Hello and help!

[vielle568]

Hello Everybody,


I'm new to the forum. The reason I've joined up is because I've been trying to build electronic projects but I'm not an EE, I'm an ME. I get along OK in general but I'm having some problems at the moment with an analog switch. I use it to trigger different audio signals on a musical instrument I've built and it often makes ‘clicks’ or ‘pops’ when it turns on. I believe that if the input and output lines of an analog switch are at the same voltage level at the time of switching the ‘click’ will not be present, but how do I achieve this? Tie-up or tie-down resistors on both sides? I’m really not sure. Maxim apparently make ‘clickless’ analog switches but these are only sold in sub-miniature packages for portable phones and other similar devices and are not suitable for my home workshop; I need something in a DIP configuration. The analog switches I’m using are MAX4514 SPST switches that come in a DIP-8 package.

There’s a schematic attached showing a typical installation of the analog switch plus a couple of photos of the assembled instrument. Again, thanks for any help you can give me with this project.

Vielle568

[wakibaki]

You may find that the MAX4744 series or other clickless analog switches are the most satisfactory way to go, despite the difficulties involved in using them. These are smart devices, and trying to bolt-on the functionality they offer may be difficult.

You have obviously put a lot of effort into your instrument already, perhaps you could get someone to assemble a custom board for you, just for this function.

Making a homemade board work with these surface mount components is not impossible. You need a good layout software, access to a laser printer, transparency material, resist-coated PCB, a UV lightbox, develop and etch chemicals, some solder paste and a toaster oven.

Or you can get boards made from your layout for reasonable prices. These are easier to oven solder because of the tinning and solder resist. Then you just need the solder paste and toaster oven. Some people like to stencil the solder paste on. You can get a cheap laser-cut plastic stencil. If you're lucky you can use one of the patterns on the company's sampler, I must have done a dozen boards with mine.

Note that the MAX4744 requires attention to power supply sequencing.

w

You could maybe have a daughterboard arrangement to fit into DIP sockets.

[john blackburn]

Hi vielle568

Is that an electronic hurdy gurdy? Looks stunning whatever it is.

John

[godfrey]

The ideal would be a zero-crossing switch. i.e. One that delays switch-on (and switch-off too?) until the input signal passes through zero.

[vielle568]

Hi Guys,

Thanks for the info on the analog switches. I checked ou the MAX4744 and it looks fine but as you pointed out it's in a tiny package just 2mm square. OK, I've a small tip on my soldering iron and some powerful glasses but I'll never manage to get that chip wired up without professional help. I did however stumble on a chip made by Analog Devices, the SSM2404P. This is a 20pin DIP package chip that houses 4 SPST 'clickless' analog switches specially designed for audio applications. I use three in my design and so I could easily replace the them with this one IC. I don't know if anyone has used this product but it has a 'make-before-break' circuit plus a surge switch to control the clicks and pops when switching different level signals. It runs off of a single or double supply if required.

Yes, it's an electric hurdy-gurdy (vielle in French). The melody comes from a humbucker pick-up tapping the string that runs through the keyboard but the rest of the instrument is electronic. The rhythm is generated by a laser that monitors the wheel speed. A pulse signal is sent to a voltage to frequency converter that controls an analog switch; this switch pulses the audio signal for the rhythm. The drone signals are generated from synthesizer modules. The instrument plays OK but could do with a just little refining here and there to bring it to prefection.

Cheers!

vielle568

[john blackburn]

Hi vielle568

I had a mate a few years ago who played hurdy gurdy and crumhorn, though not at the same time. He got work with re enactment societies playing period instruments quite a bit. He had a bombarde too but said that was very hard to play.

A lovely piece of work, I hope you get it working to your satisfaction.

John

[vielle568]

Hi John,
Thanks for your encouragement. I've got most of the teething problems out of it; there's just a few irritating things that I want to weed out that are taking some time. In fact I played it last night at a gig and it worked fine (although I didn't use all the functions).
You're right, it's difficult to play hurdy-gurdy and curmhorn at the same time. I too have played for many years in a medieval ensemble and made the instruments too. As for the bombarde, well, the reeds require quite a bit of pressure and usually the instrument only plays the first part of the phrase and not the repeat. This way the player doesn't get worn out by having to play all the time.
Here's a couple more instruments from my shop if you're interested: a bombarde and a couple of vielles...

vielle568

[john blackburn]

Hi vielle.

It just gets better and better!

The marquetry alone must have taken forever. Is there much demand for instruments of that kind in France?

Everyone in England is playing Guitar Hero. I don't think Hurdy Gurdy Hero would catch on but I would like to see it.

John

[vielle568]

Hi John,
Thanks for your compliments. The black vielle is an electro-acoustic model and this type is getting fairly popular. The electric version I have just built is a one-of-a-kind prototype and I don't know of another quite like it. It can generate all the same sounds and effects you get to hear from an electric guitar but of course the playing technique is totally different. The guitar will always remain the more popular instrument but I've always been fascinated by the vielle (hurdy-gurdy) and have been trying to develop it for quite a while.
Incidently, I used to live in Liverpool and work at the Ford plant at Halewood when I was a young engineer; but that's going back a few years!

vielle568

[john blackburn]

Hi Vielle.

Liverpool must have been quite a shock coming from your rural location. The Deux Sèvres region looks lovely by the photos on google.

It was Capital of Culture recently, it made no difference at all to the lives of the average person though. A huge amount of money was spent on fancy lamp posts for a few streets and a big new shopping centre was built. It has all the same shops you would see in any other city and all the small independent shops have closed as the city centre was blocked for so long.

Ford is now Jaguar but I hear it isn't doing too well, no car factories are in a good shape currently.

John