(Please) Help me pick a new Sig Gen - Page 1
Forum section: electronics / beginners

author: adamboon
author_rank: Contributor
timestamp: June 20, 2016, 08:06:47 am
content: Right. So We do mostly audio - I Already have a HP oscillator, that is super low distortion, 600? output and has a stepped attenuator - and I love it!I do, however, want something to drive a square wave into audio circuits - to establish ringing/overshoot - I've also found it a quick way to determine how something's Frequency Response is tracking through a circuit.I'm favouring this one:http://www.ebay.com.au/itm/162103238915?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITbut I've also looked at:http://www.ebay.com.au/itm/401071567565?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIThttp://www.ebay.com.au/itm/201590002731?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIThttp://www.ebay.com.au/itm/271274673004?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITI've watched a few HP Agilent 33120A see for more than I'm prepared to pay (I do like the look of them).I know a lot of people have the Hantek DDS 3X25, and there is one available for A$155 locally - which is good value - but I read it's a DA that spits out 7v max and then bit crushes below that - plus I don't love the idea of needing a computer to control it (although I always have a computer around... but it's usually a mac).I am concerned about the long-term reliability of the RAG101 - I'd appreciate any advise from owners of this one.Thoughts?Thanks.Adam

author: EEVblog
author_rank: Unknown
timestamp: June 20, 2016, 08:18:23 am
content: What's your budget?

author: adamboon
author_rank: Contributor
timestamp: June 20, 2016, 08:32:29 am
content: Well really I just want to make a good square wave at (and around) audio frequencies. If I get a more robust or versatile tool for a bit more $, then great (but as you know, you can quite quickly start looking at tools that are way overkill and unnecessary). I was also originally looking at some Siglent AWG units.I'm probably comfortable spending between $100 - $300, but could go a bit higher if necessary.

author: Gyro
author_rank: Super Contributor
timestamp: June 20, 2016, 08:53:41 am
content: On the other hand, if it's specifically square waves you need for audio testing, then it's about the easiest signal to generate yourself.Why not just build something with logic an switched attenuator and an AC coupled output. If you want a large output swing then you could use 4000 series logic running at 15V. You could tailor the output to your specific needs and also battery power it to avoid hum loops.Edit: You'll probably get a rather cleaner (quieter) square wave than something being generated by a micro and a DAC too.

author: adamboon
author_rank: Contributor
timestamp: June 20, 2016, 09:09:06 am
content: Quote from: Gyro on June 20, 2016, 08:53:41 amI had thought about this. I was probably just being lazy...

author: Gyro
author_rank: Super Contributor
timestamp: June 20, 2016, 09:17:33 am
content: QuoteHaha, well there I can't help you.It does come down to the cost and bench space of yet another expensive grey plastic box covered with displays, lights and encoders, versus something small, simple and dedicated that puts our (say) spot frequencies at 100Hz, 1kHz and 10kHz.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 20, 2016, 09:45:10 am
content: When i was searching for a scope it is suggested that you use 12bit DAC/ADC at least for audio.

author: Gyro
author_rank: Super Contributor
timestamp: June 20, 2016, 10:11:12 am
content: But for a square wave generator you only need 1 bit!

author: EEVblog
author_rank: Unknown
timestamp: June 20, 2016, 12:25:01 pm
content: One one these dinky things will get you by for cheap:http://www.ebay.com.au/itm/10MHz-DDS-Function-Signal-Generator-Sine-Square-Wave-Sweep-Frequency-Meter-/121633684437

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 20, 2016, 01:29:50 pm
content: Relating to audio there are some interesting bits about frequency especially if you have adjusted it on your PC. High end soundcards will do 192Khz per channel so how many Mhz you need is to take that value * number of channels (excluding the .1 or .2). Than theres also bit depth. Im not so sure how the bit depth ties into bandwidth but it may be related. Essentially even a 10Mhz signal generator should be enough.Seeing as you're working with 600ohm this means high fidelity audio so its not wrong to assume you are working on high end DACs. Good luck with your work and show us your work too. I've had bad luck with cards that use creative chips as for some reason creative chips are unreliable even though the only creative component on the card is the card CPU (the creative chip). New creative cards seem to work fine though with their "quad core".

author: MarkF
author_rank: Super Contributor
timestamp: June 20, 2016, 01:48:34 pm
content: You may want to consider theOwon AG051F 5 MHz Single Channel Waveform Generatorfor $199. It's big brother the Owon AG1012F was reviewhere.Saelig also has a discount for EEVblog members.

author: luxfx
author_rank: Contributor
timestamp: June 20, 2016, 03:07:12 pm
content: I just went through this, and JUST bought an FG (as in, purchased but it hasn't arrived yet). And I had considered that same SFG-2107 you found. But then I found the Hantek HDG2000 series and bought a HDG2012B. It's more expensive than the SFG-2107 you saw, but within the price range you mentioned. I know Hanny oscilloscopes don't have a good rep around here but haven't heard a lot about the FG.The kicker -- it's hackable. As in Rigol 1054Z style hackable. The 2012B I got is 10MHz, but with a small hack you can upgrade it to 100MHz. Turns into quite excellent value.

author: adamboon
author_rank: Contributor
timestamp: June 21, 2016, 12:48:22 am
content: Quote from: EEVblog on June 20, 2016, 12:25:01 pmI looked at 2 different things like that and I believe one has a square wave jitter issue and the other distorts waves asymmetrically (especially sine) as you wind up the amplification."System Error Message" - It's mostly pro / studio audio and almost always analog.

author: Lightages
author_rank: Unknown
timestamp: June 21, 2016, 07:31:04 am
content: Wow, so much money to do a simple thing? Just run the output of your oscillator through a Schmidt buffer or inverter and buffer that with a good op amp with some variable gain or input level control. $3 worth of parts.........

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 23, 2016, 01:33:52 am
content: Instead of splurging cash for an expensive signal gen theres a much much better signal gen but would have limited voltage. Simply get a high end soundcard, some computer software to generate the waves you wand and use it on the output. Make sure the soundcard is pogrammable. A voltage limited programmable wave gen, definitely something worth trying. perhaps EEVBlog could do a video on this on using a soundcard to generate waves as they come out as electrical signals.All you need is a PCIe to mini HDMI adapter as used for eGPUs (or even an eGPU enclosure), a PSU if one is not included and connect to your laptop/PC and run some software to make sound. Just make sure the soundcard you use has a consistent frequency response. it will take a bit of math but the output could reach Mhz depending on the output port. External soundcards can also be used too like usb and such.Seeing as it is a studio im pretty sure you should have plenty of soundcards/boards around that you can use as your signal generator.

author: luxfx
author_rank: Contributor
timestamp: June 23, 2016, 02:52:19 am
content: There are mobile app options as well -- a quick search yieldedthis iOS app. I assume it works through the headphone jack.Not being familiar with signal generators (yet!) what benefits would one get from a dedicated unit over these sound-based options? Voltage control I'm assuming. Is isolation an issue? Anything else?

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 23, 2016, 03:45:52 am
content: Quote from: luxfx on June 23, 2016, 02:52:19 amAccuracy. The phone's sound output isnt as accurate as a high end sound card/board. There are quite a lot of catogaries from various low end to mid and high end that can do all sorts of things. One of the important features a wave generator must have is that the output must be accurate to what you set it to do. So dont use your phone's sound jack because those have limited frequency and arent very accurate. if you're just messing around having fun and exploring than accuracy wont be a big deal but if it is professional work you need accuracy and this is one reason why dedicated signal generators are pricey.

author: adamboon
author_rank: Contributor
timestamp: June 24, 2016, 01:17:52 pm
content: Quote from: System Error Message on June 23, 2016, 01:33:52 amYeah - I've tried a little phone and USB / Firewire interface stuff, but found the output to be a bit ordinary - like my square waves plagued with overshoot - which is what i'm trying to test for. I haven't tried any of our very high end cards, just a couple of Pro series M-Audio and MOTU things.Quote from: luxfx on June 20, 2016, 03:07:12 pmI got excited about the Hantek - I read the first half a dozen pages of the MASSIVE eevblog post about it. all positive. I read the last half a dozen posts - everyone hated it - bugs everywhere, freezes all the time, PSU is an electrocution and/or fire hazard.I think I'll either build something, or more likely look at one of the OWON or Siglent generators. The OWON review linked was a bit long winded, and I couldn't figure out if he liked it or if it's any good or not.I did find a local deal on a used instek DDS unit, but after reading up on it - it seems to suffer from jitter like most of the other Low Frequency DDS units.It seems to go if you want a good function generator, buy a cheapish AWG - the AWG part seems to almost always be rubbish but the FG part seems okay. I wonder what you buy if you want to end up with a decent AWG?

author: Gyro
author_rank: Super Contributor
timestamp: June 24, 2016, 06:13:16 pm
content: If youreallyjust want a decent quality squarewave signal then why not just go with my suggestion of a simple logic oscillator, or Lightages suggestion of a schmitt trigger to go with your existing high quality sinewave generator.If you make sure the final stage is a divide by 2 then you're guaranteed 50:50 mark:space with a very low level of jitter. Signal quality and rise time are completely under your control.Surely it's got to be quicker, easier and more satisfying than trawling through endless threads on depressingly flawed AWGs, DDS generators and phone apps.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 24, 2016, 09:23:13 pm
content: but in a studio you have access to the high end soundcards so all you need is software to generate the waves. Other than accuracy the phone's output is limited in things like frequency. If you only test 1 channel at a time you can use a high end soundcard and set to 192KHz i know some soundcards can generate more, really depends what you have so you probably wont have to spend any money.Otherwise building your own is cheap if you only need to test 1 wave. a wave generator is useful if you need to test various different waves.

author: adamboon
author_rank: Contributor
timestamp: June 25, 2016, 12:22:51 am
content: I appreciate these great suggestions. I have solved it by winning the bidding on a lightly used Siglent SDG1025. I scored it for just over a couple of hundred bucks US - which I think is excellent value. I like that it's one machine that will generate any kind of signal I might ever wish to generate (I think), and that it's independent of computers, sound cards etc. and is reasonably portable also.On a seperate note - thanks (blueskull) for the info on the Analog Discovery line, I teach an electronics/robotics class at the local library to juniors and a couple of these will be a very versatile tool for our purposes there!

author: tautech
author_rank: Super Contributor
timestamp: June 25, 2016, 01:01:38 am
content: Quote from: adamboon on June 25, 2016, 12:22:51 amCheck the latest FW is installed when you get it.http://siglentamerica.com/download/software/SDG1000-V100R001B01D01P37R3.rarAll documentation:http://www.siglentamerica.com/prodcut-wd.aspx?id=145&tid=16&T=2Thread:https://www.eevblog.com/forum/testgear/the-sdg1000-and-sdg800-thread/They can generate waveforms with *commands* to the max BW of the SDG1000 series, rf-loop explains how in the above thread, shouldn't be hard to find.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 25, 2016, 01:06:31 am
content: Quote from: EEVblog on June 20, 2016, 12:25:01 pmAssuming they can package it right. Mine arrived in a paper-thin box, dented front and back.

author: bitseeker
author_rank: Super Contributor
timestamp: June 25, 2016, 05:09:44 am
content: Quote from: adamboon on June 25, 2016, 12:22:51 amAh, so you were the high bidder. What a coincidence (I do seem to run into lots of forum members on eBay). Congrats! I'm glad I didn't bid higher and derail your project.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 25, 2016, 11:21:50 am
content: well guys perhaps we should share about what we bid on so we can argue who should get it and work together so the bids can be low.Think about it, if 2 guys kept bidding against each other the winner is gonna pay a high price, if one decides to let that particular item go (perhaps theres also another item for bidding too) than instead of multiples bidding on multiples making it expensive we can lower ebay's salary.

author: bitseeker
author_rank: Super Contributor
timestamp: June 25, 2016, 10:20:57 pm
content: I'm open to suggestions along those lines. I've done it before, so it does work when you can determine who's there, but therein lies the difficulty. There are many members, which makes coordination and timing a challenge. Maybe a mailing list or something? Using the forum just drives prices up!

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 25, 2016, 10:43:45 pm
content: it has to be in a members only section, to make it harder for sellers to know people are collaborating.Think of how much can be saved, no more overpriced ebay stuff.

author: StillTrying
author_rank: Super Contributor
timestamp: June 25, 2016, 11:27:40 pm
content: Quote from: EEVblog on June 20, 2016, 12:25:01 pmFrequency range 0.01Hz ~ 10MHz (FY2110S)Rise and fall time of square wave 100nsI hate the way they don't use leading zero suppression on the displays of these things.

author: bitseeker
author_rank: Super Contributor
timestamp: June 25, 2016, 11:32:23 pm
content: I wouldn't go quite so far as to say there would be no more high prices. There are still crazy people on eBay who are willing to pay too much for stuff, even in the niche area of test equipment.

author: ez24
author_rank: Super Contributor
timestamp: June 26, 2016, 03:36:47 am
content: Maybe a sticky with a title like:"Ebay test equipment I am bidding on"

author: bitseeker
author_rank: Super Contributor
timestamp: June 26, 2016, 03:48:22 am
content: "Stay away, please..."

author: ez24
author_rank: Super Contributor
timestamp: June 26, 2016, 04:00:51 am
content: Corrected"Ebay test equipment I am bidding on - Stay away - Please"I think this would work