VU BUFFER KIT BUILD THREAD

Support for JLM Audio Kits

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spreadspell
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Joined: Sat Jan 15, 2011 6:42 am

Re: VU BUFFER KIT BUILD THREAD

Post by spreadspell »

Hello and happy new year to all!
this is my first post. I bought some "smart" kits from JLM, nice work!
I have one question please: Can i use one VU Buffer kit for 2 VU meters?
because is very dificullt to wait one more month to receive the kit!

thanks, best
George A. / Greece

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Joe Malone
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

spreadspell wrote:Hello and happy new year to all!
this is my first post. I bought some "smart" kits from JLM, nice work!
I have one question please: Can i use one VU Buffer kit for 2 VU meters?
If you want to show the same mono signal in 2 different places with the same type of VU meters you can run 2 meters in parellel then YES

But if you want to show a stereo signal on stereo VU meters then NO you will need 2 buffer kits for stereo.
Joe :-)
JLM Audio
Capturing Audio without Injury

spreadspell
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Joined: Sat Jan 15, 2011 6:42 am

Re: VU BUFFER KIT BUILD THREAD

Post by spreadspell »

If you want to show the same mono signal in 2 different places with the same type of VU meters you can run 2 meters in parellel then YES
But if you want to show a stereo signal on stereo VU meters then NO you will need 2 buffer kits for stereo.
OK, i must order one more, because i'm using a pair of Telefunken line amp modules and need 2 different meters.
thanks.

George A. / Greece

guyo
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Joined: Sat May 14, 2011 8:05 am

Re: VU BUFFER KIT BUILD THREAD

Post by guyo »

I have breadboarded this circuit, twice, but cannot seem to get any meter movement unless I place my audio line source (line output of a tape deck/also tried headphone output of mp3 player) directly into the +/- inputs of the opamp. I am using a 34mm meter (I beleive it to be 500uA). Anyways, not sure what to try next. Any suggestions?

Thanks!

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Joe Malone
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

guyo wrote:I have breadboarded this circuit, twice, but cannot seem to get any meter movement unless I place my audio line source (line output of a tape deck/also tried headphone output of mp3 player) directly into the +/- inputs of the opamp. I am using a 34mm meter (I beleive it to be 500uA). Anyways, not sure what to try next. Any suggestions?

Thanks!
There is a 1000+ of these out in the world now in everything from Radio and TV stations to recording and home studios. So the circuit is definitely correct and works.

So it will be most likely a mistake in your breadboarding layout I suspect as it is a messy circuit to layout on breadboard. Breadboard layouts are to hard to check by the normal email a photo method so I cannot really help you there.

The 500uA meter will be fine as the circuit can drive meters up to about 10mA.

Feeding a out of phase audio signal direct into the opamp +/-inputs is a good way to damage a lot of opamps as it can cause the internal input protection diodes to go short circuit.

Sounds like buying our VU buffer PCB would have saved a lot of time and money.
Joe :-)
JLM Audio
Capturing Audio without Injury

guyo
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Re: VU BUFFER KIT BUILD THREAD

Post by guyo »

Yes, I have no doubt your circuit is good!

I just wanted to throw one together quickly to play with, and thought/hoped you may know off hand what I did wrong based on my symptoms.

I had intentions to order some of your PCBs and actually ordered them today.

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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

guyo wrote:Yes, I have no doubt your circuit is good!
8)
I just wanted to throw one together quickly to play with, and thought/hoped you may know off hand what I did wrong based on my symptoms.
Yep that is fine. But since it is not working at all it is hard to work out what is wrong as there are to many options. if you think you have the circuit correct defintely check diodes are the correct way around and that power is getting to pin 7 of the opamp and pin 6 is sitting about 1/2volts of the power rail to prove the opamp is working.
I had intentions to order some of your PCBs and actually ordered them today.
Cool 8)
Joe :-)
JLM Audio
Capturing Audio without Injury

kante1603
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Joined: Wed Jan 20, 2010 6:12 pm

Re: VU BUFFER KIT BUILD THREAD

Post by kante1603 »

guyo wrote:Yes, I have no doubt your circuit is good!

I just wanted to throw one together quickly to play with, and thought/hoped you may know off hand what I did wrong based on my symptoms.

I had intentions to order some of your PCBs and actually ordered them today.
It´s worth it-no doubt!
Here´s a "teaser":
Front solo 2.JPG
Cheers,

Udo.
You do not have the required permissions to view the files attached to this post.

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Joe Malone
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

Nice. You have a small factory of custom gear on the go all at once there Udo.
Joe :-)
JLM Audio
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kante1603
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Re: VU BUFFER KIT BUILD THREAD

Post by kante1603 »

Joe Malone wrote:Nice. You have a small factory of custom gear on the go all at once there Udo.
Hahaha...not really,but I went into diy about 2 years ago,got "triggered"/infected and started way too many projects I was dreaming of :lol:
Now they show up piece by piece-the panel I posted is about 1 year old,and I think some of the gear/the "bigger" projects will be finished during my summer holiday.
Most of this is not only for me and my ego but mainly to "pimp" one of our small studios at which I work a lot with my students,some parts are for live sound reinforcement in our theatre.
Budgets get lower year by year so I decided to build as much as I can by myself-and everybody here is really lucky with it and I can teach my students a lot about studios,speaking and singing.
JLM parts and -kits absolutely do help me to achieve this.
So-yes, a lot of things I do at once but no-no factory here,just some tools, a good soldering-station,my kitchen table,my ears and me :wink:

Have a good time,

Udo.

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Joe Malone
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

kante1603 wrote:
Joe Malone wrote:Nice. You have a small factory of custom gear on the go all at once there Udo.
Hahaha...not really,but I went into diy about 2 years ago,got "triggered"/infected and started way too many projects I was dreaming of :lol:
Now they show up piece by piece-the panel I posted is about 1 year old,and I think some of the gear/the "bigger" projects will be finished during my summer holiday.
Most of this is not only for me and my ego but mainly to "pimp" one of our small studios at which I work a lot with my students,some parts are for live sound reinforcement in our theatre.
Budgets get lower year by year so I decided to build as much as I can by myself-and everybody here is really lucky with it and I can teach my students a lot about studios,speaking and singing.
JLM parts and -kits absolutely do help me to achieve this.
So-yes, a lot of things I do at once but no-no factory here,just some tools, a good soldering-station,my kitchen table,my ears and me :wink:

Have a good time,

Udo.
Cool. I always have to many projects on the go at one time and I think it has been the same for a few decades now so not likely to change now :D 8)
Joe :-)
JLM Audio
Capturing Audio without Injury

rooster21
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Joined: Sat Mar 03, 2012 4:23 pm

Re: VU BUFFER KIT BUILD THREAD

Post by rooster21 »

Is the capacitor between the +/- on the VU`s to reduce defeletion time possible on other meters, or is it only possible on the Flashstar VU?

I tried it on the Simpson meter that I own and I had lost all movement. I used the same value cap, except for the voltage rating (which was higher).

Any info would be appreciated.

Thanks
GdS

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Joe Malone
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Re: VU BUFFER KIT BUILD THREAD

Post by Joe Malone »

rooster21 wrote:Is the capacitor between the +/- on the VU`s to reduce defeletion time possible on other meters, or is it only possible on the Flashstar VU?

I tried it on the Simpson meter that I own and I had lost all movement. I used the same value cap, except for the voltage rating (which was higher).

Any info would be appreciated.

Thanks
GdS
Yes this cap slows fast meters down to the 300mS attack and release like a real VU meter movement. You can prove if the meter is to fast by putting a 1k tone in and adjust for 0VU on the meter then switch the tone off and on. If the meter shows more than +1dB when the tone is first turned on a cap needs to be added to damp the meter so it only goes to +1dB. This cap will not stop any meter showing a tone.

The only thing that would stop the meter would be a short between PCB meter +/- terminals.
Joe :-)
JLM Audio
Capturing Audio without Injury

blinkerss
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Joined: Sun Mar 18, 2012 3:18 pm

Re: VU BUFFER KIT BUILD THREAD

Post by blinkerss »

Hi Joe

i would like to try to build from scratch my own stereo VU meter using this schematic, but theres some question in my head :

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?

2. using unbalance connection, are this schematic powerfull enough to drive -18dBFS = 0dBVU calibration?

thank you so much Joe :D

shoebag_ape
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Joined: Tue Feb 21, 2012 8:27 am

Re: VU BUFFER KIT BUILD THREAD

Post by shoebag_ape »

Joe Malone wrote:
bassivus wrote:Hi,

first I would like to thank you for the nice VU buffer schematics. I saw it searching for something that I could use on home preamp with some old Grundig VU meters from tape machine. I have test build it on the piece of proto board. It works, but since I don't use it on balanced signal I can not adjust it to show useful levels of signal. The VU needle jumps like crazy. Can you give me some hints?
The circuit works perfect for balanced and unbalanced signal and has enough gain range for even the lowest level signals. Make sure you feed the unbalanced signal into the +/- in and if runing on a floating power supply sometimes you may need to join -in to 0v. Remember a lot of cheap meters need a extra damping 100uF across there terminals.
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?

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)

Thanks

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