Douk VU3 Review (VU Meters)

[nagster]

However the issue here are almost certainly relays in the speaker signal path. Buffering meters would not help because relays would remain there. Better relays or SSR to be used. Then it would be more expensive and probably bigger. This is just another toy.

that's right. This was not a simple meter.
The meter buffer cannot solve the problem of the switching mechanism.

 

[Madjalapeno]

Thanks @amirm and @AdamG247 - the search continues.

 

[Grooved]

I apologize for offending anyone, but do we really need to waste Amir's time and ASR space with these silly products?
Need VU meters? Buy Accuphase or Mcintosh, whatever... Can't afford it? Then get some virtual VUs on your display or tablet and don't mess with extra cables or waste SINAD.

Maybe because we can't be sure it won't be worth it, based of some other great products they made :

Nobsound 3-IN-1-OUT XLR Audio Switch Review

This is a review and detailed measurements of the Nobsound MC-103 Pro 3-IN-1-OUT XLR Audio Switcher. The unit I have came with the brand Douk on it so that is what I used in my notations below. I suspect multiple companies put their name on it. I purchased it a few days ago from Amazon. The...

www.audiosciencereview.com

 

[anmpr1]

Need VU meters? Buy Accuphase or Mcintosh, whatever... Can't afford it? Then get some virtual VUs on your display or tablet and don't mess with extra cables or waste SINAD.

Obviously these little add-ons are just a desktop cosmetic thing. However, to be clear, Mac meters are not 'VU'. Rather, they provide a wattage indication, rectifying the average voltage and current into a specific load. At least that is how they used to be. Not sure about Accuphase. Nothing for one hundred and forty dollars with shipping, though. My guess is that McIntosh meters add at least a thousand dollars (or more) to the price of the unit. McIntosh used to sell versions of their amplifiers sans meters, but I don't think they do that anymore. Customers able to afford Mac or Accuphase expect Mac and Accuphase cosmetics.

Back in the day Crown and Pioneer (probably others) sold more sophisticated 'add on' devices, designed to match their other components. These also offered features such as speaker switching.

Crown OC-150

www.crownaudio.com

https://ncstereoman.com/pages/auction.html

 

[polmuaddib]

Maybe because we can't be sure it won't be worth it, based of some other great products they made :

Nobsound 3-IN-1-OUT XLR Audio Switch Review

This is a review and detailed measurements of the Nobsound MC-103 Pro 3-IN-1-OUT XLR Audio Switcher. The unit I have came with the brand Douk on it so that is what I used in my notations below. I suspect multiple companies put their name on it. I purchased it a few days ago from Amazon. The...

www.audiosciencereview.com

Sorry, I focused (mistakenly) on VU meter aspect. Thought it was it’s primary function.
But there was another version with VU meters which also measured poorly. Looks like the VUs are hurting the switching function.
And as far as I understand these VU, wattage meters, whatever, are not lab grade accurate measurement devices, but mostly cosmetic elements. Hence silly.
What’s wrong with calling something silly?

 

[Grooved]

Sorry, I focused (mistakenly) on VU meter aspect. Thought it was it’s primary function.
But there was another version with VU meters which also measured poorly. Looks like the VUs are hurting the switching function.
And as far as I understand these VU, wattage meters, whatever, are not lab grade accurate measurement devices, but mostly cosmetic elements. Hence silly.
What’s wrong with calling something silly?

I understand, I thought you were more talking in a general POV on this cheap switches (with VU or not), more than cheap VU
Now, it's a bit strange that adding VU in these switches (same brand) looks terrible performance wise, while seriously increasing the price.

 

[AdamG]

Thanks Amir!

I found this meter before Amir had tested the VU2. @AdamG247 was looking for some meters to use for monitoring power in his home theater and so Adam purchased. I have built some amp VU meters previously, but it was more expensive to do than the $140 cost of a VU3. I had done some measurements to check and found distortion that changed with load. I gave it a listen on one of my systems and it seemed to sound ok. After the VU2 tested poorly, Adam decided the VU3 should get Amir’s scrutiny. So, I sent it to Amir.

@pma’s suggestion of relay contact resistance makes sense as I had experienced this in an aging Proton amp. After hearing low level distortion, I had sent the amp for repair twice. Each time it came back with a no problem found. Afterwards, had done some internet searches and found the relay complaint. I bought a couple of relays and replacing them fixed the issue.

Anyway, the VU3 does use traditional relays and perhaps could be fixed with solid state ones. Here is a pic of the VU3 interface board…

View attachment 155363

Adam bought it, so is his call on what happens next. Along with the VU2‘s issues, would like to hear what Douk Engineering‘s response might be.

I hereby donate this item to the ASR experimentation lab. You @Rick Sykora and @amirm are free to do whatever you want to this device. It is now ASR property. Go now and Create FrankenMeter!

 

[tomchr]

@tomchr, any chance you would take a shot at designing a proper one of these and able able to sell it near these prices? I will go up to $199 if it works well.

My work is cheap, fast, good. Pick any two.

I would be surprised if I could get the production cost below $200.

Tom

 

[tomchr]

I could entertain the thought of designing a DIY VU meter, though. Would LED indication of peak and average power be OK?

Tom

 

[Helicopter]

Thanks Amir. I agree the 'vellum' paper is sweet. It is my favorite thing about the early Superscope Marantz stuff, i.e., 1973ish.

Seems potentially harmless to me. I wouldn't put this in a serious system, but I would totally run this bad boy in the all-analog 8-track system in the basement lab area with unfinished experimental DIY speakers.

Meters are fairly expensive. I would think you'd be looking at more than $200 for something with outputs and a nice case that works. If you want to hit $200, your best bet might be to run a separate sacrificial signal to the thing, and run another signal toward your amp. I'd love to be proven wrong though.

 

[Helicopter]

I could entertain the thought of designing a DIY VU meter, though. Would LED indication of peak and average power be OK?

Tom

Talk to @Rick Sykora. He got good performance on the NC500MP amp he built me. I'd post a picture, but I need to make the adhesive for the glass cover look better first. I wouldn't want anyone to see the ugly thing I did to it.

 

[Rick Sykora]

I could entertain the thought of designing a DIY VU meter, though. Would LED indication of peak and average power be OK?

Tom

Thanks Tom! PM me if I can help. The meters I used recently are pretty nice, but were $50 for a pair. This was just the meters without the driver boards or a case.

 

[Madjalapeno]

I could entertain the thought of designing a DIY VU meter, though. Would LED indication of peak and average power be OK?

Tom

 

[solderdude]

Is it all about using meters or switching ?

When one only wants to use the meters just connect the amp out and speaker to the same input and there should be no distortion.
The relays are not in the circuit and all will be O.K.
The mains hum might still be there but seems below audible levels.

When the switching is essential look for signal relays. Will be difficult to find a signal in that footprint that can handle more than 2A. (16W in 4 ohm)
The 5A rating (100W @ 4ohm) is usually only for relays that have to switch power (DC, or AC)

The 300W used in the test is 8.7A and above the 5A rating which potentially would only be a possible issue when switching amps or speakers at full power.

Anyone know what the dummy load resistors are for and what the small (signal) relays do ?

 

[tomchr]

Is it all about using meters or switching ?

That's actually a great question. What is it that you want from this box? VU meters? Or the ability to switch between different amps/speakers? Or both?

$50 meters would make this project a non-starter for anything other than DIY.

Relays are not the way to go if you want clean switching of the speaker/amp signals. Small-signal relays are great for line level stuff, but even then get the ones with fairly exotic plating materials on the contacts for the best signal integrity. Fancy materials in this context usually means AgPd or AgPd+Au. You won't find a power relay with fancy plating as the plating would vaporize the first time you switch from one speaker to the other. You can see some spectacular examples (with video) of switch arcing in speaker protection circuits here: https://www.halfgaar.net/dc-protection-with-relays

Tom

 

[Farenheit]

Is it all about using meters or switching ?

When one only wants to use the meters just connect the amp out and speaker to the same input and there should be no distortion.
The relays are not in the circuit and all will be O.K.
The mains hum might still be there but seems below audible levels.

When the switching is essential look for signal relays. Will be difficult to find a signal in that footprint that can handle more than 2A. (16W in 4 ohm)
The 5A rating (100W @ 4ohm) is usually only for relays that have to switch power (DC, or AC)

The 300W used in the test is 8.7A and above the 5A rating which potentially would only be a possible issue when switching amps or speakers at full power.

Anyone know what the dummy load resistors are for and what the small (signal) relays do ?

Provide load to a potential tube amp.

 

[Madjalapeno]

That's actually a great question. What is it that you want from this box? VU meters? Or the ability to switch between different amps/speakers? Or both?

$50 meters would make this project a non-starter for anything other than DIY.

Relays are not the way to go if you want clean switching of the speaker/amp signals. Small-signal relays are great for line level stuff, but even then get the ones with fairly exotic plating materials on the contacts for the best signal integrity. Fancy materials in this context usually means AgPd or AgPd+Au. You won't find a power relay with fancy plating as the plating would vaporize the first time you switch from one speaker to the other. You can see some spectacular examples (with video) of switch arcing in speaker protection circuits here: https://www.halfgaar.net/dc-protection-with-relays

Tom

Personally, it would be nice to just have something to know what my input signal is doing. Don't need another source switch as you already make one!

 

[AdamG]

That's actually a great question. What is it that you want from this box? VU meters? Or the ability to switch between different amps/speakers? Or both?

$50 meters would make this project a non-starter for anything other than DIY.

Relays are not the way to go if you want clean switching of the speaker/amp signals. Small-signal relays are great for line level stuff, but even then get the ones with fairly exotic plating materials on the contacts for the best signal integrity. Fancy materials in this context usually means AgPd or AgPd+Au. You won't find a power relay with fancy plating as the plating would vaporize the first time you switch from one speaker to the other. You can see some spectacular examples (with video) of switch arcing in speaker protection circuits here: https://www.halfgaar.net/dc-protection-with-relays

Tom

In my personal pursuit I just wanted Vu Meters. But then as the discussion advanced from building something from scratch @Rick Sykora and myself discovered these inexpensive Douk VU meters and we decided to buy one and send to @amirm to be tested. If it had passed this test, great we found an off the shelf inexpensive product that would work. Just happens that both of these Douk VU2 and VU3 include some form of Switching in the build. The final solution for me is the VU meters and clip indicators. Would be happy for separate solutions. It was a little science project and provided test result data to our ASR community. To me that is value added and knowledge shared.

 

[solderdude]

The Douk is not meant as a measurement device. There is no calibration. It is just meant to see a meter jump somewhat up and down in the rhythm of the music.

The problem with meters on outputs of amps is that they can only measure the output voltage.
When they must say something about the power (and have a scale stating power) one would also have to measure current without resorting to a low resistance in series so a current probe.
With both current and voltage one can create a 'power' scale independent of the speaker impedance.

Then rises another issue.. the scale... for it to be really meaningful the meter would need to have a log scale (over many dB) unlike the Douk meters that are actually linear scale.

Then there is yet another issue IF one not just wants a needle or LED jumping up and down but have useful info.
Does one want to know actual (very short) peak power (to check for clipping levels) or average power shown (using a needle) or does one want a digital meter that can show both peak and average levels, weighted or not etc.

Creating a meter that really says something thus isn't as easy as a meter jumping up and down and really saying nothing. The latter is what most want... bling.

For that... just buy this Douk thing and connect the meter in parallel to the speakers and be done with it.

 

[solderdude]

VU meters and clip indicators

The clip indicators are not easy to build nor configure. It can really only be done properly IN the used amplifier by monitoring the powersupply rails and output voltage coming to a certain distance from it.
This cannot be done accurately externally unless you check waveforms or know exactly what output voltage is possible with what load under which time conditions which would have to be set (inputted) into the device.

VU meters that jump up and down is already there... the Douk is fine.
You just have to connect your speakers to the amp. Put an extra (can be thin lamp cord) wire in parallel to the speaker wire and run that to the meter's input and it works fine and does not add distortion.

When you want meaningful measurements it becomes a totally different matter.

I built programmable (one can set the peak voltage where the clipping indicator comes on) and battery fed clipping meters (about 35 years ago) to monitor my amps output which worked fine.
Still have them somewhere (rechargeable batteries are dead now)
I'll try to locate it and make some pictures.