Function Generator

[patlaw]

Somehow my function generator is missing in action. I may have given it to my (now deceased) brother. What would you suggest? There are some real cheapies on Amazon. There are tons of used HPs and Waveteks on eBay. It only needs to work for audio.

[gbono]

I have several HP 3311A function generators though I surprised at what they go for on ePay. Also consider a function generator that will have enough output to drive a loudspeaker - so you can sweep the driver and see if there are any issues.

[nashvillebill]

My venerable HP200CD wasn't terribly expensive, just needed recapping. Nice smooth sine wave, though not as distortion free as a high-dollar SS one. And it has enough oomph to drive a speaker, it's very handy as a quick check for voice coil rubbing.

For really low budget, Parts Express has a little kit that does sine, triangle, and square waves for something like $40. Can't drive a speaker but it's adequate for audio use. A very minor teeny-tiny touch of a spike on peaks and troughs but otherwise a very clean signal.

[Chuck H]

My sig gen is probably one of the most common designs in the industry. And sold by multiple vendors under different brand names. Probably made in Japan once upon a time. Probably made in China since... too much providence to mention. Available on SOMETHINGbay for under US$100 all day long. I can't break mine and you won't need a "function" generator for audio. This unit does sine and square. It's old, I've never had a problem with it, I only paid about forty bucks about a decade ago and it was an antique when I bought it!!!!. I will rebuild it if it ever fails just out of respect

EDIT: I just looked at mine for the brand and it's "LEADER" but I expect it's the same unit as all the others that look EXACTLY the same. My endorsement FWIW. I think this "thing" has probably been on more benches than a third string pitcher. So many of them out there. So affordable.

[J M Fahey]

The leader is the killer original one; all others are knockoffs.

Same difference as you have between these:





obviously you have the (older) good one

[gbono]

The leader is the killer original one; all others are knockoffs.

Same difference as you have between these:





obviously you have the (older) good one

and now for something completely different -------- thx JM

[Dave H]

Probably made in Japan once upon a time. Probably made in China since... too much providence to mention.

Shouldn't that be 'provenance'?

[J M Fahey]

and now for something completely different -------- thx JM

You're welcome

Could have written a lot explaining the difference between classic, affordable, but very good Leader test instruments and lookalike knockoffs, until I remembered those sage words by the philosopher Kong Foo Sion : "A picture is worth a thousand words" ... so here you have two ..... should be worth 2000 words ...... if Math is right

Or to put it another way: although this is a very serious and formal Tech Forum, we can't be all day long speaking about what's the difference between jacks and plugs, so I preferred instead to speak about ..... errrrrrrrrrr ......... forget it ..........

[nashvillebill]

I do have one of the Leader RF sig gens (the SG-17 ?), looks almost identical to its audio brother. Stable signal and easy to use.

[Chuck H]

Shouldn't that be 'provenance'?

Thanks for that. I've made the mental correction. It won't happen again.

And this is especially funny to me because I just mentioned incorrect word application and mispronunciation on another thread.

[Dave H]

And this is especially funny to me because I just mentioned incorrect word application and mispronunciation on another thread.

I know.

[nevetslab]

Log Sweep Functdion Generator

There have been loads of function generators built over the decades. A classic Audio unit is the HP 3300A with a 3305A 4-decade Log Sweep plug-in, which are hard to come by, but an excellent 100kHz unit. I just gave one away to one of the staff here at CenterStaging, while packing up my lab assets at home. I didn't want to part with it, but....I have other units that do that task equally well, and time someone else having nothing reaps the benefits form owning such a fine piece of audio gear.

My favorite is still the Wavetek 185. It's a 5-decade Log Sweep Function Generator....does the normal Sine/Square/Triangle along with tone bursts, sweeps linear and log, steps ten frequencies...has two frequency dials to set the start and stop frequencies. The log sweep conforms to printed log graph paper. It also works as an excellent swept warble-sine generator for room acoustics use, modulating the VCG with an external LF generator while maintaining a constant-percentage frequency modulation across the audio bandwidth.

I bought my first one new in 1976 for $675, and bought a Tektronix R5031 Dual Beam Storage scope to work with it...and later cobbled a log converter out of my Tektronix DM502A Multimeter, which had a dB mode....that gave me a closed-loop Frequency Response system using the Wavetek to generate 10 octaves from 20Hz thru 20kHz, one-octave per division in XY mode on the storage scope.

I've purchased other Wavetek 185's over the years on ebay, for as little as $40, sold them for over $300. One of the test set-ups I have in a composite photo uses this Wavetek with an HP 7562A True RMS Log conveter (for the dB vertical scale), showing the HP and LP filter curves of a KrohnHite 3550 4-pole lab filter:



With another device....a Compressor circuit, resident in a Bruel & Kjaer 1405 Random Noise Generator, it allows the Log Sweep Generator to generate a constant current signal for measuring speaker impedance plots. In these photos, I was using an Interstate F-47, also Log Sweep Function Generator:



While these are creating a measurement system using the function generator, without the log sweep function (and suitable log decade range), you're limited to manually spinning the frequency control. Good enough for most daily dirt applications. But, it's a buyer's market these days out on ebay. All those instruments in the photos are ebay purchases over the years.

Lots of flavors available in Function Generators. Just thought I'd shed some light on the possibilities available.