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Look Audio Function Generator

Spenser

Spenser

Mostly Discrete
Subscriber
In your opinion -- think newbie here -- is it worth it to get a "DDS Function Signal Generator Module DIY Kit" (scroll down for picture and below it a link) ...

--OR--

would you go straight for a new or used, basic audio function generator!?!?

I want something for near-term learning and functionality -- and, at the same time -- I want something that will be useful long-term on my bench for evaluation, diagnosis and repair. 1970s amplifiers and receivers.

OPTION A: $30 investment for the below DDS kit unit ($15), plus a used, ATX power supply ($15) out of a computer;

--OR--

OPTION B: beginners signal generator $50-$100 (i.e. REK RAG 101, Heathkit, B&K, other).

1)What would you do;
2) why; and,
3) specific product recommendation?

Thank you!!!

P.S. note tag line atop below picture is product author's. keep scrolling down for the link. thanks.

s-l500.jpg


http://www.ebay.com/itm/DDS-Function-Signal-Generator-Module-DIY-Kit-Frequency-Range-1-10000MHz-US/171812317597?_trksid=p2047675.c100010.m2109&_trkparms=aid=555018&algo=PL.SIM&ao=1&asc=40130&meid=ef9858665c8d44e99716c03b22e7ca4a&pid=100010&rk=5&rkt=6&mehot=ag&sd=361077176699
 
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If you just need audio bandwidth, a cell phone and a free app can do it. I use my phone and a free app called "Audio Test Tone Generator" (no affiliation)
 
Function generators (including this one) run about 1 % distortion. This is fine for speaker use and circuit trouble shooting, but keep that in mind if you are going to get into serious servicing or DIYing. I haven't seen any distortion number for the DDS type units, but I imagine its probably a magnitude better (10 bit resolution I believe) but should be researched further. Even good sine oscillators can be off if not adjusted correct. My 2 cents. Good luck with it.
 
Good to know. Thank you.

I decided against the DDS kit route and ordered one of these below on Ebay for $65 shipped.

This one, too, is from a seller unloading educational lab gear (sold 23 of these).

GW Instek Function Generator M/N GFG-8219A
s-l500.jpg
 
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OK, I don't even believe myself saying this. I like this generator!!!http://www.ebay.com/itm/182294283860?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I blew my old one to the kingdom come 3 weeks ago ( too stupid to explain here!!!). So I bought this one out of desperation and I cannot live without one and I want it fast. I am surprised it does everything I want for this price. It is more a computer based, not like the older ones, but after you get used to it, it does it's job. I since bought a used Wavetek also as insurance ( I was really desperate without a generator for a few days!!!). I use this to generate a triangular wave to gate the Wavetek to create a burst signal either square wave or sine wave.

Thing is this guy has TWO separate generators that you can program differently. It's two for one.

You can't beat the price of $65 and I would buy another one if this one gets blown up........Knock on wood......No.



BTW, it has arbitrary waveform generator and other features, I have no idea how that works. You can control with USB. All I want is sine, triangular, square wave with symmetry, DC offset adjust and I got it and I am happy camper!!!! I bought a lot of stuff that has "Fast & Free" labeled on ebay, they always came ahead of the promised date, that's the main reason I ordered this also.
 
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Alan0354 said:
OK, I don't even believe myself saying this. I like this generator!!!http://www.ebay.com/itm/182294283860?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Click to expand...

Well I'll be a monkey's uncle. This "dual-channel DDS" model is plastered all over the internet in such a way that makes one wonder. So this is helpful to hear from someone who actually got one.

I notice, according to the advertising,that it comes with some alligator clip probes and what appears to be a computer connector cable and what not, too, for that price.

Thank you for posting.
 
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Yes, it comes with quite a few stuffs and a CD rom. I never look deeper than what I need, I am happy camper. I have no idea it's all over the internet, I was desperate, so I went on ebay, looks reasonable to tie me over and I like the "Fast & Free". So I bought it. I then wheel and deal on the Wavetek before it even arrived. Sure enough, I did have a chance to use it a few days and I am happy. I am still using it everyday.

One thing I have to complain, every time I turn off the power, it will not remember my setting. I did not look into how to store anything............Ha ha, maybe I should look it up, with all the sophistications, there got to be a way to store the setting for me to call it up...........or...........just don't turn it off!!!
 
sregor said:
Function generators (including this one) run about 1 % distortion. This is fine for speaker use and circuit trouble shooting, but keep that in mind if you are going to get into serious servicing or DIYing. I haven't seen any distortion number for the DDS type units, but I imagine its probably a magnitude better (10 bit resolution I believe) but should be researched further. Even good sine oscillators can be off if not adjusted correct. My 2 cents. Good luck with it.
Click to expand...
I yet to find any generator.....even synthesizer that has low enough THD for real audio work.....not even close. I won't even mind paying quite a few hundred dollars if there is one good enough. So I just use generator for testing and other stuffs. I have a Quant Asylum QA401 for testing THD of my amplifier and I can get down to 0.001% THD reading.
 
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I did not set out to buy the QA401, I bought the QA400 like 3 years ago for only about $200 or something. I did not really use it for a year and half because my former company called me up for a contract work to do some research and design work. That lasted for a year and half. I did not pick up the amplifier design until late last year. I found there were some issues with the QA400, so I contact QuantAsylum, took screen shots of the graphs to show them. After a few email exchange, THEY OFFERED TO SEND ME A QA401.....if I pay $14 shipping!!!!:eek2::jump:!!!!:banana::banana::banana::banana:!!!!

I sent the $14 so fast!!! AND they sent me the QA401!!!! I did not even know the QA401 is a big upgrade to QA400 and double the price!!!! Now this is customer service. It is way out of warranty, I was just asking for help to fix the QA400, not expecting anything else and they gave me the QA401.

I think they have software problem, both have display problem that is insistence, but if you learn to see pass it, they work. The QA401 is much faster and you can look at the harmonics of 20KHz. You can see the FFT graph of my amplifier using the QA401.http://audiokarma.org/forums/index.php?threads/my-amplifier.764052/page-2

I am getting really good THD at higher frequency, as good as the theoretical limit given by Bob Cordell in his book. But something still strange at 1KHz, you can see the harmonics is so low, but the THD reading is 0.002%, just by reading the graph, you can tell it's way below 0.001%. So the QA401 still have some issue.
 
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