PCB/VU buffer and Calrad VUs

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guilhermea
Posts: 3
Joined: Thu May 24, 2012 12:59 am

PCB/VU buffer and Calrad VUs

Post by guilhermea »

Hi, I need advice before I try to use PCBs/VU buffer PCBs with VUs from Calrad
In the specs of that VU , it is mentioned "DiodeBr" - does it mean it has already internal rectifiers ?
Has anybody already used these VUs and know any specific tip for them ?
see at : http://www.calradstore.com/60-133.html
( 60-133, VU Meter, DC resistance: 600W+DiodeBr.+3.9kW/120W )

thanks a lot , Joe !

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Joe Malone
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Re: PCB/VU buffer and Calrad VUs

Post by Joe Malone »

guilhermea wrote:Hi, I need advice before I try to use PCBs/VU buffer PCBs with VUs from Calrad
In the specs of that VU , it is mentioned "DiodeBr" - does it mean it has already internal rectifiers ?
Has anybody already used these VUs and know any specific tip for them ?
see at : http://www.calradstore.com/60-133.html
( 60-133, VU Meter, DC resistance: 600W+DiodeBr.+3.9kW/120W )

thanks a lot , Joe !
Yes Diode bridge means internal rectifier so do both Note 1 and Note 2 from the VU Buffer build thread. See below.

Note 1. When using a meter with internal rectifiers like our Nissei AL29 do the mod shown below to disable the VU buffer rectifier.
Image

Note 2. Since the VU buffer runs on a single power rail it will have a power on voltage jump which will show as a large deflection on the meters pointer.
The size of the pointer deflection varies depending on meter type, voltage used, gain setting. This can be greatly reduced by slowing the rise of the half rail voltage on the VU buffer PCB.
This can be done by either changing the two 3k3 resistors shown below both to 47k or 100k. Or change the 10uF cap shown below to 100uF to 220uF 16v. Or doing Both changes. (VU buffer kits will have 2 extra 47k from Feb 2012)
ImageImage//www
Joe :-)
JLM Audio
Capturing Audio without Injury

guilhermea
Posts: 3
Joined: Thu May 24, 2012 12:59 am

Re: PCB/VU buffer and Calrad VUs

Post by guilhermea »

OK, thanks Joe for valuable information !
I ve alredy mounted the kit , but didnt turn it on because I´m traveling on tour...
I´ll replace the resistors first and experiment .
Any trouble if I use just one 12 V DC source to power 2 circuits in parallel (for both L/R channels)
or I should use 2 separate DC sources, one for each ?

thanks
guilherme.

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Joe Malone
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Posts: 2069
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
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Re: PCB/VU buffer and Calrad VUs

Post by Joe Malone »

guilhermea wrote:OK, thanks Joe for valuable information !
I ve alredy mounted the kit , but didnt turn it on because I´m traveling on tour...
I´ll replace the resistors first and experiment .
Any trouble if I use just one 12 V DC source to power 2 circuits in parallel (for both L/R channels)
or I should use 2 separate DC sources, one for each ?

thanks
guilherme.
One 12v source can run multiple VU Buffers fine as they only draw about 20mA each. It is VU lamps that draw usually 100mA each so add up current wise quickly.
Joe :-)
JLM Audio
Capturing Audio without Injury

guilhermea
Posts: 3
Joined: Thu May 24, 2012 12:59 am

Re: PCB/VU buffer and Calrad VUs

Post by guilhermea »

thanks again for quick responses !
good to have such a follow-up !
have a nice weekend.

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