#1
So I'm making a "Decibel meter" for my amp. It's just a line of 20 LED's in a row and it's going to be like a visual meter. The louder I play, the more LED's light up.

I've been measuring some voltages out of the line out in my Bass Amp. I'm getting about 10vac peak when I'm playing my hardest. About 4.5vac - 6vac when I'm playing mildly and 2.5vac - 4vac playing lightly. When I measure the DC using a bridge rectifier into my multi-meter, I get about the same voltage as the AC maybe losing .5-1v less than the AC. I just want to make sure this sounds right to people before I go into making my design for my display.
BRIGHT LIGHTS PUT ME IN A TRANCE.
but it aint house music that makes me want to dance.
#2
a bridge rectifier is made out of four diods (plus a capacitor) isnt it ? so you should quite expect a slight loss in voltage
#3
^no capacitor in a bridge recto. You should add filtering though.

When rectified the DC voltage is higher than the AC voltage (by approx 1.4 times)...so there is no loss.


Anyways there is lots of issues with the TSer's idea....Needs to be though out a lot more.
#4
Quote by kurtlives91
^no capacitor in a bridge recto. You should add filtering though.

When rectified the DC voltage is higher than the AC voltage (by approx 1.4 times)...so there is no loss.


Anyways there is lots of issues with the TSer's idea....Needs to be though out a lot more.


I find no issues with my idea. You also lose .7 volts with a bridge rectifier. I just need to know if my outcome of what I measured seems correct.

EDIT: I didn't mean decibel meter. It's more of just a voltage meter, visually with a ton of LED's.
BRIGHT LIGHTS PUT ME IN A TRANCE.
but it aint house music that makes me want to dance.
#6
Quote by kurtlives91
^You do not loose .7V with a bridge recto...

Try your idea, see where it gets you.


Quote by Wikipedia
An aspect of most rectification is a loss from peak input voltage to the peak output voltage, caused by the built-in voltage of the diodes (around 0.7 V for ordinary silicon p-n-junction diodes and 0.3 V for Schottky diodes)


Please, If you have nothing informative or useful to add, then don't post. You haven't seen my schematic, design or plans at all so how would you know if my idea will work or not?

With all that I've explained of my original post, please tell me the flaws in my plan. I'd really like to know, if I'm ever going to trouble shoot it.
BRIGHT LIGHTS PUT ME IN A TRANCE.
but it aint house music that makes me want to dance.
#7
That quote really dosent relate to what we are discussing here.

Take your AC voltage and multiply it by 1.414 to find your DC RMS voltage.\

That quote (from a very reliable source) is just saying there is a voltage drop because of the diodes. It does not meant that rectifying AC will give you a lower voltage than you started with.

Don't argue with the fact that rectifying AC causes a higher DC voltage because it so well known and easily prove able.


You would be rectifying your AC guitar signal...I am pretty sure you don't wanna be doing that.
#8
Quote by kurtlives91
That quote really dosent relate to what we are discussing here.

Take your AC voltage and multiply it by 1.414 to find your DC RMS voltage.\

That quote (from a very reliable source) is just saying there is a voltage drop because of the diodes. It does not meant that rectifying AC will give you a lower voltage than you started with.

Don't argue with the fact that rectifying AC causes a higher DC voltage because it so well known and easily prove able.


You would be rectifying your AC guitar signal...I am pretty sure you don't wanna be doing that.


Well since it's a bridge, I'm not gaining any DC voltage, I'm losing 1.414 from my peak AC voltage.

And yes I do want to rectify my signal, to make it DC for the circuit I'm making.
BRIGHT LIGHTS PUT ME IN A TRANCE.
but it aint house music that makes me want to dance.
#9
Joe-Fish, do you realize what would happen to the sound? You're basically sucking away your signal into a bunch of LED's. And another flaw: This will not look like a meter where more or less LED's will light up depending on how hard you strum or how loud it is. It will just change the amount of light that the LED's emit all together. In other words it will get brighter or darker, not that some totally go out and the others just stay on.
Gear:
Schecter Hellraiser Deluxe
Boss DS-1
Crate GTD65

GAS List:
Mesa Boogie Dual Rectifier Roadster
#10
Quote by Joe-Fish
Well since it's a bridge, I'm not gaining any DC voltage, I'm losing 1.414 from my peak AC voltage.

And yes I do want to rectify my signal, to make it DC for the circuit I'm making.

Yes you are gaining DC voltage. The difference between the AC and DC value will be positive not negative like you think.
#11
Quote by asfastasdark
Joe-Fish, do you realize what would happen to the sound? You're basically sucking away your signal into a bunch of LED's. And another flaw: This will not look like a meter where more or less LED's will light up depending on how hard you strum or how loud it is. It will just change the amount of light that the LED's emit all together. In other words it will get brighter or darker, not that some totally go out and the others just stay on.


I still haven't even explained my circuit yet nor I have I even posted a schematic of it. How can you assume what my LED's are going to do?

I'm barely sucking any of my signal away as well. I can take a tiny signal out and amplify it if I begin to get any distortion with my driver. I've discussed all of this with my electronics teacher.
BRIGHT LIGHTS PUT ME IN A TRANCE.
but it aint house music that makes me want to dance.
#12
schems? i want to see this
R.I.P. Les Paul, 1915-2009

A man chooses, a slave obeys.
#13
Quote by bv310
schems? i want to see this


I don't have any on the computer yet. The basics are on a notebook at school. Basically it's using resistors to decide whether or not that certain LED is turning on or not. There's more to that though.
BRIGHT LIGHTS PUT ME IN A TRANCE.
but it aint house music that makes me want to dance.