Recommendations for signal sweep generator + probe for PC/MAC?

[rccolgan]

Hi all!

I'm in the market to step up my bench tools a bit. I currently do not own an oscilloscope, but I'm wondering what you all might recommend for new ones that are not military precision grade?

My main goal would be able to generate a sweep as incoming signal to an amp, pedal, etc, and record/compare the output of the sweep for comparisons. Being able to save or directly interface with a PC/Mac is a huge plus for my YouTube videos. Especially if they are high resolution.

I'm not sure where to set my budget but I feel like I've seen some nifty ones around $100 or so but I'm having a hard time distinguishing if they do signal sweeps like I'm looking for.

Thank you in advance!
-Ryan

[trobbins]

You could purchase something like Focusrite Scarlett 2i2 USB interface, and use that interface to generate your test signals, and to record your widget response. There is a variety of software available that includes scope waveform display, test and sweep signal generation, and spectrum analyser plotting, plus heaps more capabilities. A divider/attenuator type input 'probe' reduces any highish signal voltages down to a level suitable for the interface. This is all great for audio signal testing such as 10Hz to 45k or 90kHz (ie. it does not display DC type signals like a generic oscilloscope, or typically above about 90kHz), as the software is miles ahead of anything for a scope or collections of equipment, except for the very high end audio testing facilities like from AP.

You have to know how to use a PC and load software and read the manuals/helps when it comes to choosing drivers and configuration settings, although some software nowadays makes that really easy for the latest operating systems.

You may have to tweak a standard cheap ebay clone 10:1 or 100:1 scope probe to give a flat response beyond 50kHz. If you don't go accidentally touching mains AC or 600VDC B+ with a 100:1 probe then I find that method of probing is quite robust. There are also a few specialist interfaces around that provide a bunch of auto-ranging and calibration features, but they are custom and cost $ and you may need to make it up from a kit.

Using one interface means that the widget you are testing has a common ground that extends from input socket to output socket (or where you want to probe), as the interfaces ground may well be common also, so you need to avoid setups that somehow introduce ground noise and voltage differences.

You need a regular cheap DVM to take absolute measurements, as the interface does not typically easily do that as there are usually pots for input signal attenuation/gain, and output signal volume pots, and pot settings are not absolute references of signal level. For example if you want to identify what output power is being generated from an amplifier in to a test load then the DVM will make the rms voltage measurement, and along with the test load resistance, you can calculate power output. Same for input to output gain, you need to take two rms voltage measurements.

I use REW software, and have a decade old EMU 0404 USB soundcard, and have tweaked an ebay 100:1 scope probe, and got a BNC to 1/4" jack connector, and I can get that making measurements in a minute or so, with awesomely low noise floor and wide bandwidth, and can do a frequency response plot in about 20 seconds as I twiddle tone pot settings, and can check harmonics and distortion levels and noise quirks when faultfinding.

[Littlewyan]

I use a PicoScope. It includes a signal generator, oscilloscope and spectrum analyser. You can't do any recording with it per say, but I find it pretty useful. I used it recently when tweaking the distortion channel in an amp to see how harmonics were affected.

I also own a Focusrite Scarlett 2i2, but I've only ever done a bit of recording with it, nothing fancy!

[rccolgan]

Thank you both for the detailed suggestions and your personal experiences. Seems like there is ways to achieve what I'm sort of looking for, but might take a little effort to pull it all together with purchasing a few devices. Instead of automatically sweeping and it might be best to generate, measure, step, generate, measure, step, etc.

I just was reading about the pico scope on a Facebook forum. Super cool and almost too inexpensive! Lol. HDMI out is interesting... Would need to have a HDMI recorder like the online gamers use to connect to the PC that way. Interesting... I'll follow up with that I end up with . Thank you!

[trobbins]

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