Dissimilar triodes in CF

[macula56]

I've been thinging about using dissimilar triodes in the CF on my Marshall build and was wondering which would be better. An ECC832 or an ECC823. The 832 is a 12DW7 which has a 12AX7 on pins 1,2,3 and a 12AU7 on pins 6,7,8. The 823 is the opposite. Which one do you guys think would be a better fit?  I have 1 of each so i'm gonna try both. Thanks, JMac.

[tubenit]

ECC832. 

With respect, Tubenit

BTW, I have an ECC823 which is essentially a dyslexic 12DW7.

[macula56]

thanks tubenit. i'm using an 823 in a channel switching amp that uses V1 for the first triodes in the clean and overdrive sides. that way i keep the clean channel as is and drop the overdrive down some in the second channel. i was also thinking about using it in a cascading preamp design i have used before that had way too much gain. or maybe the 832 might be better. experimentation is a wonderful thing.

[SILVERGUN]

I've been thinging about using dissimilar triodes in the CF on my Marshall build and was wondering which would be better. An ECC832 or an ECC823. The 832 is a 12DW7 which has a 12AX7 on pins 1,2,3 and a 12AU7 on pins 6,7,8. The 823 is the opposite. Which one do you guys think would be a better fit?  I have 1 of each so i'm gonna try both. Thanks, JMac.

This is a cool idea that works well....
It depends on how you wired your tube sockets,,,but "ideally", you'll want the DW7 half as the CF triode.

i'm using an 823 in a channel switching amp that uses V1 for the first triodes in the clean and overdrive sides. that way i keep the clean channel as is and drop the overdrive down some in the second channel. i was also thinking about using it in a cascading preamp design i have used before that had way too much gain. or maybe the 832 might be better. experimentation is a wonderful thing.

If you're gonna put it in a stage that was designed for an AX7, you might want to consider changing the bias point so that the AU7 triode isn't limited by the parameters of the AX7 stage. The AU7 gives you the ability to handle a bigger input signal before clipping AND with less resulting output gain, so it can be VERY useful in a cascaded gain preamp.
i.e...A combination of a lower plate resistor value and a higher cathode resistor value will get you in a better place for an AU7......this is a great opportunity to see how the use of load lines can effect the performance of a stage.
If you don't already have it,,,download Merlin's load line plotter to see the effect of different parameters on different triodes at the click of a mouse......very cool. 

http://www.freewebs.com/valvewizard2/LoadLinePlotter.xls

[macula56]

thanks SILVERGUN. which side is the DW7?
as for the other amp, it's a BadCat Cougar and i don't want to modify it because I think I'm gonna sell it, but thanks for the info.

[SILVERGUN]

thanks SILVERGUN. which side is the DW7?

SORRY...I meant to say you'll want the AU7 side as the CF

The 832 is a 12DW7 which has a 12AX7 on pins 1,2,3 and a 12AU7 on pins 6,7,8. The 823 is the opposite. Which one do you guys think would be a better fit?  I have 1 of each so i'm gonna try both. Thanks, JMac.

Here's a link to the JJ variety of these 2 tubes.....it says that the ECC832 version has the 12AX7 triode (system l) on pins 6,7,8 and the 12AU7 triode (system ll) on pins 1,2,3:
http://www.jj-electronic.com/pdf/ECC%20832.pdf

The ECC823 is the opposite and has the 12AX7 triode on pins 1,2,3 and the 12AU7 triode on 6,7,8
So depending on which tube pins on your tube socket you wired for the CF, you'll have to choose the one that matches the pins to your application.


Or just try both, and whichever one sounds better is the winner. 

[macula56]

thanks. i have 1 of each right now and i'm gonna try both as suggested.

[tubeswell]

And with the AU7 triode, you will probably want to consider a different load (than for the AX7 triode). 22k-47k will give you heaps of current and a good signal swing.

[macula56]

i can't believe i got those backwards. the ECC823 is indeed 12AX7 then 12AU7.
you guys are a great source of info. thanks again.

[macula56]

i just put an ECC 823 in the CF of my Plexi project and it definitely changes the sound. sounds warmer to my ears. pretty nice actually.