Bogner Uberschall Power Tubes Question

Hello,

Has anyone experimented with power tubes in their Uberschall's? I have a Rev. Blue with EL 34's and I am curious to hear feedback on other tubes or even 6L6's, etc.

Thanks!

I'm running KT77s in mine. Not terribly different from EL34s, bass is a little bigger (and a little tighter), top is a little glassier (but only a touch), mids are still as present. I'd guess that 6CA7s or JJ E34Ls would be similar, probably more difference between factories or batches, but I haven't tried them out in this amp, yet. Actually, I'm really happy with the KT77s at the moment. Feels like I picked up some of the KT88 benefits while retaining the EL34s mids that I love.


Just make sure that it's biased to your preferences, even if you don't change tubes, but especially if you do. Once I got mine to about 65% dissipation, I was much happier with the sound and made a much bigger difference than the change to KT77s.

YMMV.

Ok, thanks for the input. In regards to biasing and dissipation, does the higher the % mean tubes are biased hotter or colder? Or does that have nothing to do with it?

For some reason I also thought changing tubes in the Uberschall meant changes to the power transformer...? A discussion I had with a rep. from Bogner was explaining that to me but I could of misunderstood what he meant.

Higher dissipation is biasing the tubes to run hotter. It's harder on the tubes, but can sound better in some amps. 70% is typically considered hot for Class AB push-pull amps (which most are and the Uber definitely is).

To change from an EL34 type to a 6L6 type (or vice versa) can (but not necessarily) require a change to the transformers. The primary impedance of the output transformer is a factor in how a given type will perform. More importantly, some tubes require much more current to run their heaters than other types. If the power transformer can't handle it... well, you get the idea.

KT77s are direct replacements for EL34s, as are 6CA7s and E34Ls (I believe, but I haven't double-checked the tube data sheets this morning).

Hope this helps!

Ok great. I appreciate the information. I know a little about tube amps but have a lot to learn. This stuff helps though as I am looking for information online and for books to read up on how they function/work.

Cool, lots of good books out there. I started out reading several by Gerald Weber and Kevin O'Connor years ago. I'm no expert, but I do believe that having a good working knowledge of how my gear works helps me use it better. Those books were fairly easy to follow (there are a lot more "advanced" books, but they're not necessarily better). Just remember, most of what's out there is someone's opinion of the right way to do things. Like so many things, there is usually more than one "correct" answer. There are a lot of people who will be glad to help you along the way, too. It's amazingly fun stuff!

Had Bogner mod mine to accept KT88. I'm not a huge proponent of tubes drastically change tone, but the difference was there. Not going to be night and day, in the end and Uber is still an Uber, and you'd get more drastic control from boosts/ loop EQs, etc. I digress, have fun with the hunt!

Yeah, that's been my experience, too. Power tubes aren't really going to change all that much. Sure, there is a noticeable difference, but not drastic like changing speakers, or pickups, or, arguably, preamp tubes.

FWIW, mine had been modified to use KT88s, too, but I preferred EL34-types better in my Uber. That's been true for my Marshalls that originally had 6550s (very similar to KT88s), too. I do like KT88s in my 20th Shiva and in the Twin Jets I've heard (but don't own yet).

Anyway, all that's just my opinion. Different stuff works for different people, so yes, absolutely, have fun with the hunt!!

Ok. Thanks everyone for your input and help! Much appreciated.