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

[jfrabat]

Decided to just leave it as it was...  Except for the knobs.  I will just work around the issue (it should not affect what I am trying to do).  Here is the final version:



And installed in my PC with the other stuff:

[Mark Hammer]

Very nice.

Now, since I feel some responsibility for pushing you in this direction, I have to ask: does it do what you wanted and needed it to do?

[jfrabat]

Yes, it does.  If it where not for that high freq issue, it would have been as good as anything In2ould have been able to buy (for my needs) with the flexibility to use it also with my guitar!

[kraal]

Hello,

Very nice build / journey and result. After reading the whole thread, I have some questions.

Q1. What is the max current draw of such a circuit ? (PAIA's documentation states that the wall mount transformer must be min 100mA)

Q2. How "bad" would be the impact when using +/-9V instead of +/-12V (does it differ in a voice vs instrument context, is there a big risk of clipping) ?

Q3. If the headroom provided by a +/-12V power supply is required, Would it be possible / ok to power the NE532s using a 9VDC power supply with a (or multiple) charge pump(s) + inverter(s) ? (i.e. to obtain +18V with -9V virtual ground to have a "similar" headroom). What would be the best way to achieve this (If I'm not wrong, the TC1044SCPA is capable of providing 20mA, would it be possible to use N times a TC1044SCPA ? is there a better way to achieve this) ?

Q3. If using a 12VDC power supply, what would be the best (and cheapest) way to invert the voltage ? (I was thinking for instance about LT8331, but it's quite expensive ~8x the price of a TC1044SCPA)

Thanks a lot for your answers !

Michel

[jfrabat]

Hello,

Very nice build / journey and result.

Thanks!

Q1. What is the max current draw of such a circuit ? (PAIA's documentation states that the wall mount transformer must be min 100mA)

Not sure; did not measure it.  I am using a 500 mAh power source, but I think the 100mAh would do fine.

Q2. How "bad" would be the impact when using +/-9V instead of +/-12V (does it differ in a voice vs instrument context, is there a big risk of clipping) ?

Have not really tried it, but I would imagine you would loose headroom boost.

Q3. If the headroom provided by a +/-12V power supply is required, Would it be possible / ok to power the NE532s using a 9VDC power supply with a (or multiple) charge pump(s) + inverter(s) ? (i.e. to obtain +18V with -9V virtual ground to have a "similar" headroom). What would be the best way to achieve this (If I'm not wrong, the TC1044SCPA is capable of providing 20mA, would it be possible to use N times a TC1044SCPA ? is there a better way to achieve this) ?

Here you are going above my knowledge...  not sure what would happen, to be honest.

Q4. If using a 12VDC power supply, what would be the best (and cheapest) way to invert the voltage ? (I was thinking for instance about LT8331, but it's quite expensive ~8x the price of a TC1044SCPA)

Same here...  Sorry I could not be more helpful!

[antonis]

Q3. If the headroom provided by a +/-12V power supply is required, Would it be possible / ok to power the NE532s using a 9VDC power supply with a (or multiple) charge pump(s) + inverter(s) ? (i.e. to obtain +18V with -9V virtual ground to have a "similar" headroom). What would be the best way to achieve this (If I'm not wrong, the TC1044SCPA is capable of providing 20mA, would it be possible to use N times a TC1044SCPA ? is there a better way to achieve this) ?

By adding series-pass transistors should be more space/cost efficient configuration..
(in case of a V_BE (+/-) loss in headroom should be acceptable, of course..)

[jfrabat]

Just wanted to update you guys; my daughter (who recently got a PC in her room) wanted to make her own recording setup.  She bought an interface, but she wanted some more gear (you know, cause daddy can make it!).  So I decided to make her (among other things) a copy of this EQ (I had 2 boards of it laying around, because the minimum order is 3).  Anyway, I just finished populating the board (only the LEDs are missing), and lo and behold, this one does not have that high frequency oscillation that the original one has.  So it is certainly an issue with one (or more) component(s) in the original build rather than a design issue.

Now with the new board, I will go measure component by component and compare (with pots all the way down in both cases so that I know it is the same) and see if I can find the culprit.

[Rob Strand]

this one does not have that high frequency oscillation that the original one has.  So it is certainly an issue with one (or more) component(s) in the original build rather than a design issue.

Good to know.

[11-90-an]

Just wanted to update you guys; my daughter (who recently got a PC in her room) wanted to make her own recording setup.  She bought an interface, but she wanted some more gear (you know, cause daddy can make it!).  So I decided to make her (among other things) a copy of this EQ (I had 2 boards of it laying around, because the minimum order is 3).  Anyway, I just finished populating the board (only the LEDs are missing), and lo and behold, this one does not have that high frequency oscillation that the original one has.  So it is certainly an issue with one (or more) component(s) in the original build rather than a design issue.

Now with the new board, I will go measure component by component and compare (with pots all the way down in both cases so that I know it is the same) and see if I can find the culprit.

Swap yours with hers... assuming her box is the same as yours...

Jokes aside, its always good to see people do a one-try success in pcb populating etc.

[jfrabat]

Swap yours with hers... assuming her box is the same as yours...

I am sorry...  Did I leave any doubts that my intention was to swap them?   

Jokes aside, its always good to see people do a one-try success in pcb populating etc.

Well.... SORT OF!  LOL!  You see, I had marked the pots (cut/boost) as A10K in the schematics, so, obviously, I used A10K pots...  And, OF COURSE, I had swapped them out for B10K pots in the original.  So now parity is at about 70% turn.  I am still debating if I will remove the pots and replace them (probably will)...  but not right now.  I am tired!  I feel so dumb for pulling that little stunt!  Oh, and did I mentioned I only got 2 B10K pots in my stash?  In the words of a famous philosopher (Homer Simpson), "DOH!"

[jfrabat]

New update; since I had to order the pots (B10K), and shipping is expensive, I figured, the right thing to do would be to order MORE stuff so that the shipping makes sense, right?  Sounds like a logical plan, right?  (For some reason, my wife thinks it does not; cannot see why she feels that way!  LOL!)  ANYWAY, as some of you know, I am making myself a compressor, for which I had already purchased some parts...  But both the compressor and the interface have a frontal panel, and my EQ has a top panel.  It just does not match!  SO, since I had an extra board for the EQ laying around (3 unit minimum order and all that jazz), I ordered myself some additional Hammond 1402B enclosures so that I can have the compressor and the EQ in matching cases with frontal panels on both (which makes A LOT more sense considering where they are located on my desk!). 

So I started building my pedal while I wait for the enclosure.  This is it so far:



As you can see, I had to drill 3 holes at the corners that had space for the holes to mount the board to the new case (no pots to hang from on this one!) that I will use nylon mounts (which I already have) to attach to the bottom plate of the enclosure to keep it from rattling about or shorting out the bottom of the board.  As for how the front panel will look like, it will be something along these lines (ignore the colors; those are just layers in AutoCAD):



I will carry on the idea of having different color knobs for each band, as will the compressor, which will have different color knobs for the compressor controls and the gate controls, but, unlike the original on top, I will be using smaller anodized aluminum knobs of these, as they make more sense size-wise.  And as you can see, deign-wise, it will be a nice match to the compressor:



I also ordered a DP-1010 Mic Preamp Kit from Fivefish Audio and the vented version of the enclosure (the Hammond 1402BV enclosure) so that it will all match.  In fact, I will have an additional non-vented enclosure, and the idea is that if the compressor works well, I will make myself 2 compressors and chain them for smoother compression.  The FMR Audio RNC1773 I have uses 4 when using the Super Nice mode, and I like that a lot (that compressor would be given to my daughter for her recordings, along with the PreSonus TubePre V2 I currently use).

Oh, and the name changed from 4TWEQ to 4 TweEQ at the suggestion of my wife (she says 4TWEQ sounds more like 4TWECK and that makes no sense).

[rankot]

Looks impressive!

What's the final schematic for this?

[jfrabat]

Looks impressive!

What's the final schematic for this?

Just for the sake of documentation, here is the final schematic:

Just use B10K pots instead of the A10K pots listed and B100K pots instead of A100K pots.

[rankot]

Thanks!

[jfrabat]

Not sure how I manage it, but I do!  I built the 2 other boards for this project, and each has different issues from the other!  LOL!  On the one in the Hammond 1590Q case, band #3 is not working.  On the one in the Hammond 1402D case, nothing is working right!

I am starting troubleshooting them now, but it is frustrating how I manage this!

Here is how the 1402D case looks like, by the way:



Now, I just noticed that I wired ALL the pots backwards, so I have to fix that, but I think there is more troubleshooting in store after, as it currently sounds like the frequencies got both cut and boosted at the same time (if that makes sense).  But I will start by wiring the pots the correct way and work up from there...  Oh, and I messed up a pad to the bypass switch, so I had to wire the input wire directly (so at least bypass now works!).

The 1590Q one I already damaged the finish (almost identical to the original, but brushed aluminum instead of polished and changed the word TwEQ for TweEQ).  So, 3 exact boards built, and 3 different issues!   Tomorrow I will re-solder the pots of the 1402D, then move to the other pedal to try to get band 3 working properly (at least this one is not oscillating in band 4!).  After that, it is back to the 1402D one...  The original I will leave as a memento, as it has that oscillation, and I only got 2 12VAC power supplies!

[bluebunny]

I'm ashamed to say that I've not been following this thread as closely as I might, but this . . .



. . . is eye-poppingly incredible!  Top work, Felipe.  Well done. 

[jfrabat]

I'm ashamed to say that I've not been following this thread as closely as I might, but this . . .



. . . is eye-poppingly incredible!  Top work, Felipe.  Well done. 

Thanks, but top work will be when it actually works!  (It will, but I need tontrouble shoot it!)  As of now, it is just a pretty but expensive paper weight!  But it will look really cool once all the studio harware (compressor, de-esser and 2 preamps) are finished with a similar finish and the same type of enclosure.  The compressor is next...  PCB just got manufactured and is on its way.  I also got one of the preamps half built (waiting for some parts to arrive).

I will post a pic of the other version of the EQ as well (the one I am making for my daughter).
The brushed aluminum makes it look a lot nicer.

[Ben N]

But, Lordy, those enclosures are pricey! Is there a source for, shall we say, less "pedigreed" 1/3-1/2 rack size enclosures?

[jfrabat]

But, Lordy, those enclosures are pricey! Is there a source for, shall we say, less "pedigreed" 1/3-1/2 rack size enclosures?

They are.  I was looking for 1/3 or 1/2U, but did not find any, so if you do, let me know!!!

Now, (AS USUAL!) I need some help figuring out what the heck I did...

Of the 2 pedals, the 1590Q is working fine now (I had a small short in band 3 that has been corrected).  I am very proud of myself for finding that one on my own; I am getting better at this! 

As you can see, no issues with oscillation in any of the 4 bands.  Of course, the 2 gang pots being Audio taper, the frequency sweep is a bit of a thing, but it works fine.

Here is the pic of that one:



As you can see, there is a lot of damage to the sticker from taking this thing apart so many times!  You may also notice it is the same design as the original, but I went with brushed aluminum look instead of polished, and the name was tweaked (pun totally intended!) to sound better.

So, the 1590Q is officially finished.  The 1402B, however, is not!  AND I NEED HELP!  I AM STUMPED!!!

It is exactly the same board (print 3 out of 3), using the same components, except:

• Violet LED's instead of white
• CLRs increased resistance dim the LEDs a bit (my daughter wanted to spotlights; I told her I was going to adjust them, but she said no.  Go figure!)
• Dual gang pots are A100K in the 1590Q and B100K in the 1402D
• 12K resistors are from a different batch (Mouser 5% in the 1402B and cheap Chinese Amazon 10% in the 1590Q)

Apart from that, the changes between the 2 are:

• Pots wired off board (all 8 in the 1402B, and only the dual gang in the 1590Q)
• AC Jack (they both use DC jacks, really, but the one in the 1402B is the smaller type while the one in the 1590Q is the one with the provision for a battery, which is not used obviously)

I did a comparison of values between the 2; here is the final circuit, so you can trace the values:



And here are the values:



I also measured resistance.  Normaly, I would not bother measuring resistance when everything is in the board, but since I have 2 identical boards, I figured it would make a good comparison.  For this, I turned the pots all the way to the left (all 8 of them) to have a consistent reading in both EQs:



Here is a shot of the interior in case it helps:



Excuse the rats' nest!  I tried to tidy things up a bit stuffing the extra cable under the board so that you can see clearly all the components...

Here are the symptoms of that one:

Any ideas on what to do will be greatly appreciated.  Becasue I ran out of ideas.  I did find some errors (like the dual gang pots being wired backwards, and the cut/boost ones being wired wrong), but I cannot dins anything else, and the problem persists!  I imagine the issue is in the last band (AGAIN!), but I cannot narrow it down!