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Old 8th October 2005, 05:39 AM   #1
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Default t-amp vu meter and volt meter question....

I actually have a few questions, but I will try and take it one step at a time. I have been looking online for a while and haven't actually found any answers, so I am humbling asking for your help.....

I am putting together a t-amp (the Class-t-amp-2020-m from autocostruire actually) and am using a power supply from Astron, the rs-a4. I like the look of analog vu meters and want to be able to use them but I dont exactly know how to wire them, or if I can even use them with the power supply I am using. I am a newbie if you can't tell. Or I was thinking of using a dc volt meter if the vu meters are viable, but I'm not sure if that will work either.

I'd love to just be able to solder a vu meter directly into the inputs without any fuss, but I doubt thats the way things work.

I even went as far as e-mailing the guys from Sifam, but that wasn't much help. Thanks for your response in advance........
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Old 8th October 2005, 01:25 PM   #2
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Elliot Sound Products has a VU Meter schematic -- it really isn't a VU meter (a VU is 1 milliwatt dissipated into a 600 ohm load) -- but more of a loudness meter, buffered from the line.

Peak reading meters are preferred to VU -- the VU meter was damped so that it would respond to a high % of the peak signal in 300 milliseconds -- the peak reading meter can be damped to respond in 4 to 30 milliseconds, and hold the signal level until your brain can register it.
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Old 9th October 2005, 09:50 AM   #3
dillo is offline dillo  Italy
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Hello rectaacies,
it seems we have very similar tastes! I'm also building an autocostruire kit and am going to put two analog vu meters on it.
Like you i was wondering how to do that
My meters, like the vast majority, read only dc signal, so I have to rectify the audio signal to be fed to the meters.
The article by Rod Elliot is very good about this subject, anyway the complexity you have to face depends on what you want: if you just want two needles that dance with the music and give you a rough indication of the volume, you can simply use a diode (or a bridge) before each meter. Prefer germanium diodes, as they have smaller voltage drop than silicons, and you will lose less low level reading ability.
I think I am going to connect them on the output of the amp, where the voltage swing is higher and I think that there will be less insertion distorsion. I will try this before, with a switch to disable the meters, and if I'll hear some difference in audio quality, I'll try to buffer the signal sent to the meters with an opamp.
Anyway, if I need to do this extra complication, I think I will do something better and use the precision rectifier by Elliott, for more accurate readings.
And obviously you need a resistance in series, to match the sensitivity of the instrument to the voltage you are measuring!
In this forum you can find a lot of info about the subject: just make a search about vu meters!
A last note: I don't know if the fact that the amp's output are bridged will make some problem, but I don't think so; I'll just read the voltage difference of the plus and minus terminals.
I whish you a good result, and the first of us who will manage to do it right shall post, ok?
It will be a lllong time for me, because I am currently very busy with work.
good luck!
Angelo
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Old 10th October 2005, 01:15 AM   #4
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Ya, this is my first project that I will have to actually put some forethought into, but that is what makes it more worth while. There are tons of vu meters on ebay a various sites and I'll share some links that are collecting in my bookmark folders.....

http://www.quasarelectronics.com/1039.htm
This one seems to be the easiest to connect. It comes with its own circut board and it even has teo vu meters. To me it seems easy, but the meters look awful......(I want illuminated)

http://www.sifam.com/vuppm.lasso
These are awesome meters. The AL20 & AL20SQ are the two at the bottom. They are th eones I want to use, but again, they are like 60 dollar meters.....so I dont want to wire them wrong and destroy them in one shot.

http://www.surplussales.com/Meters/MtrVU.html
There are a few one this site too......the ADL ones for 65 seem to be a hot item. On a side note, on another page on the same site (http://www.surplussales.com/Meters/MtrDCAmps.html) about half way down there is an awesome meter. It is number (MTR) M1957. Apparently its for nuclear use? But anyways, for 300 bucks, its dead sexy.

So ya, tell me what you guys think...thanks for the responses and all...its nice to know I'm not alone.
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Old 10th October 2005, 02:21 AM   #5
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Naaahhh, you gotta strap a soldering iron onto your fist and make it yourself -- buying a kit is for "girlie men" to quote the "Governator".
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Old 10th October 2005, 07:16 PM   #6
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Ha, well if this goes smoothI will probably make another. I also have another question. (im just full of them) The Vu im going to use will be backlit and will need some juice from my psu. Should I just solder it directly in with the leads from the t-amp? Or do I need to make a "hub" of sorts that I can connect the t-amp and whatever else to? Kind of like a power strip? Thanks for your patience guys
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Old 19th November 2005, 04:25 AM   #7
jwb009 is offline jwb009  United States
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Just want to know the progress of this, because I just bought an old tape deck with a couple VU meters that I'd like to put on my T-amp. I have no clue where to start though.

So have you made any progress?
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Old 3rd February 2006, 11:22 AM   #8
Xor is offline Xor  Sweden
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Has anyone made any progress in this matter?

Im planning to use the exact same setup: T-Amp + 2 backlit vu meters..

I dont have the knowlege to do this myself, so I was hoping someone had done it before me..
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