LED/VU/DB meters

Member
Joined 2021
Paid Member
how easy would it be to intergrate a real time meter for each channel
i guess you wouldnt be able to use the speaker output directly as it would drag the output down?


i want to experiment with an old amp i have that i dont mind messing around with the from to insert an led array or a couple of db/vu meters on the front panel with the view to doing a realy good proffesional modification to one after one i have done a successful test mod.
 
It is simply a high impedance voltmeter calibrated in VU or dB.
The input can be taken from pre amp out, that means from the input to the power amp section.
High impedance should not affect the amp performance, as the signal draw will be small.

IC based kits, with bar graph and sometimes hold function, are available, in steps of 5 or more LEDs.
School kid level stuff.
Or find old VU meters, or use an analog meter in 0-10 ACV scale, keep them outside and see how they dance around.
Careful with the connections, a small short and you may have a bigger job on your hands.
 

ICG

Disabled Account
Joined 2007
There are a lot of boards for VU meters (analog and LED) on eBay and Aliexpress. Though, there are LED VU meter boards which got an AGC (automatic gain control), that's nice for show but they say nothing about what's really going on.
 

ICG

Disabled Account
Joined 2007
Yes, that's what I assumed. I just wanted to mention you can get what you want but there are boards which are - just what you said - 'christmas trees'. Just read the description or the print on the board. You can of course build it completely on your own but at the prices of the chinese boards you often don't even get half of the parts.
 
how easy would it be to intergrate a real time meter for each channel
i guess you wouldnt be able to use the speaker output directly as it would drag the output down?


i want to experiment with an old amp i have that i dont mind messing around with the from to insert an led array or a couple of db/vu meters on the front panel with the view to doing a realy good proffesional modification to one after one i have done a successful test mod.

Very easyly done. Having some analog VU-meters in my cupboard, I built one around an opamp - any will do - and a CD4538 for peaks vizualiation. As it was for a studio tape recorder, I added a gain selector (0,-10,-20,-30dB) and associated adjustment trimmers for sake of precision. I first built a protototype on a test board. As it worked as expected, I had a PCB made. See construction here.

As said by AIM65, an LM3915 will do the trick perfectly

vumetre-lm3915-20-led-schema.webp
 
music soothes the savage beast
Joined 2004
Paid Member
each of these devices should have buffer/its own preamp in front of them not to load your signal
there was another thread here where member had preamp with high output impedance, and when he attached VU meter, it lowered the signal
simple jfet buffet, ot even better jfet with bjt pre would do
I have lots of VU meters, analog, led based, fluorescent vacuum based, tube based, I love this stuff
cheers!
 
music soothes the savage beast
Joined 2004
Paid Member
"how easy would it be to intergrate a real time meter for each channel
i guess you wouldnt be able to use the speaker output directly as it would drag the output down?"

no, the power output will not mind...you can connect it directly
your power (vu) meter should have some trimmer to adjust the sensitivity
ideally switch to adjust high and low sensitivity