Signal generator

[C Moore]

We have been hit real hard by the "recession". It is very possible we may loose our home. I know times are bad for most of us. Good Luck to us all.
So, for this reason, I am wondering if there is a "affordable" way to generate a 1 KHz signal to use for amp repair. I have a cheap BK 2120B, 30 Meg scope. But I do not have a Sig Gen, or a dummy load.
Hope this does not sound too stupid but, is it possible to download frequencies from the INTERNET?
Thank You

[martin manning]

Go here:

http://www.trueaudio.com/rta_down.htm

Digi scope and spectrum analyzer too.

[vibratoking]

Really sorry to hear about your situation. It can happen to the best of us.

You might want to check out the following:
ICL8038
XR8038A
AD5932

Some Rs and Cs, a regulator, and one of these will allow you to cobble together a quick and dirty sig gen. These are not high precision, but...

The ICL8038 and the XR8038A may have been obsoleted.

[Andy Le Blanc]

Any instrument tuner with a tone, Behringer cable tester has a 1/4 out with test tone.

Check out the right mark audio analyzer

http://www.rightmark.org/

theres older version for free download

Try and save up for a couple ohmite 8ohm 300w resistors at Mouser.

588-C300K8R0E

their $24 each but it will get you 4/8/16 ohm load and handle up to a 100w full tilt.

hang in there, gifts come in strange packages.

[xtian]

Do you own an iPhone? Plenty of good apps for this. I use Oscillator, which lets you type specific frequencies, and generates sine, square, saw and noise. The DAC in the iPhone is a marvel. Really low noise. And good smooth sines, too--I set it to 60 Hz, recorded the signal into my MOTU 828mk3 and took a close look. Perfectly round and smooth, with 96+ dB S/N.

[sliberty]

+1 on the iPhone idea. But it is not limited to iPhones. I went to the web and downloaded a free tone generator application. Running it on Windows, I generated severl frequencies, each for 1 minute or more, and saved the resulting mp3 files. I then copied these mp3 files to my iPod. Now when ever I need to inject a tone, I plug my iPod into the amp's input, and tell it to loop the 1K tone forever. Only downside is you don't have fine control over the amplitude. You can make it louder and softer, but you have no way to dial in exactly x db for example.

[Cliff Schecht]

I could draw you up a simple circuit to build. Constant amplitude sine-waves are quite easy to generate and only takes a handful of very inexpensive parts. If you are interested..

[C Moore]

I could draw you up a simple circuit to build. Constant amplitude sine-waves are quite easy to generate and only takes a handful of very inexpensive parts. If you are interested..

I would be happy to see it. Do you want to post it here, or should I send you a PM or E-Mail?
Thank You

[Cliff Schecht]

I'll post it here. Let's do this.. What parts do you have available? There are more than one ways to skin this cat. If you have access to a relatively standard set of resistor and cap values then you can build a single op-amp phase shift oscillator. This, a frequency knob, an amplitude knob and your oscilloscope are all you need to get "accurate enough" sine waves for amplifier testing. If you have access to more parts, say some Zener diodes and a standard JFET, then you can get an even more accurate sine-wave. But this is getting fancy, a phase-shift oscillator would do the job just fine IMO..

Depending on your circuital skills you could probably decipher what you need from this TI app note: http://www.calvin.edu/~pribeiro/courses ... lators.pdf

Everything in there is simple enough and they give you the transfer functions that allows you to choose an operating frequency around the parts that you have on hand. The circuit on page 16 with one extra op amp (i.e. a quad op amp) would get you what you want pretty easily and it's simple to modify the values for what you have on hand.

[KindaFuzzy]

I usually use this one:

http://www.geofex.com/FX_images/q&dosc.pdf

[C Moore]

I have parts bins with all the caps, resistors, and diodes that are commonly used in the guitar amps that are discussed on this forum. I do not have any Op-Amps, but those are kind of affordable I guess, Maybe the shipping from Mouser will cost more than the part, but that is just a guess .
Anyway....
You guys have given me a lot to look at/think about. So let me digest some of this and I will let you know what I decide.
Thanks To Cliff and Kinda
Thanks To Everyone
A couple of you guys asked if I had an I-Phone. I did not mean to ignore you. But, no, I do not have one of those.

[Structo]

Do you have a Fry's nearby?

They carry a fair amount of electronic parts. Mostly NTE but just the same when I needed a miniature 12v relay a couple weeks ago they had it.

[Cliff Schecht]

Or a Radioshack..

[selloutrr]

I've been throwing around the idea of offering a test CD.

calibration test tones
pink noise
white noise
freq sweeps
guitar playing

is this something people might be interested in.

I use it with a portable cd player and a mini to 1/4" instrumet cable for field testing.
Select the track put it on repeat, adjust the output volume, and run the test function.

My thought was to make a package that included the Test CD and a 4ft cable. either mini to 1/4" or RCA to 1/4" I'd have to add up the cost of parts but I'm hoping to keep the cost under $15 plus shipping.