TAD Tube Problems

[jzucker]

Anyone else experiencing problems? Did I just have a run of bad luck? I've had several bad 6L6 tubes. Also, the plastic seems to be very fragile and I've had two of them with the registration pins break off.

[Structo]

I had a set of TAD 6L6GC's that sounded great! ..........for about 8 hours of operation.
Then out of the blue, one redplated.

Didn't have any problems with the pins.
But after that scary ordeal I probably won't use them again since I had heard of others having the same issue.

BTW, anybody know what brand of tube these really are?
They have to be relabeled something or another.

[slider313]

I stay away from all power tubes made in China.

[jzucker]

The other interesting thing about my TAD tubes is that they were biased at about 35ma in my vibroverb. When I replaced them with a set of winged C 6L6 tubes the initial bias measured showed 95ma!!! Fortunately, the bias pot had enough range to get them down to 30ma.

The same winged C tubes were running fine in a dual showman I have...

[brefmint]

Dang, I just ordered a pair for my '67 Super.

[HandOfTheHost]

That's lame. I've had a pair of the 6L6WGC short bottles in my Bassman for about three years without any problems. Did you have those or the tall bottle 6L6GC's?

[traviswalk]

Those are in some of my Two-Rocks with no issue, great tubes.

[RussB]

I ordered 2 matched quads a few years back. 4 long bottles, 4 short bottles.

2 of the short bottles turned into rattlers, and one of those shorted out.

The 4 longs were installed in customer's amps, and I never heard back, so I assume they worked OK.

They, like any and every new manufacture tube are a crap shoot. Sometimes you win, sometimes you lose. I find the SED 6L6GC's to very consistent, and always sound good. Also, with ANY new mfg tube, bias them conservatively. 50% to 60% MAX!

[cochese]

The other interesting thing about my TAD tubes is that they were biased at about 35ma in my vibroverb. When I replaced them with a set of winged C 6L6 tubes the initial bias measured showed 95ma!!! Fortunately, the bias pot had enough range to get them down to 30ma.

The same winged C tubes were running fine in a dual showman I have...
I have not tried their tubes but will pass on something my amp tech taght me in regards to biasing. It's best if you have a Variac because common wall voltage will fluctuate. Meaning you can bias a brand new set of tubes and if your wall voltage is a little off you can check the bias the next day and it won't be the same.

If you don't have a Variac measure your line voltage with a meter to make sure it's at it's normal range. In my house that's 121. Then check the bias on the old tubes and see how far off they are. All tubes drift over time and sometimes you can just readjust the bias. If they still sound ratty it's time to change. At that point turn off your amp and turn your bias trim pot down . Put in your new tubes and crank the amp up and check the bias. It should be too low. Then gradually raise your bias to the proper setting. It's too easy to fry a new set of tubes if you don't take this precaution.

Since I believe you are running your amp through the UA you will go through output tunes more often. I've had good luck with the JJ 6L6's from Eurotubes in my '66 Bassman head.

[jzucker]

That's lame. I've had a pair of the 6L6WGC short bottles in my Bassman for about three years without any problems. Did you have those or the tall bottle 6L6GC's?

My were the short bottles. Re: Wall voltage fluctuation, makes sense but a swing of 50ma seems a bit steep but maybe it's not that unusual?

[jzucker]

I ordered 2 matched quads a few years back. 4 long bottles, 4 short bottles.

2 of the short bottles turned into rattlers, and one of those shorted out.

The 4 longs were installed in customer's amps, and I never heard back, so I assume they worked OK.

They, like any and every new manufacture tube are a crap shoot. Sometimes you win, sometimes you lose. I find the SED 6L6GC's to very consistent, and always sound good. Also, with ANY new mfg tube, bias them conservatively. 50% to 60% MAX!

So, in a typical fender twin what would you set them to in ma?

[HipKitty]

We've been retubing amps with the TAD 6L6's for some time now (we give the amp's owner the choice of SED, GT or TAD) and have had less than 1% fail rate being reported back to us. Further, many of these have had retubes after their initial TAD install and have requested the TAD's.

We also will load our production amp with the TAD short or tall bottle as an option and have had zero fail rate with them in our amps. In fact, one of our show amps has been loaded with a pair of the short bottles and just keeps on sounding and operating superbly.

From what I understand, but I can't get any confirmation from any of the parties, is that the tall bottles are the same tube that Mesa (STR-440) and Ruby (6L6GCMSTR) uses.

[donnyjaguar]

Bias and HT voltage will move closer to zero when the mains voltage drops. Its almost self-regulating so there shouldn't be that much of a difference. This is the reason I don't use a voltage regulator on bias. I tried it once and the results were fine until the next day.

[Faustine Amps]

I've used lots of the TAD short bottles and haven't had any issues yet, but your story concerns me. I have one particular customer who I keep in touch with on a pretty regular basis. He works those tubes hard and gigs a few days a week. No complaints so far (fingers crossed). I typically bias them for 40 to 45mA idle plate current @ about 430 VDC.

For what it's worth, I've also found the SED 6L6GC tubes to be pretty robust in my amps.

Regards,
Tim Gregoire

[phsyconoodler]

I also retube all my amps with TAD 6L6 short bottles and have never had one single failure.The sound is superior too.
I use them because I've had JJ problems and winged C problems too.

[Old Tele man]

I stay away from all power tubes made in China.

...what? You're not gonna award China a GOLD medal for their vacuum tubes?--that's so UN-Olympic of you (ha,ha)!

[slider313]

...what? You're not gonna award China a GOLD medal for their vacuum tubes?--that's so UN-Olympic of you (ha,ha)!

No, but I will give them a gold on their fireworks show. I had a pair of Shuguang KT66's go up in lights and the fireworks were beautiful !!

[RussB]

So, in a typical fender twin what would you set them to in ma?


MY BF Twin ran at aound 470 plate volts, my '69 SF ran around 410 plate volts...and I think the later ultralinear's run over 500v!

There is no "magic number"

In the BF I ran 'em around 34mA. That's right about 55%. I'm not one of the guys that feels that running power tubes real hot makes the amp sound better. In fact, I usually find quite the opposite.

I think you'll find stories of every new tube Mfg'er having tubes live very short lives. I will venture to say that also happened in the 50's and 60's, but tubes were so cheap, plentiful and readily available, no one made a big stink about it.

[jzucker]

Thanks Russ. I've been running my BF amps at 30ma. Maybe I can up them to 34-35.

[JimiStiff]

as far as i know are their tubes made in china, but carefully tested and selected in worms, germany. They are indead very nice...but pricey as well. currently i'm testing tube-town.net tubes, which is as well located in germany and offers various tube-builders...

[HipKitty]

Their 6L6's (tall and short bottle) are Chinese (Shuguang) tubes. TAD tests them similar to GT, Ruby and Mesa.