Koolertron Upgraded 15MHz DDS Signal Generator Counter,High Precision Dual-Channel Arbitrary Waveform Function Generator Frequency Meter 200MSa/s (15MHz)

I'm having a blast just getting to know all the things this signal generator can do!It does all the obvious things -- sine, square, pulse waveforms, etc., and it also is capable of a whole lot more waveforms -- rising/falling sawtooth, triangle, and a bunch of waveforms I'll have fun figuring out what they might be useful for. You can easily adjust the phase between the two outputs, and it has every sort of modulation you can imagine.One useful feature I've discovered is the burst mode, where for example you can output a burst of say 10 cycles of say a 1kHz tone (takes 10ms). I've used this to examine the output of a high power amplifier where I don't want to overstress it.As others have pointed out you can easily adjust the duty cycle of the output, but not with sine or square waves for which only symmetrical output is available.I'm not clear who actually manufactures this device -- it looks like it is available with various labels, but is actually a JDS 8000 manufactured by Hangzhou Junce Instruments. The short manual it comes with is pretty useful but I got a more complete manual online from Hangzhou Junce.I have a couple of complaints.1 - when you switch it on it doesn't go back to the settings you last used it at, which would be very useful. Instead it reverts to the default setting of 10kHz sine wave at 10v p-p, which would not be good to input into a conventional audio amplifier or preamp, which is what I'm using it for mainly. It has multiple memories where you can store settings, but you have to remember to do that manually each time you turn it on.2 - the output level is indicated only in peak-to-peak volts, which is useful for many waveforms but not so much for sine waves -- I wish you could switch to other units such as rms volts.3 -- minor complaint -- the connecting lines for the device use standard BNC connectors to attach to the actual device, but have some pretty crude alligator clips on the other end -- the kind where when you squeeze on the vinyl insulation surrounding the alligator clip it tends to just rotate around rather than open. Not a big deal if you already have some good BNC cables with quality microclips or something similar.4 -- THD is pretty high -- around 0.3% or so, meaning although this waveform generator is going to be very useful for many things, measuring amplifier THD is not going to be one of them. On the other hand I don't think there are many general purpose waveform generators with very low THD -- you need another source for such a signal.

Edited review: regarding the duty, I realized that there was specifically a pulse wave which is affected, and that the square wave is not. This was confusing since duty is selectable for all waves, but it does work. I also took this into the lab today and compared it to lab quality generators. I’m creating very low voltage, low frequency signals on this thing (10 Hz at 0.1V) and attenuating it down to about 200uV. This thing is a beast and does that no problem, even slightly better than some of the lab grade equipment we have. Do your own tests, but for my purposes this exceeds my expectations. I still have not tried creating software defined arbitrary waves, but if that works reliably I’d give this 6 stars if it was possible.Original Review: I’m using this for very low frequency, low voltage stuff (10Hz @ 0.1V) and it does a pretty good and reliable job. So far the only thing that doesn’t work is the duty. Adjusting it still results in a fully symmetrical wave. I also haven’t tried uploading arbitrary waveforms yet, but watched a YouTube video that tracked down the required software and it seemed a bit annoying to set up. So far it’s been a productive instrument, but unfortunate that I didn’t get a feature I paid for.

I’m impressed by the capabilities of this signal generator. Not long ago, a device like this would have been prohibitively expensive. The unit is compact and lightweight yet performs exceptionally well, making it a great addition to any test bench. While I’m very satisfied with its functionality, there are a few design elements that could be refined.The display and menus, although in English, retain some stylistic influences from the original Chinese design. This has no impact on usability but may feel slightly unconventional to some users. Setting the operating frequency is straightforward, though the process is a bit unconventional—you select a specific decimal position and adjust the value with the control knob.One minor inconvenience is that while the unit offers plenty of memory slots for saving operational states, it always starts up with its default settings rather than remembering the last frequency and mode used. It would be much more user-friendly if it resumed the previous operational state upon powering on.That said, these quirks are minor and don’t detract from the unit’s overall performance. While it’s not reference-grade test equipment—understandable at this price point—it is an extremely capable and excellent value for general-purpose use.

I used my new oscilloscope to view the various output waveforms (sine, square, sawtooth etc.). They looked good on the scope, and the scope indicated that the peak-to-peak output voltage was the same as the level that I had set the generator up for. It looked to be right on the marks. You can see the digital-to-analog conversion steps in the waveform, but they were not excessive, and that is expected with a digitally synthesized generator. They were not a problem for what I needed, and will likely never be a problem for my purposes. If you will be using this to test harmonic distortion of a high-end audio amplifier, you should probably use a much more expensive generator that uses more data bits. Also, I was using a digital scope, so some of that waveform stepping (quantization) was due to the scope itself.I placed a 50 ohm load resistor across the output terminals, and the p-p voltage dropped to 1/2 of what it was without the resistor. This is just what should happen with a generator that has a 50 ohm output impedance. It is light-weight (feels almost like a cheap toy), which made it easy to carry to a job site. I simply needed to generate a consistent modulating tone for testing a piece of radio equipment. It served my purpose very well.