Stereo VU meter kit BUILD THREAD

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Re: Stereo VU meter kit BUILD THREAD

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mobtownstudios wrote:
Mon Apr 12, 2021 5:59 am
Joe Malone wrote:
Fri Apr 09, 2021 9:36 am
Hi Mat yes they look fine. Any 2 clear white 5mm led around 1000mcd or more will work in there with the 680R. Each led has about 2.5 to 3.5v across it. So voltage at terminals will be 5v to 7v as the 2 are in series. They maybe brighter or duller so RLamp can be changed afterwards to make brighter down to 470R or duller up to 2k. Mount them exactly the same way as they are in the back of the meters. They have a polarity which is easy to see internally in the led as they are clear.

Continuity testing doesn’t really work with the leds. If you tried the reversing of the lamp power wires with no luck then they will be dead. But they should have been very bright for a couple of seconds if they burnt out.
Thanks Joe!

New LEDs and fixing the resisters/diodes did the trick! Glowing wonderfully!

If I wanted to use 1 LED in each meter for a gentler glow would I have to do anything else other than that? Would I need a resister anywhere in the chain?


Screen Shot 2021-04-11 at 3.59.06 PM.png
Either make RLamp resistor larger in value to dim or add a resistor in series with one of the meter wires on each meter.

Going to 1 led will make it brighter and unbalance the backlight to one side.
Joe :-)
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mobtownstudios
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Re: Stereo VU meter kit BUILD THREAD

Post by mobtownstudios »

Perfect!

I put the 3k3 resistor in place of the 680 and it's working WAY better for me!

Thanks Joe!

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Re: Stereo VU meter kit BUILD THREAD

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mobtownstudios wrote:
Tue Apr 13, 2021 12:03 am
Perfect!

I put the 3k3 resistor in place of the 680 and it's working WAY better for me!

Thanks Joe!
Cool. Must be very high Mcd LED like 10000. More efficient less power needed :-)
Joe :-)
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Nonsense
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Re: Stereo VU meter kit BUILD THREAD

Post by Nonsense »

Hello from Brazil!

Just finished building my kit and it seems to be working. However, I need some advice on how to properly put it on my signal chain. I am using a stereo system:
Turntable > pre-phono > pre-amp > power-amp > speakers.

My pre-amp is a Schiit Saga, having 2 pairs of RCA outputs. Tried to plug the second pair on the VU meters (using a XLR-rca adaptor), but a big “hum” ground noise appears on the speakers.

Connecting to speakers binding posts, the VU meter works, but I am concerned about the “loss” on putting it in parallel with the speakers (whats the impendance of the buffer?). In case this is fine, should I use a banana-TRS cable?

Thanks already and let me know if something was not clearly explained (my english is not so good).
Cheers!

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Re: Stereo VU meter kit BUILD THREAD

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Nonsense wrote:
Mon Aug 29, 2022 5:52 am
Hello from Brazil!

Just finished building my kit and it seems to be working. However, I need some advice on how to properly put it on my signal chain. I am using a stereo system:
Turntable > pre-phono > pre-amp > power-amp > speakers.

My pre-amp is a Schiit Saga, having 2 pairs of RCA outputs. Tried to plug the second pair on the VU meters (using a XLR-rca adaptor), but a big “hum” ground noise appears on the speakers.

Connecting to speakers binding posts, the VU meter works, but I am concerned about the “loss” on putting it in parallel with the speakers (whats the impendance of the buffer?). In case this is fine, should I use a banana-TRS cable?

Thanks already and let me know if something was not clearly explained (my english is not so good).
Cheers!
HI What are you using to power the VU2 kit? Photo of your wiring would help as shouldn't get hum if wired correctly which depends on if the power supply for the VU2 and your preamp have mains grounds linked to them. The input impedance for the VU2 is 100k so doesn't load RCA or Speaker outs at all. Since VU meters only show 23dB range they are best calibrated to the line signal before the volume pot unless you are using them for room audio level setting.
Joe :-)
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Nonsense
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Re: Stereo VU meter kit BUILD THREAD

Post by Nonsense »

Joe Malone wrote:
Mon Aug 29, 2022 11:43 am
Nonsense wrote:
Mon Aug 29, 2022 5:52 am
Hello from Brazil!

Just finished building my kit and it seems to be working. However, I need some advice on how to properly put it on my signal chain. I am using a stereo system:
Turntable > pre-phono > pre-amp > power-amp > speakers.

My pre-amp is a Schiit Saga, having 2 pairs of RCA outputs. Tried to plug the second pair on the VU meters (using a XLR-rca adaptor), but a big “hum” ground noise appears on the speakers.

Connecting to speakers binding posts, the VU meter works, but I am concerned about the “loss” on putting it in parallel with the speakers (whats the impendance of the buffer?). In case this is fine, should I use a banana-TRS cable?

Thanks already and let me know if something was not clearly explained (my english is not so good).
Cheers!
HI What are you using to power the VU2 kit? Photo of your wiring would help as shouldn't get hum if wired correctly which depends on if the power supply for the VU2 and your preamp have mains grounds linked to them. The input impedance for the VU2 is 100k so doesn't load RCA or Speaker outs at all. Since VU meters only show 23dB range they are best calibrated to the line signal before the volume pot unless you are using them for room audio level setting.
Hi. I am using your 12V power supply (https://www.jlmaudio.com/shop/12v-400ma-smps.html).
The Schiit has its own power supply as well, and they are not connected (how could I do that? Both power supplies are + and - only, no grounds).
Will provide photos latter, but it is as simple as that:
Turntable >RCA> preamp >RCA> poweramp >BANANAS> speakers. Each equipment has its distinct power supply connected to a panamax m5300 power management unit.

Nonsense
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Re: Stereo VU meter kit BUILD THREAD

Post by Nonsense »

Here are some pictures of the full system. The initial plan was to use the second RCA outputs of the Schiit Saga to drive the VU meters, but it doesnt seem to work well (big noise + pointers not moving much even with trimpot on max).
Feel free to sugest the best way/cables to hook the meter!
Thanks again
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Nonsense
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Re: Stereo VU meter kit BUILD THREAD

Post by Nonsense »

Another question: should I use the 10R resistor on the upper board?
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Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

Nonsense wrote:
Tue Aug 30, 2022 6:08 am
Another question: should I use the 10R resistor on the upper board?
Not fit any resistors or caps to the TRS PCB. When using our 12v power supply it is best to do the 2 x 10R in series with the DC connector and 2200uF cap across the VU2 +/- as this smooths the 12v power heaps as the VU2 draws very little load.

Running from the speaker outs is the best solution if you want the VU meters to follow the volume control up and down and show the room listening level. But usually, VU meters are run before the volume control so they show the audio level coming into the volume control. But if your preamp doesn't have a tape out of line out before the volume this will be hard to do.

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.
Joe :-)
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billface
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Re: Stereo VU meter kit BUILD THREAD

Post by billface »

I've built the VU meter and it seems to be working fine. A few questions though:

1) I've attached a diagram of my interpretation of the PSU noise filter. Would you check I've understood correctly
psuSchem.jpg
2) What does the end of this sentence mean: 'and a 470uF to 2200uF cap across the DC terminals on the VU2 with RC filter all noise out.' Mainly the 'with Rc filter all noise out
3) When calibrating the unit I have taken a -18db 1kHz tone from my DAW to equal 0VU. This seems to have the needle dancing around 0vu for unmastered music which is what I'll using it for most often, but mastered music pins the needles. Will this lead to damage, and have I got my understanding value for digital to analog equivalence correct?
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Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

billface wrote:
Sun Apr 21, 2024 12:18 am
I've built the VU meter and it seems to be working fine. A few questions though:

1) I've attached a diagram of my interpretation of the PSU noise filter. Would you check I've understood correctly psuSchem.jpg
2) What does the end of this sentence mean: 'and a 470uF to 2200uF cap across the DC terminals on the VU2 with RC filter all noise out.' Mainly the 'with Rc filter all noise out
3) When calibrating the unit I have taken a -18db 1kHz tone from my DAW to equal 0VU. This seems to have the needle dancing around 0vu for unmastered music which is what I'll using it for most often, but mastered music pins the needles. Will this lead to damage, and have I got my understanding value for digital to analog equivalence correct?
Your drawing is correct. The RC filter will remove the SMPS noise from getting to the VU buffer. You need to know what the 0dBFS level is in dBu. For 22dBu the -18dBFS will be correct. For mastering these days we often fit a -10dB switch to attenuate the level going into the buffer by 10dB. As Mastering is no longer about averaging 0VU but max compressed level before digital clipping at 0dBFS
Joe :-)
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billface
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Re: Stereo VU meter kit BUILD THREAD

Post by billface »

a -10db switch would probably be useful for me. Where would I fit that and what would it be comprised of? Have you got a circuit diagram?

Cheers

Phil

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Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

billface wrote:
Thu Apr 25, 2024 1:02 am
a -10db switch would probably be useful for me. Where would I fit that and what would it be comprised of? Have you got a circuit diagram?

Cheers

Phil
We set the pcb trimpots to +14dBu = 0VU and then use a DPDT switch to switch a second pair of trimpots across the pcb ones and adjust them for +4dBu = 0VU. Or you can switch in a -10dB U pad on the way into the VU buffer inputs.
Joe :-)
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