Changing from 5881 to EL34?

[Sirion]

Yesterday, I finally recieved a Marshall 9100 power amp I've been waiting for for quite some time now. To make a long story short, I was a bit dissappointed to see that it held 5881 power tubes instead of EL34 (but hey, that's what you get for not asking the seller in front! . The present tubes also sounded pretty worn out, so I will have to get some new ones, along with spares.

So, the question is: Could a tech relatively easy convert the amp from using 5881s to EL34s? It's not certain that I would be doing this, just curious about what possibilities I have, since I've never really explored the possibilities you have when it comes to switching tubes. Also, since this is a dual core amp (which is basically two 5o watt power amps in the same box), would it be possible to use, say, EL34s on one channel and 5881s on the other? Anyone tried something like that?

 

[Rich_S]

Re: Changing from 5881 to EL34?

It's do-able, but not as easy as some tube swaps. EL-34's use more heater (filament) current than 6L6 types. Sometimes, you have to add an extra little 6-volt filament transformer to power the EL34 heaters. Other than that, it's just minor wiring changes plus re-biasing. Done right, it should be possible to change back fairly easily.

Without looking at a schematic, I see no reason you couldn't have EL34s in one side and 6L6s or 5881s in the other.

 

[metlking]

Re: Changing from 5881 to EL34?

I had the same conversion done to my 9100 power amp years ago....switched from 5881's to EL-34's......the amp when I got it had tired 5881's in it and I had it converted immediately. It sounded great compared to before but I can't honestly say which made more difference, new tubes or a new kind of tubes. It was my first real tube amp.....The tech, a guy I know, charged something like $60 for the bias and conversion, I don't really know what he did though, must not have been too involved for only $60, I provided the tubes. The last set of tubes I used in that poweramp before buying a whole new set-up were the JJ KT-77's......I liked those the best! A good compromise between 6L6 types and EL-34.....between modern and vintage in my opinion. Beware tho......EL'34's are taller....most won't fit in the 9100! I had to bend the lid of mine in the center to be able to put it back on! Thats ok as long as you don't have anything above it in your rack!

I always wanted to convert one side back to 5881's to have both, but never got around to it and I don't use it anymore.......but I have heard it can be done!

If you decide to stay with 5881's, I tried these in another amp and like them very much. I bought them from www.dougstubes.com

Hope that helps!

 

[Dr.Mavashi]

Re: Changing from 5881 to EL34?

Yo King,
So you can just put KT77s and just bias them no extra work for moding if its EL34 amp?

 

[metlking]

Re: Changing from 5881 to EL34?

Yo King,
So you can just put KT77s and just bias them no extra work for moding if its EL34 amp?

Yup...most of the time. Their bias range is similar to an EL-34.

Info from www.boiaudioworks.com

KT77 is an excellent sounding tube now available from JJ. It is a faithful reproduction of GEC KT77 which was designed specifically for audio purpose. KT77 can replace 6CA7 and EL34 tubes.

 

[Dr.Mavashi]

Re: Changing from 5881 to EL34?

Well, I guess my next set of power tubes would be KT77 will be nice to try it in my Laney AOR.

 

[metlking]

Re: Changing from 5881 to EL34?

They're worth a try, although some love them, some hate them.......kinda like the JB of the tube world right now!

In my opinion they gave my "Marshall" a hint of "Mesa".....

 

[Dr.Mavashi]

Re: Changing from 5881 to EL34?

They're worth a try, although some love them, some hate them.......kinda like the JB of the tube world right now!

In my opinion they gave my "Marshall" a hint of "Mesa".....

Well I am not a mesa fan, but I play a lot of stuff that is "Enlg-like" but love the Laney tone, it could be the same "hint" that I need ...

 

[metlking]

Re: Changing from 5881 to EL34?

Well I am not a mesa fan, but I play a lot of stuff that is "Enlg-like" but love the Laney tone, it could be the same "hint" that I need ...

Mesa.....not for me either. I've owned two and really tried to love them but it just didn't work out for me. A hint of that Boogie grind is good though! I have a Splawn QuickRod I play now with EL-34....it'll take KT-77's and I still have 'em so I may try them in that this week......

 

[Dr.Mavashi]

Re: Changing from 5881 to EL34?

Dude, I would freaking love if you throw a few quick and dirty clips of EL34s vs. KT77s. As its obvious from my other thread Laney is heading over to a tech for biasing work and its gonna get JJ E34Ls but after that I am considering KT77s after your post and the fact that Bob at eurotubes barely can keep his pants on when he is talking about the "new" mullard like KT77s that they now have .... Thanks bro.

 

[metlking]

Re: Changing from 5881 to EL34?

Clips? I'm not sure how to do that and get them posted.....I'm a newbie when it comes to recording with a PC.....