VU2 stereo VU buffer kit Build thread

[AALF]

Thank you for your help.
Still cannot get it working, so going to order new prebuilt board.
That way i can compare and figure things out.
Thank you and Merry Christmas!
AALF

[Joe Malone]

Thank you for your help.
Still cannot get it working, so going to order new prebuilt board.
That way i can compare and figure things out.
Thank you and Merry Christmas!
AALF

First can you measure the voltages on the 8 x TL072 pins measured from Gnd and put them up so we can see if the buffer is working or not.

I also wonder if the 12v power supply designed for led lamp is smooth enough for running the buffer. Usually they have minimum smoothing so have high frequency noise all over the output

[AALF]

Ok
Replaced 12v led power with regular 12v 2A (new) plug-in power pack.
Measured voltages from Vcc-. Vcc+ 12v. All others pins are the same at 6.23v dc. Regardless of hooked input or not.
Think the chip is Kaput.

[Joe Malone]

Ok
Replaced 12v led power with regular 12v 2A (new) plug-in power pack.
Measured voltages from Vcc-. Vcc+ 12v. All others pins are the same at 6.23v dc. Regardless of hooked input or not.
Think the chip is Kaput.

The TL072 should have 12vdc on pin 8 and 0v on pin 4. All other pins should be roughly 6vdc so IC seems to be working ok. Because you are measuring dc you will not see the vac audio signal when connected.

Do you have a better input device as something very simple is wrong. CD player with RCA outputs etc.

What does the soldering under the pcb look like ? Do you have a clear photo of it.

The meter needles bounce upwards for a second when powered up?

[AALF]

The needles do bounce on power up.
And I think your right about the solder job. Been thinking about it these past few days.
Looks good but doesn't mean I missed one or two.
Going to check the RCA jacks also.
Time to retire the old Hako iron I think (20+ years). Bought a weller we-1010 last year, still in the box.
Time to give it a go. With the holidays coming up it might be a few days before I get back to you.

Thanks and Merry Xmas
AALF

[barrykilborn]

Hi Joe. Greetings from the island of Bermuda. Hope you are doing well. Thanks for such a great VU2 board it was a pleasure to build. I am using it to power the VU meters on an old Onkyo M504 power amp. I have replaced the internals with a Purifi Eval1 class D amp (https://purifi-audio.com/shop/eval1-eva ... n-kit-1610).

It all works but the VU meters need a bit more gain I think as they don't move much. I assume the Note 3 from your Notes and Errata is relevant here: "Note 3. If you need more gain change R7L & R7R from 3k3 down to a minimum of 100R. It is also then worth putting a red LED or or 2 x 1N4007 in series across the meter +(Anode) /-(Cathode) terminals to limit & protect the meter in overload conditions. You can also get more gain by changing R9L & R9R from 100R down to minimum of 22R or 10R."

I plan to follow that note. Anything else I need to bear in mind?

Thanks again! Cheers Barry

[Joe Malone]

Hi Joe. Greetings from the island of Bermuda. Hope you are doing well. Thanks for such a great VU2 board it was a pleasure to build. I am using it to power the VU meters on an old Onkyo M504 power amp. I have replaced the internals with a Purifi Eval1 class D amp (https://purifi-audio.com/shop/eval1-eva ... n-kit-1610).

It all works but the VU meters need a bit more gain I think as they don't move much. I assume the Note 3 from your Notes and Errata is relevant here: "Note 3. If you need more gain change R7L & R7R from 3k3 down to a minimum of 100R. It is also then worth putting a red LED or or 2 x 1N4007 in series across the meter +(Anode) /-(Cathode) terminals to limit & protect the meter in overload conditions. You can also get more gain by changing R9L & R9R from 100R down to minimum of 22R or 10R."

I plan to follow that note. Anything else I need to bear in mind?

Thanks again! Cheers Barry

Hi Barry, in an amp setup, you should have too much gain. So definitely shouldn't need to modify for more. Can you send me some photos of the wiring for the vu meters and buffer pcb top and photos of the back of the vu meters you are using. Are you wiring the buffers to the line in or the amp output? etc. So I can get you going correctly

[barrykilborn]

Hi Joe. Greetings from the island of Bermuda. Hope you are doing well. Thanks for such a great VU2 board it was a pleasure to build. I am using it to power the VU meters on an old Onkyo M504 power amp. I have replaced the internals with a Purifi Eval1 class D amp (https://purifi-audio.com/shop/eval1-eva ... n-kit-1610).

It all works but the VU meters need a bit more gain I think as they don't move much. I assume the Note 3 from your Notes and Errata is relevant here: "Note 3. If you need more gain change R7L & R7R from 3k3 down to a minimum of 100R. It is also then worth putting a red LED or or 2 x 1N4007 in series across the meter +(Anode) /-(Cathode) terminals to limit & protect the meter in overload conditions. You can also get more gain by changing R9L & R9R from 100R down to minimum of 22R or 10R."

I plan to follow that note. Anything else I need to bear in mind?

Thanks again! Cheers Barry

Hi Barry, in an amp setup, you should have too much gain. So definitely shouldn't need to modify for more. Can you send me some photos of the wiring for the vu meters and buffer pcb top and photos of the back of the vu meters you are using. Are you wiring the buffers to the line in or the amp output? etc. So I can get you going correctly

Hi Joe,

I hope you are doing well. Huge thanks for taking the time to reply! Sorry for the delayed response I have been travelling for work.

Here is a photo of the top of the VU board: https://www.dropbox.com/scl/fi/8axnoflo ... p2s5f&dl=0

This is all I have at the moment I will take more when I get back home.

Here is a photo from the Purifi manual of the analog input XLR connectors: https://www.dropbox.com/scl/fi/9pc7iqkp ... 7koet&dl=0

I ran wires (GND, +ve, -ve) from these XLR connectors to the corresponding inputs on the VU buffer.

For the outputs I used your '4 pin plugs pre wired'. The yellow cable (M+) goes to the +ve wire of the lamp and the white cable (M-) attaches to the -ve wire of the VU meter. I confirmed (using a battery) the +ve and -ve wires of the VU meter. Since I power the Onkyo Lamps separately from the Hypex SMPS power supply the red and black cables are not connected to anything.

I hope this helps you. Thanks again for the amazing board and the great community here! Cheers! Barry

[Joe Malone]

Hi Joe. Greetings from the island of Bermuda. Hope you are doing well. Thanks for such a great VU2 board it was a pleasure to build. I am using it to power the VU meters on an old Onkyo M504 power amp. I have replaced the internals with a Purifi Eval1 class D amp (https://purifi-audio.com/shop/eval1-eva ... n-kit-1610).

It all works but the VU meters need a bit more gain I think as they don't move much. I assume the Note 3 from your Notes and Errata is relevant here: "Note 3. If you need more gain change R7L & R7R from 3k3 down to a minimum of 100R. It is also then worth putting a red LED or or 2 x 1N4007 in series across the meter +(Anode) /-(Cathode) terminals to limit & protect the meter in overload conditions. You can also get more gain by changing R9L & R9R from 100R down to minimum of 22R or 10R."

I plan to follow that note. Anything else I need to bear in mind?

Thanks again! Cheers Barry

Hi Barry, in an amp setup, you should have too much gain. So definitely shouldn't need to modify for more. Can you send me some photos of the wiring for the vu meters and buffer pcb top and photos of the back of the vu meters you are using. Are you wiring the buffers to the line in or the amp output? etc. So I can get you going correctly

Hi Joe,

I hope you are doing well. Huge thanks for taking the time to reply! Sorry for the delayed response I have been travelling for work.

Here is a photo of the top of the VU board: https://www.dropbox.com/scl/fi/8axnoflo ... p2s5f&dl=0

This is all I have at the moment I will take more when I get back home.

Here is a photo from the Purifi manual of the analog input XLR connectors: https://www.dropbox.com/scl/fi/9pc7iqkp ... 7koet&dl=0

I ran wires (GND, +ve, -ve) from these XLR connectors to the corresponding inputs on the VU buffer.

For the outputs I used your '4 pin plugs pre wired'. The yellow cable (M+) goes to the +ve wire of the lamp and the white cable (M-) attaches to the -ve wire of the VU meter. I confirmed (using a battery) the +ve and -ve wires of the VU meter. Since I power the Onkyo Lamps separately from the Hypex SMPS power supply the red and black cables are not connected to anything.

I hope this helps you. Thanks again for the amazing board and the great community here! Cheers! Barry

HI Barry besides looking like the right side 10uF has been fitted with a 100uF which will still work that looks fine.

Looking at the original Onkyo circuit that drove the the meters they are very insensitive volt type meters with internal bridge I guess as they are driven with ac. So to start with short out R7L & R7R with something like 100R to get more drive into the meters and let me know if you now get more level out of the meters and if you need more gain or not?

Onkyo M-504 meters.png

[barrykilborn]

Hi Barry, in an amp setup, you should have too much gain. So definitely shouldn't need to modify for more. Can you send me some photos of the wiring for the vu meters and buffer pcb top and photos of the back of the vu meters you are using. Are you wiring the buffers to the line in or the amp output? etc. So I can get you going correctly

Hi Joe,

I hope you are doing well. Huge thanks for taking the time to reply! Sorry for the delayed response I have been travelling for work.

Here is a photo of the top of the VU board: https://www.dropbox.com/scl/fi/8axnoflo ... p2s5f&dl=0

This is all I have at the moment I will take more when I get back home.

Here is a photo from the Purifi manual of the analog input XLR connectors: https://www.dropbox.com/scl/fi/9pc7iqkp ... 7koet&dl=0

I ran wires (GND, +ve, -ve) from these XLR connectors to the corresponding inputs on the VU buffer.

For the outputs I used your '4 pin plugs pre wired'. The yellow cable (M+) goes to the +ve wire of the lamp and the white cable (M-) attaches to the -ve wire of the VU meter. I confirmed (using a battery) the +ve and -ve wires of the VU meter. Since I power the Onkyo Lamps separately from the Hypex SMPS power supply the red and black cables are not connected to anything.

I hope this helps you. Thanks again for the amazing board and the great community here! Cheers! Barry

HI Barry besides looking like the right side 10uF has been fitted with a 100uF which will still work that looks fine.

Looking at the original Onkyo circuit that drove the the meters they are very insensitive volt type meters with internal bridge I guess as they are driven with ac. So to start with short out R7L & R7R with something like 100R to get more drive into the meters and let me know if you now get more level out of the meters and if you need more gain or not?

Onkyo M-504 meters.png

Hi Joe. Thanks for the reply and the useful information. I can't wait to give it a try when I get home. Really appreciate everything you do. Have a good weekend! Barry