I think the title is self explanetory...
:)
Dan.
If you mean signal/function generator.... Good question!
You can use your PC,
http://www.dazyweblabs.com/vb2001/index.html
Alternatively, build a Wein-Bridge (sine) oscillator using a small incandescent bulb for amplitude stabilization. For audio it's nice to have square-wave generator option as well - just add a Schmitt-Trigger to the output fo the Sine oscillator.
I Meant Exactly that Aron... So where would we find those, and what charecteristics should it have?
I think I've decided that the best way to go is to get an old kid's keyboard and play drum loops into what you're building. That way you get a nice frequency range and it just keeps going. The problem with freq generators is you can't tell what's happening to the entire frequency spectrum, only the one you're putting into it. I suppose that's OK for things like tremolo, which aren't effected by the input frequency, but I find that it provides a more accurate protrail (that's not how you spell it, is it) of what the guitar will sound like in it.
-Colin
I use a drum machine loop.
If you are using an oscilloscope, the most useful thing is an oscillator that gives a triangle and a square wave (because, if is much easier to see distortion on a triangle than a square).
So it's best to use a multi-waveform purpose generator I guess...
So where to get a schem guys?
P.S. it should have the voltage output and frequency of a guitar as well, right?
If you have an oscilloscope...most oscilloscopes have a test output so you can test and callibrate your probes. its usualy a little tab on the front and usualy give you a 1kHz/ 1V p-p squarewave. with a few resistors and caps, you can use that one and get an dirty sine-ish 0,25v signal to trace with...
Johan
Johan,
Does it produce a really smooth sine wave? I'm pretty much just giving up and getting one of those function generators on ebay or?????
I remember Ed saying it's really important to have a "clean" sine wave for analysis.
Aron
its been a while, and I lost my filter/cable since I now use an old kenwood generator, but if you just build a series of lowpassfilters, you can reduse most of the overtones in the squarewave to allmost the pure 1kHz sine. the more pure you want it, the more signalstrenth you loose. its not perfect, but good enough for testing FX's. and since it uses the same ground as the oscilloscope probes, you dont need that annoying, silly little groundcable on the probe-tip....
when looking at distotion I want a sinewave, but when looking at what eq-filters do, its much easier to use a square....
Johan
I might just go and purchase a function generator... I've seen a bunch of them on ebay.
The only thing is that they look heavy. Shipping could be an issue.
My dad has a sinewave (pure sine wave) generator for his radio amateur hobby, and it doesn't way more than half a kilogram... :?
Where did he get it from?
Any link?
http://www.gibsonteched.net/vmk105.html is a kit available from several hundreds of places at about $9 US.
Sine, triangle, square.. i havn't built it myself, but it looks OK.
Here's someone who built one in the UK:
http://www.qsl.net/wars/construct/ian_MK105.htm
There's basically two types of commercial oscillators which are available secondhand (excluding RF stuff).
The first type are targeted towards audio. This type is ideal for audio testing. Characteristics are:
- Pure sine output - how pure depends on the model.
- A switch for square wave output.
- Frequency ranges around the 10 to 20Hz region upto 25kHz to 1MHz region. The actual end limits depend on the model, typical is 20Hz to 200KHz. The frequency control is usually multiturn. The frequency is shown on either a large wiper display or a large dial.
- A coarse switch for the output level in 10 or 20dB increments. A pot for fine control. The maxium output level is typically 3Vrms or 10Vrms.
The second type is your typical function generator. This type is for general use. Characterisics are:
- (much) poorer quality sine-waves,
- square-wave, triangle, sometimes sawtooth outputs. Square-waves often have a duty cycle control.
- sometimes DC offset function on the output signal.
- Frequency ranges from the 0.1Hz to 1Hz region upto the 200kHz to 2MHz region. The actual end limits depend on the model. The frequency control is often coarser and the frequency is often displayed on a digital readout.
- A coarse switch for the output level in 10 or 20dB increments. A pot for finer control. The maximum output level is 15V peak.
- Sometimes these have a few extra features like: digital compatible outputs that swing 0 to the set voltage instead of swinging negative, a VCO feature, ability to use internal frequency meter for external signals.
The extra things you get on these units are only beneficial *if* you have a use for them. To put the two types in perspective: you rarely need the second type for audio *testing*, mainly because the the sine output is poor. The second type is hand for general use, and the sinewave output is (usually) good enough for visual checking. I generally use the first type unless I need digital outputs, very low or high frequencies, a DC offset function. The tri-wave output can be used as an LFO *but* if your unit is tied-up for this task you can't test the audio signals - better off building a simple LFO circuit from opamps!
The first type are usually the Wein-Bridge oscillator I descibed before. The second are usually function generator chips or a custom function generator using fast opamps and compartors - you could make your own one of these with a function generator chip like the XR2206 or 8083. The prices of some secondhand stuff is cheaper then what you could make with a nice box, however, sometimes the switches are shot and these are hard to replace.