5-Band Fully Parametric EQ

[aziltz]

Hi Taylor,

I was thinking of starting with self-made, etched singled sided boards with board-mount pots.  The circuit has a lot of pots but its not quite as complicated as some of the things I've seen needing fabbed boards like your trem/delay projects and madbean's aquaboy analog delay. 

I'm hoping to mix 16mm board mount pots with 9mm external trimmer types.  You wouldn't happen to have an eagle component for these pots would you?  http://www.mouser.com/catalog/specsheets/TW-700180.pdf

That said, after I build and verify the circuit I might consider going with a pre-fabbed board.  I just haven't done that before, so I might have some questions or ask for some help if I go that route.

Thanks,

-Austin

[Taylor]

I'm hoping to mix 16mm board mount pots with 9mm external trimmer types.  You wouldn't happen to have an eagle component for these pots would you? 

I don't use Eagle, sorry.

I'll be watching to see how this turns out, good luck with it.

[aziltz]

Ok, so this is taking alot longer than I expected, but I hope the results will be worth it.

Here's a preliminary PCB layout of the high-headroom 5 Band.  18v Charge Pump, Bass/Treble Shelving, 3 Fully Parametric Mid Bands...

[jkokura]

Cool.

I noticed that there's lots of spare room - is that the size you wanted it to be? Also, the pots for each band are obviously the usual board mounted, but what about the 3 mid band freq pots?

Good stuff man.

jacob

[aziltz]

Cool.

I noticed that there's lots of spare room - is that the size you wanted it to be? Also, the pots for each band are obviously the usual board mounted, but what about the 3 mid band freq pots?

Good stuff man.

jacob

still working on squishing it down...  I like to get it all laid out, and then work my way in.  I'm designing it to fit in a horizontal 1590NS-type box.  For now, the 3 Q controls are trimmers, and treble "Shelf" is a trimmer.  Shelf Controls the Roll Off of the Treble band, so you can have it a shelf like a Bax or Gradual Roll Off.

The 3 weird looking pots are actually pc mount external trimmers like this, http://www.mouser.com/catalog/specsheets/TW-700180.pdf

These pots will control the center frequencies of the 3 parametric mid bands.

I'm thinking of adding some DIP switches to allow some preset options for the Shelf Corner Frequencies.

[Taylor]

Nice. I'm planning to build this along with a Sansamp VT Bass-inspired preamp. May actually build them together with a 100-ish watt power amp for a completely DIY solid state amp. What else do you need to do to get it done?

[aziltz]

i'll need to find some time to build and verify it.  I've simulated it and it seems to work fine.  What I've done differently here is to combine the BAX and Parametric EQs using the same OpAmp stage, as opposed to just chaining the circuits.  I'm not sure when I'll have time to test it in the near future yet.

[aziltz]

here's a second stab at the new, compact layout.

any comments or feedback would be awesomely helpful!

[Taylor]

Looks great to me. Let me know when I can buy a board. 

Few questions:

Are the best and treble cut only? And the mids are all boost or cut?
How much boost/cut is available in each band?
Is that chrome sparkle a PPP finish? Can't find it on their site.

[aziltz]

Looks great to me. Let me know when I can buy a board. 

Few questions:

Are the best and treble cut only? And the mids are all boost or cut?
How much boost/cut is available in each band?
Is that chrome sparkle a PPP finish? Can't find it on their site.

All 5 Bands offer Boost and Cut.  I think I have the Mid Bands set for about 15 dBs of boost?  At least that's what my simulation is showing.  I'm going to tweak the Bass/Treble for something similar I suppose.  It's all very easy to tweak.  The Amount of boost/cut is governed by two resistors for the 3 mid bands (R3 and R4), and another 2 resistors for the Baxandall-Style Bass/Treble (R10 and R5).

The finish is Black Chrome/Chameleon Cherry.  It's not listed under colors, but its a Custom Color and they'll put it on anything you want.  http://www.pedalpartsplus.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PPP&Product_Code=1609&Category_Code=ENC15C

[jkokura]

I like the second layout better, but I'm a little curious about how to mount pots to the spots you've designated for trimmers. I guess selfishly, I'm thinking about the two EQ's I want to build - one a 3 band Bass, Mid, Treble full parametric (9 knobs in a 1590BB) and a second a 5 band Bass, 3 Mids, and Treble partial parametric - boost/cut and Freq (10 knobs in a 1790NS)

I'm not sure I can really build either one from this board. However, it obviously suits your needs, and probably more people than just me. I think I'll have to learn how to do layouts myself to get what I'm wanting

One thing I'm curious about is the 'shelf' trimmer - what's that doing?

Jacob

[aziltz]

I like the second layout better, but I'm a little curious about how to mount pots to the spots you've designated for trimmers. I guess selfishly, I'm thinking about the two EQ's I want to build - one a 3 band Bass, Mid, Treble full parametric (9 knobs in a 1590BB) and a second a 5 band Bass, 3 Mids, and Treble partial parametric - boost/cut and Freq (10 knobs in a 1790NS)

I'm not sure I can really build either one from this board. However, it obviously suits your needs, and probably more people than just me. I think I'll have to learn how to do layouts myself to get what I'm wanting

One thing I'm curious about is the 'shelf' trimmer - what's that doing?

Jacob

Hey Jacob,

The Boxes labeled FREQ1, 2, and 3 are for these 9mm pc board mount trimmers: http://www.mouser.com/catalog/specsheets/TW-700180.pdf

They mount vertically, and with some careful drilling, will poke through the enclosure to the outside, held in place by the 5 larger 16mm pc board mount pots.

The other three trimmers, Q1-3 and Shelf are designed for internal trimmers, but you could put in external solder lug pots and wire them to the board.

This version has been redesigned with a Baxandall-style shelf boost/cut for the Bass and the Treble.  I found the parametric to be complete overkill and very hard to use for the lowest and highest frequencies.  In this version, the shelf trimmer will allow you to tailor the treble shelf all the way to a full roll off above the cut off.  One caveat however is that it has the opposite effect when boosting.  There is more boost as frequency goes up.

I'm thinking about adding some DIP switches to allow control of the Bass/Treble Corner frequencies.


You could easily make the 3 band fully parametric with this by using just the Mid Bands and adjusting the Frequency Range Caps (I have notes on this and I'm planning to share that when the project is finished).  You would have to use wired solder lug pots for the Frequency and Q Pots, but you can just leave off most of the parts for the Bass/Treble Shelf Bands.

For a full 5 bands of Boost/Cut and Freq, I'd say the original design will suit you better.  Since its verified,  I could make you a PCB and you can just leave off what you don't need, or I could revisit the layout and strip it down to the essentials and add the 18v headroom if you'd like.  Interest?


I hope that wasn't too confusing!

[jkokura]

The Boxes labeled FREQ1, 2, and 3 are for these 9mm pc board mount trimmers: http://www.mouser.com/catalog/specsheets/TW-700180.pdf

They mount vertically, and with some careful drilling, will poke through the enclosure to the outside, held in place by the 5 larger 16mm pc board mount pots.

The other three trimmers, Q1-3 and Shelf are designed for internal trimmers, but you could put in external solder lug pots and wire them to the board.

Sorry Austin, I already understood that part, what I was intending to communicate is that I wanted to use regular 16mm pots in place of those 9mm board mounting ones, and the same with the Q. Perhaps I can use them for the 3 band, just using the 3 mid bands like you're suggesting for the one version, except that I'm not sure your board fits in a vertical BB...

Not sure what I'm going to do right now. Really I want to use this with my acoustic because the graphic EQ I got from BYOC isn't 'cutting' it. (hee hee hee...)

Thanks for explaining the shelf trimmer. I'm curious why you did that with just the treble end, and not on the Bass as well.

I'm definitely interested in the 18v headroom. I'll think about which version would actually be better for my usage. Your suggestions are welcome.

[earthtonesaudio]

The latest layout looks good!  Minor suggestion: you might be able to relocate some of the charge components up closer to the treble pot, and make the short dimension a little smaller.

[aziltz]

Sorry to be so confusing. I meant to convey that you can just leave off the trimmers or 9mm pots and wire solder lug 16mm into their pads.

I did exactly this using the original layout to make trimmers into external pots.

I'll try to find a gut shot illustrating what I did.

This was intended for a horizontal 1590NS but I might be able to work out a small 3 band for a vertical layout. 

I'm at work on my iPod so it's hard to type alot. If I'm not understanding your question maybe someone else can chime in.

[aziltz]

minor updates.




Jkokura,

would a version of this that replaced the Frequency PC Mount Trimmers with 16mm PC Mount Pots be of any use to you?

[Taylor]

I'm kind of a go-with-the-flow type with PCBs I'm interested in, since I know from experience how hard it is to please everybody with a PCB layout. So I was going to be ok with whatever you decided. However, I would definitely prefer to use 16mm right angle PC mount pots for everything, if that's an option. Size of the board doesn't matter too much to me since I'm building this in an amp.

[aziltz]

thanks for your input taylor.  I really want to go with the original trimmers, I don't think DIYers use them enough...  I might even consider picking up a supply to send along with boards I might sell.  I'm still considering fab'd boards, but in all honesty, I think that's going to have to be a longer term project.  Perhaps later in the summer, I will have the funds to spring for some boards.  I'm moving in about a month, and I've got my fingers crossed that I'll find time to build and verify this circuit before then.  I have a few projects that are taking precedence at the moment.

[jkokura]

Yes, I would prefer 16mm over the trimmers, both for Freq and Q, but that's just my preference. I'd also love fabbed boards too, but since that's out of the near question, I'll just keep being patient and waiting. I don't have the ability to make my own boards, so I'll have to have someone make them for me - either you or a pcb house, either one. I have no idea what it takes to get a PCB made, but Taylor's done a few so far, so maybe having him help would be easier for you Austin.

Jacob

[Taylor]

We were talking about it, but as Austin is saying it does involve having some spare dough to get prototypes and then make a big order. I know that that has held me up in the past, as well.