3 Questions: 5F4 Tweed Super

[beckspeed]

I'm still monkeying with this 5f4 Tweed Super (the one that was someone else's kit and I'm resurrecting). You guys were a ton of help a few weeks ago and I really appreciate it. I just added an SPDT output impedance selector switch, since the OT (classic tone 40-18105) it has a multi out. I don't normally crank it above 5-6 but I was putting it through the paces and noticed once I get to full volume (8-10) the amp gets very distorted - in a bad way. Sounds farts out, all loose and messy - not a tight "good" distortion. Tried with several guitars (single coils and humbuckers) with the same basic issue. I turned the "bass" and "mid" pots all the way down and the issue persists (albeit slightly diminished).

Previous thread for background on the amp http://el34world.com/Forum/index.php?topic=21955.msg233350#msg233350

here is how I wired the switch - except I left the NFB on the jack - not to the switch, because the wiring above is to switch to add an extension cab.



1) Would the NFB at the jack cause this issue?
2) Other issues I should look for?
3) You guys mentioned it would help if I created a schematic for this exact amp - since its a bit of a homebrew/ hodgepodge "5F4". What program do you use to create the nice clean layout diagrams?

As always, thank you in advance!

[shooter]

1. did you run it to 10 before the switch?  once you get to a certain point, NFB can't make up for the amount of distortion you create.

2. you changed guitars, change speakers

3. http://el34world.com/Forum/index.php?topic=590.0
This is what I use, it's free
The "gold standard" costs more, Visio and the guys that use it create nice works, us .sch guys can do pretty well though

[beckspeed]

Thanks Shooter - yeah I ran it at 10 before  - sounded pretty good. Warm fendery overdrive sound.

Have not tried different speakers - but I'm using my known-good go-to cabinet. I do have another I'll try though.

What about this for the layout: DIY LC? http://diy-fever.com/software/diylc/

[shooter]

yeah I ran it at 10 before  - sounded pretty good.

then you know where to start looking

any tool that gets you good results and doesn't cause high blood pressure use.
I started using pc express in the way back days, for schematics I can churn all day, for layout, that takes some Zen to keep the BP down

[beckspeed]

Thanks shooter - I'll start my investigation there.

[beckspeed]

so I undid the Output switch and put back at straight 4ohm output, but the blubbery distortion over 8.5 seems to persist. I mapped out the circuit. Do you see anything here that could be the cause of my issues?

Thanks

link to full size PDF http://beckspeed.com/blog/wp-content/uploads/2017/07/MK-SUPER-WD_ab_2_Flat.pdf