Tone filtering ` before gain or after

[Harry]

Could someone please tell me the differences between putting tone circuits before a gain circuit and after the gain circuit?

[R.G.]

If the gain is purely linear, none at all.

If you are misusing "gain" for "distortion", a tremendous amount.

1. All distortion devices are level sensitive - they start being nonlinear at some signal level, or start being noticeably distorting at some level.
2. Distortion creates harmonics and intermodulation products that were not in the original signal. Harmonic distortion is always higher frequency than the original signal(s), Intermodulation can be both hither and lower.
3. Tone filtering makes some frequencies bigger and some smaller.

A little logic leads us to this:
EQ before distortion changes what frequencies get distorted (i.e., which ones are big enough to hit the distortion threshold) and by how much.
EQ after distortion changes what signal + distortion products we hear and how much.

Read "The Technology of the Tube Screamer" for how this affects one well known pedal. Bass cut before the distortion stage cuts down on intermodulated "mud", treble cut after the clipping softens up some of the treble products created.

Not many people will ever take the time to try it, but one of the most flexible distortion setups ever conceived is a distortion stage sandwiched between a graphic EQ both before and after. You can spend hours tinkering with ever-more fascinating distortion sounds.

[DuncanM]

As RG says, putting you tone shaping after the gain circuit will act on the original sound and the harmonics generated by the gain (OD/distortion) stage. If your original signal is rich in high frequency components the your gain stage will generate a lot of very high frequency products that might need to be tamed...

If you shape your tone before the gain stage you can achieve control over where the harmonics generated by cutting or boosting the signal at appropriate frequencies.

For example - you might cut bass before the gain section so that the low mid doesn't muddy up due the the low frequency harmonics generated by the bass frequencies - and then boost the bass back up after the gain stage to warm the signal back up.
Alternatively you might boost frequencies around 2.5k to add presence before the gain stage and then cut above 7.5k to tame the fourth (and above) order harmonics generated.

All a matter of taste and what you're trying to achieve.

[puretube]

You can spend hours tinkering with ever-more fascinating distortion sounds.

years... 

[Processaurus]

a cool thing is if you have enough gain, you can run a very muddy sound into a distortion, and it will make new artificial high end with the clipping, its a good way to get a synthy type of sound (especially w/ the neck pickup).  One of the Strokes' records has a sound like that all over it, its hard to tell if its a keyboard or not.

Lately I've been thinking about modifying distortion designs with a rotary switch to do different preset pre-gain eqs, like flat, rolling off a little of the high end, rolling off all high end and upper mids, mid boost, and treble boost.  There was an interesting design Mark Hammer did that did a similar idea with the "Forty-Niner", he inserted the Craig Anderton frequency booster before the clipping stages. 

[Harry]

Thanks for the replies. And again to R.G., always helpful.
I was mainly thinking about a linear booster.

Lately I've been thinking about modifying distortion designs with a rotary switch to do different preset pre-gain eqs, like flat, rolling off a little of the high end, rolling off all high end and upper mids, mid boost, and treble boost.  There was an interesting design Mark Hammer did that did a similar idea with the "Forty-Niner", he inserted the Craig Anderton frequency booster before the clipping stages. 

I think thats a good idea. Your now giving me ideas I'll never follow through! A fuzz with 1: Low-pass (Muddy) 2: Flat (Clipping will kill a lot of the bass) 3: Deep Mid-Cut (Hollow tone) 4: High-Pass (Bright) 5: Heavy High-Pass (Octave Uppish)

[cd]

Not many people will ever take the time to try it, but one of the most flexible distortion setups ever conceived is a distortion stage sandwiched between a graphic EQ both before and after. You can spend hours tinkering with ever-more fascinating distortion sounds.

Pfft, one EQ pedal is enough to make a big difference, and how many folks even bother what that?   Or even read GEO?  It makes far too much sense! 

Especially when you can pay someone the cost of a GE-7 EQ to change two or three parts and have a super-mojo-kewl new sounding pedal!!!!!!  Or DIY and pick apart the nuances of metal film this versus carbon film that or JRC this versus NJM that, all with 9V applied of course!!!!

In all seriousness, two used GE-7s will set you back $100.  Just try to come up with anything that can match that in terms of wide ranging tonal bang for the buck.  Impossible.  And no, two of those POS Dano EQs don't count   If anything, when you've got your latest OD/fuzz/etc. experiment on the breadboard (people do still use those, right?) a little 7-band EQ is perfect for experimenting with various frequency responses before you "hard wire" things into a single knob tone control.

[Processaurus]

http://namm.harmony-central.com/WNAMM02/Content/Akai/PR/G-Drive.html

A glorious flop, I think it kind of went over the average player's head.

Same with their 6 band compressor stompbox, thats something only mastering engineers would appreciate.

I tried the EQ thing with a stereo rack EQ one time and it sounded great, the only problem was this particular model had a little bleed between channels that made it squeal like a pig.

It'd be fun to run with the idea sometime and make a box with 2 of the POS dano EQs with a collection of different clipping stages that could be individually selected sandwiched in between, like a diode clipper type, 4049 TSF type, double clipper BMP type, maybe a great cheddar type, or other transistory fuzz.  Or go to rack land...   :icon_eek:Noooooo i don't think so...

[R.G.]

As processaurus notes, the way to do this for cheap is to get a used stereo graphic eq. These are usually much cheaper than the GE7 and you get a pre and a post in one box.

Not really convenient packaging, though.

[MartyMart]

Pfft, one EQ pedal is enough to make a big difference, and how many folks even bother what that?   Or even read GEO?  It makes far too much sense! 

I do and I have !!
There's a Boss PEQ-4 ( parametric eq ) directly after the OD/Distortion on my little pedal board.
Great for adding a little "warmth" and cutting the "ice pick" top end from the overdriven sounds

It makes a HUGE difference and yes, I could tinker with it for many hours !!

MM.

[WGTP]

For some reason EQ just isn't as sexy as distortion.

The way I address it, is to see my guitar pickup as the pre-EQ, in addition to the input cap to roll off some bass if necessary.  I use a Full Shred which has reduced bass and lots of highs.  It is very articulate so it doesn't turn to mush with lots of distortion.

Within the distortion, for op amps, I use the RC network to ground from the feedback loop to control the "character" or bass/gain structure.  In discrete circuits, I use the by-pass caps and in-line resistor capacitor networks for tonal contouring.

Then I use a notch filter after the distortion to cut anywhere from 4 to 10db around 800Hz.  If needed, I will roll off some highs after the distortion as well. 

This reduces the tendency to make yourself crazy using a multiband EQ.   

[jeroen_verbeeck]

http://namm.harmony-central.com/WNAMM02/Content/Akai/PR/G-Drive.html
A glorious flop, I think it kind of went over the average player's head.

I've had the G-Drive. And it sucked big time. Now don't get me wrong, the idea is great and the pedal is built like a tank, but the basic drive just sounded horrible! It sounded verry lifeless and not dynamic. It was also not a distortion, more like a crappy fuzz.
Also when you stomped the drive on, it took about a half second for any sound to come through, so you have a half second of nothing! That's pretty annoying.
If you ever come accros one, you can buy it and use the hardware and replace the drive part with something better, that will sound a lot better I guess.

[mac]

I don't know if this makes sense, but... what about dividing the signal, let's say lows, mids & highs, and applying different and controllable amounts of distortion to each path, and then mixing them back? The range of lows, mids & highs could also be variable.
This way one could apply zero distortion to the lows, 100% to the mids and 25% to th highs.


mac

[MartyMart]

I don't know if this makes sense, but... what about dividing the signal, let's say lows, mids & highs, and applying different and controllable amounts of distortion to each path, and then mixing them back? The range of lows, mids & highs could also be variable.
This way one could apply zero distortion to the lows, 100% to the mids and 25% to th highs.


mac

That'll be the "quattro fuzz" a PAIA/Craig Anderton gizzmo I believe, sounds like a winner, but I've
read some "so-so" build reports ??

MM

[phaeton]

I don't know if this makes sense, but... what about dividing the signal, let's say lows, mids & highs, and applying different and controllable amounts of distortion to each path, and then mixing them back? The range of lows, mids & highs could also be variable.
This way one could apply zero distortion to the lows, 100% to the mids and 25% to th highs.


mac

That'll be the "quattro fuzz" a PAIA/Craig Anderton gizzmo I believe, sounds like a winner, but I've
read some "so-so" build reports ??

MM

I saw a schematic about 18 months ago that was NOT the PAIA kit, (lifted from EPFG iirc). I have been trying off and on to find that one since.   Craig was musing about 8 months ago about new editions of his DIY books, so I was going to wait on buying them, but I'm starting to guess the safe bet is he's way too busy with other projects to really address it.  Maybe it's time to pick up a copy.