Magic Eye Tube Level Meter EM80/6E1P/6BR5

General Tech Discussion - Anything amp-ish goes!

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

User avatar
Michael
Frequent poster
Frequent poster
Posts: 572
Joined: Thu 05/04/06 2:00 am
Location: Charleston
Contact:

Magic Eye Tube Level Meter EM80/6E1P/6BR5

Post by Michael »

Hi Folks,

This is a cross post from AX84, but I know not everyone here lives over there as well, so thought you might appreciate the videos.

I purchased some Russian 6E1P (6BR5/EM80) Magic Eye tubes a while back and have been anxious to build a level meter for my Thick Mary HO.

I've seen one method posted on AX84, but found another one that uses rectified signal and an RC circuit to control dwell that I really liked.

I shot a couple of videos with my Canon G3 camera. Poor quality, but easy to see how it works.

Here is the prototype circuit layout connected to my HO:
http://cvrbo.com/Magic_Eye_Proto.jpg

~~~VIDEO OF MAGIC EYE TUBE~~~
Note that the AVIs below are around 10 megs, so don't even try downloading these with dialup.

Here is a clean cut (which is much more responsive than dirty):
http://cvrbo.com/Clean_Magic_Eye.avi

Here is a dirty cut, which really shows the affects of the sustain:
http://cvrbo.com/Grind_Magic_Eye.avi

This is the website where I found the schematic and short discussion:
http://www.tubes.mynetcologne.de/roehre ... m80_e.html

This is the circuit I used:
http://cvrbo.com/EM80_Schematic.bmp

I know this added another tube to the HO, but my transformer never even got warm (thanks Hammond).

Pulling DC off various filter caps varies the brightness (200 volts is dull, 230 is bright).

Totally cool, especially in the dark!

Best to all,
Mick
0 x

tubegeek
Newbie
Newbie
Posts: 87
Joined: Wed 03/29/06 2:00 am
Location: Unknown
Contact:

Post by tubegeek »

This is great eye candy for an amp! Thanks for sharing.

Can it be installed in any amp?

Do they come in different colors?

Will they affect any other part of an amp's circuitry/tone?

Do you by chance have a pic of it in your amp?

This may be a dumb question...but where does the 200-250V come from on pins 7 and 9 of the tube? Do you need another transformer?
0 x

User avatar
Michael
Frequent poster
Frequent poster
Posts: 572
Joined: Thu 05/04/06 2:00 am
Location: Charleston
Contact:

Post by Michael »

tubegeek wrote:This is great eye candy for an amp! Thanks for sharing.

Can it be installed in any amp?

Do they come in different colors?

Will they affect any other part of an amp's circuitry/tone?

Do you by chance have a pic of it in your amp?

This may be a dumb question...but where does the 200-250V come from on pins 7 and 9 of the tube? Do you need another transformer?
Hi TG,

I've only seen these in green. They were born in the days of green CRTs. Never heard of any other colors. I guess if you added a filter you could get a different color. :D

As far as I know any amp can do this. I've seen it in both PP and SEL. The main thing you need is a signal level of something like 13-25 volts (depending on the specific tube you use) and 200-250 B+. I pulled my high voltage from different filter caps in my power supply section. My High Octane B+ varies from about 228-257 VDC, depending on where I pull it on the filter caps. 228 VDC is great for a dimly-lit room, 248 VDC great for bright light. I use a Hammond PT in my HO, and it has no problem providing heater and power current for this additional tube.

I didn't notice any change in tone whatsoever. We're pulling signal from the output tube anode, so noise isn't a factor. This is going into a very high impedance, so it can't really change much. I welcome better explanations of this.

I haven't installed it in the amp yet. Still testing various versions with different shapes. I may even use one for a gain stage (mu = 15)!

If you have any other questions, shoot me an email.

Best to you,
Michael 8)
0 x

User avatar
allynmey
Verbose poster
Verbose poster
Posts: 1131
Joined: Sat 12/04/04 2:00 am
Location: Dighton, MA USA
Contact:

Post by allynmey »

That is definitely cool looking! 8)
0 x

User avatar
nutxo
Newbie
Newbie
Posts: 49
Joined: Tue 08/01/06 2:00 am
Location: Unknown

Post by nutxo »

I got an em84 telefunken one

Image

Kinda had the same idea
0 x

User avatar
NitroWoman
Occasional poster
Occasional poster
Posts: 490
Joined: Mon 09/26/05 2:00 am
Location: Venus

Post by NitroWoman »

That is just too cool!! 8) I have got to get some of these. Every amp I own needs this mod. :D
0 x
Everything I know I learned by listening to myself talk about things I know nothing about.

User avatar
Dynaflow_Donnie
Frequent poster
Frequent poster
Posts: 986
Joined: Sat 12/31/05 2:00 am
Location: Phoenix, AZ.
Contact:

Post by Dynaflow_Donnie »

Very cool, would be neat to see a socket on a bracket on the front panel like in a marshall style head with a small window for it. Make a nice light show in a dark club. Very neat.

Regards,

Dyna
0 x

User avatar
Michael
Frequent poster
Frequent poster
Posts: 572
Joined: Thu 05/04/06 2:00 am
Location: Charleston
Contact:

Post by Michael »

Dynaflow_Donnie wrote:Very cool, would be neat to see a socket on a bracket on the front panel like in a marshall style head with a small window for it. Make a nice light show in a dark club. Very neat.

Regards,

Dyna
That's what I'm going to do. Probably use a (switchable) dark blue lens filter in front of it, which really looks great.
0 x

User avatar
Michael
Frequent poster
Frequent poster
Posts: 572
Joined: Thu 05/04/06 2:00 am
Location: Charleston
Contact:

EM84, different tube and pin out, same driver circuit...

Post by Michael »

Hello All,

Last night we built the EM80 Vu Meter; tonight, the EM84. The pin out is different. Just moved the clips on the socket for the different pins. Initially changed the resistor between B+ and the amplification triode anode to 100K, but that made the meter indicate half level at idle. Changing back to the 470K brought it down to about an 1/8th inch indication on each end (see the videos below). Didn't try 1 meg, but that might have gotten the idle bars even smaller.

This is the circuit I used (noting that the pins are NOT correct for the EM84):
http://cvrbo.com/EM80_Schematic.bmp

Here is how the pins map out, so you can use the above schematic (which is meant for the EM80) with the EM84:

Pin Out Mapping:

PIN TYPE..........................EM80...EM84
Amplification triode anode..........7......9
Light emitting (target) anode.......9......6
Deflector..........................n/a.....7
Cathode.............................2......3
Grid................................1......1

EM84 Video Clips:
Note that the following video clips are about 4 megs each.

No "hold capacitor" (see schematic above). This resulted in a very nice, almost 3-dimensional, translucent green level meter, with "harmonics" visible inside of the green as it moved with level.

www.charlestonarea.com/no_cap.avi

Large "hold capacitor" (about 0.22uF). This resulted in a crisp level meter, with a bright, uniform greenish-white color and a smoothed response.

www.charlestonarea.com/big_cap.avi

Although not shown, using a smaller 0.022uF hold cap gave me fairly nice clean greenish-white and an extremely snappy, crisp response. This mirrored the tempo of attack very well and also had a nice clean edge and uniform color (almost white, but not quite as white as the large cap version).

I like all three versions and will probably use a switch to change cap values between 0/0.022/0.1uF when installed in my High Octane amp. Having a light sensitive resistor to control B+ would enable us to get bright light in sunny conditions and nicely dimmed under gigging conditions (often almost dark).

Best to all,
Mick

Last edited by Michael on Thu Sep 28, 2006 11:38 am, edited 2 times in total
0 x

Hywelsollis
Newbie
Newbie
Posts: 67
Joined: Thu 11/17/05 2:00 am
Location: Cardiff, Wales, UK

Post by Hywelsollis »

Very cool stuff!

Would it be possible to build a contraption similar to a nixie tube clock with these things? I'm thinking a mini head cab with 5 of these in a row & a mesh/plexi front panel would look great!
0 x

tubegeek
Newbie
Newbie
Posts: 87
Joined: Wed 03/29/06 2:00 am
Location: Unknown
Contact:

Post by tubegeek »

This just looks so kewl I ordered a couple of the em80 tubes to play with!
0 x

teletroy
Occasional poster
Occasional poster
Posts: 356
Joined: Fri 08/20/04 2:00 am
Location: Portland, Or

Post by teletroy »

Just wondering about the heaters, how did you wire them up? I think they are internally connected (paralleled?), and require 6.3 volts??? :S :?:
0 x

User avatar
Michael
Frequent poster
Frequent poster
Posts: 572
Joined: Thu 05/04/06 2:00 am
Location: Charleston
Contact:

Post by Michael »

teletroy wrote:Just wondering about the heaters, how did you wire them up? I think they are internally connected (paralleled?), and require 6.3 volts??? :S :?:
Wire heaters just like an EL84 (pins 4 and 5).
0 x

User avatar
Michael
Frequent poster
Frequent poster
Posts: 572
Joined: Thu 05/04/06 2:00 am
Location: Charleston
Contact:

Post by Michael »

Hywelsollis wrote:Very cool stuff!

Would it be possible to build a contraption similar to a nixie tube clock with these things? I'm thinking a mini head cab with 5 of these in a row & a mesh/plexi front panel would look great!

Hmmm, you CAN do anything, right? :wink:

What do you want to do? Not sure what affect you want, but you could actually put some dropping resistors between each tube's input signal, so the amount of deflection was diminished in each successive tube, or come in from each side with the highest deflection on tube 3 and symetrical reductions on 1,2 and 4,5. So 1 and 5 are 1/3 deflection, 2 and 4 are 4/7s, and tube 3 is full deflection. Keeeeewwwwlllllll. 8)
0 x

teletroy
Occasional poster
Occasional poster
Posts: 356
Joined: Fri 08/20/04 2:00 am
Location: Portland, Or

Post by teletroy »

Michael wrote:
teletroy wrote:Just wondering about the heaters, how did you wire them up? I think they are internally connected (paralleled?), and require 6.3 volts??? :S :?:
Wire heaters just like an EL84 (pins 4 and 5).
DOH! I was thinking about another magic eye that I saw somewhere. I just looked at the data sheet! thanks
0 x

Post Reply