Looking for good cheap Function Generator - Page 1
Forum section: electronics / testgear

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 25, 2013, 02:01:55 pm
content: I have a very limited budget and need a function generator I do speaker repairs. I need to run a sine wave through a speaker and adjust the frequency so I know what ranges are not working. I don't have a function generator and was looking at the DG1022 from Rigol.Is it any good? Is it like the DS1052E in build quality vs price?

author: c4757p
author_rank: Super Contributor
timestamp: June 25, 2013, 02:04:43 pm
content: From what I've seen it's quite good, but serious overkill for running a sine wave through a speaker. Literally any FG will do audio frequency sines.

author: Stonent
author_rank: Super Contributor
timestamp: June 25, 2013, 02:07:56 pm
content: Sounds like overkill. You can already do that with cheap audio software and a PC sound card.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 25, 2013, 02:31:29 pm
content: Quote from: WakeUpWolfgang on June 25, 2013, 02:01:55 pmits good but its overkill and "non-optimum" for the purpose you stated. but hey if you can afford it why not? it can do alot more. but for your job, if you are doing hundreds of speakers at a time, you need something with analog trimpot to adjust freq very quickly. we can suggest either the DIY one or the ready made like you proposed, but we cant since we dont know your background, skill and tools

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 25, 2013, 02:43:32 pm
content: I do have other needs for one but been getting by I am mostly using this as an excuse to get one but I can't afford too much.I know I can do it with some DIY kits or my my own really cheap but when you are working on speakers that are $1500+ each you are really concerned with liability. I don't want to get blamed for breaking it because I did not use a "real" function generator. There are a lot of people that come to me who don't like anything DIY for repairs and like to point the finger.I do more then speaker repair I do everything from installing security and fire systems, sound systems and repairing security systems fire systems, sound systems and Amps. Also make some small electronics if we can't find it on the market.

author: don.r
author_rank: Frequent Contributor
timestamp: June 25, 2013, 02:55:36 pm
content: Buy an old Wavetek from the 70's. They look the business and will do everything you need. Easy to repair as well.

author: nctnico
author_rank: Super Contributor
timestamp: June 25, 2013, 03:25:51 pm
content: I have a Siglent SDG1010 (with Lecroy firmware) and I'm very happy with it.

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 25, 2013, 03:46:32 pm
content: I got a BK 3011B 2 MHz function generator for $40 on ebay.Hereis a manual for it (402KB pdf). I paid a bit more for anHP 8111A 20 MHz pulse/function generator.

author: Anson
author_rank: Regular Contributor
timestamp: June 25, 2013, 04:09:00 pm
content: Quote from: don.r on June 25, 2013, 02:55:36 pmOr a Dana Exact. Less than a $100 easy to fix and work great.

author: saturation
author_rank: Super Contributor
timestamp: June 25, 2013, 04:22:13 pm
content: Since you're in the USA, I'd recommend looking at a used Global Specialties FG. For these reasons:They are often used in trade schools, and built like tanksIt was first designed in the 1980s, and still made nearly unchanged, to this dayThe 1980-1999 ones are dirt cheap and made when ICs were made with higher quality than today; they last "forever"The older models are made in Taiwan, who overall, still do better QC than PRC devicesThey are easy to repair, if ever need betypically sold used for $20-$50,S&H includedConsThese are analog FG, and have higher distortion and frequency instability typical of analog frequency generationhttp://www.ebay.com/itm/GLOBAL-SPECIALTIES-2001A-FUNCTION-GENERATOR-SINE-SQ-TRI-200-KHZ/231002423522?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D261%26meid%3D8629273829926417366%26pid%3D100005%26prg%3D1088%26rk%3D2%26sd%3D121123993969%26http://www.ebay.com/itm/GLOBAL-SPECIALTIES-2002-FUNCTION-GENERATOR/121123993969?_trksid=p2045573.m2102&_trkparms=aid%3D555003%26algo%3DPW.CAT%26ao%3D2%26asc%3D277%26meid%3D8629254251381961189%26pid%3D100034%26prg%3D1079%26rk%3D1%26sd%3D390565912871%26http://globalspecialties.com/test-equipment/generators.htmlIf you need a new one, general purpose, I still highly recommend the GW Instek SFG-1003, I use it very often.Its output frequency is ppm stable, low distortion down to ~ -50dB. Not "audiophile" quality, but that's a whole other issueConsNo sweep or modulationNo voltage controlled oscillatorhttp://www.tequipment.net/InstekSFG-1003.html$145 sale price, $5 cheaper than when I paid list for it at $150

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 25, 2013, 05:52:23 pm
content: Thank you for all of the suggestions. I will go over all of them later today.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 25, 2013, 05:55:55 pm
content: I am in need of one also to play around with different scopes. But I am a tight a$$. Really thinking about one of the free programs to run from sound card but have not seen one that works decent yet. if someone has tried one that works good please post up a link.Also thinking of building something along the lines of a 555 timer chip.

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 25, 2013, 06:14:19 pm
content: Quote from: Radio Tech on June 25, 2013, 05:55:55 pmI am too so I am trying to get my business to buy one so I don't to and want to take the paperwork to them saying this is what you need and why. But if I could build my own for my self that would be really cool.

author: Winston
author_rank: Regular Contributor
timestamp: June 25, 2013, 06:57:01 pm
content: Quote from: WakeUpWolfgang on June 25, 2013, 02:01:55 pmFor what you need to do, this would probably suffice. It's already built, not a kit, and can "generate frequency sweeping signals of selected waveforms, start frequency, stop frequency, and sweep rate can be independently set." Very simple and intuitive to operate (I own one):http://www.ebay.com/itm/Paneled-Portable-miniDDS-Digital-Function-Generator-Servo-Controller-DDS-USA-/160708631160?pt=LH_DefaultDomain_0&hash=item256afb1a78More tech details:http://www.jyetech.com/Products/085/e085.phpYouTube reviews:https://www.youtube.com/results?search_query=fg085+function+generator

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 25, 2013, 07:03:13 pm
content: Quote from: Radio Tech on June 25, 2013, 05:55:55 pmI suggest that for scope evaluation the best thing is to have a fast rise time on the square wave.or pulse waveform. Sub-nanosecond if possible. You might need a device just for fast rise time pulses separate from your function generator.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: June 25, 2013, 07:17:15 pm
content: Quote from: dfmischler on June 25, 2013, 07:03:13 pmI agree. Especially when repairing scopes so you get things spot on. Guess I will have to bite the bullet and invest in a decent one.In the mean time I am going to play around with some PC based ones. Here is a screen shot of one I found connected to my Owon.

author: rsjsouza
author_rank: Super Contributor
timestamp: June 25, 2013, 07:17:29 pm
content: Quote from: don.r on June 25, 2013, 02:55:36 pm+1 for the Waveteks... They do the job flawlessly.For a cheap one, checkhere.When repairing audio equipment I also used some pre-recorded waveforms and a netbook as a playback device (not ideal, but I wasn't reparing $1.5k gear). Some useful pages for that arehereandthis excellent page with pre-recorded test tones

author: don.r
author_rank: Frequent Contributor
timestamp: June 25, 2013, 08:25:13 pm
content: Quote from: rsjsouza on June 25, 2013, 07:17:29 pmThat looks like a nice one in that it has sweep as well.

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 25, 2013, 09:12:11 pm
content: Did Dave do a video comparing different function generators? If not I think it would be a good VBlog. I bet there are more people out there who would like to get one but do not know what to look for in a good function generator.

author: nctnico
author_rank: Super Contributor
timestamp: June 25, 2013, 09:50:45 pm
content: I'd stay away from the old RC generators unless when very low on money. In the end the buttons stop working and the pots get noisy.

author: c4757p
author_rank: Super Contributor
timestamp: June 25, 2013, 10:01:25 pm
content: Quote from: nctnico on June 25, 2013, 09:50:45 pmMany of them are complete pieces of crap, too. I've got an old Simpson that's suppose to do sine, square, triangle to 5 MHz. Once you hit about 2 MHz, triangle becomes sine, sine becomes "WTF is this?", and square becomes "heavily distorted sine". Amplitude, frequency and symmetry controls are so ridiculously nonlinear that you spend a very long time fighting with the controls (and there's interaction between the latter two), and the sweep and modulation are so bad that they're useless. I was able to make it usable for very limited purposes by modifying the circuit in a few spots, but it's still worse than the cheapest shit imported via fleaBay.Don't let yourself think that just because it's been around for a while, looks good and has a recognizable name that it will even meet its shitty specs.

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 25, 2013, 10:39:35 pm
content: Quote from: c4757p on June 25, 2013, 10:01:25 pmThat is why I started this I wanted to know if the Rigol DG1022 is any good.

author: mickpah
author_rank: Regular Contributor
timestamp: June 26, 2013, 01:30:55 am
content: HII've been looking for one too. John boxall did this reviewhttp://tronixstuff.wordpress.com/2013/02/06/kit-review-jye-tech-fg085-dds-function-generator/Looks ok for basic audio, but would be good to see it put to real test. but for less than $50 ...

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 26, 2013, 02:02:31 am
content: I talked to my boss and he said if he lets me buy one it will need to have AM, FM and Sweep waveforms.

author: sportq
author_rank: Regular Contributor
timestamp: June 26, 2013, 01:57:22 pm
content: Have you thought about the Digilent Analog Discovery? For $99 (depending where in the world you are) you get a good quality 5Mhz Function Generator and an Artibtary Waveform Generator, with a 10Mhz scope and logic analyser thrown in. I've had one for about a month and I can't stop playing with it, totally blown away.The downside might be that it is PC based so it's not instant on and not portable (well, connected to a laptop it is).Peter

author: valentinc
author_rank: Regular Contributor
timestamp: June 26, 2013, 03:40:08 pm
content: QuoteThe Rigol DG1022 is very good in terms of what you can buy for that sort of money. Personally I have a Siglent SDG1020, which is pretty much the same as the Rigol, only it has a bigger color screen, more waveform memory (4Kpts vs 16Kpts) and bigger resolution DACs (14 bits for both channes vs 14 bit CH1/10bit CH2)... higher sample rate (125 MSamples/s vs 100 MSamples/s)QuoteIf this is a must, then clearly an old analog function generator is almost excluded, this one has AM, DSB-AM, FM, PM, sweep, burst... And of course, you have the advantage of arbitrary waveforms... Which an analog gen can't do...

author: edavid
author_rank: Super Contributor
timestamp: June 26, 2013, 04:27:51 pm
content: Quote from: WakeUpWolfgang on June 26, 2013, 02:02:31 amA couple of good analog choices: HP 3312A or Leader LFG-1300S.It's a little odd that you want a function generator for audio testing though... why not an audio generator?

author: WakeUpWolfgang
author_rank: Contributor
timestamp: June 26, 2013, 11:14:56 pm
content: We will do have other uses for function generators but we got by without. If we do get a function generator we can use for other stuff besides testing speakers. We do have ways to test speakers but we don't have a way to find out what frequencies are not working. We would also use it for testing and designing circuits.

author: Winston
author_rank: Regular Contributor
timestamp: June 27, 2013, 02:51:50 pm
content: Quote from: mickpah on June 26, 2013, 01:30:55 amThat's the same unit I posted about in my Reply #13 above and linked to a few YouTube reviews. Being an inexpensive DDS unit, I don't know if it would be good for precision tests of audio equipment, but for what the OP needs and what I need, it's fine. No real financial advantage to building the kit since the built and tested version with front panel is only US$60.I just noticed a new post by the OP saying that his boss for some reason wants AM and FM modulation capabilities which this DDS unit doesn't provide. That's not in line with the original claim that the unit was simply to audibly test the frequency range of speakers (I assume with crossover circuits), but may be a desire by his boss to test the susceptibility of the speaker system under test to the induction of AM and FM broadcast signals into the speaker wire runs, the AM ones potentially being made audible through the speakers via rectification in the power amp's final output transistors. However, any accurate test of that would require modulated RF in the broadcast bands to be tested against.