plexichamp schematic plate driven output valve

[jackplug1]

May I run this by any of the experts on this site just to see if it's okay or if there is any errors or improvements to be made
All it is a simple plexi preamp whereby the tone stack feeds the grid of half a 12ax7 which drives the 6v6 SE
I'm sure it has been done before but I haven't seen a schematic.
It also has a variable voltage controller board.

[sluckey]

Looks doable to me, but node D should be moved to the other side of that 20K. As drawn, node D is effectively connected to the reservoir caps and there will be several volts of ripple at that point. Not good for a preamp supply.

[66Strat]

Nice project.

[jackplug1]

Makes sense, I will change that.
Does it matter that the DC coupled cathode follower before the tone stack is split between two different triodes tubes and does not share the same valve base?

[sluckey]

Makes sense, I will change that.
Does it matter that the DC coupled cathode follower before the tone stack is split between two different triodes tubes and does not share the same valve base?

no

[tubenit]

I'm sure it has been done before but I haven't seen a schematic.

I did something somewhat similar (but not the same)  and called it a Carolina Songbird. The owner likes the amp alot and I was asked to build a 2nd one for someone else but declined.

Soundclip for it is here:  https://soundclick.com/r/s86rcl

With respect, Tubenit

[jordan86]

I also did a similar thing, if you can decipher my mangled schematic. It’s basically two parallel stages (ala Plexi) into a single ended power section. Started as more of a cascaded JCM800 type pre, more complex setup than yours probably. Was an AX84 build. I run a Kt66 now. KT66’s have a warmth that very flattering to the SE nature of the amp. And I’ve tried a TON of tubes. Hope some of this is helpful.

https://el34world.com/Forum/index.php?action=dlattach;topic=27645.0;attach=92382;image

[jackplug1]

I did eventually find a schematic along the lines of what I proposed called a "seplex" in addition it has NFB, presence control and the master volume just before the output tube.
I don't understand why the HT is connected to the center of the pre-amp filaments?

https://chasingtone.com/the-seplex/

[Willabe]

I don't understand why the HT is connected to the center of the pre-amp filaments?

https://chasingtone.com/the-seplex/

DC elevated heaters.

http://www.valvewizard.co.uk/heater.html

[jackplug1]

I didn't see anything in the link to explain my question?

[sluckey]

Read it again. It's explained about half way down the page.

[jackplug1]

Ah - I see, I think I will incorporate that into my build

[jordan86]

Look how Merlin elevates the heaters on that page. Sluckey recommended that to me last year. Creating an aritifical center tap from the power tube heaters (Pin 2+7) to the power tube cathode. Simple and saves space. It’s been a while since I looked at the sePlex though, not sure if he ties the feedback in at the cathode or not. Could conflict.

[Willabe]

Creating an aritifical center tap from the power tube heaters (Pin 2+7) to the power tube cathode. Simple and saves space.

You can only do that if the amps power tubes are K bias. Wont work with - grid bias.

And sometimes you need more than 30-35dcv to quite a tube. Up to 70-80dcv.