Stereo VU meter kit BUILD THREAD

[Joe Malone]

The Stereo VU Meter kit uses our VU2 stereo VU buffer PCB run on a external 12v 500mA plug pack.
Stereo VU Meter is built into a Black Jiffy Box measuring 197 x 113 x 63mm with all holes CNC cut already.

Notes & Errata
1.New Stereo VU kit with LED VU meters only draws about 40mA total so some 12v powers supplies by cause noise or hum under this lite load. Adding 10R in series with the + red & - black power wires coming from the DC connector and a 470uF to 2200uF cap across the DC terminals on the VU2 with RC filter all noise out.
2.New 5v led meters. The 2 x RLAMP resistors = 680R for new 5v LED Lamp meters and 8 x diodes are NOT fitted just 4 wire links as shown.
3.Old 12v lamp meters. The 2 x RLAMP = 10R for old 12v lamp meters and 8 x diodes are fitted.
4.Current VU2 pcb has pin 4 of the IC socket masked over so best to solder a cut off component leg form that pin to -DC as shown below.


Build from the lowest height component to the highest. eg BAT85 diodes, Resistors, IC socket, 1uF caps, 4 pin headers, IDC10 header, 10uF caps, XLRs.

PCB built for new 5v led lamp meters.


47k = Yellow Violet Black red
3k3 = Orange Orange Black Brown
100R = Brown Black Black Black
10R = Brown Black Black Gold (Cream Body)

VU2 Stereo buffer kit parts list here

Fit Female XLRs. Then fit pot so screw to the right from front under PCB as below photo shows.
Fit TLO72 IC so its end notch and pin 1 dot are closet to the XLRs. Trim 4 wire cables to half there length.


Use one off cut red and black wire to wire the +/-DC on the VU2 PCB to the DC connector.


The Stereo IN PCB holds 2 x TRS sockets and a IDC10 header. Note Header is fitted as photo below with opening facing out NOT as Stereo IN PCB overlay shows.



Fit IDC cable between VU2 and Stereo IN PCB. XLR or TRS can be used as inputs. Also you can send in the XLRs and loop out with the TRS sockets.



Wire meters to 4 wire cables as shown and plug them into the VU2 PCB.
Stereo VU Meter is ready to screw together and plug 12v power pack in (meter back lamps should light)
Align meters using rear mounted 25 turn trim pots and a 1kHz tone of +4dBM (1.23vac on multimeter)
Or if you need a different level for your system. Play music and adjust trims for the meter movement you want.
Once movement looks roughly correct send in 1Khz tone and check both meters read the same level. If not adjust one meter to match the other.
Feel free to ask any questions on the Stereo VU meter kit below on this thread Enjoy

[slnstudios]

Hey guys, i have built one of these kits and was working perfectly until the other day when it lit up and sound passed through the vu meters but no movement? I rectified the problem by putting a high dB signal through which jumped the meters to +3dB and begun moving normally again to music.. The meters have been calibrated to -18 dBFS out of protools with the rear trim pots.. Is there a reason for this? and if there is, is there a way to fix it... Also, what do the two front flathead screws do that are under each meter? are these suppose to fully line up with the holes drilled in the front panel as only half of the screws can be seen through the hole.. Cheers, Shane.

[Joe Malone]

Hey guys, i have built one of these kits and was working perfectly until the other day when it lit up and sound passed through the vu meters but no movement? I rectified the problem by putting a high dB signal through which jumped the meters to +3dB and begun moving normally again to music.. The meters have been calibrated to -18 dBFS out of protools with the rear trim pots.. Is there a reason for this? and if there is, is there a way to fix it. Cheers, Shane.

From testing Shane's VU buffer kit which was at very near full gain setting we found the opamp can latch up depending on how the power supply was powered up. The latch up shows as the meters not responding until a loud input signal makes the meter suddenly start and work normally. This is fixed by making the half volts rail lower resistance so it can stop the latch up. All that was needed to fix this is to change the 2 x 47k in the centre of the XLRs R10 & R11 that make the half volts rails to 2 x 10k. If the VU buffer is built already adding 2 x 10k to 12k resistors under the PCB across the existing 2 x 47k resistors will work fine. New kits will have these resistor values added in and when the latest batch of PCB's run out we will change the overlay values to the new values. This info has been added to the VU2 Stereo buffer kit Build thread.

[sebasbetap]

Hello Joe,

Thanks for offering us this wonderful kit.

I have a question, thanks for your time answering it.

I want to calibrate each vu meter sepparately. One for mixing in -14dBFS and one for master in -9dBFS. Can I do that by simply turn the 5K pots? Or do I have to
do something different?

Thanks, again.

Sebastian Betancur

[Joe Malone]

Hello Joe,

Thanks for offering us this wonderful kit.

I have a question, thanks for your time answering it.

I want to calibrate each vu meter sepparately. One for mixing in -14dBFS and one for master in -9dBFS. Is there a way to do that on this kit?

Thanks, again.

Sebastian Betancur

Each Left and Right VU meter has its own 25 turn trim pot to cal it over large range.

If you mean to you want to switch the 2 meters between 2 level settings then leave the trim pots of the PCB and bring the outside trim pot pads out to wires to a DPDT toggle switch with 2 extra trimpots so you can switch between 2 reference levels.

[sebasbetap]

Thanks Joe for your swift repply!

I have already buyed and builded this kit. I'll try to calibrate each vu meter in a separate way with the 5k pot as you said.

I have another question. I want to understand this vu meter electronic operation. Do you have the electronic schematic of this project?
And can you let us take a peek on it?.

Thanks Again,

Sebas Betancur

[sebasbetap]

Hello Joe,

Thanks for offering us this wonderful kit.

I have a question, thanks for your time answering it.

I want to calibrate each vu meter sepparately. One for mixing in -14dBFS and one for master in -9dBFS. Is there a way to do that on this kit?

Thanks, again.

Sebastian Betancur

Each Left and Right VU meter has its own 25 turn trim pot to cal it over large range.

If you mean to you want to switch the 2 meters between 2 level settings then leave the trim pots of the PCB and bring the outside trim pot pads out to wires to a DPDT toggle switch with 2 extra trimpots so you can switch between 2 reference levels.

Sorry Joe for so many questions, jaja

Where can I find a dBFS reference to calibrate my stereo Vu meter?
The link you posted on the Vu buffer kit thread http://www.minorshill.co.uk/PC/Meters/S ... 20Test.zip
is not working.

I have seen the schematic of that kit (http://www.jlmaudio.com/VU%20Buffer%20Circuit.gif). Is it the same of this one but in a double way?

Greetings from Colombia.

Sebas Betancur

[Joe Malone]

Hello Joe,

Thanks for offering us this wonderful kit.

I have a question, thanks for your time answering it.

I want to calibrate each vu meter sepparately. One for mixing in -14dBFS and one for master in -9dBFS. Is there a way to do that on this kit?

Thanks, again.

Sebastian Betancur

Each Left and Right VU meter has its own 25 turn trim pot to cal it over large range.

If you mean to you want to switch the 2 meters between 2 level settings then leave the trim pots of the PCB and bring the outside trim pot pads out to wires to a DPDT toggle switch with 2 extra trimpots so you can switch between 2 reference levels.

Sorry Joe for so many questions, jaja

Where can I find a dBFS reference to calibrate my stereo Vu meter?
The link you posted on the Vu buffer kit thread http://www.minorshill.co.uk/PC/Meters/S ... 20Test.zip
is not working.

I have seen the schematic of that kit (http://www.jlmaudio.com/VU%20Buffer%20Circuit.gif). Is it the same of this one but in a double way?

Greetings from Colombia.

Sebas Betancur

Schematic is the same for VU buffer and VU2.

There is no exact setting for which dBFS. It is whatever works for your setup.
But most people try to use either K14 which would be 0VU = -14dBFS or K18 which would be 0VU = -18dBFS

[navehgrofi]

Hi Joe,

So I bought the buffer kit (waiting for it to arrive).

just to be clear, im building kind of a Volume Box, which includes the Vu meters and a volume Knob for speakers Levels...

so Basically, i need to wire the inputs of the Vu buffer also the the volume knob?

the meters will give me the volume of the inputs only right?

thanks

Naveh

[Joe Malone]

Hi Joe,

So I bought the buffer kit (waiting for it to arrive).

just to be clear, im building kind of a Volume Box, which includes the Vu meters and a volume Knob for speakers Levels...

so Basically, i need to wire the inputs of the Vu buffer also the the volume knob?

the meters will give me the volume of the inputs only right?

thanks

Naveh

Yes if you wire the VU buffer input across the input to the volume Box.

[navehgrofi]

Hi Jo

Do the 34 mm meters you sale has rectifiers in them?

i just bought 2 of them (not yours)
and for some reason i don't have any meters reading (still waiting to verify i have audio coming out (waiting for parts)

im guessing this might be the issue but I'm not sure

Naveh

[navehgrofi]

Hi Jo

I have another Question

Can You guide me please through the connection of the following parts:

inputs (balanced Trs lines) - i connected them to the mounted TRS inputs i orders from you.

Now I have XLR outputs that need to go through a 24 steps Ladder attenuator for Volume control.

the Attenuator have GND, Input, Output for each channel

So TRS Tip (from board) connects to the Attenuator input and attenuator output connects to Pin 2 in Xlr output right?

so what about pin 1 and 3 in the Xlr Output and the GND on the attenuator?

i also cannot see any meters movement...
Thanx...Naveh

[Joe Malone]

Hi Jo

Do the 34 mm meters you sale has rectifiers in them?

i just bought 2 of them (not yours)
and for some reason i don't have any meters reading (still waiting to verify i have audio coming out (waiting for parts)

im guessing this might be the issue but I'm not sure

Naveh

Our 34mm meters do NOT have rectifiers in them. You need external rectifier or our VU buffer and peak led kit or VU2 stereo buffer kit to make them work with audio.

[Joe Malone]

Hi Jo

I have another Question

Can You guide me please through the connection of the following parts:

inputs (balanced Trs lines) - i connected them to the mounted TRS inputs i orders from you.

Now I have XLR outputs that need to go through a 24 steps Ladder attenuator for Volume control.

the Attenuator have GND, Input, Output for each channel

So TRS Tip (from board) connects to the Attenuator input and attenuator output connects to Pin 2 in Xlr output right?

so what about pin 1 and 3 in the Xlr Output and the GND on the attenuator?

i also cannot see any meters movement...
Thanx...Naveh

Sounds like you have a unbalanced stereo ladder atten so either you need one stereo atten per channel to keep the proper balancing or use our dingo pup kit to take the balanced input to unbalance for the attenuator and then the unbalanced output from atten to dingo pup to convert back to balanced.

Never run VU meters directly across the output of a passive attenuator without a buffer otherwise meters will add distortion to the signal. Using VU Buffer will isolate and stop the distortion on the audio.

You can do a pseudo balanced attenuater using the unbalanced attenuator by wiring

Tip to atten in and out to XLR pin 2
Ring to atten GND and XLR pin 3
Sleeve to XLR pin 1

This pseudo balanced atten will work as volume but any noise cancellation will vary greatly depending on the length of the output XLR cables and so is not recommended.

[navehgrofi]

navehgrofi wrote:
Hi Jo

I have another Question

Can You guide me please through the connection of the following parts:

inputs (balanced Trs lines) - i connected them to the mounted TRS inputs i orders from you.

Now I have XLR outputs that need to go through a 24 steps Ladder attenuator for Volume control.

the Attenuator have GND, Input, Output for each channel

So TRS Tip (from board) connects to the Attenuator input and attenuator output connects to Pin 2 in Xlr output right?

so what about pin 1 and 3 in the Xlr Output and the GND on the attenuator?

i also cannot see any meters movement...
Thanx...Naveh


Sounds like you have a unbalanced stereo ladder atten so either you need one stereo atten per channel to keep the proper balancing or use our dingo pup kit to take the balanced input to unbalance for the attenuator and then the unbalanced output from atten to dingo pup to convert back to balanced.

Never run VU meters directly across the output of a passive attenuator without a buffer otherwise meters will add distortion to the signal. Using VU Buffer will isolate and stop the distortion on the audio.

You can do a pseudo balanced attenuater using the unbalanced attenuator by wiring

Tip to atten in and out to XLR pin 2
Ring to atten GND and XLR pin 3
Sleeve to XLR pin 1

This pseudo balanced atten will work as volume but any noise cancellation will vary greatly depending on the length of the output XLR cables and so is not recommended.

thanks a lot for the answers Jo

2 more questions please:

1. im successfully having meters read, but even with the highest gain position i cannot bring the needles over -3 dB (I'm sending high volume 1 kHz sine wave)

2. is this setup recommended:

Audio Device outputs (UnBalanced) through TRS Line (Sleeve not connected?) to VU STEREO Inputs, then Pseudo Balanced at ten wiring to XLR outputs (lines to speakers are only 1 meters or less long)

or should i use Fully balanced lines to the inputs?