Pre and Post EQ schematic

[Steben]

Would this be useful?:


Especially for fuzzes/dist. Note the AMZ preEQ since it can be set "flat". It can also be used if wanted for the post EQ, of course.
FX with tone control don't need the "BMP" tone control, yet for Fuzz Faces and Tbenders it is quite better for compatibility with the complete gear set.

[R.G.]

While any means to do pre and post EQ for an effect is useful, the simplistic tone circuits of the BMP and it's many derivative modifications are not as generally effective as a parametric or graphic EQ approach.

Sub in there a graphic or parametric EQ for those EQ blocks and you have a remarkably effective distortion shaping setup.

I say "graphic" for the function. You don't actually need the slider pots for this. You could also just mount six or eight small rotary pots in a row for the "graphic" pots and get two of these inside a stock box.

[Phorhas]

I thought of a similar concept a while back.. wish I'd have built it... I really need one - but so much to do first !

Cheers

[Steben]

While any means to do pre and post EQ for an effect is useful, the simplistic tone circuits of the BMP and it's many derivative modifications are not as generally effective as a parametric or graphic EQ approach.

Sub in there a graphic or parametric EQ for those EQ blocks and you have a remarkably effective distortion shaping setup.

Yes, true enough. But not yet looking to construct allround "generic" units I thought the AMZ was a simple aproach on getting the two extremes and in-betweens I'm looking for: treble boost ("treble"-for high gain sounds) and tone suck emulation ("bass"-for fuzzy sounds). It still is a very effective circuit for a passive one-knobber.

But it's true a crancked-AC30 or Classic Tweed Fender- sound rely on a predrive tone stack setup with a subtle (or less subtle) notch somewhere around 400hz, which is hard to achieve with one knob. Am I wrong here?

[R.G.]

I thought of a similar concept a while back.. wish I'd have built it... I really need one - but so much to do first !

There's an untested layout for that at GEO - http://geofex.com/Article_Folders/EQs/greqs.gif - in fact, two of them. One with the odd KA2223 graphic EQ chip, and another using common dual opamps but the same otherwise. It uses either trimmers or external pots of either rotary or slider. Two of these boards would do the pre/post EQ function.

[WGTP]

That is sort of the idea behind the EH Graphic Fuzz.  7 Band EQ's can be had for $30.

To me, a cool ideal would be to have an EQ on both sides of the distortion with a single slider for each band working in reverse so that raising one side would lower the other.  The overall EQ would stay about the same and the Character of the distorition would change.   

[R.G.]

To me, a cool ideal would be to have an EQ on both sides of the distortion with a single slider for each band working in reverse so that raising one side would lower the other.

No worries - since the stock variable-Q graphic EQ uses linear pots, make two boards, and use dual pots, either rotary or linear. Wire them so turning up the EQ on one turns it down on the other.

I'm not sure the overall EQ would be the same, but it would be an interesting experiment.

[WGTP]

Might need to move the post EQ bands up an octive to cover the harmonics generated by the distortion.

I have also thought about doing that with 2 BMP tone controls working in reverse with a dual pot using a dual op-amp clipper. 

Or slipping a 7 band EQ between the 2 stages of a dual op amp clipper.   

EQ's just aren't as sexxyy as Vulcans, Rats, Screamers and SRPP's.   

[R.G.]

The slick, cheap way to do this is to get an old hifi 10 or 12 band graphic EQ from ebay for a few bucks. Use one channel for the pre-EQ and one for the post-EQ.

[donald stringer]

would you have to do any mods to the circuit or is an eq an eq be it hifi or stompbox. If thats the case you would just modify the 1/8 jacks to 1/4 jacks.I am all the time seeing those in junk stores and yard sales.

[R.G.]

No circuit mods are needed. The hifi EQs are designed to work on line level signals, about 10x guitar level. They also tend to have higher voltage (like +/- 12 to +/-15) power supplies for bigger headroom.

Replace or adapt the connectors and they should work fine.

[WGTP]

Experimenting with different clipping, methods, it seems that the EQ changes, not just the amount and character of the distortion.  The bass treble balance and mid-range can all change.  Some seem to emphasis more or less mid-bass or upper mid-range.   Is that an illusion caused by the different clipping thresholds or knees, or is it really there. 

[ragtime8922]

I think this is an AWESOME topic that requires experimentation. I am a big fan of parametric EQ for guitar, at least for mids. I'd like to experiment with a parametric front and back, a graphic front and back and all variations in between. Probably ending with a low and hi knob with a two-knob parametric mid so that the mids are adjustable at 2 different frequencies.

This topic, once evolved in to a project, will add a ridiculous level of versatility to distortion/overdrive pedals. Maybe before and after a whole pedal rig as well.

Keep this going!

[R.G.]

This topic, once evolved in to a project, will add a ridiculous level of versatility to distortion/overdrive pedals.

Oh, yes, it will do that.

In fact, the problem is that it adds so much versatility that you can lose whole weekends messing with pre and post EQ in search of the ...perfect... distortion. And you'll swear that the next tweak will get it. People have starved to death tweaking fuzzes like this. 

What most commercial pedals do is to come up with some EQ settings that sound killer, then they hard-wire those in, perhaps as a couple of presets. The versatility kills you on stage when you want to flip from one sound to another. The only good solution for that is either a couple of presets or some separately EQ'd loops.

It's a hard point - versatility and complexity are two faces of the same animal.

[PaulC]

One thing I've been playing around with is using a single wide mid band eg as the actually gain stage in the front end of an overdrive.  Set it up so it doesn't cut - justs boosts.  That way you can set the gain control to have a flat eq  when at unity, and have a nice bass and treble roll off when cranked before you clip it. 

R.G. - you going to NAMM? 

Later, PaulC