Power tubes for 1968 Dual Showman

[audiorep2]

Which 6L6 GC will give me maximum clean power ?
And a good source for them ?

[johnk_10]

NOS Philips 7581A's if you can find them, and are willing to pay the price. they have the most clean, useable power of any 6L6GC types that i've ever used by far. IMO, NOS STR 38's7 or 415's (are also very good for bass and, IIRC, actually are the same tubes)

these might be a good, less expensive alternative:

http://www.parts-express.com/pe/psho...48-8812&ctab=1

I've also heard good things about the TAD 6L6GC but have never tried them.

[bluesrx]

JJ 6l6's Here: http://eurotubes.com/

[bassmodder]

I came across a guy selling some "mislabeled" TV sweep tubes with adapters on the net that you might want to look at.

They are cheap and I was contemplating buying some but I would need 6 for my Fender so I decided against it. Perhaps if you only needed 2 or 4 it would be more affordable if you didn't like the sound.

Try here

[audiorep2]

What is the benefit of a " matched quad " ? Or is that sales hipe ?

[okcrum]

Originally Posted by audiorep2

What is the benefit of a " matched quad " ? Or is that sales hipe ?

The tubes are gain matched and will bias at about the same current in circuits with only a single bias adjustment.

[bassmodder]

Matched as in with a given bias voltage per tube gives the same idle current?

Both tubes work just as hard vs. when one is working harder and wears out quicker. Matched should yield you the most clean power. As for how long do they stay matched?................. I personally go for matched if I can. At least I can hear how they were meant to sound for comparison purposes when they are new/semi-new. It also saves me a lot of time shuffling tubes around in my amp (with 6 outputs) trying to get all the "cold" ones on one side to be countered by the balance pot. I can get back to bass playing faster and with less headache to say the least!

The new ones all seem to be matched on a tester or a computer of some sort. I know tolerances and predictable operating characteristics are much wider for the tubes being manufactured today than the ones of yesteryear.

The old ones seem to wear at mostly the same rate, bias pretty close to the old ones they replaced, and hold a given bias current without adjustment longer than some of the cheap new ones I have bought whether they were matched or not. (IMO)

Now, I bought some new SED 6l6GC for my Fender (not cheap) and in 6 months of use, I had about 1ma of drift from where I originally set the bias (55-60% max dis.). These tubes are still holding virtually the same bias current as they had when new. I am impressed to say the least considering this amp gets a minimum of 5 hours of use every week. I originally biased for a 100% match across the OT primary as I have a balance control (CBS Fender) and had the least hum by far and a tone that was very satisfactory to my ears. I never felt the need to "unbalance" the sides for experimentation. I used my voltage adjustment pot (mod by me) to set how "hot" (idle current) I wanted *all* the outputs to run at. IMO 50% of the max dissipation sounded best to me. I upped it to 60% after 6 months and IMO all it really did was heat up the power transformer!


Oh, and be aware of the newest "matching" - brand matching. This was a new one on me until I went on the auction sites. Basically, they are matching a red Chevy truck with another red Chevy truck... You hope they both have the same power and idle at the same RPM; none the less, they throw that word matched in there and people spend crazy money when the internal structure is totally different to say the least.

[toobalicious]

phillips 7581a is awesome... i have a pair running in a SF fender guitard amp (no need to go into details, right?) and they are easily the best sounding glass that has been in that amp. i have seen their pricing more than double since i bought them, however. ($$$) i also had "real" sylvania STR's in a BF bandmaster, but they finally got tired. i have not seen any NOS STR's in a while. (not that i am some tube guru or something).

my 100 watt bassman has a quad of svetlana---- from before the winged "C" name change. AFAIK, the winged "C" tubes are 100% the same as the formerly svet labeled ones, NOT to be confused with current svetlana-labeled stuff, which is made in an entirely different factory (i have not tried reflektor-made svets, so no comment on those). they sound great, but can get a little crunchy as they are pushed. a raggedy-sort-of compressed crunch that i like (and the primary reason for my love affair with this amp), but it may not suit a user looking for maximum headroom.

i have so far had excellent luck with JJ 6L6--- they have survived perhaps 60-70 shows in my 400+ with no noticeable change. ditto, they seem to be holding up fine in my B25 head (with its high voltages.... spec'd for 7027), though that install is a new one. i also own stuff loaded with JJ EL34, EL84, and a handful of preamp tubes, with mostly pleasing results, save for the weird pin thing on a couple of the preamp tubes (supposed to have been corrected by now), but that may be straying OT.

if price is any kind of concern, i would recommend JJ FTW.

[toobalicious]

Originally Posted by bassmodder

I came across a guy selling some "mislabeled" TV sweep tubes with adapters on the net that you might want to look at.

They are cheap and I was contemplating buying some but I would need 6 for my Fender so I decided against it. Perhaps if you only needed 2 or 4 it would be more affordable if you didn't like the sound.

Try here

well dang.... i am curious about this... i had contemplated moving my 7581a's over to the B25B because i knew they would live and not suck... but the guitard combo sounds so danged good with them, i couldnt bring myself to do it. the tube-dudes-that-be *say* that the jj 6L6 will hold up under brutal conditions, but i *know* the mil-spec phillips will. besides, there is no way that this adapter contraption is fitting inside of a vintage fender head, except for the reverb models--- not nearly enough room. plenty of room for it in the B25B though.

i am taking it from your verbage that you have *not* tried these things... wonder what the deal is with these?

edit:

bah... not as much room in the B25B as i had thought...

[bassmodder]

Yeah, I would like to try them. I chopped my combo so there would be enough room and my guitar player has a reverb combo that those would have fit in quite nicely. I would personally just rewire the socket instead of using that adapter.

Problem is I don't have any 50ish watt amps any more! I have a 100W 8417 amp that I converted to 6550 and those tubes work well. Perhaps when I get some time I might throw a few of these in and see what happens.

My amp does 716V on the plates so I guess that would be the "high voltage" test that everyone would be curious about.

Just thought I would throw that up for the adventurous minded