Douk VU3 VU Meter Review (Updated Version)

[amirm]

That's my thinking as well. About to test parallel load and see if that does any better.

 

[solderdude]

Sounds like what they have engineered a SINAD lowering box.

Probably not on purpose.

Fortunately the lowering of SINAD is not in an audible amount.

 

[solderdude]

That's my thinking as well. About to test parallel load and see if that does any better.

While you are at it.
Can you determine what voltage level needs to be applied to get the meter to indicate 0dB in the lowest and highest 'sensitivity range' setting ?

 

[NoxMorbis]

Probably not on purpose.

Fortunately the lowering of SINAD is not in an audible amount.

1. LOL, no, not on purpose, for sure. I guess we're asking our Chinese friends for a lot out of a 140.00 box? I don't see any US or EU companies trying this!

2. Well, Amir said he wouldn't use it because of that reason. Isn't he God?

 

[amirm]

Well, as we just expected, the VU meter does load the amp down and that causes SINAD to drop even when hooking up the meter in parallel with normal amp/speaker wiring:

Prior to doing that, both channels had a SINAD of 120 dB.

 

[solderdude]

It would not stand-out/matter if the amp used was not as good as the LA90 but rather your average speaker amp.

 

[NoxMorbis]

Well, as we just expected, the VU meter does load the amp down and that causes SINAD to drop even when hooking up the meter in parallel with normal amp/speaker wiring:

Prior to doing that, both channels had a SINAD of 120 dB.

Isn't that a lot better though? And, this is just the VU meter connected, not the switch box?

 

[amirm]

Just checked meter accuracy. I set it to 0 dBu. At -5 dB signal level, it reads -3 dB. At -10 dB signal level, it reads -8 dB. Worse yet, the adjustment pot has a massive notch in it. If I try to adjust it up and down, it does nothing for a while and then jumps! It acts almost digital in the way it makes massive jumps. In other words, it is more or a less a range switch and not any kind of linear adjustment.

 

[amirm]

Isn't that a lot better though? And, this is just the VU meter connected, not the switch box?

You are right. I didn't look at what we were getting before. And yes, this is just the VU meter. No other functionality is available in this mode.

 

[danielbaen]

Someone asked about remote control causing the display to dim??? I tried the few on my desk and none do anything. I can't think of what mechanism would cause it to do that anyway unless it had an undocumented IR support.

Envié un video para demostrarlo. I sent a video to prove it
video

 

[solderdude]

Well, as we just expected, the VU meter does load the amp down and that causes SINAD to drop even when hooking up the meter in parallel with normal amp/speaker wiring:

Prior to doing that, both channels had a SINAD of 120 dB.

So it is both the (non linear ?) load of the transformer as well as the 8 extra contact points.

What happens when the amp is measured without speaker load (so only the 390 ohm vs the meter as a load) ?

 

[amirm]

Envié un video para demostrarlo. I sent a video to prove it
video

I see it but can't understand how it is happening.

 

[amirm]

What happens when the amp is measured without speaker load (so only the 390 ohm vs the meter as a load) ?

I don't know. I am going to sleep.

 

[NoxMorbis]

You are right. I didn't look at what we were getting before. And yes, this is just the VU meter. No other functionality is available in this mode.

It looks like channel one is now transparent, only CH2 dropping 5 SINAD? I wonder why?

 

[amirm]

It looks like channel one is now transparent, only CH2 dropping 5 SINAD? I wonder why?

I only connected one channel to the vu meter as to show the difference.

 

[solderdude]

It looks like channel one is now transparent, only CH2 dropping 5 SINAD? I wonder why?

A 5dB drop is better than a 15dB drop so it looks as if about 10dB drop is due to the added contact points and about 5dB may be caused by the circuit applying a non linear load.

 

[Laniciffo]

Someone asked about remote control causing the display to dim??? I tried the few on my desk and none do anything. I can't think of what mechanism would cause it to do that anyway unless it had an undocumented IR support.

Manual FAQ extract :
'Q2: When choose certain functions via remote cotrol, the backlight of VU meter will also flash?
A: This is original design and normal.'

 

[JakeK]

Well I have it to switch between 2 amplifiers.
What seemed strange to me is that it dimmed the light with the remote control but apparently I have read that it is the most normal ... as seen, I will have to buy a couple more speakers and connect them directly each to its amplifier....

Years ago I bought a similar switch made by Beresford so I could use the same speakers either side of the TV with both my 'hi-fi' stereo amplifier and 2 channel sources as well as front left and right for my AV receiver, much better than little satellite speakers. This was a much simpler passive switch with no eye candy and no remote. The idea being to save on the number of speakers in the room as well as improving the sound of the 5.1 system. This was also based on the received wisdom that AV receivers sound much worse for music than stereo amps so you wouldn't want to just attach 2 hi-fi speakers to your AVR and play your music CDs etc. through that on source direct.

It also made it possible to switch instantly between amps for an A/B listening test which really opened my eyes and ears as well as closing my wallet to lots of unnecessary upgrades. I was able to determine that my AVR sounded the same as the 'Hi-Fi' stereo to human ears if both were played at the same loudness and both below clipping. The AVR having much more power was able to go louder without audible distortion though so I was happy to sell the stereo amp and reduce clutter and complication in my setup. If you're interested you can read the full story on my blog:

Do Hi-Fi Amplifiers Sound Alike?

Note: This is a long read. Scroll down for a TL;DR at the end. Links to sources are also at the end. If you have time, please read it all. What Does An Amplifier Do To The Sound? What difference do…

jakekuyser.wordpress.com

 

[Laniciffo]

Well, as we just expected, the VU meter does load the amp down and that causes SINAD to drop even when hooking up the meter in parallel with normal amp/speaker wiring:

Sorry to ask again, but how does that compare to the voltage SINAD when the amp is connected to a real speaker rather than a power resistor ?

I can not imagine that a small measurement device with its much higher input impedance can modify the results more than the power hungry speakers.
But it would be good news if I'm wrong !

 

[solderdude]

The changes are extremely small (-115dB) and when the load is not linear, seems to be a transformer which can saturate and have hysteresis, the load it provides is very small compared to a speaker but not neglible. In the order of nV compared to a few V (5W)
To prove that Amir should load the channel with the 390 ohm resistor as well.
Another possibility is the load is linear but the non-linearity comes from the contact materials in the relays.
These relays are designed to be used to switch high power loads, not for small signals.

In any case -115dB vs -120dB is neglible and not audible in any circumstances.