Blacky's Bass Tone 
Ever wonder how Blacky got his cool distorted Voivod bass sound? Well he was nice enough to post a very detailed description in the forum here at this site. I have copied it below as he wrote it. You can follow his work by going to his website

THERIAULT.NET

or his musical project COEUR ATOMIQUE

or his small enterprise BYW Audio
 

Posted May 04, 2002 by Blacky

I received a few email with the question about how do I made that sound when I was in Voivod. Here the break down on the first setup, which I had in the first four albums.
a 1976 and a 1972 100 watt Marshall, which I used in combination with a set of four 15 inch at 16 ohm impedance speaker cabinet. Then I run the whole thing at about 7 or 8 (btw there is no 11, it stop at 10 ) , trust me that is loud, so you can also use a Tom Shotz Power Soak which I used to put on the side forcing me to re-weld the whole after a while since it was getting so hot that part became un-welded. There was also a trick that I used often and it was pretty cool, is to run the only two of the four power tube, since they run in pair (push-pull), you have to take 2 and 4 out, but be really careful, it will eventually blow the tube, I mean literally, and also you will need to run a powerful fan behind or making a whole on the side closer to the tube. One thing with the power soak, you will burn the main resistance that is under each tube socket, so be prepare to get space part. I never really use effect or distortion pedal of any kind except of course for effect like echo or reverb and harmonizer which was use in the last few records, for that I hired a technicien, Richard of Amplitech (sorry I can't remember his last name), to do a modification for Piggy’s and my Marshall which consisted in having a input and output between the pre-amp and power amp section of the Marshall, this would also add one extra pre-amp tube, this would give us the ability to pass the distortion as clean as possible into the effect, which for the bass was not such a big deal but for Piggy’s sound it was crucial, otherwise everything would sound very muddy. I later learn to do it myself since we went through many amp, and they needed some repair on tour sometime. I remember that night in LA when a beer fell in the back of my Marshall during the show, I quickly change the fuses and up it was running again, that damn thing got so hot that by the time I switched fuse all the liquid was gone, no big deal. I’ll post the whole modification on the site later on if people want to know.

The lastest setup which I still have is a Marshall 9000 pre-amp use combine with a good amp like crown or bmg or even a good old acoustic, love those, there so raw, that will do the trick ok, but in studio I always would go back to the Marshall, could be a JCM800 but always tube things. Then the instrument, the bass guitar, first the string, I used a new set of strick for each show. In studio I change string for every five to six takes in studio in average every 15 to 20 minutes, but I couldn’t affort new string, which would have been real waste anyway, so all I used to do is to take them off and wash them with dish soap. Yeap right Blacky washing is bass string, I got reall good at it, I think I spend more time in studio doing that than smoking pot.  Then there is the Liberatore, basically it’s a maple wood custom build one piece neck from bridge to head, with EMG pick-up, which I designed the shape and Mauro Liberatore created, he used to freak a little by the treatement I give them, but I love those instrument, specially the last one he made for me, the five string piece, high B, not the standard low B, so I could play chord and just sound more like a guitar but just bigger, I really was taller after all, just joking. We always make sure that our both sound and playing wasn’t getting in any conflict in the sense of alienating each other sound, which was really the whole Voivod sound, the real magic.

At last the real secret in making that sound is how you play the bass, I used to play real hard, but precise too with a hard as hell plectrum, basically it has to sound right without any amplification, also the friction and buss is a must since it will add in the distortion level but you must work on the control aspect of it, there again Kula this is why Angel Rat sound so lame, Mister Brown cut the distortion track, then when you think you are ready you turn on the whole thing and freak everybody next door. Careful or you will break the window glass~

There it is -- I thing this tells it all, so have fun. It’s pretty cool playing bass, specially when you can blast it off.

[Then I posted a few follow-up questions and he continues below:]

Super lead was the choice, I had super bass ones and it didn't work shit for me, there was simply no distortion coming out of it. The dual tube out fit was simply to get the same result of over saturation but at a lower level, but you couldn’t really sustain it too long since the tubes were cooking faster.
In regards of the power soak, Piggy and I both used it for quite sometime, basically until we had the pre-amp separation modification done, after that there was simply not much use for it. About the playing, yes playing real hard was my way to say louder is never loud enough. Funny you mention about Piggy cause he was the opposite, he played with .008 string gauge and played softly, not at all like the Metallica, Slayer dudes, but more I guess like David Gilmour or Jimmy Page, perhaps! Remember Piggy learned his skills playing over records of Gentle Giants, Yes and Led Zeppelin. (And not resin but sweat.LOL)

Here is a link to the VoivodFan forum he posted this in the Musicians topic area.