Don't worry about asking basic questions. That's why "The Entry Level" section of the forum is here. Remember we were all noobies at one point. The only stupid question is the one that goes unasked.

What kind of speakers are you using? How far are they form the front and side walls? In general most audiophiles (myself included) are pretty against EQs. For many of us the goal is to duplicate the original event as accurately as possible, adding nothing and taking nothing away. An EQ, by it's very nature is DESIGNED to change the sound. Standard EQs are a band-aids that usually create more problems than they solve. Instead of using an EQ to reduce bass the appropriate method is to reposition the speakers to interface with the rooms acoustics in more optimal manner. For example moving speakers further from room boundaries such as front and side walls will reduce overall bass and make it less "muddy" at the same time. As another example more detail (high frequency information) can be obtained by toeing in the speakers.

When you say "bypass" the EQ, do you mean you un-hook it from the system, or hit some bypass switch? If I understood correctly, when you bypass the EQ, the sound becomes too bassy and you have to use the tone controls on the pre. If you're using a bypass switch, try removing the EQ from the system entirely and see how it sounds.

While most people are anti-EQ, many of those people will give in and slightly adjust the more subtle tone controls that are on a pre. But if you're turning them all the way up or down, it seems like there is another problem.

Other than that addition, x2 on everything mrlowry said.

Another method of reducing bass without an EQ that I forgot to mention in my first post would be bass traps. An EQ treats the symptoms, but leaves the cause untreated.

Cassette makes a pretty poor source so running it through an EQ might make a little sense to some. You could give it a try. But again can you "improve" the original? That's getting a bit philosophical but I'd say NO. On a practical lever if you tried to use the EQ to compensate for the fact that the tapes were rolled off on the high-end frequencies all you'd really be doing is boosting the tape hiss because the information that you are trying to get just isn't on the tape. Or is in such small quantities that boosting it results in a proportional boost of the background noise and in effect isn't an improvement. Bass is a similar story. Cassette has really mediocre bass, especially when talking about deep bass. Boosting ultra low frequencies is of little help because again they are MIA (Missing in action) on the tape. You can't boost what isn't there. So if there is music that you love on tape enjoy it and accept the tapes for what they are instead of trying to change them. They are kind of like people that way.

However I'm sure that some will disagree with me when it comes to EQing tapes. For me the only thing EQ's were good for was TRYING to fix cassette tapes and/or mediocre speakers. As both things have begun to disappear so has the EQ. A coincidence? Probably not. Plus they don't play well with surround receivers. That was probably strike three for the category.

Good lord don't make me open that can of whoop-ass over here too!

http://forum.stereophile.com/forum/showflat.php?Cat=0&Number=57519&an=0&page=0#Post57519

Just kidding.