How much more headroom can you get from a tweed Deluxe running 6L6s?

You get a little more, but it isn't night and day. You would run a 5AR4 rectifier unless you have a power transformer that can handle a 5U4, which is doubtful. To really do this right, you need to swap both transformers for 6L6-capable iron.

 

Bias isn't the issue. The Tweed Deluxe uses cathode bias, and its default cathode resistor should give nice bias for a 6L6 as well. The problem is that the current will be too high and overload the transformer (~12 watts versus ~30 watts, at the same plate voltage and self-bias). You'll burn it right up!

Use an output transformer (and power transformer) spec'd for the kind of power a 6L6 pair generates, and you can drop 6V6 in as well.

 

I've asked Michael Clark whether I can safely run my Beaufort with 6L6s instead of 6V6 and he was 100% positive.
Neil Young uses 6L6s in his tweed deluxe and a 5AR4 for rectifier. 5Y3 can also be used along with 6L6s.

 

Doesn't Neil Young blow that amp up a lot?

A Clark Beaufort is likely fine, however. Yay for over-spec'd boutique amps!

 

This seems to be one of those cases where you are trying the make the amp what it is not.

6L6's in a 5E3 do seem to sound fuller and more balanced, and it has that famous 6L6 midrange "kink." That's really the significant difference between using 6L6's vs. 6V6's in a 5E3, and it's a perfectly good reason to do it;the headroom issue is pretty much negligible, not enough to make a difference on stage.

The problem is the 6L6's are held in check by below optimum B+ voltage and an output transformer that chokes off their extra output. To really make a difference in headroom, you pretty much have to double output. And you aren't going to get that just by plugging 6L6's and 5AR4 in there, you might get a 10-20% difference in output, but that doesn't amount to squat in actual headroom. That's why builders that offer a bigger, higher headroom, 6L6-based 5E3 use a higher voltage PT and a much bigger OT, that way they can really capitalize on the 6L6's potential.

The best bet to getting as much volume as possible out of a stock 5E3 is a very efficient speaker.

 

What wyatt said.

Are you looking for more volume, or more headroom? If you want headroom, your best bet is to get the heck away from that tweed circuit! That's what Fender did, back in the day... the brown (and later black) Fenders were a deliberate attempt to get rid of all the distortion. And the reason tweeds are popular with guitarists is because they distort so well!

More volume? What wyatt said. Use a more efficient speaker, or just plug it into a 4x12.

 

Where did that info come from? I thought it was 6V6s and some kind of out-of-the-ordinary, yet stock output transformer (as per Larry Cragg/Tonequest).

 

His tech has said in a few magazine interviews, 6L6's into (IIRC) a C12N.

I find it a moot point. A tweed deluxe is Neil tone in a box anyway, I don't think the tweaks really get anyone closer to it.

 

At the TonequestReport Larry Cragg states the use of 6L6s, as well as the C12N speaker.
As for the rectifier tube, I've e-mailed LC myself, just out of pure curiosity.
I agree, though, that none of those options will get a tweed deluxe closer to the "Neil Young territory".

 

Take it from me, someone who has built about half a dozen 5E3's and who has wasted way too much time swapping tubes; yes, the 6L6's will give you *a bit* more volume, but a good pair of 6V6's (RCA's) sound so much more sweeter. The only benefit of using 6L6's is a general tigtening up of the bass IMHO.
Personally, I like them with either the stock 12ay7, or a 5751 in the 1st slot, your choice of tube rectifier (within limits of your power transformer), and the Weber Alnico P12Q speaker, BUT the one that uses the straight cone.... Q Magnet, R Cone, I forget the model. Very american sounding, with all the low volume sweetness of the straight cone, but with more volume, and better bass handling response, with much less fizz.

 

Remember that a 6L6 draws a shade more than twice as much filament current as a 6V6. That puts a bigger load on your power transformer--it'll doubtless run hotter.

 

12A125-O

The straight cone is great for overdrive and crunch and "Neil tone," for for those who want to keep that tame and use what clean is available, I recommend the ribbed cone.

 

A little of the PT's train can be relied with a SS or Weber Copper Cap rectifier. Now freeing up the current on the 5V tap doesn't translate into extra current on the 6.3V tap, but it will save the PT some effort. I wouldn't recommend doing it in a vitnage amp, but a clone? Sure, Many modern PT replacements are more robust than their vitnage counterparts. Even MM's supposed "clone" of the vitnage piece is actually built with more current on tap.

 

I believe I was told that it is also safe to run 5V4G Recitifer (in addition to the stock 5Y3GT) in a Tweed Deluxe Clone -BUT NEVER a 5U4. True?

 

5Y3, 5R4, 5V4, 5AR4/GZ34 are have a current draw of 2 Amps.

A 5U4 has a 3A current draw. So you have to have a power transformer with a 3 Amp, 5 Volt filament winding. Most (all?) pre-Silverface Fenders (and other amps that use 2A rectifiers) DON'T have 3A winding to supply a 5U4.

Now, modern clones are hit and miss. For instance, Mercury Magentics FTDP, which is advertised as a clone of a vintage Tweed Deluxe transformer is actually built far more robust, offering 4A each on both the 6.3V taps and 5V taps. So, you could use a 5U4 with a MM PT. Heck, you could also run the 12AY7, 12AX7 and a pair of 6V6GT's or 6L6GC's or KT66's or even EL34's. But transformers from other companies may be a little more "period correct" and better suited to 2A rectifiers and a pair of 6V6GT's.

 

I played a Deluxe with 6l6's, Didn't sound like a Tweed Deluxe. It sounded like a broken Bandmaster. It must the 6v's for "that" tone.

 

Well every bodies got their own version of what "that" sound is. I tend to agree w/ you. I built my Mission 5E3 because I love that sound w/ 6V6`s . I agree w/ Wyatt, speaker makes a huge difference, perhaps more than 6L6`s or ?? I also love the sweetness and smooth breakup of the original 6V6 design.
Having stated my own preferences others may see it differently. Just part of the beauty of this simple time proven design. Makes it a fun amp to try cap values etc. I`ve had either an original or a clone for over 45 years. I would venture to say w/ the excellent clones being built today it`s hard to buy a bad 5E3. After much experimenting over the years I have a tube compliment I really like. RCA blackplate V1; 12ay7, V2; Tesla Rosnov E83CC, Brimar 6V6GTY and any nos 5Y3. Enjoy.