What signal generator for audio work?

"Chris Tansit"

** Ebay is your friend here:

Something like this will do everything and more for audio bench service work.

** High power dummy loads for 4, 8 and 16 ohms - make your own with tubular resistors and a bucket of water.

A " Variac " is a must to adjust the AC voltage PLUS an AC current meter ( moving iron) to see what is being drawn by the unit under repair.

Bute most important of all is a good stock of tubes, transistors, ICs, and passives of all kinds - especially lots of electros.

... Phil

For general work I think any decent sine-square generator in good working order would do. Use sine waves for a general troubleshooting signal source, use square waves, usually around 1 kHz as a good overall (quick) check for linearity. One thing I've noticed for example, a square wave signal viewed on a 'scope will quickly tell you if a loudness or filter switch is malfunctioning. One channel may remain boosted or attenuated when the control is back in the "neutral" position. Also, square waves seem to show more easily the effects of dirty controls, relays, etc as you are manipulating or tapping on them (when viewed on a 'scope of course). I use a Leader solid state model at work (don't remember the model) but for many years used an Eico 377 tube model. They can be found all over eBay for under 50.00. A new solid state model will run 179.00 and up.

I think most distortion analyzers sine wave generators built in - my Sound Technology 1700B does. They can be had used for maybe around 400.00 or so.

Mark Z.

I use an old Leader LAG120A.

Also have a pair of 300 wrms 8 ohm non-inductive dummy loads. You will also need a Variac with an ammeter capable of at least 8 amps. An old Sencore PR57 would do. And any decent DVM with a reasonable response time and accuracy is a must.

Look here for some other suggestions:

For general use, I use a Heathkit IG-5218 (also available in a different color as the IG-18, which is a bit older) This unit has stepped frequency selection and an output meter. Really easy to work on if it needs it. Likely available on e-bay or at hamfests for under $50. I've seen filthy ones as low as $10. Of course the build quality of the kit is a factor.

There are also lots of mods possible to make them lower distortion, but some of the mods reduce the stability and make the settling time when changing frequencies annoying at best, and damaging at worst. Also, the unit is low enough in distortion for general use as is. If you don't have or need a distortion analyzer, they are pointless.

That said, there a lots of good choices.

Regards, Tim Schwartz Bristol Electronics

P.S. Here's one on e-bay now:

190389304471

A calibrated , well at least consistently marked between ranges , attenuator on the o/p is useful

I have a heavily modded Heathkit audio generator, which I'd be happy to sell.

I don't remember the model number. About 35 years ago, "Audio Amateur" published an article on modifying this generator for ultra-low distortion. The "catch" is that when you change frequency, you have to wait a second or two for the generator to settle.

I'd sell it for the original price of the kit. If you're interested, please get in touch with me.

But these are so much nicer to keep the shop warm with. ;-)

Jeff

--
?Egotism is the anesthetic that dulls the pain of stupidity.?
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com

Chris Tansit Inscribed thus:

Knock up a multivibrator circuit ! Four resistors, three caps, two transistors & 9V battery.

--
Best Regards:
                     Baron.

A computah, of course. Get a 96KHz 24 bit sound card and some software: (see sig gen feature) There are plenty of others, including some that I use on my iPod Touch. (I need 2 tones, with very low intermod products, for testing SSB and ACSSB radios). The nice thing about the laptop or iPod Touch approach is that it's portable and can be used in the field.

More money but also more versatile are various USB oscilloscope/generator conglomerations. For example:

You're a bit late. Xsistors happened in the late 1960's.

Price limit? Any specification limits? Need anything besides a signal generator (pulse, sweep, white noise, portable, etc)? It's difficult to be specific when your requirements are a bit vague.

Sweep generator, white noise generator, pink noise generator, audio spectrum analyzer, distortion analyzer, power supply, DVM, dummy loads, soldering iron, sanity tester, coffee maker, billing software, etc.

Ok, that's a start. Add a tube caddy to the above list. It really impresses customers over 60 years old. (Yes, I have one).

Dunno. I never RTFM or Google for info until after I get into trouble.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

There are battery powered versions.

There are dedicated instrument packages.

I started using my PC's Sound Card. It was free. Gave me total control of what was produced and produced the lowest distrotion I've ever seen.

Then I started using the sound card as a 'scope' and then as a spectrum analyzer.

So now I have a two channel input high quality spectrum analyzer with two channel tracking generator outputs!

You want to test the quality of your amplifier? Best system for it.

Ya wanna give us a hint as to who's software you're using?

Jeff

--
?Egotism is the anesthetic that dulls the pain of stupidity.?
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com

"Jeffrey D. Asshole"

** Antique, overpriced junk.

** Wrong category entirely.

** Not even on the same planet.

Why don't you go drop dead- asshole ??

... Phil

Come back when your meds kick it. "Flame all you want, I'll make more"

Jeff

--
?Egotism is the anesthetic that dulls the pain of stupidity.?
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com

Much software came on CD with the soundcard, but did not do exactly what I wanted I think everything you need is free and available at sourceforge under gnu license. There may be other free, or low cost, utility software out there, don't know

Basically, you need software to talk to the soundcard and software to manipulate what you want to do.

To talk to the soundcard, I used the soundcard's 'built-in' ASIO drivers and used ASIO SDK from Steinberg. To write custom C programs, I used free MS command line C compiler. For FFT, I used the free 'fastest FFT in the west' called fftw

asiosdk2.2.zip

Thanks Robert

Jeff

--
?Egotism is the anesthetic that dulls the pain of stupidity.?
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com