Best 3-Band Active Tone Control?

[Space Jm]

Hello STM,

I just finish to build your Active EQ and it works fine ! Very nice...On the out, I add a « level setting » with 4558 AOP , copying the Boss GE7 « level » setting. It allow me the adjust +/- 15dB correction !

I did not put the 3 kind of Middle...just the 630hz first, I can not get the other values for capacitors in my dusty stock...

I just want to know something else : Could you give me the formulas to calculate the center freq and the Q factor...I can not get them when simply reading your schematic.

Thank  a lot ! Now I am building the housing of the stompbox...

[Morocotopo]

Hi, sorry for bringing this old thread up, but I want to build the last EQ circuit displayed here, and I have some doubts about the schem. I drew the things I have doubts about in red. Could anyone confirm if my drawing is righ or wrong? Thanks.

Morocotopo

[stm]

Hi, There are two important problems in the above schem:

1) All the +INPUT of the opamps should go to Vcc/2 or Vref instead of ground, otherwise you won't get any sound. This is required for single 9V operation.

2) The input impedance of the first stage is low and varieswith the pot setting, thus an input buffer is needed. This circuit was drawn as a building block, rather than a full pedal, thus your questions are valid.

I'd suggest you try this simplified version which I like better:

http://aronnelson.com/gallery/STMs-Circuit-Ideas/Three_band_Eq_non_interacting_bands

Input buffer is still necessary though.  Vref = Vcc/2 or 4.5V.

[JHS]

I like the active Baxandall tone control and would add a addtional mid-pot.
The Xotic- and TC-ODs use it too, the schems are on the net, so I would use it as a base and maybe alter some values to taste.

JHS

[Morocotopo]

Thanks for the answer STM, I kind of suspected that the + ins should go to Vref, but wanted confirmation by a more knowledgeable source (that´s you!  ). So, the usual two resistor voltage divider and cap there. About the in buffer, I didn´t put it in the drawing because I´m thinking of using this as a post distortion tone control(s) for a BSIAB2, eventually doing away with the original circuit tone pot and associated parts, the idea being getting maximum tonal flexibility. Or should it be there even for this use? My guess is that it wouldn´t hurt...

Thanks everybody

Morocotopo

[brett]

Hi

All the +INPUT of the opamps should go to Vcc/2 or Vref instead of ground, otherwise you won't get any sound. This is required for single 9V operation.

Or maybe use single supply opamps.  Equalisers are one of those things where single supplies are good value because it saves lots of unnecessary track length.
The LM324 is a quad device that should suit these designs.
cheers

[Fr_3_aK]

Meh, i just made a 3 band EQ similar to these ones. For a days effort and AU$20 i'd have to say i should've just bought a brand name EQ pedal.

My 2 cents: If you have any doubts about the plans you see here (or even if they'll give you the desired result) consider paying the extra money for something with a ___ day money back guarantee   

[phazerz]

What a great thread !
I missed it before i built the tonemender for my "multibox" which include 3 effects before Supreaux/Matchbox/thunderchief and then going into tonemender/SSS/Condor (thanks STM the SSS/Condor combo is truly great!)
I like the tonemender but sometimes it's a bit confusing and I need more transparent control over bands...
Your non-interactive 3 bands is certainly what I need ! But i don't see the 3 mid pos switch in the schem..
Anybody have a vero layout for this ?
What I would love from you STM is a graph that shows the curve effect of the tonestack at the end of the greats ROG amps sims.. (15k/22n to ground, etc).
Thanks if you can do it ! But just an explanation would be cool too and i guess i should launch a new thread for this because i have a few questions about the condor too...

[Morocotopo]

I plan to make a perfboard /PCB layout for this, just give me some time, when I do, I will post it. Since this schem and the one suggested by stm  (http://aronnelson.com/gallery/STMs-Circuit-Ideas/Three_band_Eq_non_interacting_bands ) are similar, the only difference being the parts values, it should be useful for building both and deciding wich one I (or you) like best  .

Thanks stm for your schematic and generous help

Morocotopo

[Papa_lazerous]

Sorry to Bumb an old thread like

Just been using the search function and came up with this thread.  I'm looking to put a 3 band Eq into a Big Muff clone I am making right now.  I was just wondering if anyone has built these circuits?

The schem on the first page looks like it could be suitable for my needs and also  http://aronnelson.com/gallery/STMs-Circuit-Ideas/Three_band_Eq_non_interacting_bands this one.

I was thinking of splicing this into the Big muff circuit between Q3 an Q4 in place of the tone stack.

Only other spanner to throw in the works I have built the muff with PNP trannies would it be a problem mixing positive ground with this circuit or wouldnt it matter a hoot?  Any ideas or wisdom greatly appreciated

[Izzy]

Can anyone explain how that Mid Boost circuit works? And how did you calculated the center frequency as 500Hz?
I would so Love to know that.

[axe_mechanic]

I've just built STM's tone circuit and it's a beast! Very clean, fairly simple to breadboard. Double check your lines as you breadboard it as I didn't and had to start over at one point. It also needs a .1 uf Cap at the beginning and end. Also, Vref is 1/2 of your input voltage. So if you are powering this via 9v you will need to make a voltage cutting section on your circuit to create Vref or this circuit won't work.

Good luck!

[J0K3RX]

I've just built STM's tone circuit and it's a beast! Very clean, fairly simple to breadboard. Double check your lines as you breadboard it as I didn't and had to start over at one point. It also needs a .1 uf Cap at the beginning and end. Also, Vref is 1/2 of your input voltage. So if you are powering this via 9v you will need to make a voltage cutting section on your circuit to create Vref or this circuit won't work.

Good luck!

Interested... I have been eyeballing this circuit for a while now. How are you using it? What are you using it with?

[deadastronaut]

^ cool, so does this have nice control seperation too?.. (non interactive)

[samhay]

Cool circuit.

^ cool, so does this have nice control seperation too?.. (non interactive)

It should do. Would benefit from a high-impedance input - a 4th op-amp could do this nicely...
Edit - I notice that STM mentioned this earlier in the thread.

[deadastronaut]

cheers sam,

would this tack on nicely onto the spitfire ? straight off the Q5 source?...ive been messing around with tone stacks, but this looks pretty nice.

http://www.aronnelson.com/gallery/main.php/v/chickpea/SPITFIREV3.jpg.html?g2_imageViewsIndex=1

[samhay]

It should do - the output impedance of Q5 is set by R11 and is reasonably low.
If it loads down the first band of the EQ, then you can try to drop the value of R11.

If you only want 2 bands of EQ, you could get away with a single dual op-amp. If you want 3, then you could use the 4th op-amp as an output buffer...

Have you tried a FMV tone stack after Q5?

[deadastronaut]

cool,

yeah tried all of them in the tsc, with variations ...but i just don't like the interaction, seperation is what i'm after really...being able to add/subtract without the others adjusting would be great.

3 band sounds ideal...so it's opamp time..i'll whip it up on breadboard...i already have the spitty on bread, so i'l just knock this up ..

[deadastronaut]

ok i have it on breadboard, all 3 pots working fine..

output buffer:  straight out of above circuit into spare opamp : pin 5 ...6 + 7 joined...then out 7 to output...but very quiet.

edit:  ok now, i forgot the 100n caps...

[stonerbox]

Necro-posting, deal with it sucka!


Built this one today, not bad. I edited the schematic so the circuit has an input / output buffer with the capability to boost the volume a little bit if needed. Way easier to follow if you are new to building stuff.