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adding VU-meters in the audio chain?

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#21
True true. I remember running sine wave tests through Mcintosh and Yamaha “hi-fi” amps and the stereo meters not matching. I have no experience with studio gear, and am not at liberty to say they are not accurate in such.
 

restorer-john

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#22
Power metering on power amplifiers varies from basic to very sophisticated, with accuracy from poor to excellent.

They cannot be all lumped in the inaccurate category.
 
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#23
What is the operating principal, in a (for all intents and purposes) basic hi-fi amplifier? Is it just simple case of a a current transformer before the speaker terminals or after the rectifiers of the power supply? I.e what is a cheap implementation vs an expensive one?

From my basic electrical background, could I not put a kVA power meter on the incoming AC supply to the power amplifiers, and this would pretty much mimic a Vu meter? I suppose there would be massive loses between the hypothetical two, due to amplifier class efficiencies etc
 
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#24
Was googling this and happy to see an ASR thread, so Bump.

This concept seems simple and relatively inexpensive, athough ideally it would easily hook up to existing audio equipment (ie rcas out of pre- or integrated). Or, even a stand alone with built in mic with SPL meters, so no direct connection needed. Accuracy is not really important, but just relative to either the signal or volume level.

This one looks cool:
https://www.ebay.com/itm/Hot-Power-Amplifier-Panel-Dual-Analog-VU-Meter-Audio-Level-dB-Meter-With-BackLit/153349024499?_trkparms=aid=888008&algo=DISC.CARDS&ao=1&asc=58999&meid=5c915764d7ca4665b3fb07f78e247287&pid=100009&rk=1&rkt=1&sd=254201676814&itm=153349024499&pg=2047675&_trksid=p2047675.c100009.m1982

Surprised there are not more plug and play boxes for sale. I would be very interested to add a component sized, finished backlit vu meter box to my system similar to the McIntosh or Accuphase look for say, under $100. Perhaps not as big nor accurate, but still, would be very cool.
 

solderdude

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#25
I was always partial to plasma VU meters



 
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Jim777

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#26
I have not tried them recently but the software VU meters tend to have latency that makes them out of sync with music. They can't anticipate how long it takes audio samples from the player to get to the output of the device. For this reason, while they are pretty to look at, I don't find them as satisfying as real VU meters.
That's pretty sad because I've worked on playback software in the past, using portaudio (like audacity does), and there was a way that it could report the latency well enough that we could display the playback cursor over the time-domain audio signal at the right place at the right time, even when using very long playback latency. The only "downside" with long latency was the time between keyboard input and the sound changing (one feature was switching rapidly between different versions of pretty much the same thing).
 
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Jim777

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#27
As for one attached to a power amp in a home stereo...does it matter? It's just for looks.
Exactly, if I'm not mistaken, McIntosh has models that only display voltage (even though it says watts) and other models that actually do a power measurement. I don't mind the voltage variety because it's just for looks as mentioned before, and measuring current (to get actual watts) could be more intrusive in the signal path.
 

sergeauckland

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#28
Aren’t VU meters notoriously inaccurate?
They are (or should be, if to the ANSI standard) pretty accurate, easily to a needle's width. But, on steady tone only. Their dynamic performance is very poor on programme material as their deliberately long integration time is designed to indicate 'average' levels more consistent with perceived loudness than signal peak level.
A PPM (Peak Programme Meter) has a 2mS integration time which indicates signal peak level with an integration time comparable with audible clipping. It's still not a true peak even then.

Metering audio levels is a subject in itself, and there are long debates in the Pro industry as to what meters actually mean.

S
 

TimW

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#29
I really want to find an affordable analog VU meter kit for use in DIY amps.

Here is a generic kit you can find on ebay. I like that the driver board will accept 12V DC because I want to use it with the 3e Audio TPA325x amplifiers and SMPS's which have an auxiliary 12V output. Unfortunately it will only accept an unbalanced line level input for the audio signal so I'm not sure how I would implement it. Also I doubt it is anything near accurate or more importantly, high quality.

There are also these products from a Lithuanian ebay seller which have been featured by Techmoan:
I like the quality of his driver board but he does not sell the power supply board or VU meters. It requires a +/-15V power supply and only excepts unbalanced line level inputs as well.

This cheap meter runs off of 12VDC and can be fed a speaker level signal but it looks cheesy and there's no provision for panel mounting.

Someone here shared a link to ELTIM VU meters. Unfortunately they are in the EU and their stuff is expensive. What I noticed in the photos of their products was the Tekram Technology brand name and logo. It appears Tekram has their own ebay store where they sell pricey VU meters by themselves. There are also a couple of other ebay sellers selling kits with the Tekram driver board which is the best I have found so far. You can identify it by the Tekram logo etched into the top of the op-amp. This board can be powered with 12VDC and will accept an unbalanced line level signal or speaker level signals. I'm not sure how accurate or reliable it is but feature wise it's what I'm looking for.

The VU meter and driver board kits from this seller look particularly attractive although I can't understand how the large rectangular ones are to be mounted.
 

TimW

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#30
I forgot to mention this Yuan-Jing VU meter driver board you can find at Parts Express. In a review of this board the reviewer mentions that he is using it with the SEW ST-475 VU meter. A search for that model name brings some promising results. The manufacturer even provides this nifty spec sheet on their meters.

The search also brought up an Australian DIY audio shop called JLM Audio which sells these SEW brand meters and their own DIY buffer boards which look well designed to this layman. This VU buffer build thread on their forum is well done. A pair of their buffers with Peak indicators and SEW ST-475 meters would cost about $85 including shipment to the USA.
 
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#32
I like the style/look of this new item, a USD$141 Weiliang/Breeze Audio power amplifier case with meters - even though with Hypex or ICEpower modules, the heatsinks are not necessary. One could also simply not use the front handles. I could even have a local shop powder-coat paint the front panel in semi-gloss black, and have a classy "Xulonn Audio" label made for the front. (Sometimes I really hate ASR - now I am tempted to spend even more money on this cursed hobby)
Weiliang Audio Case w VU Meters.jpg

External size: 430*359*150mm.
Internal size: 330*348*142mm.
Radiator size: 348*148*50mm.
Front panel is 10mm, rear panel is 3mm and upper and lower cover is 4mm.
Accessories: aluminum feet, aluminum handle, power switch, power socket, indicator, screws. (NO include RCA and speaker terminals)
Net weight: 8.0kg.
Weight after packing: 10kg.

The Aliexpress web ad does not confirm that the meters and meter driver modules are included (although that is what "indicator" might mean, so I posted an inquiry, and will update this post when I receive an answer.)
---------------------------------
Edit: The seller replied that the two meters are included, but not the driver
 
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Joined
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#34
So, I found an inexpensive solution - or at least a simulation.

I downloaded the iOS app below and put it on my old iPad and it works surprisingly well. I like the photorealistic look of a real sound meter and it has adjustments that make it very useful for different situations (ie C weighted seems to incorporate bass into the response and slow setting is more pleasing to watch than fast). I can monitor the relative loudness of the music from the listening position, which was a curiosity of mine as I like to listen at healthy volumes (it reads around 80db for me).
Really, my only complaint is that it is not formatted for the iPad, so I made it better by going into the ipad settings and turn on the zoom feature. It will change aspect ratio (vertical vs landscape), but does not fill the screen. If the display would be optimized for the iPad, it would be all I am looking for.

It's pretty cool and well worth the $0.99, especially if you have a spare screen for it. Not sure if there is an Android version.
https://apps.apple.com/us/app/spl-meter/id309206756
 
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