I've got a pair of VU Meters and would like to connect them to the out of my Honey Badger amp. I have followed the schematic on the eBay seller site (attached) and I see the arrow jump however I don't like that it is not really realistic. Low volume produces very little movement and high volume produces a lot.
What is the best way to connect the VU Meter to speaker out to get decent results? I don't need great precision but I want it to somewhat realistically represent the power out. Right now it is either nothing or a lot.
The meter I got is TN-73 from this eBay listing:
1pc Panel VU Meter TN-73 0dB=0.8VAC size=76x59x41mm & LED lamp NISSEI | eBay
What is the best way to connect the VU Meter to speaker out to get decent results? I don't need great precision but I want it to somewhat realistically represent the power out. Right now it is either nothing or a lot.
The meter I got is TN-73 from this eBay listing:
1pc Panel VU Meter TN-73 0dB=0.8VAC size=76x59x41mm & LED lamp NISSEI | eBay
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Meters of all kinds only sense or read a DC voltage. The way you have it noted in the schematic is that you have no provision for this property. The AC source signal needs to be rectified and then limited by resistors to establish a scale that would refer to the end point of the meter scale known as full scale deflection. This is not to be confused with hitting the peg which is a overload condition and something the meter does not want to have happen a lot. It stresses the meter jewel movement.
Rather than go through all the calculations of making a VU meter which is an average meter, you could consult some amplifiers that have meters that have already done the calculation and designs for you- this would be equivalent to saying why reinvent the wheel?
The reaction type of meter has to do with the damping of the meter drive.. This is usually done by placing a capacitor in parallel with the meter after the diode. The larger the capacitor within reason the more damping or averaging there is to take place. A very small cap would allow for peak meters or dB meters. Keep in mind that this is hard to do to a real fast rate as meters themselves have a damping and are slow to change due to the physics of the movement. This is why some meters also have LED peak indicators to signify when a certain peak level has been hit even though the meter has never reached that position. This is why they are incorporated as the meter can never indicate a +8dB signal transient as the meter ballistics and weighting have not allowed the meter to indicate that. This is why LED meters are better for fast reacting type signal displays.or what is called Peak meters or dB meters.
So basically you tap off a 8 ohm load and take that AC voltage sample and first rectify it so that it is a 1/2 wave AC signal and then limit the current so that it stays withing bounds of the scale and then add weighting to the level ballistics that you desire.
When a meter needle is sitting at -20 Vu the input of a negative going signal as would be applied by a AC signal source can not really be displayed. So 0 Vdc is at -20 Vu and then the 100% reference signal is placed at the 0 Vu or 100% and then the Full scale deflection is placed at the end of the scale indicating in an amplifier the amount of headroom it must have.
Rather than go through all the calculations of making a VU meter which is an average meter, you could consult some amplifiers that have meters that have already done the calculation and designs for you- this would be equivalent to saying why reinvent the wheel?
The reaction type of meter has to do with the damping of the meter drive.. This is usually done by placing a capacitor in parallel with the meter after the diode. The larger the capacitor within reason the more damping or averaging there is to take place. A very small cap would allow for peak meters or dB meters. Keep in mind that this is hard to do to a real fast rate as meters themselves have a damping and are slow to change due to the physics of the movement. This is why some meters also have LED peak indicators to signify when a certain peak level has been hit even though the meter has never reached that position. This is why they are incorporated as the meter can never indicate a +8dB signal transient as the meter ballistics and weighting have not allowed the meter to indicate that. This is why LED meters are better for fast reacting type signal displays.or what is called Peak meters or dB meters.
So basically you tap off a 8 ohm load and take that AC voltage sample and first rectify it so that it is a 1/2 wave AC signal and then limit the current so that it stays withing bounds of the scale and then add weighting to the level ballistics that you desire.
When a meter needle is sitting at -20 Vu the input of a negative going signal as would be applied by a AC signal source can not really be displayed. So 0 Vdc is at -20 Vu and then the 100% reference signal is placed at the 0 Vu or 100% and then the Full scale deflection is placed at the end of the scale indicating in an amplifier the amount of headroom it must have.
It's exactly the scale of a VU meter, an odd thing compared to a test instrument, but an ancient standard in the professional audio world. For a power amp, it'll do little unless the amp is clipping, so something with a more logarithmic scale might be nicer. But, this one is a 100% genuine VU meter!
Or use the dancing LEDs driven by an LM3916.
The datasheet gives a lot of information that will be helpful in deciding whether a VU meter is what you need/want.
Worth looking at the LM3914 (linear) and LM3915 (log) datasheeets.
If one sets the Maximum output voltage level to reach 0dB (just hitting the red) on the meters then at "normal" listening levels where the average power is ~-20dB ref maximum you would have the needle hovering around the -20dB mark.
If you now turn the volume down from that loud setting to a quieter level, the needle will hover around the area BELOW the -20dB mark.
The datasheet gives a lot of information that will be helpful in deciding whether a VU meter is what you need/want.
Worth looking at the LM3914 (linear) and LM3915 (log) datasheeets.
If one sets the Maximum output voltage level to reach 0dB (just hitting the red) on the meters then at "normal" listening levels where the average power is ~-20dB ref maximum you would have the needle hovering around the -20dB mark.
If you now turn the volume down from that loud setting to a quieter level, the needle will hover around the area BELOW the -20dB mark.
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Thread title corrected
You've gotten some strange responses in the thread, let me see it I can make it worse. 
I thought that a VU meter showed 0dB at 1.3 volts, but yours says 0dB at 0.8V. OK, no matter which, your Honey Badger is likely to over drive it in normal use, that's why the voltage divider is used.
I don't know what power supply you are using for your Honey Badger, but let's assume a max output of 30V RMS. That's 50X the voltage needed to get your meter to 0VU. If you divided the amplifier's output voltage by 50, that would place 0VU at your max RMS output, and +3VU at the peaks.
However, it's unlikely that you are using that much output power. Do you really know how much you are using? You could try to set voltage using a test tone. For example, go to the thread listed in my sig line. Download one of the test tones and do the following.
Set your system volume to a normal, or slightly higher than normal level. Play back one of my test tones and dial your voltage divider to -9VU on your meter. That "should" put you in a good range for your normal listening levels, with peaks falling right at +3VU. The peaks may be too brief to see on the needle, but that a good starting level. Hope that helps.
I thought that a VU meter showed 0dB at 1.3 volts, but yours says 0dB at 0.8V. OK, no matter which, your Honey Badger is likely to over drive it in normal use, that's why the voltage divider is used.
I don't know what power supply you are using for your Honey Badger, but let's assume a max output of 30V RMS. That's 50X the voltage needed to get your meter to 0VU. If you divided the amplifier's output voltage by 50, that would place 0VU at your max RMS output, and +3VU at the peaks.
However, it's unlikely that you are using that much output power. Do you really know how much you are using? You could try to set voltage using a test tone. For example, go to the thread listed in my sig line. Download one of the test tones and do the following.
Set your system volume to a normal, or slightly higher than normal level. Play back one of my test tones and dial your voltage divider to -9VU on your meter. That "should" put you in a good range for your normal listening levels, with peaks falling right at +3VU. The peaks may be too brief to see on the needle, but that a good starting level. Hope that helps.
My VU Meter arrow reacts to the amp output when connected directly (as opposite to staying idle). Does this mean my VU Meter has a built in rectifier? I wonder if it is germanium or silicon...
scottjoplin, thank you for sharing the link. I like the PPM concept. I wonder how close the performance is to a driver using logarithmic amplifier (if there is such thing).
scottjoplin, thank you for sharing the link. I like the PPM concept. I wonder how close the performance is to a driver using logarithmic amplifier (if there is such thing).
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What I mean to say is that when volume is low VU meter registers very little movement. As I gradually increase volume it stays at low levels until at some point it goes up fairly quickly. I observe very little gradual increase, which a logarithmic VU scale would imply.
VU meter is a specified standard originally using copper oxide rectifiers and 3.6k source resistance.
VU meter - Wikipedia
View attachment THECOPPEROXIDERECTIFIER.pdf
VU Meter Rectifier History
Google is your friend.
Dan.
VU meter - Wikipedia
View attachment THECOPPEROXIDERECTIFIER.pdf
VU Meter Rectifier History
Google is your friend.
Dan.
You've gotten some strange responses in the thread, let me see it I can make it worse.
I thought that a VU meter showed 0dB at 1.3 volts, but yours says 0dB at 0.8V. OK, no matter which, your Honey Badger is likely to over drive it in normal use, that's why the voltage divider is used.
I don't know what power supply you are using for your Honey Badger, but let's assume a max output of 30V RMS. That's 50X the voltage needed to get your meter to 0VU. If you divided the amplifier's output voltage by 50, that would place 0VU at your max RMS output, and +3VU at the peaks.
However, it's unlikely that you are using that much output power. Do you really know how much you are using? You could try to set voltage using a test tone. For example, go to the thread listed in my sig line. Download one of the test tones and do the following.
Set your system volume to a normal, or slightly higher than normal level. Play back one of my test tones and dial your voltage divider to -9VU on your meter. That "should" put you in a good range for your normal listening levels, with peaks falling right at +3VU. The peaks may be too brief to see on the needle, but that a good starting level. Hope that helps.
Thanks for the link, Pano. It is a very interesting tool. I used it to make some measurements... My 220Hz test tone came up at 20V RMS. My understanding (from reading your thread) is that the peak voltage should be 20 x 4 = 80V RMS, or 113V amplitude. Something doesn't connect - I have +/-67V at the rails. What divider should I use if I follow this test result?
Regardless of the test tool, if I follow the theory my amp can produce 67V or 47V RMS. The VU Meter will be at 0 with 0.78V and at +3dB with 1.1V (confirmed in tests) which means the divider should be around 43x if I want the meter to register +3dB at max output.
Now, if I follow practice, I got the most reasonable results (by just observing the arrow move and playing with the potentiometer pod) with a 14x divider. This would mean that VU meter is at 0 with 11V RMS at the speaker and the peak (+3dB) is with 15.4V RMS.
That's for trying the test. Your 20V reading is surprising, but I don't know your room or speakers. If 20V is what you get from my test tone, then your peaks will be 4X higher (12dB) meaning 80V peak, not RMS. I agree that still doesn't connect. Perhaps try again?
Setting your VU meter at 0 for 11 volts seems more reasonable to me. Remember that most music is recorded at an average level of 14 to 18 dB below peak. If your meter consistently hits +3 on peaks, it should be hovering around -15dB on average. Does it?
Setting your VU meter at 0 for 11 volts seems more reasonable to me. Remember that most music is recorded at an average level of 14 to 18 dB below peak. If your meter consistently hits +3 on peaks, it should be hovering around -15dB on average. Does it?
That is EXACTLY what a half-decent (or genuine) VU meter will do on Real Music.
I have spent many hours babysitting "dead" VU meters, recording live 'classical' performances. Some movements hardly a twitch. However I knew (from rehearsal or headcount) that some passage in the piece would swing the needle near, but not far into, the Red.
A VU meter is to indicate *impending overload*, not listening level. It was developed to monitor the hundreds of amplifiers once used for national radio networks.
You listen to, what? 16-bit audio? That is nominally 96dB min to max. More to the point: you may listen with forte passages down at 65dB SPL (background music) or 105dB SPL (LOUD!), with softer passages 20 to 50 dB lower. So over 40dB range of listening levels. The VU meter really only covers 10dB range. (That -20 is so close to -10.) The VU meter can not possibly cover a full range of listening levels. The best use is to indicate when you are near MAXimum output and should not complain about a little distortion.
The VU meter will NOT register peaks *exactly*. On modern hard-clipping electronics it is a poor guide. It comes from an era when an amp might have 5%THD @ +28dBm, so was worked nearer +8dBm where THD would be 0.5% in most of the loud passages and 1% on the peaks, but an occasional 2% would go unnoticed in live radio. We usually took a 12dB margin for live work. In recording, the same distorted peak would be heard over and over so we took +4dBm for 16dB headroom.
The BBC PPM is also an overload meter but it extends down like 40dB. You can correctly set the ratio of loud to soft within a given program transmitted at maximum level. It will not cover the full range of listener levels.
A compresser is a possible way to get "dance at all levels". This is what a PPM does internally. It has to be a "soft" compressor, not a brick-wall.
Another way is a Log amplifier. It can have a transfer function such as 10dB/Volt. Then 96dB reads as 9.6V, and 10dB reads as 1V. A linear meter will show both appropriately. Many-many digital recorders have similar metering, though with LEDs.
A VU meter "should" have a rectifier, it is in the spec. Yes, popular-price gear often put diodes on the PCB and used a rectifierless meter.
My understanding is that the VU meter is a linear meter with logarithmic scale markings. The numbers thus correspond to what you hear. The needle position does not. This is what it is supposed to do.reedcat said:
The VU meter is not intended to impress your friends, or distract them from the music; it is supposed to warn you when you are getting near clipping, or when you are in danger of disappearing down into the noise. It does this. What you want is something quite different: a meter with a logarithmic response.
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