Douk VU3 VU Meter Review (Updated Version)

[restorer-john]

I have indirectly measured these in the form of elevated distortion in the sweeps. When the screw terminals in my banana plugs get even a bit loose, the wind up creating distortion due to non-linear modulation of the current going through them. I recently upgraded my locking banana plugs to a new one that allows the screws to be tightened more and this has helped a lot. The type of wire is also a factor in well you can screw things down.

By the same token, relay contacts and such can cause similar issues. We are measuring to such high precision that these things show up. Likely not an audible thing since you don't maintain high currents more or less continuously as I do in the testing. But to the extent you paid for great performance in the amp, might as well assure the rest of it is secure as well.

The meter as designed is pass-through, which is just a dumb design for speaker level indication. Parallel connection should be employed.

 

[restorer-john]

Okay, in 1972 you may have been correct.

For the intended application no one cares if the meter reads in Watts or BTUs. For this application saying VU is like saying Kleenex.

If you really want to know, the meter should be calibrated in dB SPL.

Thanks DT

dB SPL? Haha, based on exactly what? A random speaker at one specific frequency? That's even more useless.

'Power' meters on amplifiers at least give some idea of the extent of the voltage swings you are swinging over your loads (speakers). They have their place and can be extremely useful when you question balance in a recording, especially if they are of a useful ballistic, a good frequency response, have been properly calibrated at a specific reference point, with a known load and remain reasonably accurate above and below that.

I have many power amplifiers with integral power meters, ranging from extremely sophisticated to quite simple. The sophisticated units take into account the load, contain A/D converters and display the resulting digital power outputs with selectable hold times. Yamaha, Accuphase and Luxman all produced some TOTL power amplifiers with excellent power meters.

 

[wjp007]

Seems like it makes no sense to degrade performance and limit yourself to 100W for what could amount to a pretty gimmick! Should have no effect on performance and have no significant limits, praps that's one reason Amir mentioned it should be measuring at Line Level rather than after the amplifier.

You can run the VU meter in parallel with your speakers (don't use it as a speaker switch, just use it as a VU meter) That's what I do and I can't tell any difference in performance.

 

[TonyJZX]

with only a gut feeling i have no objection to such a device if it sits between your preamp and your amp

but i really dislike the idea that it sits between your amp and your speakers

i do get that it may ad some noise but if your amp and preamp and good enough.... you can afford to lose a little snr

 

[restorer-john]

with only a gut feeling i have no objection to such a device if it sits between your preamp and your amp

but i really dislike the idea that it sits between your amp and your speakers

i do get that it may ad some noise but if your amp and preamp and good enough.... you can afford to lose a little snr

The only place for a 'power' meter is on the low impedance outputs of the amplifier.

If you want a 'VU' meter, it should be in line with the source components, but it should not place any load, let alone a non-linear load on the sources.

Placing such a 'VU' style device (like the old model) between a preamp and a power amp is only useful if the 'meter' is set to indicate the actual voltage you are driving the power amplifier, with 0dB being the rated input for full power.

 

[NoxMorbis]

Lovely style of argument... even if 'cherry picked' (but wasn't):
View attachment 284065
Will you accuse me of 'cherry picking' my avatar, next?

I wasn't trying sound accusatory. I was just pointing out that in context, the word was not used to mean "have no purpose."

 

[DualTriode]

dB SPL? Haha, based on exactly what?

Based on exactly what you want to know. What will it be?

Watts, Volts or pounds of Kleenex? I do not care, it is about visual bling to go along with your audio.

I often use a hand held A-weighted SPL meter.

You want Watts, go ahead on.

Thanks

 

[DualTriode]

Probably not, but that sounds like a pretty simple task to calibrate VUs?

It is very doable.

Get out your calibrated microphone(s). Plug in your analyzer. Program a A-Weighting filter for your measurement(s). While you are at it set up a Watt meter and a Volt meter. Now calibrate what you want for fun.

There are meters that have interchangeable scales that can pop in and out.

Thanks

 

[wwenze]

Then just think of it as an amp/speaker switcher first with a VU meter as a monitoring feature.

 

[NoxMorbis]

with only a gut feeling i have no objection to such a device if it sits between your preamp and your amp

but i really dislike the idea that it sits between your amp and your speakers

i do get that it may ad some noise but if your amp and preamp and good enough.... you can afford to lose a little snr

True, but this isn't just a VU meter. It's a switch box with a VU meter. As such, it really does have a function. I'm thinking about sending this top Amir for testing because it's about the only thing on Amazon left, for a VU meter, and that's all it is. However, I don't think I can even use that with my Aiyima 08 Pro:

Douk VU

The thing is, it's 100.00 bucks, and the VU3 is 140, so for 40 more bucks, you get VUs with a switch box.

I'm still wondering is unplugging the power supply to the VU3 would affect the noise or the amp's SINAD number?

 

[solderdude]

I'm still wondering is unplugging the power supply to the VU3 would affect the noise or the amp's SINAD number?

That would be extremely unlikely. When it is the amplifier load (the small transformer) then that won't change much. Maybe it could even be worse even.
When it is the power relay (which aren't really suited as signal relay) then it is unlikely to change.

When you want to ONLY use the meters (just for the sake of seeing meters indicating nothing really) then you should connect the speaker directly to the amp (so NOT via the VU3) and connect the VU3 in parallel to the speaker.
There will be no increase of distortion in this case. This is assuming the (inaudible amount if increase in distortion when using a high SINAD power amp/system) is not caused by the load of the VU3.
Personally I suspect it is the relay that is the culprit of the (ONLY measurable) increase of distortion.

This would have to be measured though.

Yet Amir says: "Here, SINAD is better than 100 dB so as long as your amplifier SINAD is no better than 90 or so dB, you won't notice an impact."

I bolded the important part.

 

[NoxMorbis]

That would be extremely unlikely. When it is the amplifier load (the small transformer) then that won't change much. Maybe it could even be worse even.
When it is the power relay (which aren't really suited as signal relay) then it is unlikely to change.

When you want to ONLY use the meters (just for the sake of seeing meters indicating nothing really) then you should connect the speaker directly to the amp (so NOT via the VU3) and connect the VU3 in parallel to the speaker.
There will be no increase of distortion in this case. This is assuming the (inaudible amount if increase in distortion when using a high SINAD power amp/system) is not caused by the load of the VU3.
Personally I suspect it is the relay that is the culprit of the (ONLY measurable) increase of distortion.

This would have to be measured though.



I bolded the important part.

Are there many class D amps doing better than 90 in a specturm of power large enough to matter? What I mean is if you have an amp that does 95dB but only does it in one frequency and then only for a brief time, say between 1wt and 10wts, while the rest of the time it's doing less than 90, and the other frequencies were 90 or less no matter what the frequencies or power was, would it even matter then?

Anyway, I wrote Douk about it since the old version wasn't even much worse than the new one. Maybe that one was old stock? It will be interesting to see what they say.

 

[solderdude]

The SINAD of an amp does not matter.

Most likely the extra contacts (2 extra plug/socket/clamp) + relay contacts are more than likely the culprit when routing the speakers through this (or any other) speaker switch box.
Not the device itself, nor the connection of the device through a wallwart nor it being powered or not.

Depending on several factors around the switchbox the 'extra' distortion products (way below any audible thresholds) the added distortion may become more visible in plots.
So a high SINAD amp will become a worse SINAD amp (in essence) and an amp with a low SINAD will also add the same amount of distortion but may be 'drowned' in that of the amp so not visible in plots.

So... when the goal is to see meters swing up and down there does not have to be ANY degradation at all, it is just a matter of not using the switchbox functionality in that case.
When the goal is to switch amplifiers and or speakers than any speaker switch box could add a similar amount of 'distortion'.

Regardless of the SINAD of the amp/system.
With a very high SINAD amp you can measure the differences in lab conditions, yet will remain inaudible.
With a very low SINAD amp you will not find the 'extra' distortion in the measurements and it will also be inaudible.

The key here is inaudible. Measurable is not the same as audible.

 

[PeteL]

The SINAD of an amp does not matter.

Most likely the extra contacts (2 extra plug/socket/clamp) + relay contacts are more than likely the culprit when routing the speakers through this (or any other) speaker switch box.
Not the device itself, nor the connection of the device through a wallwart nor it being powered or not.

Depending on several factors around the switchbox the 'extra' distortion products (way below any audible thresholds) the added distortion may become more visible in plots.
So a high SINAD amp will become a worse SINAD amp (in essence) and an amp with a low SINAD will also add the same amount of distortion but may be 'drowned' in that of the amp so not visible in plots.

So... when the goal is to see meters swing up and down there does not have to be ANY degradation at all, it is just a matter of not using the switchbox functionality in that case.
When the goal is to switch amplifiers and or speakers than any speaker switch box could add a similar amount of 'distortion'.

Regardless of the SINAD of the amp/system.
With a very high SINAD amp you can measure the differences in lab conditions, yet will remain inaudible.
With a very low SINAD amp you will not find the 'extra' distortion in the measurements and it will also be inaudible.

The key here is inaudible. Measurable is not the same as audible.

That is all true, but the 100W limit can be audible tough (when used as it's main functionality, a switch box). Wondering if there are more models of this type of devices on the market less limited in that regard. I think that many of us owns more powerful amps than that, that would be way more concerning to me to have to drop to low power like that when I paid for a 300W+ amp. Much more important than a few points of inaudible SINAD.

 

[solderdude]

The 5A/250V rating is actually for relay contacts while switching loads, too big sparks (connecting and disconnecting) can destroy the contact surfaces resulting in poorer contact, more and more losses.
Output relays in power amps are notorious for making poor contact after many years. Usually 'tapping' on the relay momentarily fixes the contact until the next time it has to do so.

In general, once conducting, the contact current can be higher than the rated value for switching action.

The 100W rating seems to be more limited by the dummyload that is applied to the not-used amp (when switching amps).

We would need to know what load that is (easily measured with a multimeter) and for the switching perhaps the datasheet of the used relay.
Most 5A rated relays can carry currents 50% higher when they do not have to switch those currents.
Besides, 300W power peaks in music still is about 30-40W average in power levels.

 

[PeteL]

The 5A/250V rating is actually for relay contacts while switching loads, too big sparks (connecting and disconnecting) can destroy the contact surfaces resulting in poorer contact, more and more losses.
Output relays in power amps are notorious for making poor contact after many years. Usually 'tapping' on the relay momentarily fixes the contact until the next time it has to do so.

In general, once conducting, the contact current can be higher than the rated value for switching action.

The 100W rating seems to be more limited by the dummyload that is applied to the not-used amp (when switching amps).

We would need to know what load that is (easily measured with a multimeter) and for the switching perhaps the datasheet of the used relay.
Most 5A rated relays can carry currents 50% higher when they do not have to switch those currents.
Besides, 300W power peaks in music still is about 30-40W average in power levels.

My apologies Solderdude.
I do not fully understand what you are saying. Are you saying that this is not enough to tell us that the units will clip into 4 ohms Speakers and that we need more measurments to assess that? how is it limited by the Dummy load, Amir says into 4 ohms, meaning he measured into 4 ohms? Are you saying that we would see something different if Amir had loaded the unused channel also?
Edit., Oups, I see now it's the LA90, an already low power amplifier, so not clipped at the Switch box.

 

[solderdude]

There is no clipping by the VU3 at all. There is just increased distortion visible and it is not clear what is causing that, the added contacts, the relay contacts ?
Most likely both the + and - wires are switched so that is 8 extra 'contact points' added in the signal chain (+ connector, Relay 1, relay 2, +connector and the same in the - contact). Most likely this causes the elevated distortion.

The VU3 has 2 inputs. input A and input B. When one uses input A then input B is loaded with an internal dummy load. THAT dummy load is limited in power rating and that's where the advertised 100W is for. What is not measured is that dummy load resistance. Also it is not known what power rating the actual resistors is but it looks like 5W continuous or so.

 

[PeteL]

Based on exactly what you want to know. What will it be?

Watts, Volts or pounds of Kleenex? I do not care, it is about visual bling to go along with your audio.

I often use a hand held A-weighted SPL meter.

You want Watts, go ahead on.

Thanks

I honestly also thought you where Joking... You know your hand held SPL meter has a transducer in it right?

 

[Laniciffo]

The power limit may also be a consequence of the max voltage the vu driver electronics can take. There certainly is an attenuator at the input to make the signal < 5V as I'd be surprised if the board used a voltage up-converter for its power supply, but I may be wrong.

 

[PeteL]

There is no clipping by the VU3 at all. There is just increased distortion visible and it is not clear what is causing that, the added contacts, the relay contacts ?
Most likely both the + and - wires are switched so that is 8 extra 'contact points' added in the signal chain (+ connector, Relay 1, relay 2, +connector and the same in the - contact). Most likely this causes the elevated distortion.

The VU3 has 2 inputs. input A and input B. When one uses input A then input B is loaded with an internal dummy load. THAT dummy load is limited in power rating and that's where the advertised 100W is for. What is not measured is that dummy load resistance. Also it is not known what power rating the actual resistors is but it looks like 5W continuous or so.

Well ok, not measured unfortunately, but the specs just say: Max. through power of each channel: 100W . I have no reason to doubt that weather it's only specifically when a channel is unused or not. It tells you to not pass more than 100W trough it, I would not put it at the output of an amp that can deliver 300+ W. Now if I get what you mean, OK, it's remains to be demonstrated if it would be a problem or not... But a rating is a rating, they tell you not to do it.