Converting from 6EU7 to 12AX7 ... need a little help.

[sangandongo]

Hi everyone.

As the title suggests, I want to convert an amp with a 6EU7 to a 12AX7. I have a nearly limitless supply of vintage 12AX7s but very few 6EU7s.

I've found the pinouts on tdsl and made a little conversion chart for my own benefit. The one question I have is that the 12AX7's 9th pin is designated as the center heater pin but there's no correlating pin on the 6EU7, so I don't know where to go with that.

Below is the chart I made for myself.



I'm doing this to a '65 Gibson Skylark GA-5T. I have the schematics for that up on my site as well if anyone wants them.

Thanks for any help you can offer, I greatly appreciate it.

[tubeswell]

When running a 12AX7 on a 6.3V heater winding, pins 4 & 5 are tied together on one side of the heater winding, and pin 9 is on the other side of the heater winding. So you need to run one wire from pins 4-5 of the 12AX7 to either pin 1 or pin 2 of the 6EU7, and the other wire from pin 9 of the 12AX7 to the other pin (2 or 1) conversely.

[sangandongo]

So, if I understand you correctly, the correlation would be like this (using the relationship table on my chart). Makes sense to me if that's right.

12ax7 - 6eu7
1 = 6
2 = 5
3 = 4
4,5 = 2
6 = 7
7 = 8
8 = 9
9 = 1

Thanks for the answer so quickly, by the way.

--
John

[tubeswell]

Sounds about right if you've got the pins numbers right. Check here
http://www.triodeel.com/6eu7p1.gif

[Roland]

So, if I understand you correctly, the correlation would be like this (using the relationship table on my chart). Makes sense to me if that's right.

12ax7 - 6eu7
1 = 6
2 = 5
3 = 4
4,5 = 2
6 = 7
7 = 8
8 = 9
9 = 1

Thanks for the answer so quickly, by the way.

--
John

Did this work out for you?

I am contemplating the same thing in a Minuteman GA-20RVT

Your help appreciated in advance.

thanx

[sangandongo]

Yes and no.

The OT was actually dead, so even though I rewired the preamp section for 12AX7, the amp ended up shitting itself anyhow. SO, yes, it worked and sounded great for a few minutes, but the real issue was the output tranny, so I'm going to have to rewire that in later.

--
j.k.