Finished My Express OMFG

[passfan]

Well I wired my Express up today as far as I could go (I am waiting on a multicap to come in). I couldn't stand it so I rigged some singles just to try it out. She came up nice with the obligatory plate lead swap to rid myself of the shrill and all voltages are within spec so what the heck, I fired her up.....!!!!!!!OMFG. This thing is the bomb. I have owned Marshalls, Hiwatts, Peaveys, Fenders but I have never felt like I had this much in my hands ever. I had the thing loaded with 12ax7s and 6l6gcs and the kid eight houses down the street heard me with it out in the garage and I don't think I even had it up to 1 on the volume yet. My prescence control doesn't seem to be providing much more than a treble boost right now , could be something there to figure out but wow, just wow. Many thanks to all here who put in the time to keep this site going. I have the last amp I'll ever buy now thanks to all of you.

William

[sst4270]

I'd be concerned about using 6L6's in an Express. The plate voltages in an express are approaching max values for a 6L6.

Don't be surprised if they don't last too long.

Just my $0.02

Steve


Oh... Still would love to see some photos of the amp.

[passfan]

I'd be concerned about using 6L6's in an Express. The plate voltages in an express are approaching max values for a 6L6.

Don't be surprised if they don't last too long.

Just my $0.02

Steve


Oh... Still would love to see some photos of the amp.

I actually changed them out to a set of 5881's. I have a pair of EL34M Winged C's coming in next week from AES. I dropped a GE JAN 12ay7 in my preamp to drop some gain as well. This thing rocks.

[passfan]

I'd be concerned about using 6L6's in an Express. The plate voltages in an express are approaching max values for a 6L6.

Don't be surprised if they don't last too long.

Just my $0.02

Steve


Oh... Still would love to see some photos of the amp.

I will post some amp porn first chance I get though she ain't very pretty. I used rescued transformers from a Baldwin organ and some of the leads were short.

[FYL]

I'd be concerned about using 6L6's in an Express. The plate voltages in an express are approaching max values for a 6L6.

Hmmm, the Express puts out 395V plate / 380V screen, quite far from the rated 500V /450V of a 6L6GC.

Anyway, voltage alone doesn't kill big bottles, current x voltage does : you may destroy a 6L6GC at 350V by letting the screen run amok. It's even worse for high slope tubes such as the EL34, most die because of screen shorts caused by too much dissipation.

[M Fowler]

I use 6L6, 5881, 6V6 and EL34 in my Express depends on what color underwear I am wearing.

No problems mixing up tubes in my experience but what do I know.

Mark

[sst4270]

@FYL

I've only been building for about 6 years so I'm still quite a noob at this so correct me if I'm wrong.

The quiescent plate/screen voltage of the express is more like 420/405.
Definitely below the max for a 6L6, but that's at idle.
Once the amp gets going that voltage rises dramatically and depending on how the amp is used could easily put a 6L6 outside it's max range for extended periods of time.
(albiet only small moments of extended periods of time)

I agree that it's not just the voltage that'll kill the tube, but it's just safe practice to keep below the max ratings. Now in hindsight I suppose it's not much different than using 6V6's in there... Oh well what do I know?
And the express was definitely designed for either EL34's or 6V6's. I just never tried 6L6's in 'em before. I'll have to do that on my next one.
(due to be finished in about two weeks)

-Steve

[passfan]

I'd be concerned about using 6L6's in an Express. The plate voltages in an express are approaching max values for a 6L6.

Hmmm, the Express puts out 395V plate / 380V screen, quite far from the rated 500V /450V of a 6L6GC.

Anyway, voltage alone doesn't kill big bottles, current x voltage does : you may destroy a 6L6GC at 350V by letting the screen run amok. It's even worse for high slope tubes such as the EL34, most die because of screen shorts caused by too much dissipation.

I believe I'm running them cold right now. I have 410 volts on the plate and -37volts of bias. If my calculation is correct 37 / 410 = 90ma which is 45 ma per tube , is this right ? That would be around 50 % for a 6l6gc. I'm not sure I'm doing that right will one of you guys verify this or correct me, thanks.

[M Fowler]

At 410 volts the bias range should be to taste at around 29 to 35mA for 6L6.

[dave g]

Any old Fender equipped with 6L6s typically had somewhere between 450 and 475 volts on the plates. The voltages in an Express are a good 20% lower than that.

[Jana]

yup, shouldn't be any problem running 6l6's in an express (provided bias is adjusted).

At 400 volts I would warm them puppies up to about 40 to 45 ma.

[M Fowler]

Jana, that is funny I like mine warmer as well but I was being safe.

I remember bnwitt telling me to cool off my EL34s in my Asteriod 60 when he asked what my voltages were and bias, but I liked them hotter!

[Jana]

At 400 volts, 70% of a 25 watt tube is 17.5 watts.

17.5 divided by 400 = 44 ma.

I like them hot too. Especially in the winter--it's like a musical space heater!

[paulster]

Hot definitely seems to way to go in an Express, regardless of the tubes installed.

I really must get around to trying a set of nice 5881s in mine...

[Cliff Schecht]

I've always run mine hot as well. My miswired bias supply doesn't even go to a full -30V, it maxes out at 29.5 or somewhere like that. I run E34L's at about 25V without any problems. If I run them anywhere below that the sound thins out pretty badly, but when you hit the "sweet spot" the amp really shines. This is why I like external bias pots so much, you can really tune an amp to the playing environment. People worry about the numbers too much sometimes, I just care about how the damn thing sounds!