VU meter buffer

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Brian Roth

Well-known member
Joined
Aug 20, 2005
Messages
3,184
Location
Salina Kansas
Recently on one of the boards that I frequent, someone mentioned a "universal" meter buffer circuit board made by someone in the LA area (if my memory is correct). However, my searches here failed to find that message. I am in need of at least six for some Sifam meters on a Neve 51 series desk. Thanks!

Bri
 
Brian, Do you know what model meter it is?

I have some that can be used with a couple of different terminal spacings, is that the "universal" part?
 
While I have a proven circuit in-hand, the few times I've built it was on perfboard. In this situation with 6 meters, I thought it might be wise to find an existing solution with a printed circuit board that can be mounted on the rear of the meters.

The Sifams appear to be a model number I-734V with the audiol input studs on 1" centers.


Bri
 
This is what I use. I use the LM358 for single supply or
you can use a TL072 for bipolar supplies. It features a cal
pot for zeroing the meter and lamp supply connections
for lighting. The only problem I see is the stud spacing.
These are 1.375" I don't have a schematic readly available
but I can export one out if your interested.
PM me if this will help you out.
vudriver.jpg


RonL
 
Nice looking board...wish it has 1" stud centers.

In another thread here, I posted a link to the circuit I've used in the past for 1 or 2 "off" applications:

http://www.brianroth.com/library/vu-buffer.pdf

but built on perfboard. Because of the quantity (at least six), I began digging through the message board I regularly read to find an older message about a "universal" PC card (ie, mounting holes to accomodate various meters) and came up blank.

Bri

EDIT...corrected the URL to my meter buffer.
 
Nice looking board...wish it has 1" stud centers.

In another thread here, I posted a link to the circuit I've used in the past for 1 or 2 "off" applications:

http://www.brianroth.com/library/vu-buffer.pdf

but built on perfboard. Because of the quantity (at least six), I began digging through the message board I regularly read to find an older message about a "universal" PC card (ie, mounting holes to accomodate various meters) and came up blank.

Bri
 
Hi Brian,

If you are still looking for a VU driver I may be able to help.
I have a card designed for the Sifam R22 style meter. Studs are on 1 inch centres, and the card is circular so that it can be mounted, tested and aligned prior to the meter being installed in a panel.

I don't have any photos at the moment - the cards are at work, and I am at home, but I could take photos in the morning and e-mail them to you. In the meantime, I could e-mail a PDF of the component ident if this would be of interest?
 
Gareth, that would be an interesting thing to have here! If not too much trouble...sure...email be anything that you have...my contact info is on my website, listed in my "sig" line, below.

Because of the many headaches I have facing me on this Neve 51 desk, I was trying to find the source I'd seen mentioned of a pre-made card for VU buffering vs. "rolling my own" yet again.

Thanks!

Bri
 
Gareth,

I wouldn't mind having a few boards for Sifam meters. I am purchasing two AL20SQ meters from sifam for my seventh circle N72's. Do you knoe if the circuit would work with these pre's?

What is the cost of the boards?
email me....

bob at virteckDOTcom

Thanks in advance,

Bob
 
Can't access that site. Requires membership. When pressing the Guest button it just reloads.

I'm also looking for meter buffer boards and info, for Sifam meters and others. :?:
 
Hi Tommy,

Not sure about that login problem you're having.
Maybe if you just go to the mainpage, login as a guest and go to the "How do you do that?" forum.

It was quite an interesting discourse.

Also, check your cookie settings are correct, perhaps even flush them out in your browser settings.
 
[quote author="tommypiper"]Can't access that site. Requires membership. When pressing the Guest button it just reloads.

I'm also looking for meter buffer boards and info, for Sifam meters and others. :?:[/quote]
Yep - happened to me - so I logged in as guest and then did a search on VU meter and looked at the threads
 
I'm on a Mac, so maybe it didn't like me. :?

So with another browser on my Mac (Safari) I successfully got logged in as a guest. But a "VU Meter" search didn't bring up anything with buffers in it, at least in the subject.

What was the name of the discussion? That may help me find it.

Anyway, why don't you tell us what it's about instead of just saying you'll find it interesting. Could save us a lot of time looking for needles in haystacks like this.
 
As I said, it's in the "How Do You Do That?" area.
It's the 2nd latest post, entitled "Calibrating VU meters"

As for content, it's not a specific match for the original post, but does bring up something very important that hasn't been addressed in this thread - the use of a 3k6 series resistor to maintain conformity to the VU standard.

Has anyone here heard of a guy named Bob Katz? ..... ;)
 
The series R IS indeed important to make the meter's ballistics correct.

Somewhere I should have a link to an article that Jay McKnight wrote on the topic...somewhere on the MRL website.

Bri
 
Brian,

I recently built your version of the balanced vu meter buffer for a single supply.

http://www.brianroth.com/library/vu-buffer.pdf

It drives the meter just fine but I have one problem. When the power is turned on or off, the meter slams to full scale until the output cap (100uf) discharges. Did you have this issue with your build? Since this is for a vacuum tube preamp, I'm probably going to build a delayed relay circuit to disconnect audio from outputs (disconnect meter also) until the unit is warmed up. It will also disconnect on power down.

I'd assume the JLM circuit may do the same running single supply. Am I missing something here?

Regards,
Jeff
 
mediatech,


Yep, I'm using the split rail version. This puts both opamps sitting at half the rail and this is the problem. I don't want to build a bipolar just to run the meter buffer!

Regards,
Jeff
 
mediatech,

I thought about all that. I'm splitting a +24v rail so I increased the rail split resistors to 3.3k. If I connect the meter to the "split point" the 50ua for full scale meter movement does create a shifting split point (about 165mv). This may not be an issue for a VU set up for the 300ms response. I'll first try reducing the output coupling cap to 10uf and see what happens!

regards,
Jeff
 
Back
Top