BBC Spec VU Meter Circut

[bustinjustin]

Hello to all,

I am looking into doing a DIY VU meter bridge old school style. I have researched various schematics, meters building options and successfully designed one that works well using 50k trimmers for calibration that I soldered to standard 1/4 front panel "Alpha Potentiometers"

Everything works ok and it looks sweet but now in hind site and of course the urge to dive into the next stage and make it better I have a few questions.

1. I want to design a meter circut that is pro spec using modutec and or simson that can be calibrated to represent real VU readings you know if Sound Forge says the level is 0db the meter can be calibrated as well.

This design seems to work ok for novilty purposes and definately responds and reads signal as if it were pro, but after more research I guess there is a strict guiline and standard to follow to achieve this...

Any advice or links would be greatly appreciated. I am new to the group and very glad to be getting into this stuff. I have for sure found a major passion for building my own audio gear after countless DAW systems I am just burned out since you can only push it so far with computers. This has for sure opened up a new door for my music and I plan on building the LA2A, G9, 1176 and who knows what kind of franken modded PC...

Anyways I have blown my horn long enough, just excited to join the group and tear into it. I am pretty stoked about the VU meter thing I picked up some old 2U network chassis for cheap 25 of them or so and they are 19" x 3.5" x 14.5" minimal holes in them. I am simply going to order a front panel express plate, dremel out the front of the rack and screw on the panel. The back has nothing my than three prong connector!!

Yee Heee!!! :grin:

Sincerely,

Justin

www.dawbox.com

PS. If anyone wants or needs a cheap enclossure for there project this is ther perfect anwer, just paypal me for shipping and $15 for the enclosure. I seriously do not need 25 of them. If your not interested no big deal I will have all the chassis I need for 5 years of DIY. I am getting alot of crap from the wife about taking up a closet with junk. Sorry for the spelling expect more of it in the future..

 

[gyraf]

BBC-type meters were logaritmically scaled from 1 to 7:

http://www.distel.co.uk/asps/specials.asp - halfway down

For meaningfull use with DAW systems, VU-meters are probably not fast enough. VU is a tradition that bears close relationship to how tape machines behaved - but DAW's are much more (only, actually) about peak levels.

Jakob E.

 

[bustinjustin]

So what you are saying is that other than a retro novelty idea, Analog VU meters would not work well at measuring sound levels. What about for just a general level from a distance view. I know the response times are slow characteristcly.

What about the meters for recording on the way in to my DAW VS using it for playback referenc? So in other words the circut that I a using may be fine for just general levels...

Thanks for the response Jacob and your work is an inspiration.

 

[fazeka]

Hey, justin.

Got any pics of the chassis?

Thanks,
Chris

 

[asm]

*bump* on wanting pics/more info on the chassis. how many U are they.

are they blank enclsoures or server chassis like your DAW's use?

 

[bustinjustin]

Sure,

Let me get my camera out of the shop and take some pics of it. Give me a few days. If you do not hear back from me hit me up again and remind me. These have worked wel for PC mods, as well as the VU meter DIY. They are super lite all aluminum and painted standard white.

The VU kit was 12V DC so I just rigged an old PC PSU, far more than I need for power but I have a good 100 of them sitting around (hehe) I just took the psu out of its case and then used a 80mm silent fan to keep the psu from frying.

This should work perfect for any of the Gyraf projects that need a 2U enlosure. Your just going to have to dremmel out the right amount of space for the pots and the vu and then spray paint the chassis. I noticed that rustolium hammered steel in any color dark or grey (Cherry Red)works the best and drys in 30 minutes. Be good to the dremmel and get two of them so that when one heats up a bit you switch. I fried at least 6 of them just doing the last few. Another good thing is that the enclosure has a EMI mat on the bottom of it. Aluminum is lke butter to drill, be sure to wear gloves though otherwise your going to get nasty slivers that hurt for days I am sure Jacob and the rest of you guys can feel me on that one (LOL)

As apposed to front panel express you can also buy blank plates at music stores/electronics stores. You need at least a good power drill two dremmels for $50 each and some ear plugs and safety glasses. A drill press is best. Picked one up from home depot for $129

In hind sight after all the work though on the front plate, front panel express despite $30-$50 is well worth it VS the pain and hours it takes to dremmel.

Anyways I will get you some pics very soon so hold tight. :grin:

 

[bustinjustin]

No none of those,


They are old used network chassis in mint shape 2U with rack ears powder coated white. They have a 80mm fan hole in the back and a standard style PC power plug the rest of the back is blank so perfect for XLR inputs and outputs. The front has holes on it for nework connections but I just took al that crap out dremmelled the front and used a front plate I dremmeled myself. Then I painted it and it looks sweet.... I got these for super cheap and i would be willing to pass on the love to DIY.

 

[SSLtech]

BBC spec meters were NOT VU they were PPM.

When you say 'Sound Forge says something is 0dB', you have to specify 0dBFS or 0dBVU... (if indeed Soundforge has any VU replication ablility).

Remember that VU has basically no place in digital. YOu have to know the peak level to know whether or not the signal is going to be damaged... VU won't help you one little bit.

Basically, in digital, "VU" = Virtually Useless. :wink:

Seriously though, do you understand the difference between 0Vu and 0dBFS? -If not you might not appreciate that you really can't use a VU meter for digital.

Keith

 

[bustinjustin]

Thanks for the schooling (LOL)

You can tell I was born in the digital domain...

I think I was miss understood with my reference to soundforge.

Lets drop the digital reference all together, what if I want to use the meters to monitor input of an analog signal.

Other gear has VU meters in it and it is used with DAW's I am talking about post D/A output of a soundcard or metering line level input from an analog source....

1. I want to design a stand alone meter box with in's and outs that has an adjustable calibrator on the front using modutec, or simpson meters. I want to use VU meters like the ones found in LA2A, 1176, ect...

Example:

I have a mic pre without a VU meter but I want to patch the meter to it's line output between it and my DAW....

Here is a link to the article I read....

Thanks for all your help!

 

[SSLtech]

Then all you need is what Kev often suggests: a VU meter and a 3.6k resistor. sniff the signal and you're golden :thumb:

However, be aware that you need to refer to the peak meters where all things digital are concerned. The VU is for general guidance only.

Keith

 

[Kev]

thanks Keef ... :green:

do I say that ... I say too much
didn't know anyone still listens to what I have to say :wink:

VU meters are still useful to have in the Digital Studio. It is still nice to know what the RMS/average/VU ... whatever you want to call it
levels are.

Yes 0dbfs is most important with tracking but eventually the RMS does matter when you get to the end of the mixing and then mastering end of proceedings.

It's just another tool to help you do your job. Learn how to use all of them.

 

[JustinS]

Just adding my $.02, I always find VU's useful for setting level into a digital system. In a quick I've got the whole band in and need to get everything set up kinda situation they're great for getting the levels about just right before checking nothings clipping on the digital meters. You do have to know the calibration of your A/D inputs and have an understanding that transient instruments like your kick and snare meter on VU's at least 3dB below where they actually end up on your DAW! And while I'm at it, I love EL8 Distressors, but I find them much harder to set up with the peak lights rather than a VU. I find VU gain reduction measurement so much easier to get a handle on. Most of the time I don't really care about the little twitches it's doing, more the overall gain reduction....

Justin.

 

[ToobieSnack]

I think if you do a search of the forum for:
meter AND buffer AND circuit
you find a lot of useful information
hope this helps
ts

 

[bustinjustin]

Thanks for the info guys, I just remembered how much I loved VU meters as a 70's child and of course for real world use in mixers, compressors ect.

I built a simple kit that supports a stereo VU using general purpuse diodes a pair of bi-polar transistors and a 50k trimmer as well as some 2.2uf 16V capacitors.


The kit says it will work perfect for tape based applications. The meters it came with are crap so I tried out a bunch of others that seem to work way better.

I changed the conection specs to balanced XLR

So Kev are you saying as long as I have a pro meter such as a modutec or a simpson with a one resistor setup this will work for measuring input?

Forgive me for my neophite-ness here but what meters would be the best for accuracy and what simple circut could I be pointed to that would alow me to use a potentiometer to adjust for different gear outputs inputs -10 +4 ect, ect......

I will look into the search, thanks for al the help...

 

[fazeka]

Hey, man. Where are the pics? :?: I'd be willing to buy some, but I gots ta see the goods!

Thanks!

 

[Kev]

[quote author="bustinjustin"]Forgive me for my neophite-ness here but what meters would be the best for accuracy and what simple circut could I be pointed to that would alow me to use a potentiometer to adjust for different gear outputs inputs -10 +4 ect, ect......[/quote]

A pro meter will work as it was intended and in the situation it was intended.
-10 may be a little difficult passively for a true VU and so it is usually done actively.

I use Sifam and Kyoritsu (see beloow) ... but then I have a stock of old and recycled meters. Like good pots ... good meters are getting harder and harder to find new, at reasonable prices.

My site has a simple passive meter project and many meters could be used as a single reference to a steady sinewave 0dB VU meter ... the VU goes to ballistics as well
... and only the good VU meter give this a fair shake.

I always have a couple of my passive VU meter laying aroujd and connect them as i need
both on the work bench and in the control room while recording.

 

[bustinjustin]

Sweet thanx!

I have this kit I rigged up that runs off of 12V DC now and I had an old PC power supply sitting around that is 12V, a little beefy for just that use (LOL) but hey otherwise it is just sitting there collecting dust since I have a good 100 of them from years of DAW building.

I found some old Beede Meters at a surplus store that are massive and only $7, they are DC volatage meters, so for fun I removed the plate on them and re-did the graphics so they are VU. I am not sure if they are even ballpark as far as balistics but they work with this circut and they can be seen from miles.. hehe

I like the look of the Sifam and the Modutec as well as the size. I will give your DIY a try and see how it goes.


PS. I will have the pics soon for the enclosures, my digital camera is in the shop just have to pick it up then I will post a link of a before and after.

One more question for a newbie num-scull...

Is it possible to Mod any of these DC power supplies to work with any of the projects out here like the 1176 or the G9? I have 300W, 400W...ect...

What is the average power consumtion for the gear you guys are building. 24V DC/AC ?

Sorry for the dummy questions I feel like I did with DAW's in 1995. (LOL) hey you gotta start somewhere and this feeds the soul for creativity!

Justin

 

[gyraf]

Switch-mode supplies are not easy at all to modify for work like ours.

And they're inherently noisy electrically.

So to sum it up, don't use these for audio work unless you have a VERY good reason to do so..

Jakob E.

 

[bustinjustin]

http://ww.dawbox.com/X-2U-DIY.htm

here you go... sorry for the delay...

 

[bustinjustin]

ok thanx for the tip jacob. So what you are saying is they introduce noise into the signal path. What about Ferrite rings or shielding the wires as well?

Justin