Passive EQ with an op amp preamp- Gain set suggestions?

[Electric_Death]

Is there a common gain set used when simply wanting to drive a signal through a passive EQ stack?

I suppose I could take the middle ground and just go with 100x but I figured I'd ask the vets first. The intentions is a basic preamp to drive a mic signal with a Marshall style tone stack for adding shape pre mixer which will of course give me heaps of frequency boost/cut. I'll slap a master volume on there as well so if I get excessive with the gain, no big deal but if I don't go high enough, I'll bleed the signal dry with the tone stack.

[slacker]

Check out the runoffgroove tonemender that's basically what you're talking about.

[d95err]

Are you sure you want an FMV (Fender/Marshall/Vox) type tonestack? This tonestack is specifically designed for guitar amp use, and probably won't work too well with microphones. It has a big mid dip regardless of how you set the knobs and you can never achieve a flat response.

I think a passive Baxandall style tonestack would work better for a microphone signal. Checkout the Tonestack Simulator program over at www.duncanamps.com to see the frequency response of different tonestacks.

[Electric_Death]

I hadn't said anything about wanting that circuit, I was just asking what would be a good gain multiple to go with for driving a dynamic mic signal through a passive tone stack. slacker mentioned the FMV and while it's an interesting circuit, I'm just planning for a passive to drive the signal through after boosting it with an op amp stage. The FMV did however give me the idea to slap a couple switches in there for toggling between cap values to jump focal points.
In my opinion, active EQ is the wrong way to go due to the level of alteration which occurs.

I've had the Duncan Tone Stack Calculator for several years now, the Marshall is pretty easy to get flat response out of but that's of course subjective to the wave form going in. A couple minor cap value changes makes it quite suitable for vocal frequencies but having tested one made with the OEM values, it sounded just great with the mic I built. My treble cap is tantalum so maybe that is a factor.
10X might be a little low, 100X will probably be overkill but I suppose it might be handy to be able to kick in some overdrive so going 100X might not be overkill. The mic canister is pretty large and fancy looking so I should add plenty of options. As planned it's 3 band tone, volume, maybe some switches for alternating cap values and I guess I'll go ahead and slap some diodes for distorting vocals.

I was mainly curious to know if anyone's ever tackled such a project and what type of gain they found suited a mic preamp with tone controls best.

[dano12]

I built a three-band baxendall type tonestack a while ago and needed to make up for the insertion loss. I used an opamp booster and had the same question as yo re: gain settings.

What I ended up doing is making it variable gain with a pot and then testing it on my specific pedal board to determine how much gain was needed, through listening tests, as I changed the tone controls. Also, having the gain adjustable turned out to be a good idea later as I placed the tone stack (in a pedal) at various different locations in the pedal chain.

[PerroGrande]

If the EQ/stack is adjustable, I don't see how you're going to avoid using a variable gain design like dano12 mentioned if what you want is no perceptible volume change with the eq off center... 

I suppose you could calculate the "worst case" attenuation for the eq and then build a booster of similar amount.  But then, when you don't have the EQ cranked all the way down, you'll be getting gain.  This may or may not be okay, as it will depend a little bit on the level of the incoming material and the stage's (and subsequent stages') headroom.