Thoughts on Tung Sol reissue 12AX7 and reliability?

[daz]

I bought 4 of these maybe 4 years ago. 2 of them hummed loudly. I sent them back for replacement and of those 2 one did. I've been using the good ones since but i'm down to one left and i really love this tube in V1. But before i buy more, can i get some thoughts on this and whether that has changed at all? And no, i didn't use them in the cathode follower position.

[Jazz P Bass]

One thought that may or may not help.
All current production tubes are hit or miss.
Period.

[big_teee]

I bought 4 of these maybe 4 years ago. 2 of them hummed loudly. I sent them back for replacement and of those 2 one did. I've been using the good ones since but i'm down to one left and i really love this tube in V1. But before i buy more, can i get some thoughts on this and whether that has changed at all? And no, i didn't use them in the cathode follower position.

I like the tone of the TunSols in my 2204, but I had the same issue as you.
I went back to the much cheaper JJs. lol
Not had any problems with them.
T

[daz]

One thought that may or may not help.
All current production tubes are hit or miss.
Period.

It's relative. I've used tons of current prod tubes, but while what you say may be right to some degree, nothing like this ! I have never found any current prod to be 50% bad, not even close.

I like the tone of the TunSols in my 2204, but I had the same issue as you.
I went back to the much cheaper JJs. lol
Not had any problems with them.
T

Well, i just absolutly love these in V1. They do something to the tone and feel i can't explain in my amp. But i MUST use them. I just thought maybe they might have fixed the issue. It's obviously a lack of consistent precision in the manufacturing process because some are as quiet as anything.

[Leo_Gnardo]

I bought 4 of these maybe 4 years ago. 2 of them hummed loudly. I sent them back for replacement and of those 2 one did.

Hummy tubes OK for use in circuits where filament supply is DC. So they may be suitable for something other than target practice. Reading an old (2008) thread @ TGP one old timer said sourcing tubes in the 60's and 70's was a crapshoot too. Do you repair as well as build? Mark the hummers & install as needed in amps that have DC preamp filaments.

[Enzo]

The problem is making broad inferences from a single sample of four tubes. What if they are all fine except YOUR box of four fell off the back of the UPS truck to the pavement? Your four tubes were not only shipped together, they also probably came out of the same bulk box at the dealer end, and as such were probably from the same production batch.

Now maybe they are crummy tubes, but until we get similar reports from guys who bought from different suppliers at different times, we are expecting way too much from our data.

Imagine you wanted to bet on an American football game. If you watched one four play sequence, would that be enough to decide which way to bet?

[Steve A.]

The problem is making broad inferences from a single sample of four tubes.

I do agree but I am glad that Daz did post his observations with them and requested that other people post their own observations. It does sound like they tend to hum in the V1 position of a high gain amp unless they have a DC filament supply. "No gain, no pain?"

Steve Ahola

[Mick Bailey]

Just put a set in a Dr Z MAz 18 and they're really nice in that particular amp, no rattles or microphonics.

I tap every tube these days. If they rattle too much or ring I don't fit them. I wonder if a lot of tubes get onto the open market because they've previously been filtered out by companies that test them. Let's say they get 15% (my made up figure) that fall below their standards. If your business is selling tubes, that's a lot. But then you can put a premium on the 'good' ones you sell. So what happens to the ones that fail? Would they get sent back half way round the world? Or does the supply contract allow a certain failure rate and they get passed off to find their way back onto the market.

I'm pretty sure they dont get crushed.

I bought a batch of Chinese 12AX7 at trade wholesale price and roughly 30% were too microphonic to use, but they still worked out pretty good value for the price I paid. The second batch bought about 10 months later were the same. However, the gain varied enormously between tubes and the pins needed straightening on every one.

Here in the UK you can buy tubes from Hotrox (other tube vendors are available) that are dynamically matched triode halves tested for microphonics and noise. Not cheap, but they work right out of the box.

[daz]

The problem is making broad inferences from a single sample of four tubes. What if they are all fine except YOUR box of four fell off the back of the UPS truck to the pavement? Your four tubes were not only shipped together, they also probably came out of the same bulk box at the dealer end, and as such were probably from the same production batch.

Not likely tho Enzo. The 2 bad ones i sent back and the replacements were 50/50, 1 bad one good. I also pulled one out of an amp that was humming a while back. Plus i've heard this mentioned by others. I really don't think theres a question on this tube, it's just problematic.

That said, does anyone know of a seller who is anal about testing and would test these in an amp before sending? The ones i got were bad out of the box so chances are that would eliminate this problem at least in large part. I usually buy from tube depot but i'm not sure how they test if at all.

[Steve A.]

So what happens to the ones that fail? Would they get sent back half way round the world?

I have wondered the same about resistors. I bought 2 sets of the assorted Velleman 1/4 carbon film resistors (10@ of 22 values for $8) and I haven't found one resistor yet that was the actual value. They do come from rolls so maybe Velleman buys batches just barely within rated tolerances.

Steve Ahola

[big_teee]

That said, does anyone know of a seller who is anal about testing and would test these in an amp before sending? The ones i got were bad out of the box so chances are that would eliminate this problem at least in large part. I usually buy from tube depot but i'm not sure how they test if at all.

Tube Depot Does, if you pay them to.
Look at the drop down tab, at what they offer.
Tung-Sol 12AX7 New Production Preamp Vacuum Tube

[daz]

Tube Depot Does, if you pay them to.
Look at the drop down tab, at what they offer.
Tung-Sol 12AX7 New Production Preamp Vacuum Tube

That list has only one extra cost test ("low noise or microphonics +$4") that would have to do with the issue i posted about, but to have to pay more for that doesn't seem right because this is not a issue of one tube just being noiser than the next, this is a DEFECTIVE tube. I would think the standard test which it shows is free should weed these out. But it was tubedepot i believe i got them from so apparently not. If this amount of noise is considered acceptable then all i can do is shake my head and wonder how we came to this. It's unusable to anyone other than maybe some 16 year old who knows 3 chords. I guess i'll just pay my nickel and takes me chances eh?

[big_teee]

That list has only one extra cost test ("low noise or microphonics +$4") that would have to do with the issue i posted about, but to have to pay more for that doesn't seem right because this is not a issue of one tube just being noiser than the next, this is a DEFECTIVE tube. I would think the standard test which it shows is free should weed these out. But it was tubedepot i believe i got them from so apparently not. If this amount of noise is considered acceptable then all i can do is shake my head and wonder how we came to this. It's unusable to anyone other than maybe some 16 year old who knows 3 chords. I guess i'll just pay my nickel and takes me chances eh?

That's where I got mine too.
I bought a more expensive Mullard 12AX7, and in my 2204 it had more hum, so I put it in the PI slot, and it was fine.
I have to do like you, and hunt for that special tube for V1.
I have a $8 generic JJ in that slot now and it is fine, not quite as Plush sounding as the TungSol, but not thin like a Sovtek either, and it has held up well too.
Good Luck,
T

[eschertron]

That list has only one extra cost test ("low noise or microphonics +$4") that would have to do with the issue i posted about, but to have to pay more for that doesn't seem right because this is not a issue of one tube just being noiser than the next, this is a DEFECTIVE tube. I would think the standard test which it shows is free should weed these out. But it was tubedepot i believe i got them from so apparently not. If this amount of noise is considered acceptable then all i can do is shake my head and wonder how we came to this. It's unusable to anyone other than maybe some 16 year old who knows 3 chords. I guess i'll just pay my nickel and takes me chances eh?

That's curious enough for me to do the math:
4 tubes @ $14.95 = $59.80 at today's prices
add $4 per tube for testing low noise and microphonics (is this guaranteed to meet OUR specs?)
3 tubes @ $18.95 = $56.85
I used qty 3 for the second equation because, as you said, even after the return you only got three of the four tubes to be hum-free enough to use in V1.

Maybe it is cost-effective to pay the extra cash...

[Steve A.]

That said, does anyone know of a seller who is anal about testing and would test these in an amp before sending?

I think that a testing rig could be devised which would find the tubes which would be "hummy" but its probably cheaper for the distributors to let the end user be the tester. Not that bad for us unless we got stuck with the postage to return them.