[ProAudio] VU meter permitted overdrive with a sine wave...
bobkatz at digido.com
Fri Jan 29 07:32:25 PST 2021
Thanks, Bill. I've cc'ed your comment to the Pro Audio list.
Not all VUs to my experience incorporate the 3.9k internally. The oldest
Weston meters required you to add an external resistor. I can't remember
if the Sifams incorporate the resistor internally or not.
As a matter of fact, depending on the source impedance, you might want
to be anal about it and decide to use a slightly smaller resistor if the
source impedance is fairly high, as would have been the case in
transformer coupled, older vintage gear, where a 3.6k plus the 300 ohm
source impedance would have been a better match.
But I quibble in today's world, you would use a vu meter driver with
negligibly small output impedance and admittedly a 3.9k ohm.
And who uses VU meters anymore? I have a couple of outboard vintage
pieces of gear with real VUs incorporated!
On 1/28/21 1:12 PM, Bill Whitlock wrote:
> I'll tell you what I know about vintage VU meters: internally, there's
> a series resistor, 3.9 kΩ usually, going to a copper-oxide rectifier
> and then to the meter "movement" coil, which I believe has a
> full-scale sensitivity of about 1 mA. Electrically, even if the
> resistor is only a 1/4 watt type, an input of 31.2 Vrms or +32 dBu
> would do no damage to the electrical parts. I doubt that any
> mechanical damage would occur if the level slowly rose to that level
> and remained indefinitely. But if suddenly or intermittently applied,
> I'd expect that the "slamming" of the needle against the stops might
> bend the needle!
> Bill Whitlock
> Whitlock Consulting
> Ventura, CA
> Office (805) 755-5018
> engineer_bill at verizon.net
> -----Original Message-----
> From: Bob Katz via ProAudio <proaudio at bach.pgm.com>
> To: proaudio at bach.pgm.com <proaudio at bach.pgm.com>
> Sent: Thu, Jan 28, 2021 9:26 am
> Subject: [ProAudio] VU meter permitted overdrive with a sine wave...
> This list has been remarkably silent, but I am very grateful that it's
> around when I have a question to ask AUDIO EXPERTS.
> Who here knows the acceptable rating of a standard mechanical VU meter
> above 0 VU with a sine wave? If I recall correctly, they are designed
> to accept as high as +6 VU or even higher. For example, when doing
> testing of a tape recorder for headroom. It's still ideal to shut off
> the meter, but in some cases that's not possible.
> Thanks and happy New Year!
> If you want good sound on your album, come to Bob Katz 407-831-0233
> DIGITAL DOMAIN MASTERING STUDIO Author: *Mastering Audio* Digital
> Domain Website <https://www.digido.com/> No trees were killed in the
> sending of this message. However a large number of electrons were
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If you want good sound on your album, come to Bob Katz 407-831-0233
DIGITAL DOMAIN MASTERING STUDIO Author: *Mastering Audio* Digital Domain
Website <https://www.digido.com/> No trees were killed in the sending of
this message. However a large number of electrons were terribly
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