Choices for a simple transparent 5 to 10 band EQ (for vocals)

[jfrabat]

Hi, guys.  I am updating my home studio (got a pre-amp, new mic, new monitors, etc.) and I thought a good hardware addition would be to ad a hardware equalizer.  I started looking online for options, but then I remembered I have already done pedals with 3 band EQ, so I figured, "why spend money on this, when you got most of the parts in stock?". 

What I have:

[/li]

• Resistors (most of the relevant values)
• Caps (most relevant values; I got polirized in uF, box and film in nF and ceramic for pF)
• Pots (most relevant values, though I would have to see if for each value I have audio curves; but we will cross the bridge when we get to the river!)
• Diods (most relevant ones, though I suspect I may only use them for voltage control)
• OpAmps

• 741 (2)
• LM833 (3)
• JRC4558D (5)
• NE5532 (1)
• NJM13600D (3)
• RC4558P (3)
• RC4559P (3)
• TL071 (3)
• TL072 (1)
• TL074 (2)
• LM386N (2)
• MC1458P
• C4558C (4)
• NE5532P (6)

[/list]
I also got some other IC's (NE556N, PT2399, MCO41100) which I doubt will be relevant to this build, and I got all kinds of transistors (2N3904, 2N3906, 2N4123, 2N4124, 2N4125, 2N4401, 2N4402, 2N5087, 2N5088, 2N5089, and a bunch more) but I doubt I will need them for an EQ as well.

I looked online, and found some options, but I am still not good at predicting how good a circuit will be...  Keep in mind this will be used for a MIC, not a guitar, so I need it to be clean.  I found this simple option, and I figured I can replace the OpAmp with one I have:



What do you guys think?  Or do you have any good recommendations I can look up?

[Mark Hammer]

Use a KA2223.  It's a 5-band EQ on a chip.

[jfrabat]

I kind of want to use the parts I got in stock if at all possible...  I live in Panama (Central America) and all electronic parts shops around here are closed (actually, all RETAIL stores are closed), and ordering online becomes very expensive due to shipping overseas...

[antonis]

On the contrary of Mark  , I should propose you BL3812(L)..

From what you have, NE5532P should be excellent choice..
(you can use all of them or use TL072 for IC1/1 & IC1/2..)

Of course, you can use 2N5089 for gyrators with almost the same performance..

P.S.
IMHO, 10 band "graphic" EQ for audio band might be useful but for guitar is should be overkill..

[deadastronaut]

la3600?


https://www.diystompboxes.com/smfforum/index.php?topic=107612.msg978821#msg978821

[Mark Hammer]

On the contrary of Mark  , I should propose you BL3812(L)..

From what you have, NE5532P should be excellent choice..
(you can use all of them or use TL072 for IC1/1 & IC1/2..)

Of course, you can use 2N5089 for gyrators with almost the same performance..

P.S.
IMHO, 10 band "graphic" EQ for audio band might be useful but for guitar is should be overkill..

Nothing contrary at all.  I just mentioned the first chip of that type I saw in my directory of audio-processing chips.  BA3812 is good, too, as is LA3600.  I think choice of resonant frequencies will be just as important as chip-choice, if the purpose is to tailor vocals.  Most graphic EQs are not designed around any particular purpose, so they try to cover as many possibilities as possible with the number of bands they offer.  Many of those bands have absolutely nothing to do with voice.  Five of the right bands may be all you need for voice.  And some might argue that 3 bands of parametric or semi-parametric would be enough.

[antonis]

And some might argue that 3 bands of parametric or semi-parametric would be enough.

I'm one of those "somes"..

But I totally agree about resonant frequencies "customization" for each particular purpose/use..
(although double/single/half octave spacing for the entire EQ band is definately easier to design/build..) 

[jfrabat]

From what you have, NE5532P should be excellent choice..
(you can use all of them or use TL072 for IC1/1 & IC1/2..)

How about LM833?  Is that a good choice for a transparent sound?

IMHO, 10 band "graphic" EQ for audio band might be useful but for guitar is should be overkill..

Remember this is not for guitar, but rather my home studio mic...  And I am thinking 5 band now, as I may run out of OpAmps...  But optimize the frequencies to vocals.

I think choice of resonant frequencies will be just as important as chip-choice, if the purpose is to tailor vocals.  Most graphic EQs are not designed around any particular purpose, so they try to cover as many possibilities as possible with the number of bands they offer.  Many of those bands have absolutely nothing to do with voice.  Five of the right bands may be all you need for voice.  And some might argue that 3 bands of parametric or semi-parametric would be enough.

I totally agree about resonant frequencies "customization" for each particular purpose/use..
(although double/single/half octave spacing for the entire EQ band is definately easier to design/build..) 

Which frequencies would you guys recommend?

One more question; the schematic above does not include any of the power side of the circuit, and since I am unschooled in such things, I found [url+https://bestengineeringprojects.com/5-band-audio-equalizer-circuit-using-lm833/]this other schematic[/url], which I really like, but ran into a small snag;



The issue is that (1) I only have 3 LM833N chips, and I need 4 (well, 3.5 really!).  So I was thinking using a TL072 for IC1A and IC2A and using the LM833 for the rest (I am not adding one more band because I only got 5 5K pots).  I could even use the TL071 instead of the TL072 (for IC2A) and leave that for when I need a dual OpAmp (only got one TL072 left).

Also, the parts list is suggesting the following caps:

C1, C3, C6, C9, C`12, C15, C18, C19 = 10 µF (Electrolytic Capacitors) - NO PROBLEM
C2 = 100 µF (Electrolytic Capacitors) - I THINK I GOT ONE LEFT IN A BREADBOARD PROJECT, BUT SHOULD BE OK
C4. C5, C7, C8, C20 – C23 = 0.1 µF (Ceramic Disc) -  NO PROBLEM (JUST HAVE 5 100pF LEFT!)
C10, C11 = 0.047 µF (Electrolytic Capacitors) - ELECTROLITIC?  I HAVE CERAMIC, AND THEY ARE NOT LABELED AS POLARIZED, SO I PLAN TO USE CERAMIC
C13, C14, C16, C17 = 0.0022 µF (Electrolytic Capacitors) - AGAIN, ELECTROLITIC? I HAVE 3 CERAMIC LEFT, BUT I COULD FUDGE IT BY USING 2 X 10pF FOR THE LAST ONE.

So, main questions are, you think this will work by replacing one LM833N with a TL072 or TL071?  Or having one different OpAmp will affect the sound too much?  And will the cap change to ceramic affect too much the transparency of the sound?  And, as I stated above, which 5 frequencies would you recommend?

[jfrabat]

Oh, and one more question; any good circuits you guys can recommend to filter a bit the power supply and have polarity protection (just in case) considering the above circuit is 12V?  The ones I have used are typically 9V...

[antonis]

LM383 is an audio amplifier so it can't be directly substituted by a general purpose op-amp..
(it could be done but in the expence of significant circuitry changes..)
Forget the above.. Eye-typo..

I'll vote once more for NE5532 but desicion it's up to you..

Any good circuit for 9V can also be good for 12V..
(16V rated filter cap should be OK and 25V should be fine..)

[Mark Hammer]

I always thought the NE5532 and LM833 were largely interchangeable.

As for "what frequencies would you recommend?", that's probably the best recommendation for a simple semi-parametric (i.e., boost/cut with sweepable frequency).  The optimal frequencies will really depend on the voice itself.  I'm not trying to be evasive.  Rather, it's like asking what EQ would work best for a kick drum, for a cello, for a flute.  They all have their particular voices and sensitive ranges.  Individual singers are like different instruments.  That's why they all have their individual preferences for this mic or that.  If it is not possible to know in advance what frequency bands are going to be most relevant for a particular voice, then best to make the bands sweepable, so that you can find the ones most relevant.

The PAiA 4-Band equalizer is probably a suitable unit for you.  Though you probably only need the first 3 sections.
https://www.scribd.com/doc/96494162/4-Band-Equalizer-Www-circuitdiagram-net

[jfrabat]

I'll vote once more for NE5532 but desicion it's up to you..

The issue is I only have 1; and I have 3 LM833.  I could use it instead of the TL071 I am using in the breadboard...

Any good circuit for 9V can also be good for 12V..
(16V rated filter cap should be OK and 25V should be fine..)

OK, I will find one and use.

The PAiA 4-Band equalizer is probably a suitable unit for you.  Though you probably only need the first 3 sections.
https://www.scribd.com/doc/96494162/4-Band-Equalizer-Www-circuitdiagram-net

Wish I had seen that one before I started breadboarding.  Looks interesting.  I will finish this one, and if I do not like it, I will certainly give that one a shot.

[antonis]

I'll vote once more for NE5532 but desicion it's up to you..

The issue is I only have 1;

What I have:
NE5532 (1)
NE5532P (6)

My maths suck but I can ensure you that, by adding anything but zero to unity, the last loses its uniqueness..

P.S.
Differences between the many versions of NE5532 (other than price..) are unimportant for your task..
(they have to do with lowest guaranteed noise, THD measure, etc..)
http://e2e.ti.com/support/amplifiers/f/14/t/344

[jfrabat]

My maths suck but I can ensure you that, by adding anything but zero to unity, the last loses its uniqueness..

Well, yes, but what I mean is that I want something that will not add color to the sound (even if it is adding volume to a frequency).  Does that make sense?

P.S.
Differences between the many versions of NE5532 (other than price..) are unimportant for your task..
(they have to do with lowest guaranteed noise, THD measure, etc..)
http://e2e.ti.com/support/amplifiers/f/14/t/344

Ah, I checked my list from the original post, but I did not notice I repeated the same OpAmp...  Thanks for checking my counting!  I guess math is not my strong point either!

By the way, I ran out of 0.1uF caps anyway, so I had to place an order.  By the way, anyone got any good replacement alternative to Small Bear?  They are out of all the caps I need...  and I also need some pots.

[jfrabat]

The PAiA 4-Band equalizer is probably a suitable unit for you.  Though you probably only need the first 3 sections.
https://www.scribd.com/doc/96494162/4-Band-Equalizer-Www-circuitdiagram-net

Mark (and the rest of you), I started looking more into this EQ, and I like it, but I have a question; looking at the diagram, I cannot figure out what the dotted lines mean.



From what I can see in the PAiA page for this product, it seems the kit only has 2 pots per channel, but the schematics show 3 (trim pot?).

[Mark Hammer]

It's intended to show that the two 100k pots are each half of a dual ganged 100k pot.

[Marcos - Munky]

Just a few things I noticed:

1) C2 = 100 µF (Electrolytic Capacitors) - I THINK I GOT ONE LEFT IN A BREADBOARD PROJECT, BUT SHOULD BE OK
2) C4. C5, C7, C8, C20 – C23 = 0.1 µF (Ceramic Disc) -  NO PROBLEM (JUST HAVE 5 100pF LEFT!)
3) C10, C11 = 0.047 µF (Electrolytic Capacitors) - ELECTROLITIC?  I HAVE CERAMIC, AND THEY ARE NOT LABELED AS POLARIZED, SO I PLAN TO USE CERAMIC
4) C13, C14, C16, C17 = 0.0022 µF (Electrolytic Capacitors) - AGAIN, ELECTROLITIC? I HAVE 3 CERAMIC LEFT, BUT I COULD FUDGE IT BY USING 2 X 10pF FOR THE LAST ONE.

1) it's for power filtering. Probably a 47uF cap would do it, but you can use any bigger value you have.
2) 100pF? You need 0.1uF, which is 100nF, which is 100000pF. Watch for the unit prefixes! And you need 8 caps, not 5.
3) not eletrolytic. You can use ceramic or film caps.
4) again, watch for the unit prefixes! 0.0022uF is the same as 2.2nF which is the same as 2200pF. By using 2x 10pF caps, you'll end up with 20pF, which is 100x smaller than the required value.

Also:

I am not adding one more band because I only got 5 5K pots

The schematic calls for 3 4.7K (or 5K) pots and 2 47K (or 50K) pots, not 5 4.7K/5K pots.

I don't know if you're still interested in this exact project, just want to point out the unit prefixes, so you don't use the wrong values on this project (or any other one) and end up with something that doesn't work as expected.

[jfrabat]

I don't know if you're still interested in this exact project, just want to point out the unit prefixes, so you don't use the wrong values on this project (or any other one) and end up with something that doesn't work as expected.

This is much appreciated.  I started breadboarding, so I may finish just to try it, but the other schematic (4 band) seems a lot more interesting now...  That is the one I am going to build as a final build, as I can tailor the frequencies on the fly, but if this one sounds good, I may end up building both.  It's not like I have a bunch of other stuff to do right now anyway!

[jfrabat]

It's intended to show that the two 100k pots are each half of a dual ganged 100k pot.

Ah...  You learn something every day!  Good to know!

[rankot]

If you're aiming to have a good quality and low noise EQ, all those capacitors in the signal path shall be polymer type, not ceramic! Those 10n (0.1uF) in power supply can be ceramic. It is also better to have regulated power supply with linear regulators.