Poor man's signal generator.

One of the things I haven't got at home is a signal generator so what I usually do it generate waveforms on my computer and feed them out the sound card. The quality and especially the frequency response and noise floor is not that good, so I was thinking I might generate a number of waveforms using Cool Edit or similar and burn them to an audio CD as separate tracks, and then play them using the CD player's much cleaner output.

I am looking for suggestions as to what I might put on this CD, the kind of things people use for standard tests of one kind or another.

Circlotron said:
I am looking for suggestions as to what I might put on this CD, the kind of things people use for standard tests of one kind or another.

Might be easier just to order one of the Bass Zone CDs from John at Stryke. I found this quite useful until i started using the software wave generator that comes with Mac-the-Scope which i have been using on my PowerBook -- for my purposes so far it hasn't had any noise problems.


Either buy an audio card with an SPDIF output or get an SPDIF add on, they are pretty cheap. You can then run right into a receiver and use the DACS in it. That gives pretty good quality.

I use a Soundblaster Extigy. I find it is quite good. The basic Soundblast Audigy is down in the $60-$70 range if you look. It has pretty good quality.

What good is a sound card sig gen?

What is the "utility" of a sound card signal generator if it's in an environment (your PC) abounding with EMI, if it doesn't have a precise load or attenuation system, if you can't be certain of it's output over a 3 decade span of frequencies?

A precision, stable, low THD sine generator can be built for less than $30, a Heathkit IG18 can be retrofitted for distortion levels less than 0.01% for less than $20 and the IG18 is about the size of a shoebox. You can make a wobulator with a pair of XR2206's -- and it will fit in the palm of your hand.

Hi Graham,
Some usefull test tones on test cds that I have used are tracks like digital silence and tones at 0dB and reducing in 10 dB steps down to very low level (-80dB etc) - these can reveal some pretty shockingly yukk spurii (digital, servo and psu induced) coming out the end of a system.
In my experience the RF (out of audio range) junk emitting from a DA stage can cause all sorts of mostly imd and signal reflection problems downstream.
How well the complete amp input/amp output/cable/louspeaker/room chain behaves electrically (handles the whole thing) when fed this in band and out of band noise junk is critical in our now digital age, and is the maker or breaker for long term enjoyment - an electrically correct sytem sounds correct.

When I make my own test disc (gunna) I will include extras like ascending or descending sawtooth tone and rectangular pulses for verifying system polarities, two and more tone type IMD tone sets, and white/pink noise.
Also musical passages that have been filtered (LP, BP, HP) with different types and slopes.
Also usefull would be short grabs of particular musical passages looped many times for purpose of 'on the fly' component A/B sonics testing - an UN earthed solder tip is mandatory for this.
Also the same looped musical passage grabs recorded with alternating polarity.
Also natural sound recordings of places that you are familiar with - eg your back yard or family members recorded in alternating polarity.
Also a short announcement track (PC generated voice or natural voice) before each test track.
Magix Samplitude Producer 2496 v6.0 (15 Mb) 90 day trial is a very good audio editor and has all sorts of in built effects and a signal generator giving all the above signals.
ps - I just downloaded 'Samplitude Master' and it seems the same.