This is a review and detailed measurements of the Little Bear / Douk VU2 input selector and VU meter. It was kindly purchased new by a member and drop shipped to me. VU2 costs US $189 from Amazon including Prime shipping.
The main attraction here are the VU meters and Douk delivers with two large sized ones:
When turned on it lights up with the standard yellow glow. Alas, it only lights up the middle third and nothing like the uniform yellow their advertising shows. A horizontal bulb that covers 1/4 of the meter provides lighting with no diffuser (it is diffused itself).
The rear labeling is confusing:
How could one channel be in, and the other out? Then I realized it is bi-directional and can form 4 to 1 or 1 to 4. At least I think that is how it works.
More confusing are the front panel controls. They do NOT operate on the signal itself but the action of the meter. Delay is not delay but filtering of the VU meter. All the way to the left is "fast" and to the right, slow. I say "fast" in quotation mark because typical of these meters, it is slow to begin with. Still, nice to have the control.
The gain control is again for the meters. This is essential in my view to get reasonable movement out of them. And nicely so, there is AGC (automatic gain control) so it can optimize the movement for you.
In use, I found the Gain control and output to be quite erratic. At some settings of gain the meter with a steady signal would jitter back and forth. Strangely, even the green LED above it would do the same! The gain setting was also not linear. I got most of the range from minimum to just hair above. Then the output would strangely drop. I could not make any sense out of it.
In case you are wondering, that USB connection is for power. They give you a USB cable but no power supply. At this price, I expect one included. I used a high power one I have for RPi computer boards.
Little Bear Douk VU2 Measurements
I treated the unit like a pre-amp and fed it 2 volts and got this:
Oh boy. I expected a simple pass through link so did not at all expect distortion let alone at this very high level.
I suspected that the input stage of this thing is loading down the AP. So I put the AP in loopback mode meaning it is measuring itself. With nothing connected to AP, I would get SINAD of 121 dB+. But the moment I connected the output of the AP to VU2, I got this:
In other words, the VU2 is severely loading down the AP output causing such significant amount of distortion!
So not only can't you use this as a switcher, but you can't use a wired connection to sample your audio as that distorts that source. Maybe you have a buffered output in your pre-amp or something but if you don't, watch out.
Fortunately this thing also has a Microphone that can sample the audio that way. I did not measure this but just turning it on and tapping on it and such, it seemed to produce a movement on the VU meter.
Conclusion
Ah, what a missed opportunity to build a decent VU meter.
I remember building a blinking disco light to the tune of music when I was 10 years old and it too distorted the heck out of the input when connected. I was concerned that this thing would do the same and it does. Its input needs to be buffered and high impedance to avoid this.
Sadly, as much as I love VU meters, I can't recommend the Douk VU2. It is just too broken.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The main attraction here are the VU meters and Douk delivers with two large sized ones:
When turned on it lights up with the standard yellow glow. Alas, it only lights up the middle third and nothing like the uniform yellow their advertising shows. A horizontal bulb that covers 1/4 of the meter provides lighting with no diffuser (it is diffused itself).
The rear labeling is confusing:
How could one channel be in, and the other out? Then I realized it is bi-directional and can form 4 to 1 or 1 to 4. At least I think that is how it works.
More confusing are the front panel controls. They do NOT operate on the signal itself but the action of the meter. Delay is not delay but filtering of the VU meter. All the way to the left is "fast" and to the right, slow. I say "fast" in quotation mark because typical of these meters, it is slow to begin with. Still, nice to have the control.
The gain control is again for the meters. This is essential in my view to get reasonable movement out of them. And nicely so, there is AGC (automatic gain control) so it can optimize the movement for you.
In use, I found the Gain control and output to be quite erratic. At some settings of gain the meter with a steady signal would jitter back and forth. Strangely, even the green LED above it would do the same! The gain setting was also not linear. I got most of the range from minimum to just hair above. Then the output would strangely drop. I could not make any sense out of it.
In case you are wondering, that USB connection is for power. They give you a USB cable but no power supply. At this price, I expect one included. I used a high power one I have for RPi computer boards.
Little Bear Douk VU2 Measurements
I treated the unit like a pre-amp and fed it 2 volts and got this:
Oh boy. I expected a simple pass through link so did not at all expect distortion let alone at this very high level.
I suspected that the input stage of this thing is loading down the AP. So I put the AP in loopback mode meaning it is measuring itself. With nothing connected to AP, I would get SINAD of 121 dB+. But the moment I connected the output of the AP to VU2, I got this:
In other words, the VU2 is severely loading down the AP output causing such significant amount of distortion!
So not only can't you use this as a switcher, but you can't use a wired connection to sample your audio as that distorts that source. Maybe you have a buffered output in your pre-amp or something but if you don't, watch out.
Fortunately this thing also has a Microphone that can sample the audio that way. I did not measure this but just turning it on and tapping on it and such, it seemed to produce a movement on the VU meter.
Conclusion
Ah, what a missed opportunity to build a decent VU meter.
I remember building a blinking disco light to the tune of music when I was 10 years old and it too distorted the heck out of the input when connected. I was concerned that this thing would do the same and it does. Its input needs to be buffered and high impedance to avoid this.Sadly, as much as I love VU meters, I can't recommend the Douk VU2. It is just too broken.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
