Repost over in the "Amps Technical" forum. I've swapped 6L6 and 5881 tubes into DRs with a rebias, but I'm not an amp tech. Somebody over there will know for sure -- and, best of all, know why it will or won't work.
Yes, all you need to do is rebias. Some people like to use a higher rated rectfier to further increase clean headroom.
Technically there are reasons, such as added heater current draw and plate load resistance mismatch, why you shouldn't do this. But many people have done this over the years and have lived to tell about it, so go ahead and do it at your own risk. Just be aware that the added heater current could damage the power transformer, and you really won't gain much volume, and the 6L6's won't overdrive like the 6V6's. So it may not be worth it to you. But you won't know unless you try. Hope that helps, Hasse
Thanks that's what I was trying to find out. I have a line on a super clean 76 for a pretty decent price, just worried it might not have enough headroom for strictly pedal based drive.
The stock amp might not have enough headroom for you, the 6V6's do breakup a bit. But the amp is actually pretty loud. You might just want to use a different order of pedals with it. Tube Screamers always sound good in front of them, as do clean boosts.
I hear ya', just being a butt head. I have a 70 DR I thought about changing to 6L6 myself. But the guy that I works on my stuff talked me out of it. Somthing about the heating issue. Another thing you could think about is what speaker you put in it. I have tried lots of speakers in mine, some break up alot sooner than others. Find a good tech and have it changed to blackface specs. I don't work on them, so I can't tell you what they change, but I am glad I had it done to mine Who knows you may really dig the 6v6, it is a cool tone. Enjoy, a very cool amp either way. CC
another thing that will help that DR might be a different speaker, as well. I've heard many people rave about 6L6-equipped DRs w/ an EV speaker, and know that the stock speakers in the 70s Fenders can pretty easily be improved.
I assume you want to do this to increase the clean headroom. Changing to 6L6's will make less difference than you think. There are other things you can do to increase headroom in a DR: 1. Recap if the caps are old 2. "Blackface" circuit changes ( this won't actually give it more headroom but it will sound a lot better ) 3. Better speaker-this can make a huge difference-many good 'uns to choose from nowadays. Only about 200 threads on this here if you do a search... 4. Pull the first tube ( V1 ). It is for the "normal" channel which I assume you don't use. 5. Try a lower gain tube in V2 like a 12AT7 or 5751 6. Then sell it and buy a Twin ( kidding!-by now it should be sounding awesome and much easier on your back than a Twin anyway ) Good luck Dan
"4. Pull the first tube ( V1 ). It is for the "normal" channel which I assume you don't use. " will this really increase the headroom? i think the opposite. it will give more dirt to the second channel, right?
I used an early SF Twin for years and still get bitched at by the bass player for getting rid of it!! He refuses to use anything other than a small 1x15 cab so I just tell him "get you an Ampeg Fridge and we'll talk about a Twin"
I bought a DR that had been modded with a bassmen tranny,& 6L6's. I changed it to original specs liked it better.My .02 worth.
Hmm. You are probably right that it is adding a bit more GAIN at that stage of the amp. I LIKED what it did to my amp a lot. I guess it made it sound bigger and better to my ear. Mine did not sound DIRTIER with that tube pulled. I'll tell you this, I did all the above listed tweaks to mine and it is the punchiest cleanest sounding DR I've ever heard ( except for Ken Brakebills, but that doesn't count as he is a mutant amp tweaker, but I digress......... ). If you are adding more signal from that first tube and your amp is breaking up already because of using the original oxfart speaker and some tired caps then it probably would make it break up sooner. So, I guess, try the tube pull and let us know what you think. It is a safe, quick and easy reversible mod. Dan
altho it's not much of a difference, pulling v1 will also decrease the current demand on the PT, which might have some sonic benifits...
Hi Dan Thanks for your reply. That was something I had read (check Blue Guitar - KCA NOS Tubes site f ex). I haven't tried it myself but I will someday soon. I just got my first DR a couple of months ago. A super clean from '65 everything stock except the power tubes. Caps are still fresh! Amazing! However, I think it can get a bit "better" tone, probably with another speaker (original Oxford) and some "small" mods. It doesn't have to get more headroom, just a bit fatter and cleaner. I have a clean 66 Super Reverb with stock alnico speakers. AMAZING tone!
The heater current may be an issue - although it doesn't seem to be, especially if a SS rectifier is used as well, which will reduce the power draw on the transformer. But oddly, the plate load mismatch is not an issue at all - because the stock OT ratio is incorrect for 6V6s into an 8-ohm load, and actually much closer to that for 6L6s. I didn't believe that when I first read about it, so the next time I had a Deluxe with 6L6s to measure, I checked - and sure enough, it's true! You get more power into 8 ohms than 4 (which would be the correct match for 6L6s if 8 was right for 6V6s) - quite substantially, which if you're fitting 6L6s for extra clean headroom and a fuller tone is what you want. Add in a SS rectifier and you get a much bigger, tighter tone that does not flub out at the bottom end like the stock amp tends to. In fact, the correct load for 6V6s is closer to 16 ohms, and if you do fit a 16-ohm speaker, you will also notice a tighter, punchier tone with less flub and a little more volume (assuming similar speakers).
