using the FET engine but the harmonic content sounded nice. Honestly, at the default trimmer setting there is sufficient headroom but the trimmer is there if need be. The trimmer is set down below the PCB board so good luck identifying the original default setting.


Secondly, there is a switch marked Headroom which allows you to switch from the default 9 volt to 18 volt for increased headroom. Important: use only a 9 volt power supply regardless of how you set this toggle switch. 18 VDC is provided by an internal charge pump circuit. I tried the device extensively in both 9 volt and 18 volt settings. There is a discernible difference between the two but I never really felt like I need to operate the pedal in 18 volt mode. Expect a difference in how each of the dials reacts in each of the modes. I didn't find 9 volt or 18 volt to be better but having the option to switch to 18 volt might be helpful for some use cases. I would encourage you to experiment with your particular input path as every case is different.


Lastly, there is a make up gain switch allowing you to select either High or Low output for the make up gain circuit. Selecting High adds an extra 8db boost. For me, there was already enough make up gain so I found leaving the switch in the default low position was just fine. However, you could certainly use the Phi V2 as a boost pedal with the switch in the High position.


The input and output jacks, as well as the power input jack, are top mounted. There is a LED that illuminates bright white when the pedal is activated by the true bypass soft-click foot switch.


On a scale of 1 - 10 for versatility, the Golden Ratio Phi V2 probably deserves a 10.

Not only do you get a comprehensive stack of controls, you also get three different compression engines in one pedal. You get full control of your ratio range, attack, release, the threshold at which compression kicks in and also a blend control. The Golden Ratio compressor is quiet and sounds great. True, there isn't a radical difference between each engine, but it is after-all, a compressor. Given time your ears and fingers will have you identifying specific nuances of each engine. Because of the three different compression engines I would highly recommend the Golden Ratio V2 to musicians playing guitar and bass or using multiple different guitars or basses. It retains the low end quite well, especially when including the blend control. If you are new to the world of compressors and willing to take the time to really understand how compression works, this would be a great device to try because it comes with a descriptive user guide, gain reduction LED, and useful controls over all of the core compression engine variables. For all of these reasons the Golden Phi would make a good device to learn from. Then add in the three different compression types, you can use it to train your ear. I say that knowing full well there will be some who express that they don't hear much of a difference between each engine type. To that I would say, give it time. Use your ear, use on and off, and even record (if you can) yourself playing with the device on and off. There are tradeoffs with each engine. On the other hand, if you want a quick set-and-forget type of compressor you would be better suited looking elsewhere.


The Crazy Tube Circuits Golden Ratio Phi V2 compressor can be as subtle and transparent as any good clean compressor but can also be squishy and offer a little color.

With the OTA engine the Golden Phi makes a nice limiter. In FET mode, you get a little color or sparkle and a nice punchy feel. And then the warm and smooth vibe of an Optical compressor engine is often irresistible. In front of a tube amp I really liked the FET engine. In front of solid state gear, I found the optical engine to my liking. That right there is a major benefit of this device — versatility. At the same time, it's also a lot more fun than many compressors.


I found the Golden Ratio Phi V2 neither clinical nor "effecty". Don't expect something delivering a high level of tonal color like compressors from Diamond or Mad Professor or tube devices like the LA-1A or PC-2A from Effectrode. It will fatten up your tone or add sustain or even out your playing though — all of those things we expect a great compressor to do for us.


There's a lot to like and not a lot to be critical off. The Golden Ratio Phi V2 is a real nice device and really doesn't have much in the way of direct competition due to the integration of three compression engines. If you are considering the Walrus Audio Mira, Broughton Omnicomp, or Empress MKII/Bass Compressor you should take a look at the Golden Ratio Phi V2. The Source Audio Atlas might be the closest competitor. Because of the app and computer editor you can highly customize your Atlas compressor engines. It is a digital device. There is no editor for the Golden Ratio Phi V2 — its an all analogue design. If you are the type that doesn't want to mess around with a computer editor the Golden Ratio Phi might be a great option.


I like this one. It sounds great, is extremely versatile, well-built, quiet, and fun to use.

It's not going to highly alter your original tone, but it will make everything sound better. If you are the type that wants some serious squeeze, well the OTA engine is for you. Want something more organic and neutral? Start with the Optical engine. Looking to tame the spikes in your gain and tighten things up, and maybe introduce a little bit of tube-amp style warmth? Well, give the FET engine a go. Compression is one of those things where different types work better with different styles and with different guitars and amps as well as what effects are placed before and after the compressor in the signal path. It's all about discovering what suits your playing the best. The Crazy Tube Circuits Golden Ratio Phi V2 is an excellent foundation and can handle whatever signal you want to compress. Pros: • Versatility • Three compression engines in one pedalboard friendly device • Quiet

• Sounds great

• Gain reduction LED • Nice price considering functionality

Cons • Possibly too complicated for some users • Not a set-and-forget type of compressor

• Not necessarily dramatic differences between each engine


Retail price: $249 at time of publication


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