EM84 based VUmeter "lines" don't go to zero

Danko · 17th August 2006, 08:23 PM

Hello!

I have built this circuit:
http://www.jogis-roehrenbude.de/Lese...igeplatine.htm
The problem is, when there's no input signal to the circuit, then there are still lines on the tube.
The lines are a little bit longer than they:
http://www.jogis-roehrenbude.de/Lese...-Foto-EM87.jpg

What could be the problem? Could somebody help me? :-)

EC8010 · 18th August 2006, 03:50 PM

Do remember that "magic eye" tubes are not precision devices. What you're seeing is quite normal...

jane · 18th August 2006, 04:16 PM

Is there any difference if you ground the grid of the magic eyes (e.g. short the 1M2 grid-leak)? If yes, you might try to decrease the value of the grid-leak.

Just my 0.2dB

anatech · 18th August 2006, 04:27 PM

Hi Jane,

Quote:

Just my 0.2dB

I like that!

EC8010 is right Danko. They were only ever meant for rough signal indication. Good luck on your project! It will look really neat.

-Chris

coresta · 18th August 2006, 11:32 PM

Hi! the NIXIE IN13 or 14 bargraphs look more linear . I've been testing one and linearity is

my 0,5 dB

Simpleton · 19th August 2006, 12:04 PM

On my magic eye vu-meter, i simply biase the tube as a grounded cathode, for the fully closed voltage. Works a treat and it's simple! Just about 3 resistors and you're done.

Danko · 20th August 2006, 11:29 AM

Thanks for everyones response!!

If I short the 1.2M resistor, then the signal doesn't get to the tube, so that's not a solution.

I tried to insert a trimm.pot between the cathode and the GND. But when I started to increase the trim.pot's resistance, then lines started to grow longer.

When I turn off the amplifier, the lines are getting longer, when the B+ is decreasing.

Maybe the B+ isn't high enough in my amplifier? Under steady state, when all the tubes are warmed up, the B+ is 320V.

17th August 2006, 08:23 PM	#1
Danko diyAudio Member Join Date: Apr 2004 Location: Hungary	EM84 based VUmeter "lines" don't go to zero Hello! I have built this circuit: http://www.jogis-roehrenbude.de/Lese...igeplatine.htm The problem is, when there's no input signal to the circuit, then there are still lines on the tube. The lines are a little bit longer than they: http://www.jogis-roehrenbude.de/Lese...-Foto-EM87.jpg What could be the problem? Could somebody help me? :-) __________________ Best regards, Danko

18th August 2006, 03:50 PM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Do remember that "magic eye" tubes are not precision devices. What you're seeing is quite normal... __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

18th August 2006, 04:16 PM	#3
jane diyAudio Member Join Date: Jul 2004 Location: Norway	Is there any difference if you ground the grid of the magic eyes (e.g. short the 1M2 grid-leak)? If yes, you might try to decrease the value of the grid-leak. Just my 0.2dB __________________ http://www.veiset.net/

19th August 2006, 12:04 PM	#6
Simpleton diyAudio Member Join Date: Jan 2005 Location: Lisboa	On my magic eye vu-meter, i simply biase the tube as a grounded cathode, for the fully closed voltage. Works a treat and it's simple! Just about 3 resistors and you're done. __________________ "There's something organic about a happy cloud of electrons" - Neutron Bob

20th August 2006, 11:29 AM	#7
Danko diyAudio Member Join Date: Apr 2004 Location: Hungary	Thanks for everyones response!! If I short the 1.2M resistor, then the signal doesn't get to the tube, so that's not a solution. I tried to insert a trimm.pot between the cathode and the GND. But when I started to increase the trim.pot's resistance, then lines started to grow longer. When I turn off the amplifier, the lines are getting longer, when the B+ is decreasing. Maybe the B+ isn't high enough in my amplifier? Under steady state, when all the tubes are warmed up, the B+ is 320V. __________________ Best regards, Danko

18th August 2006, 11:32 PM	#5
coresta diyAudio Member Join Date: Mar 2005 Location: Paris	Hi! the NIXIE IN13 or 14 bargraphs look more linear . I've been testing one and linearity is my 0,5 dB

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