stupid nOOb question

robert_ross · 02-02-2008, 05:24 PM

Hello

As the title suggests, i have a question that you'll probably all know the answer to. Nevertheless, here it is:

I have an epiphone valve junior, which has an EL84 and a 12AX7. What difference would it make if i changed the EL84 for, say, an EL34? Will it work? Or will it sound awful? Do the numbers mean anything? I'm pretty clueless...

Thanks

Robert

John_H · 02-02-2008, 06:10 PM

Sorry Robert; It won't work. There are plenty of simple mods for that amp though. Before you dive in study some. Here's a good start. Jack Darr Book

Wakculloch · 02-03-2008, 10:32 PM

You'd have to drill the chassis for a larger valve base as the EL34 is an octal, whereas the EL84 is a B9a, and wire that up. Then the heater would probably demand too much current( the EL34 takes 1.5A, the EL84 - 0.76A), so youd need a new mains transformer. Change the Cathode resistor to 330ohms, and do various other tweaks to get it to work properly.
This may sound like i'm taking the piss, but many years ago I did this and ended up with an amp that sounded almost the same as the one I started with.

robert_ross · 02-05-2008, 06:44 PM

Thanks for the info, i think i'm slowly beginning to understand it all.
I do know one thing for sure - i should have payed attention in Physics class!

tubeswell · 02-05-2008, 10:11 PM

Quote:

Originally Posted by John_H

Sorry Robert; It won't work. There are plenty of simple mods for that amp though. Before you dive in study some. Here's a good start. Jack Darr Book

Hiya John H

Ya happen to have the other chapters to that book .pdf'd there by any chance (or a web source for the same)?

(Cain't get anything like them old-timer books in the Southern hemisphere).

Cheers

John_H · 02-05-2008, 10:30 PM

Quote:

Originally Posted by tubeswell

Ya happen to have the other chapters to that book

Sorry; That's all I have.

oahu · 02-11-2008, 11:58 PM

hello.

Quote:

Ya happen to have the other chapters to that book .pdf'd there by any chance (or a web source for the same)?

don't know, if you allready have, but here you can find chapters 1 - 8 as pdf from this book:

http://www.pacificrecone.com/JackDarrBook.html

greetings from vienna...

Chuck_Farlee · 02-12-2008, 12:18 AM

You might want to check out www.sewatt.com

There is a dedicated Valve Junior forum there. You will have to sign up to view the forums, though.

A few of the posters have put in 6L6s, EL34s and one guy even put in a KT88. The Valve Junior's power transformer seems to be capable of supplying current for all the aforementioned tubes.

chuck

tubeswell · 02-12-2008, 12:27 AM

Many Thanks oahu

I love the bit in the Chapter on Customer Complaints where he says:

"You must work on the assumption that the guitar and amplifier were practically distortion-free when new, and try to make them work as well as they did then."

Shows how times have changed.

02-02-2008, 05:24 PM	#1
robert_ross Junior Member Join Date: Feb 2008 Posts: 2	stupid nOOb question Hello As the title suggests, i have a question that you'll probably all know the answer to. Nevertheless, here it is: I have an epiphone valve junior, which has an EL84 and a 12AX7. What difference would it make if i changed the EL84 for, say, an EL34? Will it work? Or will it sound awful? Do the numbers mean anything? I'm pretty clueless... Thanks Robert

02-03-2008, 10:32 PM	#3
Wakculloch Senior Member Join Date: Jan 2008 Location: Galashiels, Scotland Posts: 149	Valve change. You'd have to drill the chassis for a larger valve base as the EL34 is an octal, whereas the EL84 is a B9a, and wire that up. Then the heater would probably demand too much current( the EL34 takes 1.5A, the EL84 - 0.76A), so youd need a new mains transformer. Change the Cathode resistor to 330ohms, and do various other tweaks to get it to work properly. This may sound like i'm taking the piss, but many years ago I did this and ended up with an amp that sounded almost the same as the one I started with.

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02-02-2008, 06:10 PM	#2
John_H Supporting Member Join Date: Jul 2006 Posts: 194	Sorry Robert; It won't work. There are plenty of simple mods for that amp though. Before you dive in study some. Here's a good start. Jack Darr Book

02-05-2008, 06:44 PM	#4
robert_ross Junior Member Join Date: Feb 2008 Posts: 2	Thanks for the info, i think i'm slowly beginning to understand it all. I do know one thing for sure - i should have payed attention in Physics class!

02-12-2008, 12:18 AM	#8
Chuck_Farlee Member Join Date: Oct 2007 Posts: 70	You might want to check out www.sewatt.com There is a dedicated Valve Junior forum there. You will have to sign up to view the forums, though. A few of the posters have put in 6L6s, EL34s and one guy even put in a KT88. The Valve Junior's power transformer seems to be capable of supplying current for all the aforementioned tubes. chuck

02-12-2008, 12:27 AM	#9
tubeswell Supporting Member Join Date: Feb 2007 Location: Wellington NZ Posts: 2,663	Many Thanks oahu I love the bit in the Chapter on Customer Complaints where he says: "You must work on the assumption that the guitar and amplifier were practically distortion-free when new, and try to make them work as well as they did then." Shows how times have changed.

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