5F6A

[davidwpack]

Hey guys. I was perusing through some of my printouts of Doug's  and noticed the old version of the 5F6A differs slightly. The cathodes of V-1 are tied together on the old version. The new version has a 1.5K/22 on V1-8. I was just wondering if anyone has built both versions of this preamp and wondered how subtle the differences was. I'd imagine the newer version would have slightly more gain and bass response? Any facts, or otherwise opinions? Thanks...Dave

[shooter]

opinions?

never built either, but when I do build a shared cathode design I give each it's own R&C, prime reason - unwanted stage coupling, 2nd reason, easier to tweak, I quit at 2, 3's just an odd number

[davidwpack]

Hmm. Interesting. I thought when they were tied together they typically shared the R&C.

[sluckey]

Hmm. Interesting. I thought when they were tied together they typically shared the R&C.

They do. I understand Shooter to be saying whenever he builds an amp that uses a shared RC design he removes the shared RC and gives each cathode it's own separate RC.

[davidwpack]

Ohhhh. Got it now. I was wondering how that would work. I couldn't understand it the way I interpreted it.

[davidwpack]

Still thinking about this. Just out of curiosity, I wonder what would happen if you tied the cathodes together without removing a set of RC. Use the RC set with the least value R? I wouldn't try this on a build but just curious how that would work besides having a confused tube.

[pompeiisneaks]

The resistor would act like resistors in parallel and then you'd get slightly less resistance than the smaller of the two, also the caps would add up, caps in parallel are like resistors in series.   

So it would have an impact too.  I think you may be referring to how Doug's 5F6A is setup with the separated inputs cathodes.  That's definitely an improvement as you get a slightly more guitar like input on one, and the other is more like the original bassman.

~Phil

[davidwpack]

If there's a dramatic difference, if both are pleasant sounds, I wonder if it would be difficult to design it to be able to switch between shared/separate cathodes? Or has this been done? Or is it rediculous altogether?

[shooter]

I understand Shooter to be saying

been married 27yr's n counting , +12yrs, communicating with other humans isn't my strong suit

Or is it rediculous altogether

add a couple turrets n a switching of choice, begin 

[davidwpack]

Yeah,. I'm beginning my component collection for breadboard stuff. Tryin to think of fun experiments to make it worthwhile.