• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Difference between a Audio Signal Generator and Audio Oscillator?

Checksum47

Checksum47

New Member
Just like the title of this thread asks. What is the difference? The few that I have looked at look to be nearly the same machine. I figure this thread will get a quick answer or two and then fade away...
Thanks,
 
Register to hide this ad
Some people use oscillator or signal generator for a sine wave source, while function generator does square, triangle, and maybe other wave forms as well. Also, an oscillator usually has lower distortion. Bottom line, check features and specs, and take descriptions with a grain of salt....
 
So the Function Generator could be considered an All-In-One device? I would like to be able to just buy one device and be done with it..
 
The function gen makes more wave shapes. The only real difference is that an audio oscillator is potentially "cleaner" than a function gen, though of course there are crappy oscillators and good generators. If you want to use it for signal measurements, you would want to try and get one with a fairly low THD output. Under 0.1% would be good, and the lower you can get the better.

For audio work, frankly the only ones that are really useful are squares and sines. Sines are audio, squares are useful for testing amplifier performance as a "snapshot". A single frequency square can give you a pretty good insight into low and high frequency performance at the same time.
 
If you're in "purchasing mode," rather than just "definition mode" I'd be real interested in the function generators that let you define an arbitrary waveform. That seems like it would be pretty handy to have. (I'm pretty sure the origin of that waveform would be digital, however.)

Chip
 
I don't know much about oscillators or signal generators or function generators, but I can share some of what I've learned from researching and buying and using them recently.

If this is for working on audio equipment, you only need something that produces between 20 Hz (well, maybe a little lower than that) and 20 KHz. Many used oscillators on eBay and lots available commercially are not necessarily for audio-range work. For example, many are for FM or RF or even microwave applications and therefore your ability to produce and control signals down in the range you care about is limited (think about only being able to use between 0 and 1 on a dial that goes from 0 to 100). So, if you're working on stereos, you probably want a unit that was made specifically for the audio 20-20k Hz range.

What are you measuring? If you aim to measure distortion or noise produced or introduced by a piece of gear as it does something with that audio signal, then you need an oscillator/generator that has fairly low distortion. I have some Heathkit gear that is cool, but it was made at a time where and for a market that though 1% distortion was good enough. Now that I'm working on newer gear (think 1980's and present), I need a generator that produces less than 0.01% distortion of it's own so I can measure the higher-than-that level of distortion the receiver I'm working on produces.

Lastly, the amount of distortion these (older) devices produces varies with frequency. I was REALLY surprised to learn that a generator with 1% distortion actually produce 8% distortion at 100 Hz and less distortion higher in frequency. Whoops.

May not be helpful to you, but that's what I've learned recently.

What are you working on?
 
dlucy,
I am trying to amass some tools so that I can attempt to build a stereo hi-fi amplifier for music, also I want to build a custom/DIY guitar Amplifier (preferably Tubes). And finally, I want to be able to calibrate my Tascam TSR-8 analog reel to reel recorder. About a year or so back I bought a new head for it but have been afraid to use it because I have a good feeling that it is not properly aligned and will start to wear the heads funny.
Now that I recently bought a Iwatsu SS-5711 Oscilloscope I can align the heads. But in the TSR-8's manual it says that for the rest of the calibration I will need an "Audio Oscillator", it recommends a Hewlett Packard Model 204c or equivalent.
Thats kind of what I want to get accomplished...
 
I see that even though it is eight track it is two head.

One of the main things in that is that the head is aligned to the erase head, if you want to do certain things that is.

Do you have any other tapes ? Or are you like starting a band or something ? Just curious here.

Anyway, I have not read the procedure but it may be one of those they want you to use a marker on it and run the tape a bit to see if the head height is right. Sorry I did not realize before that it is a half inch deck.

Some of them had a tape that was purposely abrasive that you ran AFTER you thought you had it aligned. You did not run it long at all so there was not much wear. But it kinda "lapped them in" like valves on a car. I've even seen that on ¼" decks.

I think on yours this will not be necessary unless you have to align the erase head.

I will RTFM in the next few days and figure it out. but alot of them did use a dye or whatever that the tape wore off and told you if you were high or low. In an eight track, that is pretty critical. Way more than azimuth.
 
Checksum47 said:
dlucy,
I am trying to amass some tools so that I can attempt to build a stereo hi-fi amplifier for music, also I want to build a custom/DIY guitar Amplifier (preferably Tubes). And finally, I want to be able to calibrate my Tascam TSR-8 analog reel to reel recorder. About a year or so back I bought a new head for it but have been afraid to use it because I have a good feeling that it is not properly aligned and will start to wear the heads funny.
Now that I recently bought a Iwatsu SS-5711 Oscilloscope I can align the heads. But in the TSR-8's manual it says that for the rest of the calibration I will need an "Audio Oscillator", it recommends a Hewlett Packard Model 204c or equivalent.
Thats kind of what I want to get accomplished...
Click to expand...

You could just use a PC or a smartphone to produce a simple audio signal if you don't care about a precise amount of distortion. It sounds like you're in this camp, so something like would work and be low or no cost https://itunes.apple.com/us/app/signal-generator-audio-test/id543661843?mt=8

An inexpensive, new device without precise distortion could be a cheap, Chinese device like the SainSmart FG-100 at $35 on Amazon or similar.

The HP 204 series is old, sturdy and typically needs some amount of work. They are a good level of distortion and you can easily find them on eBay, but you typically have to refurb them (open up, replace some old parts, calibrate, etc.)


There are many "low distortion" units on eBay like the Leader LAG-125. That's the first one I got and I paid too much for it for what I do. These produce the same signal as the HP 204 class units, but they are commonly newer and they have a more precise level of distortion. You would want this level of precision if you were comparing modifications to an existing piece of gear (e.g. upgrading the power supply diodes in a stereo to reduce background noise) or making a new, DIY piece of gear (e.g. a preamp or a power amp) and you wanted to assure yourself or hit a specific level of noise / THD performance.

Then there are kinda mid-fi signal generators for cheap that can do the same job. I like Heathkit gear just because I'm nostalgic, they are cheap and plentiful, and it is fun working on them. Heathkit made several audio signal generators and one in particular, the IG-18 and its slightly newer but nearly identical brother IG-5218, are decent in the distortion department and many mods have been published in the last 30 years that allow you to change components inside the unit to make it very, very low distortion. If you search Google for "greening the IG-18" you'll find many of these. Again, this would require you to work on you test gear before you could use that test gear to work on your real gear, so this is more than most sane people would do. So, that's what I did.
 
Checksum47 wrote: "Yes I have a test tape from MRL. I forgot to mention that. Its 250 nWb/m IEC 15 I/S"
Good! You can check my sig for accuracy, then!

For deck work, having a frequency counter and meter that can measure the bias frequency and voltage level required for your deck would be handy, too -- although your scope should do that as well.

I have an oscillator that will sweep full audio range with one knob in one turn. Handy, but dialing in specific frequencies takes an extra few seconds.

Did you replace both heads, or is one still at factory position, height-wise?

Chip
 
One consideration is that most oscillators have a maximum frequency of 1MHz or so . I think that it's always best to buy a piece of equipment that's in front of the curve of your current project. Also, while vintage test equipment has a nostalgic allure to it, they often are temperamental and require effort to keep them working. When I reach for a piece of test equipment, I simply want it to work, not become another poject that gets in the way of what I'm working on
 
Another low-cost option would be to purchase one of the amazing multi-component "transistor testers" from China, like this one

http://www.banggood.com/DIY-M12864-...ester-Kit-LCR-ESR-PWM-With-Case-p-997023.html

and use the "frequency generator" function it offers. That would give you a very low cost audio frequency generator, albeit a crude one, AND give you the amzing abilities of a component tester, transistor tester, ESR meter, LCR meter, etc.

These things are dirt cheap, they are not very high quality, but they work far better than they should for just $12-$35.
 
dlucy said:
Another low-cost option would be to purchase one of the amazing multi-component "transistor testers" from China, like this one

http://www.banggood.com/DIY-M12864-...ester-Kit-LCR-ESR-PWM-With-Case-p-997023.html

and use the "frequency generator" function it offers. That would give you a very low cost audio frequency generator, albeit a crude one, AND give you the amzing abilities of a component tester, transistor tester, ESR meter, LCR meter, etc.

These things are dirt cheap, they are not very high quality, but they work far better than they should for just $12-$35.
Click to expand...

Well... I re-read the description and I think these only offer square wave signal generation, so that probably won't suit all your audio needs. I've found I need both square and sine wave generation for my testing.
 
Well the difference depends on the units in question. There are audio oscillators that have square and sine wave functions and that would seem to be all that would normally be needed for the audio work. Determine what you want the unit to be used for which sets the range of features needed to accomplish those goals and you can chose a proper device with research on the units available.
 
A big difference of a function generator is that it would be triggerable (you could start it at a particular instant from an external signal edge), whereas an oscillator (and most likely a "generator") would just run continuously at on its own schedule once configured. You can usually get a lower distortion sinewave from a decent quality PC soundcard and software than you would from a vintage oscillator or generator (or function generator), even ones coming from the big name test equipment companies.

The soundcard solution isn't usually a great choice for square waves though because of capacitor coupling and bandlimiting.
 
You must log in or register to reply here.
Back
Top Bottom