VU2 stereo VU buffer kit Build thread

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Re: VU2 stereo VU buffer kit Build thread

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GreenhouseHum wrote:
Wed Jan 25, 2023 6:17 am
Novice Post Incoming :mrgreen:

I am retrofitting two PR&E Radiomixer consoles with modern gear (link to old Radiomixer brochure). https://www.steampoweredradio.com/pdf/p ... 201991.pdf

I purchased two VU buffer kits with the intent of using the original Radiomixer's VU Meter Bridge in conjunction with my existing setup. I've gutted the Radiomixers of all their original parts, except for the VU meter bridges, and I am in need of some assistance.

Below is a link to a photo of the VU meters in question. They are labeled with these markings: SIFAM 1.734V Ext 3K6 NO. 54997/3 -010B S24 I'll also add the photo as an attachment if the link does not load or vise versa.

https://imgur.com/a/6TtK5mb

I am following the build thread to get the JLM VU2 PCB put together, but as a novice I have two questions so far:

1. What type of Power supply should I be utilizing for these two buffers?
2. Do my meters have internal rectifiers?

Best,
GHH John
Ok these meters have internal rectifier so need the VU2 rectifier bypassed as shown at the beginning of this thread. The VU2 has 3k6 resistor already so you can connect directly to the meter with +/-meter wires from the VU2 either way around will work. Any power from 12v - 32vdc @ 30mA will run the VU2 buffer not including any lamp current. Do you know what volts the bulbs are ? And are these meters going into a project that has some power rails already or not ?
Joe :-)
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GreenhouseHum
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Re: VU2 stereo VU buffer kit Build thread

Post by GreenhouseHum »

Got it, so I will bypass the rectifier!

I can connect directly to the meters, but if I connect directly will that power the lamps? In the original design these meters and bulbs were connected to a shared PCB board that then had a four pin connector that connected to the original radiomixer electronics (see attachment #1).

Lamp bulbs are JKL 73's which have the following specs: 1.70 Watts, 14 Volts, 0.12 Amps.

I am flexible when it comes to power solutions. On this meter bridge I will have two VU2 buffers, powering four meters, and then a Raspberry Pi and possibly a TC Electronic Clarity M. I would love to have all of those devices tied to the same power switch. (see attachment #2 for a diagram)

Thank you for your help, I'm going to be placing another order for additional VU2 units here shortly for I have another sidecar to build after I complete this one. Additionally, I found you on Instagram - my handle is @greenhouse_hum if you'd like to see how these turn out. I'll be sure to post photos on here too!

Best,
John
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Re: VU2 stereo VU buffer kit Build thread

Post by Joe Malone »

GreenhouseHum wrote:
Tue Jan 31, 2023 1:22 am
Got it, so I will bypass the rectifier!

I can connect directly to the meters, but if I connect directly will that power the lamps? In the original design these meters and bulbs were connected to a shared PCB board that then had a four pin connector that connected to the original radiomixer electronics (see attachment #1).

Lamp bulbs are JKL 73's which have the following specs: 1.70 Watts, 14 Volts, 0.12 Amps.

I am flexible when it comes to power solutions. On this meter bridge I will have two VU2 buffers, powering four meters, and then a Raspberry Pi and possibly a TC Electronic Clarity M. I would love to have all of those devices tied to the same power switch. (see attachment #2 for a diagram)

Thank you for your help, I'm going to be placing another order for additional VU2 units here shortly for I have another sidecar to build after I complete this one. Additionally, I found you on Instagram - my handle is @greenhouse_hum if you'd like to see how these turn out. I'll be sure to post photos on here too!

Best,
John
Check the 3 x 14v lamps are in parallel which I think they will be? These 14v lamps were made to run on 12v. So fit a wire link to RLamp and then you can wire the +/-Lamp to the 2 pins for the lamps on the original meter pcb and the other +/-meter wires to the other 2 meter pins on the original meter pcb. One 12v power supply of 2A should run the 2 x VU2 buffers and 4 meters and lamps fine. Yes please share on Instagram and here :D 8)
Joe :-)
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vladi
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Re: VU2 stereo VU buffer kit Build thread

Post by vladi »

Hi, i just need some advice with the VU2 stereo buffer.

i build it and tested , and it works perfect with a small radio VU meter so all good.

Then i tried with a new Sifam vu the: SIFAM AUDIO LEVEL METER AL39WF

and it did not work as supposed , after calibrating to show 0 VU i lower 1 db and the meter shows -2
when i lower 2 db it shows -5. not accurate at all.

i have all the diods on the board i did try with only 2 as suggested i the first post and that did not give me enough level.

and was also not accurate.

That to do???

Many TNX Vladi

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Re: VU2 stereo VU buffer kit Build thread

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vladi wrote:
Sun Jun 11, 2023 12:15 am
Hi, i just need some advice with the VU2 stereo buffer.

i build it and tested , and it works perfect with a small radio VU meter so all good.

Then i tried with a new Sifam vu the: SIFAM AUDIO LEVEL METER AL39WF

and it did not work as supposed , after calibrating to show 0 VU i lower 1 db and the meter shows -2
when i lower 2 db it shows -5. not accurate at all.

i have all the diods on the board i did try with only 2 as suggested i the first post and that did not give me enough level.

and was also not accurate.

That to do???

Many TNX Vladi
A AL39WF has the 4 diodes in it so needs none on the VU2 buffer pcb. Just the 4 wire links shown in the first post on this thread

Image
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erhard58
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Re: VU2 stereo VU buffer kit Build thread

Post by erhard58 »

Hi,

could you please tell me which R numbers are the output buffer resistors, I need to reduce the value to increase the calibration range for the VU meters I am using, I assume that is the way to go about it in order to increase the calibration range, thank you.
Also, any chance you coult post the schematic for the VU2 driver. You posted the schematic for the VU Buffer & Peak LED kit, but I cannot find it for this VU2 kit, thank you.

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Re: VU2 stereo VU buffer kit Build thread

Post by Joe Malone »

erhard58 wrote:
Fri Nov 17, 2023 7:10 am
Hi,

could you please tell me which R numbers are the output buffer resistors, I need to reduce the value to increase the calibration range for the VU meters I am using, I assume that is the way to go about it in order to increase the calibration range, thank you.
Also, any chance you could post the schematic for the VU2 driver. You posted the schematic for the VU Buffer & Peak LED kit, but I cannot find it for this VU2 kit, thank you.
R7L & R7R are the 3k3 series resistors with the diode bridge going to the meter. Only reduce these if you have a very low sensitivity meter. The minimum R7 value would be something like 470R. If your meter has a diode bridge built in make sure you disable the one on the VU2.

The VU buffer circuit for the VU2 is the same as VU buffer but instead of 2 x diodes + 2 x 3k3 to make an output diode bridge, the VU2 has 3k3 in series with a full 4 x diode bridge.
Joe :-)
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AALF
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Re: VU2 stereo VU buffer kit Build thread

Post by AALF »

Hi there, awhile back I bought a VU2 board and a pair of sew-160 meters. The purpose to build a case to match with my Technics.
I built the board as per your instructions, everything seem to come on, the meters jump a little when power on, but no movement from audio input (tried multiple sources) I think I messed up my input connections. Currently hooked up to IN+/IN- .
I'd like to included photos but can't figure out how to. (insert image wants a online photo while mine sitting on my drive) Sorry don't post stuff often.
My understanding that the sew-160 need the internal rectifiers to function or maybe I'm wrong on that.
Image

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Re: VU2 stereo VU buffer kit Build thread

Post by Joe Malone »

AALF wrote:
Sat Dec 16, 2023 4:37 am
Hi there, awhile back I bought a VU2 board and a pair of sew-160 meters. The purpose to build a case to match with my Technics.
I built the board as per your instructions, everything seem to come on, the meters jump a little when power on, but no movement from audio input (tried multiple sources) I think I messed up my input connections. Currently hooked up to IN+/IN- .
I'd like to included photos but can't figure out how to. (insert image wants a online photo while mine sitting on my drive) Sorry don't post stuff often.
My understanding that the sew-160 need the internal rectifiers to function or maybe I'm wrong on that.
Image
The VU2 needs the diodes for the bridge rectifier fitted to work with ST-160. You can click attachments below and add the photos so I can check your pcb top and bottom and wiring to the meters
Joe :-)
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AALF
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Re: VU2 stereo VU buffer kit Build thread

Post by AALF »

Attachments? Oh ok, I see it.
I installed a cap on the meters as a buffer, then cut them thinking that was the problem
I can take better pics if you need them
Thanks
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Re: VU2 stereo VU buffer kit Build thread

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AALF wrote:
Sat Dec 16, 2023 11:31 pm
Attachments? Oh ok, I see it.
I installed a cap on the meters as a buffer, then cut them thinking that was the problem
I can take better pics if you need them
Thanks
That all looks fine. What is powering the buffer pcb? Photo of power wiring.

And what is the inputs wired to? Always best to wire input to audio before volume control unless wiring to amp output for watts. Photo of input wiring as I see nothing to the 0v,

How many turns if the 25 turn trimpot have you turned up?
Joe :-)
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AALF
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Re: VU2 stereo VU buffer kit Build thread

Post by AALF »

Hi,sorry for the delay. Was in the middle of typing when the power/internet went out!
The power is 12v connected direct to board via lighted power switch. The board has power, the meters light up and the needles jump a little on power up. The audio input is hooked up to a set of rca plugs. Hooked up to the + and -, the ground has nothing (maybe thats where I went wrong). The board has a 3 wire connection but audio only has 2. I'm missing something.
Tested with Y cable connected to my old ipod.

Thanks
AALF
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Re: VU2 stereo VU buffer kit Build thread

Post by Joe Malone »

AALF wrote:
Wed Dec 20, 2023 9:02 am
Hi,sorry for the delay. Was in the middle of typing when the power/internet went out!
The power is 12v connected direct to board via lighted power switch. The board has power, the meters light up and the needles jump a little on power up. The audio input is hooked up to a set of rca plugs. Hooked up to the + and -, the ground has nothing (maybe thats where I went wrong). The board has a 3 wire connection but audio only has 2. I'm missing something.
Tested with Y cable connected to my old ipod.

Thanks
AALF
You will need to link -in to 0v at the pcb as well since the input device is fully floating. Also the ipad will have to be on basically full output volume.

How many turns of the 25 turn trimpots have you turned up????????
Joe :-)
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AALF
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Re: VU2 stereo VU buffer kit Build thread

Post by AALF »

"You will need to link -in to 0v at the pcb as well since the input device is fully floating. Also the ipad will have to be on basically full output volume.

How many turns of the 25 turn trimpots have you turned up????????"


SO, connect -in to gnd
Trimpots, I think i turned them counterclockwise 5-6 turns. don't where they are at right now.

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Re: VU2 stereo VU buffer kit Build thread

Post by Joe Malone »

AALF wrote:
Wed Dec 20, 2023 12:13 pm
"You will need to link -in to 0v at the pcb as well since the input device is fully floating. Also the ipad will have to be on basically full output volume.

How many turns of the 25 turn trimpots have you turned up????????"


SO, connect -in to gnd
Trimpots, I think i turned them counterclockwise 5-6 turns. don't where they are at right now.
Yes -in to G pad next to it on pcb. Make sure ipad is on close max output and best if you have a 1khz tone recorded at 0dBFS on the ipod to set levels. Or use the free audio test software mentioned at the first page of the forum to output a 1Khz tone from laptop etc
Joe :-)
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