Typically those bigger bands have bigger budgets which means higher quality gear. I'd say a majority of the professional/gigging deathcore bassist's tones come from their bass and head only, maybe a preamp of some sort, like the Sans Amp Bass Driver.

Your best bet (other then buying a $1000+ head) would be to get the Sans Amp Bass Driver, that will give you the thick, meaty tone with a decent amount of distortion.
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down tune to get that aggressive floppy sound
i dunno about "that steel sound" but the sansamp bass driver also gets my vote cuz it can get you a real gritty and mean sounding tone, not so much distortion as it is drive, but it doesn't cut your low end and in my opinion is great for any type of death metal/deathcore whatever
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Actually, the MXR M-80 has a better distortion and EQ than the SansAmp does - the SansAmp only has knobs for "High" and "Low."

Although, the programmable ability of the SansAmp is a plus.

To get a real awesome tone, look into the Sansamp RBI.
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alright sansamp sounds really good, yeah i'm looking more for a heavy tone then a distortion

Your title says distortion, you should specify that you don't want a distortion in your post/title.

Anyway, get the MXR M-80, I have it and I love it, it suits both of my (very different) bands, me and it's sizeable list of endorsees, check it out at least.
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I know exactly what you mean, I'm looking for the same tone but mostly the deathcore bass players get their sound out of their amp an bass.

for example, job for a cowboy's bassist has my dream tone, he play a warwik trough a ampeg svt and a 8x10 cab without effects.

just save allot of money and buy an ampeg ^^ then you'll get the sound
and buy warwick strings they have a very good tone for deathcore but that is just my opinion
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I believe a lot fo bands simply overdrive their (often tube) preamps, as said already.

Therefore, if you want a pedal, you need one that overdrives ina similar way. From experience, I can recommend the Fulltone Bass Driver (on higher setings) and the Sansamp DI. Can't comment on the MXR though.
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