Douk VU3 VU Meter Review (Updated Version)

[Robbo99999]

I can think of one possible reason to get one, that is, to AB compare two mono or stereo amps, as it can switch between them quickly.

I suppose so, it's an edge case product anyway, I wouldn't really want it in my audio chain (due to it detracting from the signal), not that it's compatible with my system anyway as I don't use speaker wire (active speakers).

 

[pseudoid]

Isn't the whole music thing about fun ?
Music is superfluous but makes life so tasty, just like candy ;-)

I am sorry to disagree whole-heartedly!
Let's go to the dictionary for a definition of that word:

"Serving no useful purpose; having no excuse for being"

Hate to give you an example with music and the reasons why it DOES serve world-wide purpose:
SteelPulse - "Life Without Music"

 

[Multicore]

The next time one of those threads full of incredulity about the vinyl revival starts up, we can link this one. There's nothing so enduringly fashionable as nostalgia. And you can bank on that! (Literally.)

 

[KEFCarver]

But if something can load speaker connection so bad, how bad will it load RCA?

The purpose of the RCA to banana jack adapter was so that I could test the VU3 using my analyzer which requires a RCA input/output cables. My use for this would never be for anything other than doing a/b testing between amps or speakers.

 

[KEFCarver]

When will our Asian friends realize that 'VU' is NOT an appropriate legend to have on a speaker level pair of meters?

0dB represents 1.228V@600R/1kHz. It is a line level/record level scale. There is nothing remotely useful about 'VU' meters with dubious ballistics, and a variable pot to simply adjust the meter so it dances mindlessly in the middle range where it looks pretty.

The scale should be watts, with either a switchable pair of ranges and a reference to 0dB being a specific power over a rated load. And by all means, provide a trio of load options (4/6/8R).

Plenty of proper amplifiers with calibrated meters exist. Even the original vintage Radio Shack APM-200 and 500 are more useful IMO.

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Really good point. Love the APM-200- saw one in use just a few days ago. Own an apm-100 and 500 - love me a power meter!

 

[testp]

it's nice, but all it needs now is bigger & more expensive case (~5000$) and we're done..

 

[Laniciffo]

Technical questions...
When Amir measures the sinad of an amplifier I suppose he connects it to power resistors and then analyzes the *voltage* with the Audio Precision APxxx.

Amir measured that the sinad gets worse when the signal is routed through what should normally be just wires, and contacts, that I considered transparent up to now.

I did not expect that such a small device which should be insignificant compared to the very low impedance of a speaker could have a 10+ dB effect.

Now my question is : how do the amplifiers behave when connected to real loads ? I mean, is the voltage still so finely controlled with the varying and very low impedance of a speaker ?
Compared to a high impedance meter, isn't the speaker going to reduce the sinad of the *voltage* even more ?

The Douk vu-meter does not transform the signal that goes to the speaker, it just adds (possibly varying) impedances in series and in parallel to the speaker.
What order of magnitude are these loads compared to a speaker load ? How can they have such a dramatic effect ?
Supposing these impedances are very small (series) and large (parallel), don't they have to be wildly non-linear to create distortion ?

Which of the two has the largest effect ?
If it's the series impedance, then am I right to suppose that the sinad reduction would be much less if the meter was wired parallel to the speakers ?

Going even further, following Amir's experience that wiring does change the results when they're extremely good, did anybody try to measure the sinad of banana plugs, high awg wires or relays ?

Sorry if this has already been answered in other threads.

 

[thecheapseats]

...the original vintage Radio Shack APM-200...

one of the things I wish I'd purchased years and years ago... and yes - 1,288v into600ohms - or go home...

 

[NoxMorbis]

The 100W limit is not only caused by the relay.
The 100W (music power) limit is applicable for the not to the speaker connected amp.
The moment amp A is connected to the speaker the amp B is loaded with a 100W dummy-load (not specified what load that is, @Amir could measure the resistance of the not used input). Most likely the dummyload resistor is not capable of handling 100W continuous, it would need a huge heatsink for that.
When overloading smoke might come out, the resistor may burn out maybe even scorching the PCB.

The other limit is the 250V/5A rated relay. This tells me this is a relay intended to be used for switching mains power. In general these relays 'weld' a bit when a high current is passing through them and this makes these types of relays (in general) less suited for switching low power levels as there is no spark and contact depends on contact pressure and contact material in that case.
5A in 4ohm means 20V input voltage = 100W, 5A in 8ohm = 40V = 200W


The distortion could be caused by the load the meter circuit applies, could also be the relays that do this or even a combination.
The main difference the mkII seems to have is a (small) audio isolation transformer is used in the audio path to the meter circuit.
That could add the distortion and might explain why it seems to saturate/stabilize.
Above 1.7V the distortion seems to rise about 5x (still only 22μV opposite 4.5V) but.... 0.0005% is still inaudible and only measurable.

It could thus be the extra load (transformer) or the relay contact (no spark, so pressure contact only) or even a combination.
That transformer may not have been in there in the original version and its purpose is to ensure there can be no LF 'leakage' from mains (via the wallwart) into the connected amps which @amirm showed to be there.

In order to find out a bit more one would have to apply the load not through the relays but before the relays. When distortion still increases it is the load the VU3 applies.
When distortion does not increase it is the relay contacts that is the culprit.

That doesn't have any bearing on the measurements, though, right? It still introduces too much noise?

 

[NoxMorbis]

Isn't the whole music thing about fun ?

Music is superfluous but makes life so tasty, just like candy ;-)

An interesting comment. "Playing" is superfluous, but is it? For example, when the lower animals seem to play (they don't make a conscious decision "Hey, let's play!") although if you measured them, their dopamine levels would be up (pleasure), they are actually learning to survive by exercising eye-muscles coordination to avoid being eaten.

I would say that "playing" which for humans includes listening to music is not anywhere near superfluous but more along the spectrum of extremely necessary for a healthy human, perhaps as necessary as creating stuff. Working people just don't get enough of security and play. For instance, you can't really say, "Ok, human, NOW PLAY." Ok, human, "NOW WORK." Humans really don't work that way.

 

[NoxMorbis]

Just trying to determine how much of a performance hit this unit will cost when put in the audio chain. The unit itself has no SINAD. I guess we could call it a distortion/noise insertion generator. Some Audio projects are just for fun.

"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." --Amir

 

[NoxMorbis]

I am sorry to disagree whole-heartedly!
Let's go to the dictionary for a definition of that word: "Serving no useful purpose; having no excuse for being"

You must have cherry picked a definition. This is what I found:

• Being beyond what is required or sufficient.
• More than is wanted or is sufficient; rendered unnecessary by superabundance; unnecessary; useless; excessive.

Taking his or her comment in context, I believe the first entry is how the author is using the word.

 

[DualTriode]

When will our Asian friends realize that 'VU' is NOT an appropriate legend to have on a speaker level pair of meters?

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

 

[NoxMorbis]

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

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

 

[solderdude]

That doesn't have any bearing on the measurements, though, right? It still introduces too much noise?

I cannot say what introduces too much distortion based on the current measurements as it is not clear what causes the increased distortion.
In any case it is far, far, far below any audible levels anyway. No one can detect an increase of about 0.0004% distortion even if they wanted and were using single tones, let alone music.

 

[amirm]

Going even further, following Amir's experience that wiring does change the results when they're extremely good, did anybody try to measure the sinad of banana plugs, high awg wires or relays ?

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.

 

[NoxMorbis]

I cannot say what introduces too much distortion based on the current measurements as it is not clear what causes the increased distortion.
In any case it is far, far, far below any audible levels anyway. No one can detect an increase of about 0.0004% distortion even if they wanted and were using single tones, let alone music.

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."

 

[pseudoid]

You must have cherry picked a definition.

Lovely style of argument... even if 'cherry picked' (but wasn't):

Will you accuse me of 'cherry picking' my avatar, next?

 

[DualTriode]

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.

Changing the speaker relay in a NAD 216 THX amplifier improved the measured SINAD 15dBs plus.

Thanks DT

 

[Laniciffo]

You must have cherry picked a definition. This is what I found:

• Being beyond what is required or sufficient.
• More than is wanted or is sufficient; rendered unnecessary by superabundance; unnecessary; useless; excessive.

Taking his or her comment in context, I believe the first entry is how the author is using the word.

Deaf people do not die of lack of music although I'm very sorry for them.

That said, I'm almost certain that 90+ % of the readers of this forum feel that music is an absolute necessity in their lives.

What I meant is that the value we give to things not necessary to sustain life is very much subjective.
I love music and like very much spectrum analyzers and dancing needles but do not care for clothes.

Others may find my eye candies stupid.

Ascetes may consider music stupid.

Beautiful clothes, music, sightseeing, good food (including candies), dancing needles are all for our pleasure.

One may find one of those superior to the others but in the end it's just pleasure, dopamine or whatever you call it.

I'm no philosopher but enjoy very much that Amir is a chief FUN officer.

Why should our pleasures be serious or purposeful ?

But ooops, I just fell in my own trap !
Who am I to scorn the *pleasure* of being knowledgeable and serious about music hardware ?


Did any of you listen to the 'Final Fantasy X in concert' video available on YouTube ?
I find video game music wonderful when orchestrated so skillfully and, although it was not necessary, I also *enjoyed* watching the artists playing.

Have fun with music !