VU meter wiring?.

[deadastronaut]

hi guys, i bit the bullet and bought one of these vu meters (havent got it yet) on a slow boat etc....

but they look really cool with the warm backlight bulb...and can run on 6v to 12v etc...ideal.

anyway i figured it would need a buffered splitter, so it doesnt affect the sound etc...

does this look right? or am i missing something obvious..

i know the light will have its own supply etc...

i'm building a rack  delay, reverb, cab sim....

cheers rob. 

[iainpunk]

don't those need envelope followers to work right?
simple diode and cap should do right

cheers

[deadastronaut]

i dont know , ive never played around with non led vu meters...

[Phoenix]

Signal needs to be rectified and filtered (envelope follower) to drive the analog meter movement. See Elliott Sound.

[deadastronaut]

aha...right. thanks. 

when i get it i,ll give that 'simple rectifier' stage a go then....

[iainpunk]

real VU meters need rectification, but there are ''fake'' vu meters that just are voltage meters with a fancy face plate added. most cheapo chinese mechanical voltage meters i have seen, seem to not care about direction/polarity, where true VU meters do.

cheers

[deadastronaut]

i just found a very old vu meter in my boxes of bits, so i will bread it up later

and see how it goes. 

[rankot]

I have one of those w/o driver circuit, and two more with drivers are on their way here, so I will report when I get them.

[jatalahd]

One example of a cassette player VU meter circuit (click to expand):



This is screencopied from the John Linsley Hood article of home made cassette deck. Link here:

https://www.keith-snook.info/wireless-world-magazine/Wireless-World-1976/Low-noise%20low-cost%20cassette%20deck.pdf

[deadastronaut]

hi guys, thanks....

i breaded this one up, and works well. fig 7.

http://objectivesounds.co.uk/articles/vu-meter/


i swapped C3 22uf for a 1uf as the reaction was slowed with the big cap.

i also swapped R5 for a 5.6k. which prevented it slamming the needle all the way... and maxed out at 0db..


it works fine, however i tried it with the splitter buffer, which worked....but added a bit of hiss, especially when using hi gain dirt.  which isnt there without it .  (using true bypass breadboard)

so.....looking at another way of wiring it up...hmmmm....

[jatalahd]

Did you try fig 8, as that is the single supply version? It has that cap to ground at the op amp leg, which might help with the hiss (or maybe not 🙂).

Also, instead of increasing R5, you could try increasing R4.

[deadastronaut]

Oops yes it was fig 8 i tried.....

[anotherjim]

Maybe the light in the meter is a PWM'd RGB?
Hat, coat, ducks out through the door 

Maybe the opamps need to be separate? Also, I'd feed the meter from line buffer opamp output rather than the same input for both.

[deadastronaut]

^ oi!..dont start..

hmmm yes , seperates might be worth worth pursuing

have a you a line buffer example?

[anotherjim]

Buffer? You started out with one. I just meant a buffer in the thru path can drive the line out and the VU.

[deadastronaut]

sorry jim, im confused (doesn't take a lot ha ha)

a buffer in the thru path? drives both?

[anotherjim]

Both the line out and the VU meter. The VU meter will still need an opamp for the rectifier (if yer still on that fig8).
I thought you're making a thru box with a VU meter, although if the VU meter input is high impedance, the thru line out doesn't need a buffer, the signal goes straight from in to out jack and the VU input taps off it

[deadastronaut]

hi guys, update:

got my little meter, these things are sweet. lovely warm glow too...

had a tweak, and it works great.

heres a vero i knocked up .  (from the previous schematic)

i matched it to my mixer level too....so is good to go level wise..

[rankot]

No hiss anymore?

[deadastronaut]

 i put it in the path of the straight dry guitar signal

and its fine.

guitar>>>>>>>>/>>>>>>>>>out
                           /
                           /
                    meter input.