Way Huge Green Rhino Mk IV

I had to buy this pedal after I got the MK V version. Apart from being much bigger, the Way Huge Green Rhino Mk IV has a different knob layout. Instead of the Curve knob, it has 100Hz as well as 500Hz, so you can influence both frequencies at the same time. The inside holds no hidden knobs or switches.
Controls are pretty simple. You get your Volume/Drive/Tone that work like they do on the Mk V.
I still cannot really tell if the tone knob is cut only at 3kHz or if it is capable of boosting, too – with it wide open I do get more treble, but that could also be from the added harmonics. The switch in the middle gives you the option between the classic Tube Screamer sound (which means it gives you a rather drastic low-cut and therefore is more or less useless for bassists) and the modern sound which is the default (and only) setting on the Mk V. Apart from that, there are the two knobs for 100Hz and 500Hz, both active with boost and cut and a center detent.

With the switch in the modern position and one of the two EQ knobs at noon, I can make the Mk IV and Mk V sound nearly identical. There are minute differences, but I would not have the slightest chance in a blind test, and it might as well be that I’m imagining things here and they sound completely identical.
I really loved the MK V with the 100Hz dimed, so I could not properly explore the options the 500Hz band has to offer – it was not worth sacrificing the low boost for that. It made me curious enough to buy the Mk IV for that option, though. I said in the review of the Mk V that cutting the 500Hz band gives your bass a crisp and tidy sound that sounds epic in the bedroom, but in a band mix it’s as buoyant as a brick.
I also said that diming that knob gets pretty honky – using a P bass makes it even worse. But what about the options between massive cut and massive boost. I know 500Hz is a pretty important frequency and a little goes a long way. So if I were to copy my favorite settings from the Mk V to the Mk IV and then started raising 500Hz by small increments until that sweet spot is hit where the bass takes a small step forward in a guitar heavy mix, without putting on the clown shoes (honk honk!) — would that be a significant enough advantage over the Mk V to justify the bigger enclosure?
I must admit that I had my doubts about the Mk V as soon as I found out the Mk IV has the 500Hz option and I really wondered what the people at Way Huge were thinking, putting those two bands on one knob and letting you access only one of them at a time. Testing the whole thing in a band setting in a room that’s way too loud, with heavy guitars that take up lots of sonic space was a bit of a surprise.
The one thing I had hoped for did not happen – the Mk IV was not really able to push itself through the mix a little better – this effect was tied to the honky sound you get when you do it too much and I was unable to find the sweet spot where there is no audible honk, but the bass is sitting better in the mix.

That said, the Way Huge Green Rhino Mk IV is still a great pedal, because it can sound absolutely identical to the Way Huge Green Rhino Mk V. In direct comparison, the only downside I can see is that it is much bigger. The advantage is that it can run on battery – so if you’re thinking about bringing only a single pedal to a gig, this could be useful.
For my part, I decided to keep the Mk V. The smaller footprint and the fact that it works very well for me with every single knob dimed (except for the volume), which brings a certain simplicity with it were the things that won me over.