AMP EQ question (Peavey)

There are two "shelving" controls on Peavey amps. A high and a low. The "low shelving" simply controls all the lower frequencies and the "high shelving" controls all the higher frequencies. These controls will give you a starting point to control your frequencies (basically , your over all tone.)
The slider EQ controls are for specific frequencies. If one string or just a few notes seem stronger or weaker than the rest , you can use the sliders to adjust them. Your overall tone comes more from the shelving controls.
The corner frequency is (I believe) supposed to be the high frequency of what the low shelving controls. I never paid much attention to frequencies on the shelving controls because due to harmonics , they have an effect on all the frequencies. I just use my ears to find what sounds good to me.
On my Peavey amps with similar controls I usually set both shelving controls around 1 or 2 o'clock (a slight boost for both controls.) When I'm using my P Bass , I set the sliders for a slight mid boost (frown face.) When I'm using my Ibanez , I usually set the sliders for a slight mid cut
(smiley face.)
Play around with all the controls to find the sound you like. The shelving controls will have the most effect on your tone and the EQ sliders will let you "tweek" those tones. Enjoy.

 

I think the manual means that everything from 50Hz down will be boost/cut by the same amount with the pivot at 100Hz... But the -3dB is beginning to confuse me.

 

Here's model of a fairly typical bass control at various boost settings; the green trace is full boost and that is the way tone controls are usually spec'ed, at full boost or cut.




So you can see that max boost (center of the shelf) occurs around 35Hz in this particular case -- that would be +12dB at 35Hz. 3dB down from 12dB would be 9dB, which occurs around 100Hz in this case. The -3dB point is a standard engineering (textbook) definition for the half power point, and coincidentally it also often better describes what the user perceives the control doing at more "normal" boost settings, which the purple trace might represent since it's the middle of the boost range. You can see that the meat of the affected frequencies shown in purple are an octave below to an octave above 100Hz, or 50-200Hz, more or less.

There's a very thorough thread explaining all this and much, much more here: http://www.talkbass.com/threads/some-discussion-on-amp-eqs.950782/

 

Yes, thank you. I like graphs!!!