SLO + 6L6/5881 Mix = ???

[Mr. Willy]

I had a problem with a power tube awhile back, so I pulled the problem one and ran 2 5881’s to get me through until I could order another pair of 5881’s. Well, I also have a quad of JJ 6L6 tubes that I’d snagged awhile back to try out in the SLO. I was curious what mixing them would do, so I popped two in.

I didn’t like all 6L6’s back when I tried it. Thought the tone was too laid back and boomy. But I don’t hate this mix with 5881’s. It’s not as aggressive as all 5881’s but it has more bottom end and a smoother top end. Some guys might really like this combo.
At any rate, I’ve never heard of anyone doing this, so I thought I’d share my results, FWIW. Side note, not all 6L6’s can handle the high plate voltage the SLO runs, but these can. See the attachment for specific model. It’s a JJ.

 

[SpiderWars]

I didn't think those Sovtek 5881s ever died. Cool that you found that combo just as a pure coincidence.

How old are the other Sovteks? I recently bought a 5F6A Tweed Bassman and can use those in matched pairs if you want to just start with a new quad.

 

[Mr. Willy]

I didn't think those Sovtek 5881s ever died. Cool that you found that combo just as a pure coincidence.

How old are the other Sovteks? I recently bought a 5F6A Tweed Bassman and can use those in matched pairs if you want to just start with a new quad.

Man, I’d consider these fairly old. At least 2016. I gigged them pretty regular 2017-18. They’ve got some miles on them.

 

[ZEN Amps]

How are you biasing your amp to handle mismatched pairs?

 

[Mr. Willy]

How are you biasing your amp to handle mismatched pairs?

I honestly couldn’t answer that. Curt Granger biased it up for me when I got those power tubes. I think it’s up around 28ma, somewhere around there. I’m a bedroom warrior these days, so I’m not pushing them hard. I did push it up to halfway on the MV today, and the bottom end was pretty huge and big.

 

[ZEN Amps]

I honestly couldn’t answer that. Curt Granger biased it up for me when I got those power tubes. I think it’s up around 28ma, somewhere around there. I’m a bedroom warrior these days, so I’m not pushing them hard. I did push it up to halfway on the MV today, and the bottom end was pretty huge and big.

Ok tell me to take a hike if I sound preachy, but you shouldn't just swap output tubes around without a rebias. They're sold in pairs and quads for a reason and they'll likely be running seriously out of whack without proper adjustment. Pretty easy to fry your tubes this way, regardless of how loud the amp is.

Keep an eye out for a seriously bright glow man!

 

[Mr. Willy]

Ok tell me to take a hike if I sound preachy, but you shouldn't just swap output tubes around without a rebias. They're sold in pairs and quads for a reason and they'll likely be running seriously out of whack without proper adjustment. Pretty easy to fry your tubes this way, regardless of how loud the amp is.

Keep an eye out for a seriously bright glow man!

I’ll take my chances, but thanks for your concern. If I fry a tube, I fry a tube. I’m aware of the risk. I think everything is ok. The amp was biased for the 5881’s. Those 6L6’s can handle that high plate voltage.

 

[Racerxrated]

I’ll take my chances, but thanks for your concern. If I fry a tube, I fry a tube. I’m aware of the risk. I think everything is ok. The amp was biased for the 5881’s. Those 6L6’s can handle that high plate voltage.

I think he’s talking about a super hot tube that might be up in the 50ma range which could go south pretty fast. That can be dangerous to your amp. If you’ve had those in before then I’d check with your tech as to where he biased them vs your 5881s to compare.
I have to mention though, I’m not sold on ‘matched’ quads anymore. I’ve compared my closely matched sets to other sets that are say 10ma apart; like between 30-40ma with all 4 and the non matched quad sounded better.

 

[SpiderWars]

I think he’s talking about a super hot tube that might be up in the 50ma range which could go south pretty fast. That can be dangerous to your amp. If you’ve had those in before then I’d check with your tech as to where he biased them vs your 5881s to compare.
I have to mention though, I’m not sold on ‘matched’ quads anymore. I’ve compared my closely matched sets to other sets that are say 10ma apart; like between 30-40ma with all 4 and the non matched quad sounded better.

Was watching a Karl Sandoval video where he described an early VH sound check where Eddie would play a bit, then go behind his stack and reach into a box; he would hear glass clanking around, and then he'd pull out a tube or two and swap with the existing ones. Rinse and repeat until it sounded right to him.

I've heard that SLO's are generally biased a bit cold and sound best that way so it could be fine. I'd want to know for sure tho.

 

[Racerxrated]

Yep 28-32ma is where I always biased the 3 I owned over the years. The very first one I bought off a forum member here, worked great for 1 day then started popping fuses. I panicked and called Soldano. In literally 15 minutes Mike himself called me back and told me it was probably a 5881; told me who to order from and in a few days all was well. He did mention the amp sounded best biased low like that. He was super to talk to though. Great customer service!

 

[Mr. Willy]

I think he’s talking about a super hot tube that might be up in the 50ma range which could go south pretty fast. That can be dangerous to your amp. If you’ve had those in before then I’d check with your tech as to where he biased them vs your 5881s to compare.
I have to mention though, I’m not sold on ‘matched’ quads anymore. I’ve compared my closely matched sets to other sets that are say 10ma apart; like between 30-40ma with all 4 and the non matched quad sounded better.

I feel you on all that. I’m not sold on matched pairs either. I’m in complete agreement that the amp bias needs to be checked. I’m not going to do that in this case b/c, 1) I don’t know how to do it myself, 2) I’m not going to play it that much to warrant doing it now, 3) I’m going to retube it back to 5881’s as soon as I get a chance. While I definitely preferred this mix to all 6L6’s, I still prefer the aggression and compression of all 5881’s. I’m just slapping these 6L6’s in there for now out of curiosity. It really added a good bit of low end.

 

[Racerxrated]

^^^Then I would check the tubes while you are playing every so often to make sure they don’t redplate without you knowing. Good chance they won’t since it probably would have happened pretty quickly…..but I had bought some Peavey Super Six Sylvania 6L6 as spares for my SRG C+ 6 yrs ago…popped them in and the amp hummed but they played fine. Decided to check ma and they were above 70!! Pulled them immediately and they still sit in my stash. The Mesa 415s by comparison were at 34ma per tube. So they might be super hot without redplating..just keep an eye on them.

 

[Mr. Willy]

I dig up Curt’s email to me when I had those 5881’s biased. It’s biased at 32mA per at 498V on the plates. That was January 2017. Yeah, she needs some new output tubes. I gigged/rehearsed fairly regularly between 2017-2018.
Here’s a live iPhone clip from around then:

 

[Mr. Willy]

^^^Then I would check the tubes while you are playing every so often to make sure they don’t redplate without you knowing. Good chance they won’t since it probably would have happened pretty quickly…..but I had bought some Peavey Super Six Sylvania 6L6 as spares for my SRG C+ 6 yrs ago…popped them in and the amp hummed but they played fine. Decided to check ma and they were above 70!! Pulled them immediately and they still sit in my stash. The Mesa 415s by comparison were at 34ma per tube. So they might be super hot without redplating..just keep an eye on them.

I’ve been walking over and looking at them when I play. They look fine, not glowing any more than the 5881’s. Nothing weird happening. That’s a pretty scientific analysis, I know.

 

[Mr. Willy]

Totally would not gig this combo without double checking the bias with a professional. Just want to make sure everyone knows my position in that. I did do some research back when I was interested in trying 6L6’s, and these where the ones pointed to that could handle the high plate voltage that the Sovtek 5881’s can handle. If they crap the bed, I honestly don’t care. It’s only two and I got two more. I don’t use JJ’s for anything if I don’t have to. I don’t think I’ll harm the amp at all. Wouldn’t even attempt this if I thought it’d hurt the amp.