Ross "clones" and variations:
The grey Ross comp pedal is without a doubt the most frequently copied compressor circuit. A huge percentage of "boutique" compressor pedals, including many that claim to be original designs, are just based on this one circuit. A surprising number of them don't even add anything new, just the same design with better capacitors and a 3PDT footswitch. Also one of the all time best-selling mass-production comp pedals, the MXR Dynacomp, is the same basic design.
The Ross/Dynacomp clones and OTA variations are known for adding plenty of sustain, and boosting the mids and high mids, while losing some of the low end. There is no good/easy solution to the low end rolloff--increasing the value of the input capacitor does nothing to help, and increasing the output cap improves the lows but causes a loss of highs. The discontinued Barge Concepts RC-3 is one example of a Ross clone with the switchable option of a larger output cap. Many guitarists complain that they also lose some high end, even with the best versions like the Keeley, but I haven't found that so terribly noticeable myself. Generally speaking, they are perfect for guitarists who like a mid-rangey singing vintage tone; and they may also work well enough for bassists who don't go lower than an open low E. One other thing is these pedals tend to be a bit noisy.
Because there are so many of them, and because they are all so similar sounding, and because the majority of them lose low end, I am really not interested in reviewing any more pedals based on this design. If you like this type of comp and just want "the best" one, I'd say the Wampler is the one that gets the most positive hype (on forums like TGP) at this time. The ones that will do the most acceptable job on bass are the ones with a clean blend, like the Barber and BYOC, as that allows some of the original low end to pass through.
Ross/Dyna clones and adaptations that I know of include:
Keeley, Analogman CompRossor, Xotic SP, Barge RC-2/RC-3, Sitori Sonics, Barber Tone Press, Retro-Sonic Vintage Vibes, MXR Supercomp & Custom Comp, AYA R-Comp, Ocean EFX Comp Box, Uncle Ernie's Honey Driver, Visual Sound Route 66/Comp 66, Teese RMC FK-1, Bone Picker Tight Squeeze, Wampler Ego Comp, Goudie FX, CMATMODS Signa Comp, BYOC 5-Knob & "Vintage", Guyatone ST2 & Stm5, Valco, Moolon, Whirlwind Red Box & Byrdbox, HipKitty Boa, T-Rex CompNova, Morley MOD-PCB, BMF Little Red, Nobels, Rogue, E-wave, Rockson, Glen Burton, Rocktron Reaction, Eden Analog Cold Compress, DVK The Mrs, BBE Benchpress, Homebrew/HBE CPR, Ibanez/Maxon CP5/CP9/CP10, Biyang CO-8 & Compress-X, Hofner, Providence, Kaden, Daphon, Behringer DC9, Tonerider, Maxtone, ProTone, ModTone, DreamTone... and there are doubtless many more.