Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Dorrough vu meters for monitoring
Dorrough vu meters for monitoring
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th February 2018, 01:52 PM   #1
jkojic is offline jkojic
diyAudio Member
 
Join Date: Feb 2017
Location: falmouth uk
Default Dorrough vu meters for monitoring

im thinking of purchasing the above-problem is ive never got my head around 0dbfs- im looking at a comparison chart where digital max is +18dbfs

standard dorrough meter goes to = +14db- whats the point- why not +18db like an old mixer?

please help - i know a lot of people confused by this
  Reply With Quote
Old 4th February 2018, 02:04 PM   #2
ticknpop is offline ticknpop  Canada
diyAudio Member
 
Join Date: May 2005
Location: toronto
Dorrough vu meters for monitoring
You can adjust the gain of the Doroughs with the rear trim pots and set it for whatever Odbfs you want. There are also internal trim pots for calibration . And you can replace the feedback resistor on the first opamp if you need even more gain. Depends on the exact board version.
  Reply With Quote
Old 5th February 2018, 02:55 AM   #3
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
Classic "zero VU" level is 1.23V measured on a slow mechanical meter which does not follow speech/music peaks. We added a fudge-factor to allow for the peaks. In AM radio, 10dB was ample: we need a high average level to overcome atmospherics, and occasional clipping is tolerated. Also older technologies clipped softly. In tape recording a clipped peak will be heard many times, 14-16dB was customary lead for "clean" (but tape was often hit harder). In digital, when you use-up all your bits, "dBfs", it clips HARD, so 18dB is often used. Statistics show that zero VU with 18dB headroom will clip only every few years.

Those Dorroughs go to 20dB over a "0 dB" mark chosen to match classic zero VU.
  Reply With Quote
Old 7th February 2018, 09:04 AM   #4
dotneck335 is offline dotneck335  United States
diyAudio Member
 
Join Date: Dec 2012
Quote:
Originally Posted by PRR View Post
In tape recording a clipped peak will be heard many times, 14-16dB was customary lead for "clean" (but tape was often hit harder). In digital, when you use-up all your bits, "dBfs", it clips HARD.
Aaahhh, yes the beauty of good old tape!! I love it!!
  Reply With Quote
Old 10th February 2018, 06:13 PM   #5
cbdb is offline cbdb  Canada
diyAudio Member
 
Join Date: Oct 2008
Location: Vancouver
Quote:
Originally Posted by jkojic View Post
im thinking of purchasing the above-problem is ive never got my head around 0dbfs- im looking at a comparison chart where digital max is +18dbfs

standard dorrough meter goes to = +14db- whats the point- why not +18db like an old mixer?

please help - i know a lot of people confused by this
That chart is wrong or your reading it wrong. 0dbfs is the very max level you can record, you've used up all the bits. It's the last LED on the meter. The nominal level is in VU and is -14dbfs so the last LED on the meter is marked +14db VU The nominal level ( where you want your average level to show on the meter, is -14dbfs. This gives you room for 14db peaks. Or 14db of headroom. Some tape machines in studios are calibrated at -20dbfs for recording where you can have a lot of dynamic range. For mastering music this nominal level has crept up with the loudness wars to as little as -4 dbfs.

What do you want to use the meter for? They are designed for recording and mixing and are not suitable, as many people here believe, for power amp output.
  Reply With Quote
Old 13th February 2018, 10:13 AM   #6
Monte McGuire is offline Monte McGuire
diyAudio Member
 
Join Date: Jul 2013
Dorrough vu meters for monitoring
Some terminology problems here. The definition of dBFS is the level of a digital signal relative to a full scale digital sine wave. So, a full scale digital sine wave will by definition have a level of 0dBFS. A full scale square wave will have a level of around +3dBFS.

So, "+18dbfs" cannot be the level of anything, digital or analog.

What you might be thinking of is a +18dBu analog signal voltage being equivalent to 0dBFS. That would be a calibration equivalence for a DAC or ADC that handles both analog and digital signals. You can pick whatever voltage level you want to be equivalent to full scale, and there are tradeoffs for the various choices. I think +18dBu is a good idea for full scale, but let's not write "+18dBFS"!
  Reply With Quote
Old 13th February 2018, 02:08 PM   #7
dotneck335 is offline dotneck335  United States
diyAudio Member
 
Join Date: Dec 2012
Quote:
Originally Posted by Monte McGuire View Post
Some terminology problems here. The definition of dBFS is the level of a digital signal relative to a full scale digital sine wave. So, a full scale digital sine wave will by definition have a level of 0dBFS. A full scale square wave will have a level of around +3dBFS.
So, "+18dbfs" cannot be the level of anything, digital or analog.
What you might be thinking of is a +18dBu analog signal voltage being equivalent to 0dBFS. That would be a calibration equivalence for a DAC or ADC that handles both analog and digital signals. You can pick whatever voltage level you want to be equivalent to full scale, and there are tradeoffs for the various choices. I think +18dBu is a good idea for full scale, but let's not write "+18dBFS"!
Yeah, that was along the lines I was thinking---0 dbFS is FF---you're out of numbers!
  Reply With Quote

Reply


Dorrough vu meters for monitoringHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Monitoring B1 volume pot value gbuilder Analog Line Level 12 19th March 2017 11:59 PM
A new IC for monitoring tubes gingertube Tubes / Valves 13 20th June 2013 04:24 PM
Do domestic Kwh meters (ordinary electric meters) record reactive power. Mooly Power Supplies 17 30th October 2011 10:18 PM
Monitoring I2 Daryl Digital Source 4 20th July 2006 10:01 AM
Power Monitoring led_zeppelin Solid State 1 22nd April 2004 11:13 AM


New To Site? Need Help?

All times are GMT. The time now is 09:41 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki