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DIY - Building a simple analogue filter

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DIY - Building a simple analogue filter

Postby librat3 » Fri Jan 10, 2014 11:31 pm

Yo people, thanks in advance for any help i may receive on this one!

I've recently become interested in the idea of building a simple analogue filter of some kind. Mainly because I'd be really interested to find out how filterbanks/other audio hardware work, But also just for me to have a little fun on whilst working on music!

I'm a total beginner in audio electronics, so any help whatsoever as to how to go about building something like this would be great.

The goal i have in my head is something like this: a 6.5mm jack input, mix/reso/freq knobs and an output. Sounds simple to me but I could be very wrong haha.

Any suggestions on how to get started with something like this?

Thanks very much,
-Joe
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Re: DIY - Building a simple analogue filter

Postby Mac.Dyson » Fri Jan 10, 2014 11:54 pm

Check out PAIA - http://www.paia.com/about.asp. They're an American audio electronics kit manufacturer for over 45 years and might have something in their catalogue that would suit.
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Re: DIY - Building a simple analogue filter

Postby Hugh Robjohns » Sat Jan 11, 2014 12:00 am

Yes, search out a kit, like this:

http://www.paia.com/proddetail.asp?prod=6760K

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Re: DIY - Building a simple analogue filter

Postby MikeGorman » Sat Jan 11, 2014 11:05 am

As a complete beginner, I would suggest starting with a recent book from Ray Wilson :

Make: Analog Synthesizers

Apart from giving you an excellent introduction to Analogue Synths, it also describes a simple module based on a PCB that is available from Ray's Music From Outer Space website, which is another good DIY resource.

There has been an explosion of availability of DIY synth projects in recent years, bringing back to life many old synth designs from the likes of Moog, Buchla and Serge.

You can also look to some more local suppliers like Oakley and Thonk. Oakley has been around for years and if you were a bit more experienced, their Filtrex II project would be ideal for a stand alone project. Thonk is a relative newby, with an ever growing collection of kits and parts that supports the synth DIY community.

Hope this helps.

Regards

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Re: DIY - Building a simple analogue filter

Postby ef37a » Sat Jan 11, 2014 11:36 am

Get Duggy Self's book "Small Signal Amplifiers".

Several simple filter/EQ circuits and just about all else you need to know about audio electronics save power amps.

My standard bogtime reading.

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Re: DIY - Building a simple analogue filter

Postby Folderol » Sat Jan 11, 2014 6:16 pm

Do all of the above

Also get kits of small resistors and capacitors so you've got some 'stock' for trying out different values.

Learn the resistor colour code. It is invaluable, and is also used for a lot more than just resistors these days.

Get some veroboard and some hook-up wire and practice soldering, making 'components' out of the wire. Try and get nice neat soldered joints without the insulation softening and sliding back.
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Re: DIY - Building a simple analogue filter

Postby ef37a » Sat Jan 11, 2014 6:41 pm

Folderol wrote:Do all of the above

Also get kits of small resistors and capacitors so you've got some 'stock' for trying out different values.

Learn the resistor colour code. It is invaluable, and is also used for a lot more than just resistors these days.

Get some veroboard and some hook-up wire and practice soldering, making 'components' out of the wire. Try and get nice neat soldered joints without the insulation softening and sliding back.


And! Get one of those "S-Deck" component assembly boards. I bought and used one for the first time about a year ago and was surprised at how handy it was. Also makes a great online teaching aid.

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Re: DIY - Building a simple analogue filter

Postby BillB » Sun Jan 12, 2014 12:40 pm

Get one of those "S-Deck" component assembly boards.


Wossat? Link please...

When I put <"S-Deck" component assembly boards> into Google, it linked to this thread!

Thanks

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Re: DIY - Building a simple analogue filter

Postby Martin Walker » Sun Jan 12, 2014 1:57 pm

Yes, I'm intrigued too


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Re: DIY - Building a simple analogue filter

Postby ef37a » Sun Jan 12, 2014 5:36 pm

Martin Walker wrote:Yes, I'm intrigued too


Martin

http://www.maplin.co.uk/p/ad-12-solderless-breadboard-bz15r

Found it at last. Never thought to look under "breadboards"!

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Re: DIY - Building a simple analogue filter

Postby James Perrett » Mon Jan 13, 2014 3:41 pm

BillB wrote:
Get one of those "S-Deck" component assembly boards.


Wossat? Link please...

When I put <"S-Deck" component assembly boards> into Google, it linked to this thread!


That's because it was really spelt S-dec. They're an old style breadboard for discrete components and, in my experience, they wear out pretty quickly. I found it just as easy to learn to solder and use veroboard. The modern ones with an 0.1" pitch seem better and they work with DIL IC's too.
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Re: DIY - Building a simple analogue filter

Postby Martin Walker » Thu Jan 16, 2014 12:09 am

Oh, is that what they are?

I've already got one


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Re: DIY - Building a simple analogue filter

Postby Folderol » Thu Jan 16, 2014 9:35 pm

Tried them. Didn't like them, went back to sniffing flux fumes
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Re: DIY - Building a simple analogue filter

Postby baron_de » Thu Jan 16, 2014 9:49 pm

The Q&D (quick and dirty) filter by Tom Escebedo seems to be the simplist good sounding filter design around:

http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/s...

Image
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Re: DIY - Building a simple analogue filter

Postby ef37a » Fri Jan 17, 2014 12:22 am

baron_de wrote:The Q&D (quick and dirty) filter by Tom Escebedo seems to be the simplist good sounding filter design around:

http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/s...

Image

Those high resistor values are going to make for a noisy circuit and I would guess the ICs are FET input jobbies, likely TL072s. Better is the NE5532 and MUCH better is the LM4562 dual IC. Much more expensive than either TLs or NEs but that is the beauty of home builds, one off the costs are puny.

Again, check out Duggy Self.

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Re: DIY - Building a simple analogue filter

Postby baron_de » Fri Jan 17, 2014 12:33 am

Did you mean "Small Signal Audio Design" by Douglas Self?

Because I don't think that covers what the OP is asking for.
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Re: DIY - Building a simple analogue filter

Postby ef37a » Fri Jan 17, 2014 10:20 am

baron_de wrote:Did you mean "Small Signal Audio Design" by Douglas Self?

Because I don't think that covers what the OP is asking for.

Well, Self covers quite a range! The classic Baxendall and several variations thereof, varible F shelving filters, Ambler tilt, middle cut/boost, Wien sweep mid cut/boost, variable peak/shelving filters, V F , V Q state variable, graphics and Sallen and Key HP/LP and their attendant shortcomings. Surely there is something in there that can be adapted? I just offer the information but I think anyone who wants to dabble in audio electronics should buy the Self book.

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Re: DIY - Building a simple analogue filter

Postby Hugh Robjohns » Fri Jan 17, 2014 10:24 am

Yes, Dave was referring to that book, and while it doesn't cover the specifics of the kind of fourth-order resonant filter you might find in a synth, Chapter 10 does cover the principles of filter designs in general, including full parametrics and graphics, and lots of stuff on optimising noise and headroom etc. Well worth reading for anyone interested in exploring audio electronics at whatever level.

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Re: DIY - Building a simple analogue filter

Postby baron_de » Fri Jan 17, 2014 1:00 pm

I have the book too, but it doesn't cover voltage controlled filters - which is what the OP will need for what I presume are primarily music creating processes.

I read that the OP needs to build something like a Mutron or Moogerfooger or Sherman etc - that can receive control voltages from an LFO or envelope follower, etc

Looks like Self has a lot of advocates, me included - and it is an extremely interesting book especially for his take on making a circuit low-noise from design up, but I'm not sure that it is a a beginners guide to making creative boxes (it's more hi-fi and mixing orientated) - and it's £40.

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Re: DIY - Building a simple analogue filter

Postby baron_de » Fri Jan 17, 2014 1:05 pm


If the OP needs to start really simple and beginner level, which is where we all started, then he could just try putting a capacitor and variable resistor across an audio output and experiencing what it does.
That's the first low-pass filter I ever built:

Image

From there develop into making bigger circuits, with more features.
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Re: DIY - Building a simple analogue filter

Postby baron_de » Fri Jan 17, 2014 1:12 pm

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Re: DIY - Building a simple analogue filter

Postby Hugh Robjohns » Fri Jan 17, 2014 1:25 pm

baron_de wrote:I have the book too, but it doesn't cover voltage controlled filters - which is what the OP will need for what I presume are primarily music creating processes.


The OP said: "I've recently become interested in the idea of building a simple analogue filter of some kind. Mainly because I'd be really interested to find out how filterbanks/other audio hardware work."

No mention of VCFs, at all -- and I'd hardly call a VCF a simple filter either!

As I said previously, Self's book doesn't cover the specific design of that kind of filter, but it's coverage of general filter design is excellent, and given the OP's general interest in audio electronics, it would be well worth a read IMHO. Other tomes are available... The Art of Electronics (Horowitz and Hill) would be another worthy educational source.

I'm not sure that it is a a beginners guide to making creative boxes (it's more hi-fi and mixing orientated) - and it's £40.


No it's not, but for anyone who wants to properly understand the compromises and priorities of good electronic design, it is well worth the price in my view.

In any case, I don't think are considered opinions are being heard since the OP has never returned!

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Re: DIY - Building a simple analogue filter

Postby baron_de » Fri Jan 17, 2014 1:36 pm

I'm sure what he needs is a VCF - otherwise, how to make it do interesting musical things?

The Escobedo VCF is pretty simple, and the online examples sound pretty good to me - an interesting design, too, with the LED as a control element.

Still it's a question I jumped on because I built the same kind of thing (out of a Maplin SSM kit, years ago) and am considering building another up-to-date one at the moment.
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Re: DIY - Building a simple analogue filter

Postby Richie Royale » Fri Jan 17, 2014 3:37 pm

A VCF will be more useful, but he does say:

librat3 wrote:
The goal i have in my head is something like this: a 6.5mm jack input, mix/reso/freq knobs and an output.

So he really just wants a simple filter circuit.
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Re: DIY - Building a simple analogue filter

Postby librat3 » Wed Jan 22, 2014 1:12 am

Sorry for the late response everyone.

Fantastic, so much stuff here to get started with, really appreciate the help!

Going to start practicing some soldering before I go any further, also some of the beginner kits mentioned look really great.

Again thanks for the help people and I'll be sure to return to this thread if i come across any issues

Cheers!
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