Signal generator recommendation.... - Page 1
Forum section: electronics / general

author: danander11
author_rank: Unknown
timestamp: March 08, 2012, 09:50:47 am
content: OK.. I might get a few tomatoes thrown at me for asking, but I've used the search function a bit and haven't gotten very far.I need a decent, albeit simple, signal generator for use in testing some audio gear that I'm building, and to have on hand for troubleshooting. I've looked around for a good DIY project that would allow me to build one, but I'm not really sure that they wouldn't be 'noisy' or accurate.Can anyone suggest a good DIY project or even a decent S/G that I can look around for and buy for not a lot of dough?The audio stuff I am building is some solid state, and more transformer/tube based (if that makes a difference).I'm really new to all of this but keen to learn.Thanks!

author: steve_w
author_rank: Regular Contributor
timestamp: March 08, 2012, 10:13:21 am
content: A bit loose in the specification department;Do you want a sig gen with accurate level and frequency with low distortion for measuring performance or do you want a rough and ready 400hz or 1 KHz signal with variable level for signal tracing or fault finding?What sort of test gear do you have multimeter or CRO etcfrom your original post I seen many that can be done on proto board for a few dollarstry this for $30 you cant go wronghttp://www.altronics.com.au/index.asp?area=item&id=K2544

author: vk6zgo
author_rank: Super Contributor
timestamp: March 08, 2012, 10:18:10 am
content: For audio,you could use a cheap function generator,but I'm not sure if their distortion figures are up to the job.A possibility is picking up an old Broadcast quality generator on eBay,or at a real auction.The AWA ones from the 1960s & '70s are very good,are solid state,& usually have a choice of output impedance.You may find other good brands.A Noise & Distortion meter would also be useful----the later auto tune AWA is good,as is the HP.

author: jimmc
author_rank: Frequent Contributor
timestamp: March 08, 2012, 10:22:16 am
content: As has been said your request is a bit open ended but I would say that for most audio work you do not need the frequency stability of a DDS based sig gen, and the distortion of an analogue function generator will be too high.Most low distortion audio generators are based on the Wein bridge, Google for ideas.e.g. for a good introduction seehttp://www.ti.com/lit/an/sloa060/sloa060.pdfand for a practical circuit seehttp://sound.westhost.com/project22.htm.However if you have a reasonable sound card in your PC then (free) program such ashttp://www.sillanumsoft.org/will give you a low distortion generator, 'scope, spectrum analyser, distortion meter and more.I would strongly recommend building a simple interface to protect the PC from overload.Jim

author: T4P
author_rank: Super Contributor
timestamp: March 08, 2012, 10:38:07 am
content: Hantek DDS 3x25 if you can find 'em .They aren't bad .

author: danander11
author_rank: Unknown
timestamp: March 08, 2012, 10:52:42 am
content: Wow! Thanks.I'll dig through these and try to form a bit more of an opinion as to what I need.. As I've said, I'm a greenhorn and trying to get my head around some things.For my soundcard I have a protools HD system, but I'm not really all that excited about connecting it to gear that's untested or not operating properly..I'll probably build the Altronics one just for grins.. They claim low distortion so we'll see.My test gear so far is a semi-decent DMM, (though I'm looking for a better one), and a Rigol DS1052E (hacked to DS1102E).Thanks gents!

author: olsenn
author_rank: Frequent Contributor
timestamp: March 08, 2012, 01:45:18 pm
content: You can't go wrong with an Instek SFG-1003: they're only ~$150 and they work very well. It provides (up to) 3MHz Sinusoid/Square, and I can't remember the max frequency of Triangle waves; has two outputs, one TTL (for digital) and one regular 50-ohm output; and you may control the amplitude, phase, and duty (square)If you're looking for something higher end, then the Rigol DS4000-series is the way to go. This baby can go up to 160MHz and do Sine/Square/Triangle/Pulse/... and can output arbitrary waveforms. It also has modulation features, sweep, and burst. It obviosly costs more, but it's worth it if you have the dough

author: LEECH666
author_rank: Frequent Contributor
timestamp: March 08, 2012, 02:05:39 pm
content: I would like to build up this litte project, however I think I'll need some help with it as I most certainly would have to replace/substitute some hard to get parts (like the , and since I blow at understanding electronics, I most likely won't know what to look for, if I had to select alternative parts.http://www.microsyl.com/index.php/2010/03/24/function-generator/#more-213

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 08, 2012, 02:19:04 pm
content: Quote from: olsenn on March 08, 2012, 01:45:18 pmThe Rigols violate the OP's: "buy for not a lot of dough" But they do look sweet. I've been pretty happy with my SFG-1003.

author: T4P
author_rank: Super Contributor
timestamp: March 08, 2012, 03:35:57 pm
content: Quote from: olsenn on March 08, 2012, 01:45:18 pmHAHAHA , no . DG4000 series is just out of reach .Hantek DDS3x25 = 25MHz AWG and apparently up to 75MHz sine .-40DBc @ 10MHz

author: tekfan
author_rank: Frequent Contributor
timestamp: March 08, 2012, 04:45:00 pm
content: Quote from: jimmc on March 08, 2012, 10:22:16 amI built that circuit from those schematics and measured it with a distortion analyzer and it's under 0.02% (two least significant digits on the analyzer!). So I'm guessing it's actually lower than that. Amazing little circuit that covers the entire audio range and beyond.

author: Lawsen
author_rank: Frequent Contributor
timestamp: March 09, 2012, 05:12:17 am
content: I do not know if this will work for you, but the most inexpensive signal generator store bought is my pocket sized function generator is the Velleman HPG1 for about $129.99. I like it because I do not have much space in my room and even when I was a student at the state university. It is small and pocket sized and great to experiment and do stuff with.http://www.amazon.com/Pocket-Function-Generator-Velleman-HPG1/dp/B006YTWMZW/ref=sr_1_cc_2?s=aps&ie=UTF8&qid=1331269641&sr=1-2-catcorr