no more tone stacks for me..

[deadastronaut]

Well that's it, ive finally given up on passive tone stacks...after much tinkering etc they just don't cut it imo..

too much interactivity, not enough bass adjustment...etc etc etc...

so its 'graphic equalizer time'..

ive breadboard this :

but no joy..not a peep..(using half a an opamp)

http://www.electronicecircuits.com/electronic-circuits/6-band-graphic-equaliser-using-741-op-amp-ic

does this ^ look complete?.. ..hmmm...
...

so i decided to breadboard RG's ' a simple, easy graphic eq'' which i have had in mind for a while

http://www.geofex.com/article_folders/eqs/paramet.htm

to be honest i just breadboarded the 1st 60hz but that should work right...hmmmmm,

and its behaving like an unbiased fuzz...i really have to hit the guitar
hard to even get a brief farty sound..

any ideas?...on both.

cheers guys..


edit: got RG's working on 60hz...dodgy cap. .

but i'd be interested to try the top one still...?

[tca]

Try a chip EQ, much smaller parts count.
See: http://www.diystompboxes.com/smfforum/index.php?topic=99493.0

Cheers.

[mth5044]

I can't say why the first doesn't work, but I've built the GEOFEX graphic with great success. I ended up using the other half of the opamp as a buffer as well as adding a gain control. Switched it up to run on +/-9V since it was going to need to be compatable with a synth as well. Schematic is in the first post here.

http://www.diystompboxes.com/smfforum/index.php?topic=110408.msg1012500#msg1012500

The point of the thread was to figure out how to disable certain frequency bands. I ended up just putting the pot on one side of the switch and two fixed resistors on the other to simulate a pot in the middle, or off, position.

Anyway, point was, the GEOFEX one works well 

[Transmogrifox]

Maybe you had the same dodgy cap in the first one?

In the first one, just make sure you have ~4.5V at both + and - inputs.  No sound at all sounds like the op amp isn't biased between + and - supplies.
The connection dots on the schematic are a little weak.  Make certain R9,R10 and R11 are all connected together and it measures Vcc/2 here.

The 741 EQ is a combination of high/low shelving tone controls -- looks like a tubescreamer tone with a bunch more pots.  It will also be very interactive.  For example, if you boost the lows, everything else above the low band comes up with it.  It looks like the kind of EQ they used to put in cheap boom boxes.

[deadastronaut]

nice one guys..

some great ideas there...especially the chip one..

good to know the RG one is fine too.excellent...looks good matt,

however i won't need a buffer , this is going after a distortion (built in)


i'll just leave the other one if its a boom box type thing..

i'll pop the other bands on the RG and see how i get on....thanks guys.

back later..

[Mark Hammer]

The highest control in that 741-based unit is essentially a shelving type control; i.e., boost and cut of everything above a given frequency.  You'll find that as the highest band on a bunch of equalizers.  But the other controls do the identical thing, just at a lower starting point.  So, it will "work", but how the hell is a bunch of staggered treble controls useful?  None of the lower controls are resonant and focussed on a specific range.

I say go back to the passive tonestacks, but play with the values in the Duncan Tonestack Calculator to get something that meets your needs.

[deadastronaut]

I say go back to the passive tonestacks, but play with the values in the Duncan Tonestack Calculator to get something that meets your needs.

cheers mark,  ive tried stacks with lots of variations and switching using the tsc,

in the end i plugged an equalizer pedal straight after my distortion circuit, and it hits the spot much better..

proper mid scoop and a chunky low end for 7 string metal etc...

that's why i'm going down this route...i'll see how it goes as an experiment..

[GibsonGM]

I had something like this going on a couple of months back..had built a nasty (in a good way) version of the 12AX7 "GTFO"...used an eq pedal and found a  few VERY sweet spots.   Had the same complaints as you, Rob.   No way I can get that awesome tone with just a tone stack.  I tried many variants, from Muff to FMV to simple mid scoops, 2nd order mid scoops...nope.

So, same thing here...either a pedal, rack unit or will MAKE a board to pop in a preamp I intend to put the thing into.  Too bad to have to be so 'impure' as to mix real tubes and Si (for some - I'm ok with it), but that really IS the only way to get the tone I really wanted!   

[deadastronaut]

hi mike, yeah man, those stacks just don't do it for hi gainers for my ears,

they are fine for a mild drive i guess , but to get that full on chunk without being flabby

or fizzy you defo need more overall control of it..

ive spent the last few weeks trying to get IT with tsc...to no avail,

so i rigged up my eq pedal straight after a mu amp setup...voila' its there with plenty of variation...

so its going in..

[MrBinns]

look at Parametric EQ's so much more fun

[J0K3RX]

Rob,

If you have not already done so, you might want to try something like the Wampler SLOstortion.. There's room for changes to personalize it for your design.. I think it works really well, the different frequencies are independent of each other.. The Spitfire or variant would be almost a direct drop in!

https://dl.dropboxusercontent.com/u/11178619/SLO/slostortion.jpg

[deadastronaut]

cheers jim, that looks cool...much better control..

i'll persevere with the equalizer for the mo, and see how i get on..

if it turns out to be a PITA then i'll take another look..

nice one.

[Kipper4]

Check out the ROG Thunderbirds eq DA some mods for modern metal in the thread too.

[anotherjim]

I'm nowhere near playing with this kind of thing at the moment, but I too have been thinking of putting more powerful eq after distortion, and I was imagining something a lot like the SLOstortion solution. I'd probably just borrow Sansamp  design.

The fixed filter network after Q5 looks to me like a HF roll off combined with a mid notch - is that correct? Would it be relevant to Rob's needs given the 3 band eq coming afterwards?

[Kipper4]

Here it is

http://runoffgroove.com/thunderbird.html

[deadastronaut]

well i have the EQ working...kind of.

i'm getting 8.12v on the in resistor, if i stick a 1uf cap as shown to block the dc

i get no sound...if i bypass that 1uf cap i get sound but scratchy guitar pot/switch  etc....hmmmmmm..

is there meant to be a buffer in front of this?...

anyway, besides that issue, its nice to have good proper seperation on choice of freq's at last..

(which i shall no doubt dabble with to suit my needs/amp /guitar etc)..I stuck my dist in front temporarily

and it sounds way better than a ts imo...

http://www.geofex.com/article_folders/eqs/paramet.htm


cheers rich, interesting..

[J0K3RX]

Try a chip EQ, much smaller parts count.
See: http://www.diystompboxes.com/smfforum/index.php?topic=99493.0

Cheers.

I would like to give this suggestion a try, looks easy to layout and tailor to suit your needs! looks like you can determine the cap values for the bands you want..
http://media.digikey.com/pdf/Data%20Sheets/Rohm%20PDFs/BA3812L.pdf
I am leaning towards this one but either look fine..
http://www.electronics-lab.com/projects/audio/018/index.html

[deadastronaut]

hi jim, yeah i was looking at those too..

any idea on the dc cap issue?..

[tca]

is there meant to be a buffer in front of this?...

Yes, I think so.

[deadastronaut]

Ahhh...i,ll try that then, cheers man. 

btw tiago, i came across your mesa 5 eq last night...cool.