VU BUFFER KIT BUILD THREAD

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Joe Malone
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

For unbalanced signals do you mean tie both the + and - inputs to the signal source, or should one be connected to the source and one to ground?
+in to signal center conductor of unbalanced cable and -in to shield of unbalanced cable.
If using the circuit with a dual PSU, obviously the half-rail biasing is not needed, so R14, R15 and C4 can be discarded, but should R5 be connected to ground or can it be removed as well? (Component numbers taken from http://www.jlmaudio.com/VU%20Buffer%20Circuit.gif)
You can do this "R14, R15 and C4 can be discarded, but should R5 be connected to ground" and remove R9 & R10.

Or only remove R9 & R10 and connect +power rail to +V on VU buffer and -power rail to 0v on VU Buffer with no 0v from the power supply and leave the rails splitting parts.

Main thing to remember is when run this way that the ground plane on the VU buffer is at the -power rail voltage.
Joe :-)
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shoebag_ape
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Re: VU BUFFER KIT BUILD THREAD

Post by shoebag_ape »

OK cool, thanks for the quick reply Joe

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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

1. i would like to add a second trimpot and ON-ON switch to select between 2 calibration level, -18dBFS = 0dBVU (mixing), and -6dBFS = 0dBVU (mastering), where and how should i put the second trimpot and the switch on the schematic?
You would have to switch a second trim pot for the high gain setting across the existing trim pot which would be set for the lowest gain setting.
2. using unbalance connection, are this schematic powerfull enough to drive -18dBFS = 0dBVU calibration?
Yes if you connect the shield of the unbalance signal to the -in on the VU Buffer.
Joe :-)
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blinkerss
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Re: VU BUFFER KIT BUILD THREAD

Post by blinkerss »

thank you Joe for the reply :)
Joe Malone wrote:
1. i would like to add a second trimpot and ON-ON switch to select between 2 calibration level, -18dBFS = 0dBVU (mixing), and -6dBFS = 0dBVU (mastering), where and how should i put the second trimpot and the switch on the schematic?
You would have to switch a second trim pot for the high gain setting across the existing trim pot which would be set for the lowest gain setting.
i attach some schematic modification picture based on you scheme, does this will work?
You do not have the required permissions to view the files attached to this post.

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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

blinkerss wrote:thank you Joe for the reply :)
Joe Malone wrote:
1. i would like to add a second trimpot and ON-ON switch to select between 2 calibration level, -18dBFS = 0dBVU (mixing), and -6dBFS = 0dBVU (mastering), where and how should i put the second trimpot and the switch on the schematic?
You would have to switch a second trim pot for the high gain setting across the existing trim pot which would be set for the lowest gain setting.
i attach some schematic modification picture based on you scheme, does this will work?
That will work fine.
Joe :-)
JLM Audio
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ciscan.81
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Re: VU BUFFER KIT BUILD THREAD

Post by ciscan.81 »

Hi Joe

I am planning to use some VU buffer kits and your small round 34mm meters on a 1290 build and a BA 312-style build.

I am using the 40w 48v PSU. (shared between these two pres and a couple of BA's)

I see the buffer kit can run on 9v-30v. What is the best way to reduce the voltage supplied to the VU buffers/lamps? Trimpots? Series Resisitors?

Also what voltage would be best? 12V so I can run the meter LED's from the buffer power rail?

I got as far as figuring R= V/I, but wasn't sure what figure to use for current...

Thanks again

-W

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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

ciscan.81 wrote:Hi Joe

I am planning to use some VU buffer kits and your small round 34mm meters on a 1290 build and a BA 312-style build.

I am using the 40w 48v PSU. (shared between these two pres and a couple of BA's)

I see the buffer kit can run on 9v-30v. What is the best way to reduce the voltage supplied to the VU buffers/lamps? Trimpots? Series Resisitors?

Also what voltage would be best? 12V so I can run the meter LED's from the buffer power rail?

I got as far as figuring R= V/I, but wasn't sure what figure to use for current...

Thanks again

-W
All that is needed is a 10k resistor from the 48v to each +V in on the buffers will reduce the voltage down for the VU buffer to work fine.

Same goes for each white led backlight for the 34mm meters. 10k from the 48v rail to +led and -led to 0v. Led terminals are the outside ones on the 34mm meter.
Joe :-)
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safety fast
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Re: VU BUFFER KIT BUILD THREAD

Post by safety fast »

Hi Joe,

I'm building an amplifier equiped with your VU buffer kits.

The amp boards are connected to a SMPS power supply (http://connexelectronic.com/product_inf ... r1ltl0e1c7) which has an auxiliary +/-12v output.

For some different VU buffer kits, it's clearly written that the buffer shall be fed by an independant power supply from the Amp.

Do you see any problem to use this aux. output to feed the VU buffers?

Thanks,

Fred

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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

safety fast wrote:Hi Joe,

I'm building an amplifier equiped with your VU buffer kits.

The amp boards are connected to a SMPS power supply (http://connexelectronic.com/product_inf ... r1ltl0e1c7) which has an auxiliary +/-12v output.

For some different VU buffer kits, it's clearly written that the buffer shall be fed by an independant power supply from the Amp.

Do you see any problem to use this aux. output to feed the VU buffers?

Thanks,

Fred
The VU buffer can run on any positive power rail from +12 to +35v. Even higher with a series resistor inline to the +V. It does not need to be isolated.
The aux +12v output and 0v will power it fine. The negative rail is not needed or used for the buffer.
Joe :-)
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safety fast
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Re: VU BUFFER KIT BUILD THREAD

Post by safety fast »

Hi Joe,

Thanks for reply! I'll test it very soon.

beatnik
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Re: VU BUFFER KIT BUILD THREAD

Post by beatnik »

I'd like to use the vu buffer to monitor the ouput of an ssl compressor.

Since it's a stereo unit, and I have space only for one vu-meter, I'm thinking about displaying the L+R sum.

How should I wire and calibrate the vu-buffer?

drabina
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Re: VU BUFFER KIT BUILD THREAD

Post by drabina »

Noob needs help. I have two JLM Audio VU buffer boards and bunch of VU meters that I can use with them. I am just not clear where do I get the signal from. Can I connect the boards to second set of speaker binding posts on my amplifier or the signal has to be taken from the source? If speaker terminals are going to work, can the VU buffers be run together with the speakers off the same terminals (in case of amplifiers that can only run one set of speakers)?

Thanks.

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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

beatnik wrote:I'd like to use the vu buffer to monitor the ouput of an ssl compressor.

Since it's a stereo unit, and I have space only for one vu-meter, I'm thinking about displaying the L+R sum.

How should I wire and calibrate the vu-buffer?
Easy just use 4 x 10k resistors to sum the two balanced outputs together and feed that into the VU buffer PCB input. Send in stereo 1k +4dBM signal to the comp with no makeup or compression and set the VU trimpot so the VU meter shows 0VU.
Joe :-)
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

drabina wrote:Noob needs help. I have two JLM Audio VU buffer boards and bunch of VU meters that I can use with them. I am just not clear where do I get the signal from. Can I connect the boards to second set of speaker binding posts on my amplifier or the signal has to be taken from the source? If speaker terminals are going to work, can the VU buffers be run together with the speakers off the same terminals (in case of amplifiers that can only run one set of speakers)?

Thanks.
You can connect the VU buffer to balanced or unbalanced sources like line level RCA XLR JACKS or Power Amp outputs and adjust the trim pot on the VU buffer to get the correct level on the meter.

The VU buffer is best connected before any output volume control it you do not want the meter to turn up or down with the volume control.
Joe :-)
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bernbrue
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Re: VU BUFFER KIT BUILD THREAD

Post by bernbrue »

Hi Joe,
I've got a few of your vu buffer pcbs stuffed and use them with Sifam R28 VU meters. Since they have built in rectifiers I bypassed the rectifiers on the pcb. Unfortunately I don't get enough gain to set the meters to 0dbu. I tried various resistor value changes but that didn't help. Could you help me to make them work properly?
Regards
Bernd

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