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Old 28th Jan 2023, 9:58 pm   #1
Bufo Bill
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Default Help with EQ Build

Hi I am about ready to start building my second Homebrew project, an active multi band EQ unit. The details of the project so far can be found in this thread:
https://www.vintage-radio.net/forum/...d.php?t=192226
I'm just wondering if anyone has any tips for placing input and output jacks and the power input? Or maybe someone could point out a good article on the Web which covers such things?
By the way, if the Moderators would like to merge this with my linked thread from a few months back, that's okay.
Cheers from Bill.
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Old 29th Jan 2023, 6:01 pm   #2
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Default Re: Help with EQ Build

http://www.diyaudioprojects.com/Tech...ing-Shielding/
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Old 30th Jan 2023, 7:55 am   #3
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Default Re: Help with EQ Build

There's this - https://www.sound-au.com/project149.htm which AFAIK has a PCB available which would save a lot of hassle laying out grounds.Inna nutshell when laying out such a project make sure you use or make a decent PSU with low ripple and using a good shielded transformer.

For the rest use a ground bus to connect all grounds from IP's & OP's this in turn is grounded is grounded to the PSU ground then at one point ground the ground to the chassis in one place only. this article though valve guitar related gives some idea - http://www.valvewizard.co.uk/Grounding.html

Andy.
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Old 30th Jan 2023, 12:01 pm   #4
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Default Re: Help with EQ Build

Thanks for the links guys.
Cheers from Bill.
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Old 30th Jan 2023, 5:36 pm   #5
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Default Re: Help with EQ Build

Had a bit of a read of the links above, all very useful stuff! Thanks guys. The circuit in Andy's first link looks very interesting, but I decided on a circuit from the National Semiconductors handbook linked back in the old thread, and have been buying parts ever since.
I learn best by doing, and a big part of the appeal of this project is the massive learning curve. That same curve will probably make me a bit of a pest to my regular tutors here on the forum, but the spirit here is such that I know I will get there in the end.
Cheers from Bill.
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Old 21st Feb 2023, 2:26 pm   #6
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Default Re: Help with EQ Build

Hi, I'm now working on the layout of components on the veroboard. Could I use one track on the board as a "ground rail" for the whole circuit? Or would that create ground loops?
I can post a schematic if necessary.
Cheers from Bill.
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Old 21st Feb 2023, 4:00 pm   #7
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Default Re: Help with EQ Build

Schematic.
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Old 21st Feb 2023, 4:23 pm   #8
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Default Re: Help with EQ Build

It's fairly complex and the layout will be difficult. Veroboard can make it rather difficuly to make sure things are stable.

I'd consider a PCB with a groundplane on one side as a finished job, or dead-bug construction over raw PCB material ground plane for a prototype.

David
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Old 21st Feb 2023, 4:56 pm   #9
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Default Re: Help with EQ Build

Thanks David. This project is about learning the practical aspects of circuit construction. I can buy a similar device for £30 on any music store website.
I wanted to learn about component placement, EMF, groundloops etc.
With that in mind am I approaching this from the wrong angle?
Should I be more concerned with learning to use PCB design software and take the plunge into SMD components etc?
Cheers from Bill.
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Old 21st Feb 2023, 5:54 pm   #10
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Default Re: Help with EQ Build

I never use veroboard (never liked it tbh), just copper PCB and use the whole thing as the ground plane/ earth.
With audio I have sometimes isolated the 4 holes for the mounting in the corners of the board though by cutting the copper round the top of the nut/ bolt mounting points. Then you can connect them to gnd individually with a jumper to see if an earth loop develops.
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Old 21st Feb 2023, 8:22 pm   #11
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Default Re: Help with EQ Build

When you say veroboard is difficult to keep stable, do you mean it can send circuits into oscillation? What is it about veroboard that makes it prone to this?
I had thought PCBA's would require to much money and equipment to be practical. Is this assumption incorrect?
Many thanks for your help from Bill.
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Old 21st Feb 2023, 9:14 pm   #12
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Default Re: Help with EQ Build

When I say copper board, I mean just that, plain copper board not etched, where you solder the chips on board with the appropriate pins connected to the copper.
To do this (in my case anyway) I flatten out the chip pins and bend down only those needed to go on the copper board. They act as anchor points too.
It looks crap, but works well for me anyway.

There will be other ways no doubt, but vero construction leads to long delays in prototyping as it needs a helluva' lot more thought, and "can" lead to instability if tracks aren't cut near the point they lose any usability (and layout neeeds a lot more thought too).

The finished product would need PCB design, if you wish, but isn't necessary for a one off.
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Old 21st Feb 2023, 11:36 pm   #13
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Default Re: Help with EQ Build

There can be quite strong RF coupling between strips, and that can see things hooting at a few MHz.

Grounds along strips look inductive and that...... as above.

It's actually quite difficult to find a workable layout on it for things much more than yet another Practical Electronics egg timer.

What cruisin marine and myself are on about is using the copper surface of an unetched lump of PCB as a cheap (used to get scrap offcuts) solderable plane. Components were soldered above it with ground connections soldered onto the plane. If more supports were needed, I'd add innocuous 1 meg resistors as standoffs, of is a supply rail, I'd add decouplers as standoffs.

An artform in its own right.

David
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Old 21st Feb 2023, 11:43 pm   #14
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Default Re: Help with EQ Build

That's very ingenious, thanks for taking the time to explain it to me guys. I'll definitely give it a go.
Cheers from Bill.
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Old 21st Feb 2023, 11:51 pm   #15
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Default Re: Help with EQ Build

I've been building stuff for ~60 years and that looks like quite a demanding project to me, and certainly so for a "second Hombrew project".

I've used Veroboard a lot on small projects but wouldn't use it on this.

As David says, EQ are cheap to buy. But if you really want to do it as a construction project, I wonder if you could find a kit complete with PCB? Take a look at the Quasar website and then at whatever Velleman call themselves now.

I've reached an age where I now think there is much to be said for kits .


P.S. Looks like Quasar had just the kit you want...but it's discontinued!
B
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Old 22nd Feb 2023, 8:30 am   #16
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Default Re: Help with EQ Build

I think he said earlier that he was wanting to learn about layout techniques, so while a kit with a PCB might be a rapid way to getting a working graphic equaliser, it doesn't make much contribution on the learning front. All you get to do is follow the assembly instructions.

Andy needs the freedom to make some mistakes, track them down and try alternatives.

David
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Old 22nd Feb 2023, 9:05 am   #17
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Default Re: Help with EQ Build

Quote:
Originally Posted by Radio Wrangler View Post
I think he said earlier that he was wanting to learn about layout techniques,
Andy needs the freedom to make some mistakes, track them down and try alternatives.

David
Yes, but weren't they secondary considerations to actually having a working EQ for his beloved 5-string?

Mastering something like Kicad PCB software is a challenge; my personal view is that my current age, I'll leave that out.

Andy may well learn from making mistakes, just so long as he doesn't reach the point where he loses interest, and that does happen. And.... Spring is coming, and soldering irons will be put down and trowels picked up .

B
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Old 22nd Feb 2023, 10:08 am   #18
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Default Re: Help with EQ Build

Quote:
Originally Posted by Radio Wrangler View Post
There can be quite strong RF coupling between strips, and that can see things hooting at a few MHz.

Grounds along strips look inductive and that...... as above.

It's actually quite difficult to find a workable layout on it for things much more than yet another Practical Electronics egg timer.

What cruisin marine and myself are on about is using the copper surface of an unetched lump of PCB as a cheap (used to get scrap offcuts) solderable plane. Components were soldered above it with ground connections soldered onto the plane. If more supports were needed, I'd add innocuous 1 meg resistors as standoffs, of is a supply rail, I'd add decouplers as standoffs.

An artform in its own right.

David
Are we talking dead-bug construction? One of the real experts in this was the late great Jim Williams. See for example https://www.analog.com/media/en/tech...tes/an47fa.pdf

Craig
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Old 22nd Feb 2023, 10:15 am   #19
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Default Re: Help with EQ Build

Talking about Veroboard. Sorry if I wasn't clear.

Jim Williams was good and an artist at it. I've built dead bug breadboards which have covered a full bench surface.

Dead bug is pretty favourable for stability and RF performance, so it's good to prove a circuit, and then comes the interesting bit of transferring it to a PCB layout.

THere are courses on PCB layout, but they are really about how to drive the CAD tool, rarely do they go into how you decide what needs to go where.

Jim Williams was the author of many superb applications notes from Linear Technology inc. Highly recommended reading. LT (as also in LT Spice!) got taken over by Analog Devices, so LT stuff can be found via ADI's website. There was a sort of farewell doo for Jim rather than a formal funeral. To compound the loss to the electronics community, Rob Pease died on his way home when his beloved Beetle left the road and went down a canyon. Rob was National Semiconductor's analogue guru, and boy did he act up to it.

There were some interesting characters around in those days.

David
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Old 22nd Feb 2023, 10:26 am   #20
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Default Re: Help with EQ Build

Guys, thanks so much for your help.
Originally this was as Bazz says to argument my banjo kit, but it's really just an optional extra. As David says, I now want to make this project into a learning opportunity. I'm happy to just potter about and learn from my mistakes. I just hope I don't send you guys nuts in the process!
Cheers from Bill.
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