Although 90% of how I use SONAR is about music, that other 10% is test and measurement related. I used the tip about noise and using the QuadCurve flyout to quantify the performance of different wah-wah pedals in the Line 6 Helix, and I think it's pretty revealing in terms of showing exactly why different wah-wahs sound different. This link takes you to the thread, go to post #51 to see a video and hear the accompanying audio example. Yes, SONAR as test equipment...
 

On the Sonar-as-test-equipment theme, I have a project setup with a sine wave generator and an oscilloscope plug-in that is surprisingly useful for examining cross-over distortion when biasing a valve (tube, sorry) guitar amplifier. I put the sine wave into the amp and pick up the output via a Koch Dummybox. A purist would probably argue that the Dummybox is not identical to a physical loudspeaker, but it serves the purpose of getting the output of the amp into Sonar and it a whole lot easier on the ears.

So you bias the the tubes based on the cross over distortion you observe on-screen? I'm curious if your display will also give you plate voltage and cathode current.
 
I've wanted to use Sonar to observe the true frequency response of an amp from 20 Hz to 20 KHz. Any ideas on how I might accomplish this? I can't afford to buy the required hardware. I have a scope and a signal generator plus all the required dummy loads.

That is a good approach for the wahs. That also looks like a good review, I'll have to go back and read it.

ampfixer
So you bias the the tubes based on the cross over distortion you observe on-screen? I'm curious if your display will also give you plate voltage and cathode current.
 

Yes to the first. But, because the scope is driven off the audio coming into Sonar, I can't look at actual voltages that way. I cross-check voltages (and currents, via voltage drop in a suitable resistor) using a digital multimeter.
 

ampfixer
I've wanted to use Sonar to observe the true frequency response of an amp from 20 Hz to 20 KHz. Any ideas on how I might accomplish this? I can't afford to buy the required hardware. I have a scope and a signal generator plus all the required dummy loads.

Not sure exactly what you want to do here, but if you can get a suitable audio output voltage across your dummy load (and the dummy load itself is not filtering any meaningful frequencies) you can input it into your soundcard (and then into Sonar) via a capacitor (to filter out any DC) attenuating it via a resistor network. Once it's in Sonar you can do whatever you can do to audio in Sonar, of course.
 
[Apologies to OP for this distraction]

ChristopherM
[Apologies to OP for this distraction]

Actually I find the "SONAR as test equipment" very interesting. Carry on...

I have modelling software to design EQ circuits. It shows how the output frequency will be effected by the EQ controls, but it's theoretical. Listening to the finished product doesn't usually reflect what the simulator predicted. If I use an approach similar to Craig's experiments with a wah pedal I hope to see what the EQ is doing in real time.
 
The amplifier output could be anywhere from 5 to 25 volts AC when pushed into clipping. I won't push it that hard when looking at the output so I think I'll be OK if I keep the input signal going into the interface below 1 volt.
 
I typically would use a 100 mv sine wave at a fixed frequency between 800 Hz and 1 KHz. I need to test all the frequencies at once. Is Pink noise the way to do this? If so what can I use as a noise generator?
 
PS - If I can make this work I'll share the results with the community.

ampfixer
 
I typically would use a 100 mv sine wave at a fixed frequency between 800 Hz and 1 KHz. I need to test all the frequencies at once. Is Pink noise the way to do this? If so what can I use as a noise generator?
 

What you could do is add an audio track with the volume right down.  Then insert this free plugin from Meldaproductions:

https://www.meldaproduction.com/plugins/product.php?id=MNoiseGenerator

I say put the volume down before adding this plugin is because this effect is generating noise at all times, even when your project is not playing.  If you leave the volume up, you get a nice dose of Artic Blast as soon as you add the plugin.

Recently I've been spending more time testing than creating. And I find Sonar to be faster, easier to set up and more stable than some other DAWs.

ampfixer
I have modelling software to design EQ circuits. It shows how the output frequency will be effected by the EQ controls, but it's theoretical. Listening to the finished product doesn't usually reflect what the simulator predicted.

What modelling software are you using? As most EQ circuits in guitar amps are entirely passive, they should not present too much difficulty in modelling. I've used LTSpice with reasonable success on passive EQ. Even on valve/tube based circuits, it gives usable results, although the end results will be limited by the accuracy of the spice models of the valves. You can even use wav files as input and generate wav files as output (although it's a bit tedious). I haven't found a role for Sonar in any of this, I would add.

ampfixer
The amplifier output could be anywhere from 5 to 25 volts AC when pushed into clipping.

For the sake of the soundcard's health, I would use a simple potential divider (just a couple of resistors with adequate power ratings) to scale the output. I would then push that into the soundcard via a small capacitor just to ensure that no stray DC from the amp can get to the soundcard. As the resulting RC network is itself a high-pass filter, you might need to select values that do not compromise your results. And this is probably a good moment to point out that I only do things this way via Sonar because I don't have access to hardware 'scope or signal generator these days.

ampfixer
I typically would use a 100 mv sine wave at a fixed frequency between 800 Hz and 1 KHz. I need to test all the frequencies at once. Is Pink noise the way to do this? If so what can I use as a noise generator?

The (free) Melda plug, MNoisegenerator, can produce various types of noise, including pink, and there is also another, MOscillator, that handles other signal generation. I use an ancient 32-bit plug S(M)exoscope as a 'scope. That said, I'm still not really clear on what benefit you will get from noise, as opposed to a swept sine wave. The output will be noise filtered by your EQ and I'm not sure how you will make a meaningful interpretation of that. Nevertheless, I'll be interested to see what you find. I'd also be interested if anyone knows of a decent 64-bit Oscilloscope plug-in, ideally free.