# Installing LED/Analog Vu Meter to Front Panel



## zkool448

Hi guys, 

 I've looked at several suggestions and options mentioned here, however I'm kinda just looking for a quick (and cheap), something that does not take a great deal of time and research to build. Sort of like a "Buy it Now" type of solution for simple LED vu meters. 
	

	
	
		
		

		
			





 I'm thinking about including something like this to my next project, and you can see it in action from here. Does it look simple enough to install for a complete novice? (I plan to get it for a Bijou, *if* it would work). Thanks!


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## rshuck

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Hi guys, 

 I've looked at several suggestions and options mentioned here, however I'm kinda just looking for a quick (and cheap), something that does not take a great deal of time and research to build. Sort of like a "Buy it Now" type of solution for simple LED vu meters. 
	

	
	
		
		

		
		
	


	




 I'm thinking about including something like this to my next project, and you can see it in action from here. Does it look simple enough to install for a complete novice? (I plan to get it for a Bijou, *if* it would work). Thanks! 
	

	
	
		
		

		
		
	


	




_

 

Looks simple enough, I don't know why you wouldn't be able to put it in. I am not familiar with the Bijou, but IIRC it's a tube amp. Will you have any DC in the case with it?


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## linuxworks

lm3914 or 15 for bargraph led chip.

 its a one-chip solution.

 radio shack used to sell bargraph led chips (10 segments lined up nicely in a DIP). if you can find those, you can gang them next to each other for 20 segs or 30 or whatever 
	

	
	
		
		

		
		
	


	




 the chips daisy chain, too.


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## rshuck

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_lm3914 or 15 for bargraph led chip.

 its a one-chip solution.

 radio shack used to sell bargraph led chips (10 segments lined up nicely in a DIP). if you can find those, you can gang them next to each other for 20 segs or 30 or whatever 
	

	
	
		
		

		
		
	


	




 the chips daisy chain, too._

 

I hadn't even thought of that... you have given me the awesomest idea ever.


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## zkool448

thanks rshuck, linuxworks 
	

	
	
		
		

		
		
	


	




 Though the lm3914 solution is an option, aside from a datasheet, that requires a tiny board, parts, soldeing and lots of bainwork for me though 
	

	
	
		
		

		
		
	


	




 ..just want to do hookup wires and series power resisors to the ps haha


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## linuxworks

there's almost NO circuit to the 3914 (or 15 for log VU use). I think its 1 or 2 R's and just the leds and the chip!

 come on. you can do that. in your sleep, probably. its really really simple. airwiring will even work.


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## zkool448

haha, it's either I'm already overwhelmed and confused as hell getting everything to sink in as I try to figure out how I'm gonna build the Bijou, so I just want to drop $15 on this and be done with it.

 also, I have to say if i do build one I guarantee it won't resemble or even look half as decent as the one being offered, just leaning towards an "idiot proof" solution 
	

	
	
		
		

		
		
	


	




.


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## linuxworks

dude, here's how simple it is:

Schematics Depot (tm) - LM3914 based battery monitor

 and

LM3915/LM3916 VU Meter

 I'm telling you, you can air-wire it. 

 this is the display chip I was talking about:

Digi-Key - 160-1066-ND (Lite-On Inc - LTA-1000HR)

 they used to sell them at radio shack, years and years ago.

 so now, its just 2 things to connect together. no biggie.


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## zkool448

omg, I cannot possibly screw that up -- now i feel like an idiot 
	

	
	
		
		

		
		
	


	




 thanks man!






 On another note, since I'm currently designing my Bijou front plate I'm researching other vu meters and saw some analog ones <sigh>

 Anyway, I'll post a mock up over at the casework thread and hope to get some opinions/feedback either with LEDs or analog for a vu meters. I'm so set and plan to do everything in my power to get a pair integrated 
	

	
	
		
		

		
		
	


	




 cheers.


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## linuxworks

the red 10-pack bargraph led displays are quite cool when they're a-bouncing 
	

	
	
		
		

		
		
	


	




 I did a few stacked (to get 20 segments) and that was a blast.

 they also take up little room (just a rectangle). mounting can be 'interesting' - but you can deal with that 
	

	
	
		
		

		
		
	


	





 note: on the diagram you showed, they might have left out the current lim resistors. I remember using them when I built this kind of thing. one per segment, in series between the driver (chip) and the led chip thing.


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## linuxworks

and remember, the 14, 15, 16 series varies by linear and log and VU. don't get a 14 by mistake. I'm not entirely sure of the diff of the 15/16 - but if you check the spec sheets I bet you'll see what you need.


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## zkool448

oh great, now you've just planted another bug in my head: spectrum analyzer 

 NOOOOOOOO!!!!


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## mattcalf

http://i21.ebayimg.com/06/i/001/45/bb/364f_1.JPG
 I bought a couple of those and also a surplus of blue LEDs so my next few projects are 'meter' covered. 

 Just gotta choose between them all!


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## akcrusier

I would love a DIY version of the VU meters that are on the front of McIntosh amps. We dont have that many nice stores in Alaska so I heard/saw a McIntosh for the first time today. I think one of those VU meters would look really good on the front of my AMB B24.


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## individual6891

where would you take the signal from without degrading the audio output?


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## linuxworks

I would tap into a buffered side of a signal chain (so that there's plenty of drive to supply both the analog section that follows as well as the 'meter' device).

 you could also have a buffer JUST for the meter. that way you could also adjust its gain (sens).


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## linuxworks

another idea is to use a cpu and an lcd display 
	

	
	
		
		

		
			








 even a 16x2 line display would be enough to have a L/R meter going horiz across the display. the problem is that you can't update the lcd 'really fast' and have it bounce if you use the slow (but cheap and affordable) 16x2 char cell displays. you can, however, average the data as you sense it at one of the a/d pins and update the lcd display every second or two with the new value.

 also, while on the subject, the lm3915 style chip doesn't really do 'peak hold' stuff well. you can't get a really clean display with the 3915 chip unless you front-end it with a sample-hold kind of stage (so that you don't get really fast flicker in the led display).

 by going with the cpu method, you can more easily control the 'look' of the meter, if that's one of your goals.

 (I may work on the lcd VU meter idea, if I get a chance).


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## mattcalf

Quote:


  Originally Posted by *akcrusier* /img/forum/go_quote.gif 
_I think one of those VU meters would look really good on the front of my AMB B24._

 

Pics and details on your build please!


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## zkool448

Neat. Lots of nice options!

  Quote:


  Originally Posted by *individual6891* /img/forum/go_quote.gif 
_where would you take the signal from without degrading the audio output?_

 

BTW, not sure if you guys have seen this post, but Ferrari has had a couple of builds already with analog vu meters and kind enough to share his circuit:


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## amb

McIntosh's analog power meters are indeed nice. They have an extraordinary dynamic range, much more so than the typical "VU" meters that could typically manage only about -20dB to +3dB.

 For a meter to be of practical use (rather than just as visual amusement), 0dB would need to be calibrated to the maximum rated output power of the amp. Let's take the β24 as an example, 0dB would be around 180W into 8 ohms. On a conventional analog "VU" meter, the meter needle would hardly move when the amp is putting out 1.8W, and that's usually already a fair amount of sound pressure level on most speakers. If you crank up the sensitivity of the meters to show movement at low/mid volumes, then the meter would simply peg on the right hand stop when the amp is called upon to deliver more of its power (not to mention that the meter then ceases to "measure" anything meaningful). 

 Notice that the meter on the 1200W monoblock McIntosh MC1.2KW amp, the meter has almost 60dB of range:
McIntosh | Power Amplifiers/Integrated Amplifiers
 Now, THAT meter will show something from _pianissimo_ to _fortissimo_!

 An analog meter like that could only be achieved with a special meter drive circuit that has compressive gain. Not only that, if you have actually seen these meters in action you'll notice that they have a very fast attack time but slow decay. So they are peak-reading meters that could actually register music transients, rather than the ballistics of ordinary VU meters that could only show average levels. I've yet to see any DIY amp with an analog meter that sophisticated (I'd like to be proven wrong, though -- and am especially interested in knowing what meter mechanism is used and what circuit is used to drive it).

 Btw, McIntosh is just one example. Back in the late '70s and early '80s there were a number of commercial amps with comparable analog meters (until LED or fluorescent bar graph meters became popular).

 LED/fluorescent bar graph meters don't have to deal with a mechanical moving mass, so the attack/decay times can be controlled easily with electronics, and the dynamic range issue is also easy if you use the right chip/circuit to drive it (and have enough segments to give adequate resolution). I've built a few power amps with LED meters way back when, but these days I just find that flashing lights distracting.


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## linuxworks

I bet mapping a voltage range to a new non-linear voltage range and also doing peak hold attack stuff is JUST what a small cpu would be good for!

 no circuit needed at all - just the chip and the rest would be firmware.

 you could compress ranges with any scale or algorithm you want.


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## amb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I bet mapping a voltage range to a new non-linear voltage range and also doing peak hold attack stuff is JUST what a small cpu would be good for!_

 

No doubt -- for an electronic display. For an analog meter, a lot of the attack performance will be in the meter mechanism itself. No electronics, cpu or not, is going to force a needle to move faster than it could.

 I contend, though, using a CPU and firmware just for a meter display is overkill in a certain sense. Nevertheless, if you want the display to be accurate at 20KHz then you need to A/D the signal at >40KHz. Assuming we want 60dB of dynamic range, you can see that there is quite a bit of data to be sampled and processed. I haven't done the math, but I have a gut feeling that a little CPU like the Arduino would be insufficient.

 CPUs and digital are good, but some things are easier/better done entirely in the analog domain.


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## linuxworks

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_No doubt -- for an electronic display. For an analog meter, a lot of the attack performance will be in the meter mechanism itself. No electronics, cpu or not, is going to force a needle to move faster than it could._

 

not even if we dedicate a whole b22 board as a meter/needle driver?

 then, the needle will get there even before the command to get there finishes!






  Quote:


 
 I contend, though, using a CPU and firmware just for a meter display is overkill in a certain sense. 
 

I like the ability to place ANY curve you want on there, with no pain and with fast turn-around to see the results. even hot-swappable (user selectable) ranges.

 you could do trick stuff like, if the signal goes below a certain range, you can go into 'expanded scale' mode. nite time listening, as one use-case.

 do I want to see average, peak, rms or just a bunch of needle movement to show the channel is active? all selectable if you go the software route.

  Quote:


 Nevertheless, if you want the display to be accurate at 20KHz then you need to A/D the signal at >40KHz. Assuming we want 60dB of dynamic range, you can see that there is quite a bit of data to be sampled and processed. I haven't done the math, but I have a gut feeling that a little CPU like the Arduino would be insufficient. 
 

I was *never* thinking of sampling *that* much. enough to drive a meter, which would be a fraction of the audio freq. maybe a few hundred samples per second, if even that. I'm not doing DSP, man; I'm just trying to get some needle movement trackage 
	

	
	
		
		

		
		
	


	




 how fast DO you have to change the needle's position in order to make a good VU meter? I'm not sure we can easily define what an ideal VU meter is, anyway; its a meter, afterall, and if you wanted a peak-hold led display you would have asked for that (the OP would have).

 so front-ending a physical meter movement with an arduino class cpu sounds entirely reasonable to me. you get some sampled audio that is smoothed with a cap and read that via the a/d port as fast as you can, then for each reading you apply the mapping (linear or non-linear; probably via some lookup table to make it run faster) and then you come up with a resultant output voltage that gets sent out via another analog pin on the cpu, to the meter movement. and the cpu would do all the 'fades' that are needed (so if the signal suddenly dropped out, the user might want the meter to slowly sink down instead of dropping suddenly. or not - but it would be up to the user to specify).

 the ard. can sample an IR receiver module, for example, and 'follow' its waves (38khz carrier, usually) and be able to find where the transitions are and count bits to decode the raw IR protocol. if the ard can follow an IR stream at this bit level, I bet it can keep up with enough analog sampling and also some transform mapping to a new output voltage, in enough time to keep onlooking humans amused enough


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## linuxworks

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Neat. Lots of nice options!
 BTW, not sure if you guys have seen this post, but Ferrari has had a couple of builds already with analog vu meters and kind enough to share his circuit._

 

that's the kind of thing I'd use as a front-end to the cpu. a rectifier stage, then a cap and then the a/d would tap in here and the meter would be at the other end of the processing/cpu chain.

 want to get fancier? have a switchable C so that you can choose how much sample/hold effect you get. how much you charge the cap and smooth out the analog value, vs having a smaller cap and having a more instantaneous reading style meter.

 again, bringing the cpu into it, I think you could choose a smaller charge cap and just read it more frequently (in the cpu) and have the best of both; be able to react faster to changes but also simulate the smoothing effect via software.


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## amb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I like the ability to place ANY curve you want on there, with no pain and with fast turn-around to see the results. even hot-swappable (user selectable) ranges.
 ...
 I was *never* thinking of sampling *that* much. enough to drive a meter, which would be a fraction of the audio freq. maybe a few hundred samples per second, if even that. I'm not doing DSP, man; I'm just trying to get some needle movement trackage 
	

	
	
		
		

		
		
	


	


_

 

So you want all the bells and whistles, except you neglect (IMHO) the primary function of the meter -- to display the output power (either in watts or a relative dB scale) in an accurate manner? If you only sample the waveform a few hundred times a second, the frequency response of the meter would only be good for bass. Anything in the midrange or treble will be missed entirely. I don't think such a meter is very useful.

  Quote:


 how fast DO you have to change the needle's position in order to make a good VU meter? I'm not sure we can easily define what an ideal VU meter is, anyway; its a meter, afterall, and if you wanted a peak-hold led display you would have asked for that (the OP would have). 
 

Actually there are industry standards governing the ballistics of a VU meter, and it's basically slow and averaging:
VU meter - Wikipedia, the free encyclopedia

 A VU meter will still display high frequencies accurately, as long as the waveform is sustained long enough in time. This is unlike a meter that only samples the waveform a few hundred times a second -- on such a meter the mids and highs are simply lost.

 Now, slow VU meters have their place, but a fast peak-reading one is much more useful as an indicator for amplifier output. Fast transients will not be averaged away, and potential amplifier clipping on such transients can be easily observed. How fast is fast enough? Here again there are industry standards for them. The standard terminology for this type of meter is Peak Program Meter (PPM):
Peak programme meter - Wikipedia, the free encyclopedia

  Quote:


 ... the ard..., I bet it can keep up with enough analog sampling and also some transform mapping to a new output voltage, in enough time to keep onlooking humans amused enough 
	

	
	
		
		

		
		
	


	



 

If amusement is the only criterion, then you win.


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## linuxworks

if you use a sample/hold charge cap, why would you miss ANY frequencies?

 you aren't in the freq domain here, you are simply having the cap do the peak hold for you. that gives you - I think - a lot more breathing room to scan that value for changes and update your meter display.

 in terms of calibration, its just a mapping, a scale factor that you can enter or adjust.


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## linuxworks

just read the wiki for VU:

 "The rise and fall times of the meter are both 300 milliseconds, meaning that if a constant sine wave of amplitude 0 VU is applied suddenly, the meter will take 300 milliseconds to reach the 0 on the scale. It behaves as a full-wave averaging instrument, and is not optimal for measuring peak levels."

 300ms is pretty slow, cpu wise. and they even say its a full wave averaging, so the idea of a bridge and a cap (just like ac to dc) works here.

 and I still believe that if you use a smaller cap than one that would normally give the 300ms time figure, you could still read that stored value in the cap and set ms-level timers to start the climb-up and climb-down from any given value.

 I'd have to play with it for a while 
	

	
	
		
		

		
		
	


	




 but my first idea would be to have an ISR routine that keeps that 300ms timer going (or some fraction of it) and looks at the current measured value and starts to fade it up or down, on each interrupt timer-tick. that would be the realtime synchronous background process. the foreground one (in a polling loop) would just read the value of the cap and note the timestamp that it took the value at, then store that in RAM and go back and do it again, endlessly. I wonder if that approach would work.


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## zkool448

Sorry I can't even paticipate in this conversation, I'm just way in over my head after seeing the complexity just to get one integrated to a panel. My only intent really is to mount a signal meter mostly as visual amusement and for aesthetics reasons. 
	

	
	
		
		

		
		
	


	




 I really appreciate you guys taking the time to give your inputs. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_http://i21.ebayimg.com/06/i/001/45/bb/364f_1.JPG
 I bought a couple of those and also a surplus of blue LEDs so my next few projects are 'meter' covered. _

 

mattcalf, I like the dial on those, do you have plans yet on how you'll implement yours? cheers.


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## mattcalf

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_mattcalf, I like the dial on those, do you have plans yet on how you'll implement yours? cheers.
_

 

No idea, haha and don't plan to implement them for a while sorry. Well I figure it won't be until i can understand the majority of this thread.


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## flecom

i have a bunch of service manuals for my mcintosh gear, some if it is older (2505/2105) and uses a rotary switch to adjust the meter range (-20dB, -10dB, 0dB) but ive got the manual somewhere for my MC4000M that does have the full range meters... probably wouldent be terribly difficult to replicate if you had the right meters


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## zkool448

Thanks flecom. 

 I'm fortunate enough to meet a fellow head-fi'er today who lives in the same city as I do. He's got more electronics skills and enough knowledge than I could ever possibly learn in my lifetime 
	

	
	
		
		

		
			





 Anyway he's actually working on a balanced version of the Bijou, ironically the same amp I'm about to build (but not balanced) once my parts arrive from GlassJar. We discussed the topic of VU meters and coincidentally he had managed to source several VU meter units from overseas that he plans on putting on his his amp projectss, including ones that almost look like the McIntosh's. Long story short, he's going to start working on the design and get some working vu meter installed on our builds.

 Here's a draft of the Bijou case I'm currently designing, and I also included below a photo of the actual dual VU meter that he graciously loaned me today to get its exact dimensions from.

 LED VU meter:





 Analog VU Meter:





 The VU meter:





 We didn't really get into the nitty-gritty deatails too much but it sounds very promising with a very high probability that we can get this thing going (finger crossed)!


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## nullstring

I feel that an LED meter for a tube amp is a bit of a mismatch

 I'd go for the analog meter.

 I plan on putting two in my bijou when I make it


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## zkool448

I agree. LEDs were the original plan, but by the looks of it I belive I'll end up with analog instead.


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## zare

Not exactly like McIntosh..






 BTW, it's little bit bigger the one above ..


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## zkool448

I think those look even better. I can just picture all five tubes uplit with matching blue LEDs, and a blue ring Bulgins


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## mattcalf

New thread with similar stuff here.

This is a good link, not sure if it's been mentioned here yet.

 Just for general info, don't want to make you have to choose between more cool Vu meters zk.


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## kuroguy

ZK, 
 If what you want is an amusingly bouncing needle then just install a 100K pot across the output and tie the meter to the wiper through a series resistor and to ground. Adjust the pot for a sufficiently amusing needle bounce and be done with it. Requires 2 trim pots, 2 resistors, and 2 meters. Couldn't be easier.


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## zare

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_ZK, 
 If what you want is an amusingly bouncing needle then just install a 100K pot across the output and tie the meter to the wiper through a series resistor and to ground. Adjust the pot for a sufficiently amusing needle bounce and be done with it. Requires 2 trim pots, 2 resistors, and 2 meters. Couldn't be easier._

 

That depends what kind of meter it is(DC/AC). All this cheap meters are DC so you'll need rectification. This pdf  is nice read(original link).


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## zare

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_New thread with similar stuff here.

This is a good link, not sure if it's been mentioned here yet.

 Just for general info, don't want to make you have to choose between more cool Vu meters zk. 
	

	
	
		
		

		
		
	


	


_

 

Nice feed. I was looking into making something on those lines with atmel, but more in the line for controlling the pre-amp(plus LED(OLED) VU), but still prefer the look of the classic VU.


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## zkool448

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_That depends what kind of meter it is(DC/AC). All this cheap meters are DC so you'll need rectification. This pdf  is nice read(original link)._

 

Nice article indeed 
	

	
	
		
		

		
		
	


	




 JLM Audio looks to be based in Australia (mattcalf, you should check the neigborhood 
	

	
	
		
		

		
		
	


	




). The nice article was featured on Audio Tech magazine -- a nice read indeed.


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## mattcalf

JLM is smack bang in Brisbane, in the same state as me but still *1,685 km *away. 
	

	
	
		
		

		
		
	


	



 Good to see another Aussie audio store though.


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## CptanPanic

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_dude, here's how simple it is:

Schematics Depot (tm) - LM3914 based battery monitor

 and

LM3915/LM3916 VU Meter

 I'm telling you, you can air-wire it. 

 this is the display chip I was talking about:

Digi-Key - 160-1066-ND (Lite-On Inc - LTA-1000HR)

 they used to sell them at radio shack, years and years ago.

 so now, its just 2 things to connect together. no biggie._

 

For that bargraph display, do they make one that is panel mount? How would you mount that to a case?


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## linuxworks

here's a shot of that bargraph chip being used on a board for debugging:






 I'm displaying 7 bits out of the 10 possible on that display. so I cover up 3 with tape (lol).

 it fits into an IC socket (careful with its pins, though). that socket could be soldered to a board and that board be parallel mounted to the front panel. a rectangle hole could be cut.


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## Alpha 1 Omega

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_McIntosh's analog power meters are indeed nice. They have an extraordinary dynamic range, much more so than the typical "VU" meters that could typically manage only about -20dB to +3dB.

 For a meter to be of practical use (rather than just as visual amusement), 0dB would need to be calibrated to the maximum rated output power of the amp. Let's take the β24 as an example, 0dB would be around 180W into 8 ohms. On a conventional analog "VU" meter, the meter needle would hardly move when the amp is putting out 1.8W, and that's usually already a fair amount of sound pressure level on most speakers. If you crank up the sensitivity of the meters to show movement at low/mid volumes, then the meter would simply peg on the right hand stop when the amp is called upon to deliver more of its power (not to mention that the meter then ceases to "measure" anything meaningful). 

 Notice that the meter on the 1200W monoblock McIntosh MC1.2KW amp, the meter has almost 60dB of range:
McIntosh | Power Amplifiers/Integrated Amplifiers
 Now, THAT meter will show something from pianissimo to fortissimo!

 An analog meter like that could only be achieved with a special meter drive circuit that has compressive gain. Not only that, if you have actually seen these meters in action you'll notice that they have a very fast attack time but slow decay. So they are peak-reading meters that could actually register music transients, rather than the ballistics of ordinary VU meters that could only show average levels. I've yet to see any DIY amp with an analog meter that sophisticated (I'd like to be proven wrong, though -- and am especially interested in knowing what meter mechanism is used and what circuit is used to drive it).

 Btw, McIntosh is just one example. Back in the late '70s and early '80s there were a number of commercial amps with comparable analog meters (until LED or fluorescent bar graph meters became popular).

 LED/fluorescent bar graph meters don't have to deal with a mechanical moving mass, so the attack/decay times can be controlled easily with electronics, and the dynamic range issue is also easy if you use the right chip/circuit to drive it (and have enough segments to give adequate resolution). I've built a few power amps with LED meters way back when, but these days I just find that flashing lights distracting._

 

i would bet it is a new stepping motor like they use in a lot of new car gauges .


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## linuxworks

too easy to front-end a mech meter with a processor and change its curve.

 steppers are more expensive so I doubt they'd waste such mechanics when only sending 'smoothed dc' to a meter is all you'd need.


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## zkool448

Definitely no McIntosh here, but a proudly handmade Bijou case which also has a meter 
	

	
	
		
		

		
			





_(*note feet are not permanently installed)_


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## linuxworks

that works well. blue 'works' there, I think.

 super job.

 the photo also has a soft feel to it. so, good on the photo, too


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## DKJones96

Very clean look, great job!


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## zkool448

I luv it when it 'works' for linuxworks! 
	

	
	
		
		

		
		
	


	




 Thanks Kyle!


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## dbfreak

That turned out excellent! Who sells analog VU meters like that?


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## zkool448

I got the analog VU from a fellow headfi'er here in Toronto (thanks zare). I think these VU's are made by a company called Flashstar in Asia but zare can confirm this. 

_edit_: Just did a google and found this linky (check page 3). cheers.


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## dbfreak

Thanks much!


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## sachu

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Definitely no McIntosh here, but a proudly handmade Bijou case which also has a meter 
	

	
	
		
		

		
		
	


	


_

 

You seriously have outdone yourself Joel. Man I am at a loss for word. Brilliant 
	

	
	
		
		

		
		
	


	




Masterpiece!

 errmmm..what next?...an EHHA to complete the Cavalli audio line up?


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## akcrusier

I know this is a bit off topic but I was wondering where zkool448 sourced those feet? I have been looking all over for some like those at a reasonable price.


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## linuxworks

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I got the analog VU from a fellow headfi'er here in Toronto (thanks zare). I think these VU's are made by a company called Flashstar in Asia but zare can confirm this. 

edit: Just did a google and found this linky (check page 3). cheers.
_

 

we might need a group buy (?). I bet there is going to be a little interest in getting some dual meters like this 
	

	
	
		
		

		
		
	


	




 I wonder if its easier to mount a dual or just mount 2 singles?

 even though its not needed at all, it really does add a touch of something to the front. it fills the front space up and gives interest. I really like it


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## zkool448

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_You seriously have outdone yourself Joel. Man I am at a loss for word. Brilliant 
	

	
	
		
		

		
		
	


	




Masterpiece!

 errmmm..what next?...an EHHA to complete the Cavalli audio line up? 
	

	
	
		
		

		
		
	


	


_

 

lol I'm waiting until after the Colorado meet to hear some impressions between the EHHA vs the Bijou before I make any plans first 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *akcrusier* /img/forum/go_quote.gif 
_I know this is a bit off topic but I was wondering where zkool448 sourced those feet? I have been looking all over for some like those at a reasonable price._

 

The case feet I'm using are quite reasonably priced, I got them off eBay. Here's the link.



  Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_we might need a group buy (?). I bet there is going to be a little interest in getting some dual meters like this 
	

	
	
		
		

		
		
	


	




 I wonder if its easier to mount a dual or just mount 2 singles?

 even though its not needed at all, it really does add a touch of something to the front. it fills the front space up and gives interest. I really like it 
	

	
	
		
		

		
		
	


	


_

 

I'm really glad I installed one on mine. I really like the look of it. They'd go really nice especially if installed on a buffalo32/source of some sort.

 Which is easier? I think mounting either a dual or two single would probably be the same, however the round ones are possibly the easiest.

 I heard from zare that dealing with the meter vendors from overseas was quite a nightmare so a group buy would probably difficult to do.


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## Voodoochile

So much nicer with analog meters than leds, especially with a tube amp.


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## zare

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I heard from zare that dealing with the meter vendors from overseas was quite a nightmare so a group buy would probably difficult to do._

 

Well, did order some samples from here, but communication was poor and the shipping cost is more then the meters. Also they have sent me the wrong once with excuse: we did not have that color in stock. 
 Anyhow, I have some ST-160 and ST475 from here for the F4 and F5 passlabs builds. This company was much better to work with. I might have some extra to share if anyone is interested. 

 Gjorgji


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## shldn

Hi Guys,

 I would like to implement analog vu meters on my power amp front panel and so far i've got Rod Elliott's circuit working satisfactory.

 However if calibrated properly, at normal listening volume the meters will have little to no needle movement as amb says,
  Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_For a meter to be of practical use (rather than just as visual amusement), 0dB would need to be calibrated to the maximum rated output power of the amp. Let's take the β24 as an example, 0dB would be around 180W into 8 ohms. On a conventional analog "VU" meter, the meter needle would hardly move when the amp is putting out 1.8W, and
 that's usually already a fair amount of sound pressure level on most speakers. If you crank up the sensitivity of the meters to show movement at low/mid volumes, then the meter would simply peg on the right hand stop when the amp is called upon to deliver more of its power (not to mention that the meter then ceases to "measure" anything meaningful)._

 

How can i implement something like a toggle switch on the above circuit to switch between vu mode and another mode that just samples the music playing to indicate needle movement for visual amusement. 

 What is required for this, a buffer before the circuit or

  Quote:


  Originally Posted by *amb* 
_An analog meter like that could only be achieved with a special meter drive circuit that has compressive gain._

 

Any links/schematics for this kind of compressive/adaptive gain circuit or something i can adapt to for this purpose? linuxworks has mentioned CPUs, but CPUs and firmware/software is not my forte.


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## amb

shldn, one way to do it is to use a logarithmic amplifier to drive the meters, in order to expand its dynamic range (google "logarithmic amplifier" and you'll find examples and even specialty chips that implement this characteristics), but doing so will render the dial markings on your meter meaningless.

 The other option is to simply have switchable gain characteristics, so that "0dB" would correspond to full power or 1/10th power (or even 1/100th power if you use a 3-position rotary switch), and calibrate each position separately. Sort of like changing gears.


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## shldn

Thanks for the prompt reply amb. I think switchable gain would work for me.


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## nightanole

Any updates on this project? 

 I got na old 1960s analog meter that has nothing to do with audio on its labeling, on the case im using. All i want is eye candy out of it. Just hop around and not affect the audio quality. My main problem is just summing the stereo signal into a mono single for the meter. Or maybe i should just hook it to one channel since its not not sending any useful info...


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