S6424 to AC15/Rocket conversion

[Herec]

Hey guys,

I've always wanted an ACXX, and have been looking for a project, so I'm going to change up my S6424 clone.

I was planning on using the Rocket Preamp, and the AC15 PI/output/PS.

Sound okay in theory?

The OT for the S6424 has a 6k input impedance, so it would be fine if I wanted to switch to EL84s from the 6973s that are in the amp now (I think?).

The only thing that makes me think this isn't terribly straightforward is the output of the PI into the output section.

What's with the 470K/12K/270K divider to the output tubes? Why does it seem to be mismatched? Or am I just screwing up with my resistor network calculations?

[Herec]

Well I drifted away and found myself back again.

Does anyone have an idea of what's going on with the output of the PI into the output section? Thanks!

[Kagliostro]

That is a Paraphase PI

many people say that the Paraphase add mojo to the amp

K

p.s.: Just to let you know:

http://el34world.com/Forum/index.php?to ... #msg235747

http://el34world.com/Forum/index.php?to ... #msg236102

http://el34world.com/Forum/index.php?to ... #msg235834

[Herec]

Thanks very much! Just getting back into this again, need to brush up, thank you for the pointer.

A while ago I had bought one of Merlin's books (as well as Richard Kuehnel's), forgot what a great resource he is after searching for a synopsis on paraphase PIs.

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

Will watch those Supro threads as well to see if there's any low hanging fruit/simple changes I may be able to try out.

[tubeswell]

I've built a couple of t-bolty amps with goosed up front ends along the lines of this schematic. This iteration works particularly well (in a recycled Jansen 25 SS amp chassis).

If running the 5881s in total PP Class A, then remember to use a reflected load that gives proper Class A operation for each 1/2 of the OT primary. That way you will get more power out of the amp.

[Herec]

That looks really interesting! Thinking of maybe going more along those lines now, just tweaking this build a bit for a bit more of the sound I get when it's fully cranked, rather than a complete redo. Thank you! I'll let you know how it turns out