How to build a bi-color led signal meter...

[TomWaterman]

Hi!

Anyone know a way of getting 1dB per segment accuracy from those LM3916 log chips? I looked at it before but the application notes suggest that a LM3916 daisy chained with a LM3915 was needed to get +10 segment displays.

As the LM3915 is linear (I think?) IIRC it was only capable of 3dB steps at the bottom of the range.

An expensive alternative to the Dorroughs and maybe a bit out of the DIY price range but....

You can get a 53-segment stereo meter from PrimeLED for $450. Its a DSP controlled tri-colour meter that can do PPM dot, VU bargraph and a 3rd parameter simultaneously, you can program as well, so it could do phase correlation etc.

Very very cool, its available as an analogue meter (using an AD) or a digital one with AES input.....digital one is used in the DangerousMQ.

Just thought I'd give a heads up as they do sell singularly, can be mounted in whatever box you choose. One for those with stupid spending habits or a well paid job!

Good luck with your meter Neeno!

Cheers Tom

 

[PRR]

> DIY a meter with such accuracy?

Accuracy or resolution?

You can lash piles of LM339 and LEDs, make a 999-LED display if you like. Hmmmm.... you could even approach the implied 0.1dB accuracy without elaborate trims.

But you also have to ask what you want to measure. Peaks? How short? Held? How long? Decay long or short? Or maybe RMS, a good guide to "loudness" (if you pick good time constants) but a poor guide to overload? Or Average, which on most music is not inferior to RMS and a lot easier to compute?

The Dorroughs does much-much more. IIRC, it has peak and average but also a finely tuned loudness value, all on one scale. You could probably build one for $100, but it would take $10,000 of your time to develop an algorithm that was "as good as" the Dorroughs.

Anyway I thought the original question was a 1-lite indicator?

 

[Kev]

[quote author="PRR"]Anyway I thought the original question was a 1-lite indicator?[/quote]

:green:
you get that
these threads can side track quickly

I have never been a fan of the single LED signal indicator.
More frustrating than useful.

Did find use in the 4 LED ... two green, yellow then red.
That can help identify visualy the signal you are hearing.

... horses for courses

 

[Guest]

do these sorts of things need to be buffered or anything in order to not mess with the audio signal? vu meters need to be dont they?

 

[Neeno]

I think think that the lm39xx are alredy buffered...

 

[TomWaterman]

Yeah I meant resolution....sorry!

Thanks for the info PRR, sorry to sidetrack the thread!

Cheers Tom