ammoon 5.8G Guitar Wireless System

 Wires can be such a nuisance when you are playing an instrument, it is easy to tread on the wire and pull the plug out - or even worse break the cable or plug. Also other people can trip over them. I wanted to get a wireless link for my guitar, and I also wondered if I could use it as an audio link between a mixing desk and a PA amplifier.

After looking at what was on offer on Ebay and some of the music shops I decided to buy this: https://www.ebay.co.uk/ipp/164367572025?transactionId=2043101513006&_trksid=p2047675.l48352

It has a very good spec. 10Hz to 20kHz, 110dB dynamic range, 24bit digital audio. Some of these devices work on 2.4GHz and are a bit cheaper, but this one is on 5.8GHz, where I figured there would be less interference from Bluetooth, WiFi, microwave ovens, etc. Also the 2.4GHz version has a slightly less good dynamic range.

So here's my review. 

First thing was to use a USB adaptor to charge the two devices up. It comes with a special "Y" USB cable, so both can be charged from on charger. Each one takes 300mA, so 600mA for the pair. The batteries are said to be 600mAh, so it should charge up in 2 hours, from completely flat. 

The LED's don't line up with the windows in the case, which is a bit annoying, but you can see that the RED charge LED is on by turning it slightly sideways. It is the same with the green LED which indicates whether the two units are "paired" correctly. 

Once fully charged, I plugged one end into my Tanglewood electro-acoustic guitar and the other end into a combo amp, and straight away it worked. I didn't have to mess about pairing the devices, just switch them on. Nice sound too. Turning the EQ and the volume to maximum on the guitar and playing loudly - no distortion. It is difficult to tell how noisy it is because the amp is quite noisy anyway, but it didn't seem to add any extra noise.

One thing the specification doesn't tell you is what the maximum signal handling is. So I set it up on the bench, with the signal generator and an oscilloscope. 

I found that I could turn the input signal (at 1kHz) up to 2V peak to peak (0.7V r.m.s.) where clipping just started to occur. It didn't do anything nasty with the onset of clipping, the top of the waveform was cut off in the usual way.

The clipping level was the same at all frequencies as far as I could tell. 

In the spec it says that the delay is less than 6mS, I measured it as 6.2 mS, which is close. The signal at 10Hz is inverted, but the effect of the delay is that the signal is back in phase at 750Hz and then goes in and out of phase with the input as the frequency is increased. So be aware that strange things will happen if you mix the input signal with the output.

One thing that did worry me a bit, was the fuzzy trace (see photo at left. There is about 20mV of noise superimposed on the output signal. 

The oscilloscope here is set to 50mV/div with a 1kHz signal input. 2mS/div on the horisontal axis. The top trace is the output of the receiver, and the bottom trace is the input from the signal generator. You can also see the phase shift here, and also that there is a very slight gain through the system. The output is about 12% bigger than the input.

When I looked at the noise with the input signal turned off, I couldn't trigger on it, and I think it is all very high frequency. It maybe some kind of breakthrough of the sampling frequency. 

I might add a passive filter to remove it when I use it with the PA amplifier, just to preserve the tweeters!

All considered I am quite happy with this purchase. seems good to me.

73

Hugh

The signal