Ignition Coil Toobe Amplifier

Mark A. Gulbrandsen · 30th January 2007, 02:01 PM

Ok guys.... its a bit hard to start on a cold morning

but .this toobe amp that uses an ignition coil certainly is an odditie in itself.... I wonder how it sounds? BTW: The guy that wrote up this little gem seems to dislike buying NOS toobes from now defunct American manufacturers.... Go figure....

Mark

Zen Mod · 30th January 2007, 02:17 PM

nice article for noobs
besides that-driving anything (besides grid of next toob ) with 12AX7 is same as driving 50 mosfet gates with one 2SJ109.
go figure

lt_texan · 30th January 2007, 02:22 PM

the mains fuse is labeled "optional"

Mark A. Gulbrandsen · 30th January 2007, 03:20 PM

Quote:

the mains fuse is labeled "optional"

Yea... go figure....

qq · 30th January 2007, 04:49 PM

Quote:

BTW: The guy that wrote up this little gem seems to dislike buying NOS toobes from now defunct American manufacturers.... Go figure....

Maybe he didn't want the vast throngs of people trying his project to use up the remaining stock of NOS 12ax7s?

jrevillug · 30th January 2007, 05:36 PM

Quote:

Originally posted by qq

Maybe he didn't want the vast throngs of people trying his project to use up the remaining stock of NOS 12ax7s?

This appears to be a part of an electronics course- there would be no point in spending £££ on a NOS 12ax7 when a current production one will work for the demonstration.

Parafeeding the 'OPT' would appear to be a good, if expensive, idea- no high voltage DC on the speaker terminals.

James

Mark A. Gulbrandsen · 30th January 2007, 06:31 PM

So which coil would work the best...One from a Model-T, one from a Jaguar, or one from a Mercedes?

poynton · 30th January 2007, 06:36 PM

Quote:

Originally posted by Mark A. Gulbrandsen
So which coil would work the best...One from a Model-T, one from a Jaguar, or one from a Mercedes?

No, with a Sovtec tube, only a Lada will provide the correct load.

Andy

Glenn_G · 30th January 2007, 07:41 PM

I have seen discusion of the use of two low voltage transformers back to back to produce the HV on this forum. How do you calculate the amperage on the final 115v?

Dave Cigna · 30th January 2007, 09:07 PM

I've seen this idea somewhere before, but never tried it. I'm sure I have an ignition coil around here somewhere. If I were more motivated I'd measure the inductance and stepdown ratio...

Anyway, it seems to me that the coil is not really hooked up right. As drawn, the speaker voice coil (along with any interconnecting wire) is riding up and down with the plate of the tube. That's a huge common mode signal that serves no purpose and loads the tube with all of the capacitance to earth.

It makes a lot more sense (to me) to put the small section of the winding (the part that the speaker is connected across) at B+ rather than at the plate of the tube. To make the change just swap the plate and B+ connections in the drawing: connect B+ to the '+' terminal on the ignition coil and connect the plate to the center plug.

-- Dave

30th January 2007, 02:01 PM	#1
Mark A. Gulbrandsen diyAudio Member Join Date: Sep 2001 Location: Salt Lake City	Ignition Coil Toobe Amplifier Ok guys.... its a bit hard to start on a cold morning but .this toobe amp that uses an ignition coil certainly is an odditie in itself.... I wonder how it sounds? BTW: The guy that wrote up this little gem seems to dislike buying NOS toobes from now defunct American manufacturers.... Go figure.... Mark __________________ KSA-100 WIKI

30th January 2007, 02:17 PM	#2
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	nice article for noobs besides that-driving anything (besides grid of next toob ) with 12AX7 is same as driving 50 mosfet gates with one 2SJ109. go figure __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

30th January 2007, 06:31 PM	#7
Mark A. Gulbrandsen diyAudio Member Join Date: Sep 2001 Location: Salt Lake City	So which coil would work the best...One from a Model-T, one from a Jaguar, or one from a Mercedes? __________________ KSA-100 WIKI

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30th January 2007, 02:22 PM	#3
lt_texan diyAudio Member Join Date: Mar 2005 Location: NY	the mains fuse is labeled "optional"

30th January 2007, 07:41 PM	#9
Glenn_G diyAudio Member Join Date: Jan 2007	I have seen discusion of the use of two low voltage transformers back to back to produce the HV on this forum. How do you calculate the amperage on the final 115v?

30th January 2007, 09:07 PM	#10
Dave Cigna diyAudio Member Join Date: Oct 2003 Location: Finger Lakes, NY	I've seen this idea somewhere before, but never tried it. I'm sure I have an ignition coil around here somewhere. If I were more motivated I'd measure the inductance and stepdown ratio... Anyway, it seems to me that the coil is not really hooked up right. As drawn, the speaker voice coil (along with any interconnecting wire) is riding up and down with the plate of the tube. That's a huge common mode signal that serves no purpose and loads the tube with all of the capacitance to earth. It makes a lot more sense (to me) to put the small section of the winding (the part that the speaker is connected across) at B+ rather than at the plate of the tube. To make the change just swap the plate and B+ connections in the drawing: connect B+ to the '+' terminal on the ignition coil and connect the plate to the center plug. -- Dave

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