Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: birt on November 29, 2011, 08:17:08 am

Title: using a magic eye as an audio amplifier
Post by: birt on November 29, 2011, 08:17:08 am: i was wondering if it would be possible to use a magic eye tube (like an EM84 for example) as triode gain stage in a guitar amplifier. It is a double triode after all. and would it light up with the amplitude of the signal?
i can't find the characteristics of the triode, probably because nobody really needs them :p
Title: Re: using a magic eye as an audio amplifier
Post by: jjasilli on November 29, 2011, 08:40:31 am: http://www.mif.pg.gda.pl/cgi-bin/vs4.pl (http://www.mif.pg.gda.pl/cgi-bin/vs4.pl)

looks like you might have to plot your own curves.
Title: Re: using a magic eye as an audio amplifier
Post by: HotBluePlates on November 29, 2011, 11:55:44 pm: You'll want to solicit TubeGeek's help.

He built a project amp that uses a magic eye tube (http://www.glacieramps.com/Glacier_Amplification/18_Watt_Magic_Stout.html), with input from this forum several years ago.
Title: Re: using a magic eye as an audio amplifier
Post by: PRR on December 01, 2011, 11:36:38 pm: Yeah, but please don't. Magic-eyes wear out. They aren't making new ones. The radio restorers need them for future restorations.

No, it won't "wiggle" unless badly biased for audio amplification.
Title: Re: using a magic eye as an audio amplifier
Post by: kagliostro on December 02, 2011, 03:27:11 am: Look to this

(http://i81.photobucket.com/albums/j207/merlinblencowe/th_CIMG4628.jpg) (http://s81.photobucket.com/albums/j207/merlinblencowe/?action=view&current=CIMG4628.mp4)

(klick on it)

Kagliostro

p.s.: also if I agree with PRR, the use of one tube in an amp, as level indicator, I think is admissible :icon_biggrin:
Title: Re: using a magic eye as an audio amplifier
Post by: birt on December 02, 2011, 03:50:39 am: Quote from: PRR on December 01, 2011, 11:36:38 pm
Yeah, but please don't. Magic-eyes wear out. They aren't making new ones. The radio restorers need them for future restorations.

No, it won't "wiggle" unless badly biased for audio amplification.

good point.
Title: Re: using a magic eye as an audio amplifier
Post by: kagliostro on August 25, 2012, 01:19:55 pm: An unusual use of a V.F.D. (Vacuum Fluorescent Display)

Quote
VFD's have been used in place of valves/vacuum tubes in order to simulate low-mu triodes

I didn't imagine that this can be done

http://www.eham.net/articles/20809 (http://www.eham.net/articles/20809)

this radio uses V.F.D. instead of normal triodes also for AF section output

(http://www.eham.net/data/articles/20809/tn_VFD-in-action.jpg)

(http://www.eham.net/data/articles/20809/tn_Undercon-6.jpg)

K
Title: Re: using a magic eye as an audio amplifier
Post by: tubeswell on August 25, 2012, 02:16:46 pm: Quote from: HotBluePlates on November 29, 2011, 11:55:44 pm
... TubeGeek's ...

http://www.glacieramps.com/Glacier_Amplification/ (http://www.glacieramps.com/Glacier_Amplification/) ...

Nice website James!
Title: Re: using a magic eye as an audio amplifier
Post by: eleventeen on August 25, 2012, 02:38:44 pm: From the website Kagliostro linked: :icon_biggrin:

(http://i172.photobucket.com/albums/w32/ttm4/preamp.jpg)

Monster single ended amplifier with room to try 50 different preamp types?
Title: Re: using a magic eye as an audio amplifier
Post by: tubeswell on August 25, 2012, 02:42:26 pm: Quote from: eleventeen on August 25, 2012, 02:38:44 pm
From the website Kagliostro linked: :icon_biggrin:

(http://i172.photobucket.com/albums/w32/ttm4/preamp.jpg)

Monster single ended amplifier with room to try 50 different preamp types?

Or Party Hat
Title: Re: using a magic eye as an audio amplifier
Post by: Willabe on August 25, 2012, 03:12:43 pm: Quote from: tubeswell on August 25, 2012, 02:42:26 pm
Or Party Hat

I'm gonna ask Santa to bring me one for Christmas.

Brad :laugh:
Title: Re: using a magic eye as an audio amplifier
Post by: HotBluePlates on August 25, 2012, 03:32:40 pm: 50 miniature tubes bowing to the King tube?
Title: Re: using a magic eye as an audio amplifier
Post by: eleventeen on August 25, 2012, 04:06:34 pm: Those little tubes are all JAN Western Electrics, too. They'd probably be worth a fortune today...even if they were monodes.
Title: Re: using a magic eye as an audio amplifier
Post by: jeff on August 26, 2012, 01:28:14 pm: What's a monode? A light bulb?
Title: Re: using a magic eye as an audio amplifier
Post by: eleventeen on August 26, 2012, 03:05:06 pm: I guess it'd have to be, LOL. I just made it up.
Title: Re: using a magic eye as an audio amplifier
Post by: Ritchie200 on August 28, 2012, 11:26:40 pm: I could mount that array in my HVAC ductwork - it looks like about 50,000 BTU!

Jim
Title: Re: using a magic eye as an audio amplifier
Post by: tubeswell on August 29, 2012, 05:25:45 am: Whatever it is, its from the days when they based the design of widgets around the shape of tubes. All that glass does look pretty.