Mid Booster

[tube man in a kilt]

well, how could i go about making a mid booster w/ a pot to control the boosting?

[cd]

Buy/borrow "DIY Projects for Guitarists" by Craig Anderton, or do a search for "mid boost" here.

[tube man in a kilt]

oh come on guys, SOMEONE here has to know something more about this!
thanks cd.

[Mike Burgundy]

A mid booster is a bandpass filter. A simple but good bandpass is an LC-filter, but you might want to reolace the inductor with a gyrator (circuit that mimics a coil with active components)
You could then choose to set a fixed frequency, fixed Q (experiment), and have yourself a mid cut/boost.
You could also keep the pots for F and Q, so you're able to dial in exactly what you want.
See:
http://www.geofex.com/Article_Folders/EQs/paramet.htm
http://users.balpol.tudelft.nl/~Burgundy/bin/schem/parametricguitarhybrid.gif
(in which the 330Ohm resistor can be replaced by a 1k pot for Q control)

[petemoore]

Smaller* cap in signal path cuts lows
 Larger* cap from signal path to ground cuts highs
 Whats' left?: Mids!
 check out ROG amp sims and look at the cap/R to ground>Cap/R to ground at the end of these circuits, these rolloff highs but with a different 'slope' to the cutoff IIUC.
 * adjust values for different frequency attenuations

[DDD]

tube man in a kilt,
maybe you'll find it interesting to look through on-board mid-boost schematic used by Eric Cl*pton in his Str*t.
The schematic is easily available on the Net.

[tube man in a kilt]

so the GEOFX parametric filter is what i want for a simple midrange cut/boost? what value caps would i use in that one to get midrange? and how many pots are there in that one and how do i wire them in?

[tube man in a kilt]

ok, i think i got it. if i use the cap values that they specify in the GEOFX parametric filter, you get a midrgange cut/boost right (90hz-2000hz)? from what ive read thats generally the midrange frequencies, so how would i go about wiring up the pots for that? and are there 2 pots if u use 4 variable caps?

[petemoore]

Wah

[tube man in a kilt]

haha, if i use the value of caps 1,2,3, and 4 that they suggest, i'll get a cut/boost of 90-700hz and 450-2000hz. thats right in the midrange right? and the other question i had is: how would i wire the pots into that circuit? are there multiple pots if i use the 4 variable caps? also: it looks like if i used the 4 cap setup id need 2 9v, im very confused. help. please.  

PLAINLY: HOW WOULD I WIRE THE POTS INTO THE 4 CAP SETUP iN THE GEOFX PARAMETRIC FILTER? HOW MANY POTS DO I NEED IF I USE 4 CAPS? AND DO I NEED MULTIPLE 9V BATTERIES TO POWER THAT CIRCUIT?

[nero1985]

u should try using SOCKETs for the caps to get the right sound, i actually drew the schematics for mine wich has 3 bands bass and treble would be cut and MIDs would be Boosted, but im going to use a DPDT toggle switch to BYPASS it and then ill use TRIM POTs for the cuts and boost so that i wouldnt have to deal with them while im playing.... let me know if u want the layout

[nero1985]

go to my photo gallery and check the SCHEMATICS section, theres a RG KEEN's EQ and another MID BOOST wich i havent tried yet but for what i know should work really good, one of them is after the FETZER VALVE so that it u dont lose the signal's power when u lower the HIGH or LOW....
LINK
http://albums.photo.epson.com/j/AlbumIndex?u=4241292&a=31434379&f=

[ragtime8922]

I have an 80's Charvel Model 6 with a Jackson mid-boost pre-amp. It's a great little on board mid-boost that can be made in to a pedal very easily. The ammount of mid-boost was controlled by a pot that replaced one of the tone pots. I think it goes up to 25dB of boost but it's variable. Of course the range can be altered but I love where it's at. It boosts the very low mids. The guys that had this guitar or model 4's at the time thought they had active pick-ups. This is not the case. The mid-boost used the battery and when the battery went dead so did the guitar.
      I found a link at one time for this very circuit (simple circuit). I'll see if I can find it. I think it was called JAX or something like that.

[tube man in a kilt]

thanks nero, but i dont get why a mid boost has treble and bass pots. do you turn them all the way down to boost the mid? i just want a booster that has one pot: A MID BOOST CONTROLL! but nero, i like the schems, i just dont quite understand the mid boost schem.

[Mike Burgundy]

Whoa there pard'ner!
That schem is not a mid boost. Per se, anyway.
It's a combined bass/treble eq, with a parametric mid, that you set to a certain frequency and either cut that frequency or boost it. It's also shamelessly lifted from a metalzone and an SWR amp. I just meant it to illustrate the parametric bit - the right-most two opamps, with their surroundings.
This is actually the long way round, even without the other controls ( I get carried away sometimes)
The EC midboost is a good thing to start with. If you then want something with more control (sound/frequency-wise), maybe look to a parametric.

[tube man in a kilt]

ok, well, what about the AMZ presence controll? if someone could tell me how to make that and how i would go about wiring a booster in the same box, id be set. i dont understand how i would make that AMZ circuit a standalone, so if anyone could help me there i could probably figure out how to wire a booster up by myself i guess.

[aron]

Well, it is as simple as cutting the lows, rolling off the highs and what you get is mids. So do this passively and boost your signal into the passive filter and you get a mid boost.

I would fool around with the Duncan tone stack simulator - following the AMZ article as a reference. In any case, you should be able to make most of the tone stacks in the simulator cut lows and highs and then simply tack that on to the end of a booster like the LPB-1 or an op amp booster or the beginner project.

[Ge_Whiz]

Mr Kilt

Start with the AMZ 'presence' circuit. Take a dual op-amp, use half of it to construct a unity-gain buffer before the AMZ, and the other half to build an amplifier (inverting or non-inverting) with a gain of about 5x after it. Then adjust the value of the 'presence' pot and add fixed resistors in series with it until you achieve the range that you want, and eliminate any dead ranges in the pot operation.

[tube man in a kilt]

thank you aron, huge help. i'll replace the pots in the AMZ stack w/ resistors and hook that to the end of a booster. will a 9v power the whole cirucit though (booster and filter)?

[petemoore]

The filter is passive [no active components]
 The booster must contain at least one active device to boost gain, the filter schemtic shows no supply symbols, none are needed, it 'takes out' or filters frequencies...the actives amplify, and need power supplied to do so.