6AU6

[patlaw]

Most Hammond organs use two 6AU6s in the AO-28 preamp. That 6AU6 is not manufactured any longer. There must be a train load of them in inventory throughout the world. What happens when the worldwide inventory is depleted? Is there a similar pentode that can be substituted with rewiring (if necessary)? Is it possible that one of the tube manufacturers will start making them?

[mozz]

They are very common and there will always be a supply. I have used them for tremolo ala silvertone, i should have my friend make me a pcb so i can add this about to anything. I have too many.

[loudthud]

I have about a hundred NOS and a similar number of 12AU6. Data sheet shows a nice amplification factor of 36 when triode connected. Only bad thing is I don't have any 7 pin sockets

[Justin Thomas]

I manage to get about a dozen every time I get a box of tubes. I doubt we'll run out anytime soon. Haven't used any in a build yet though.

Jusrin

[patlaw]

It's good to hear that they are plentiful. I'd still love to know why there are SO many new tubes still around after all this time.

[J M Fahey]

It's good to hear that they are plentiful. I'd still love to know why there are SO many new tubes still around after all this time.

I was puzzled by the same idea, until if found that tubes were:

* made in *monster* quantities,

* their use stopped cold turkey, not kidding, so whatever surplus was produced (millions) will take a loooonnnngggg time to dry up.

We find shortages because we all want the exact same 4 or 5 types, "whatever Leo/Jim/Dick used" so these are scarce and expensive, all others are still out there and nobody wants them.

Now apply demand and supply to the situation .

What does Monster mean, in numbers?

I once read a 60s report about Tube Manufacturing Industry in Canada" from the 60s and they mentioned "50 to 80 MILLION tubes per year.

Mind you: Canada.
An industrialized Country but not THE tube powerhouse, imagine production in US, UK, Germany, Holland, Russia, China, Japan.
Mind boggling numbers.

Use and production was so high that some unexpected contenders appeared: besides , say, Hungarian French, Italian, Czech factories, EI Electronics was a plant set up buy Yugoslav Army for their own use .(remember Yugoslavia was independent both from Soviet and Occidental political blocks), Czechs had a WW2 Telefunken sub-plant built there, India created UR/USHA tubes and transistors for its own Armed Forces use, etc.

Even we Argentines had TWO heavyweight tube factories built here: Philips (FAPESA brand) and none less than RCA (Deltron brand).

I bought 1000 Ukrainian made ECC189 , dual triodes designed for TV cascode front end which work perfect for Audio at 50 cents each.

NOS is a treasure trove if you can handle tubes "not used by Leo" he he.

[Justin Thomas]

NOS is a treasure trove if you can handle tubes "not used by Leo" he he.

I've been preaching this for years to folks who either don't have the money (which I understand) or who have the money but don't want to pay a tech to retube or retrofit their amp or don't want to pay the "ridiculous" prices for NOS or new production tubes. Okay, take the time to learn. I've got a practical lifetime of spare tubes to build with for mere nickels per tube. Worst thing I might have to invest in is a filament transformer...

It's such a flexible technology. I just keep a copy if RC30 on ny phone & Frank's Electron Tube Data Sheets bookmarked & go to town.

I tend to "take advantage of" sellers who don't feel like sorting through their collections. And sometimes I evrn do get some nice 6L6GCs or a good 12AX7 or 2. And 12AD7s are nice, too.

Jusrin

[mozz]

A lot of these TV tubes, may not have worked perfectly. The repairman swapped it out to a new tube and the customer was happy. The old tube was saved and may work perfect in another tv set. They were cheap and many spares were made. So that particular tube and many others were always in the repairman's caddy.

[Chuck H]

And 12AD7s are nice, too.

I'm afraid people have cottoned onto the 12AD7 tubes. Prices are similar to AX7's anymore.

[Justin Thomas]

Chuck H then I guess I shall keep picking up broken reel-to-reels & other such stuff for $10-25 & scavenging them. I think the only times I actually "buy" tubes is for my Fenders that need 6L6GCs or a 12AX7, neither of which I have a huge stash of for obvious reasons. I've also got lots of 12AV7, 12AZ7, & for some reason I'm still able to find good quantities of 12AT7s for stupid cheap...

But I do think that future builds will be using power tubes of the 6_6 variety that suck up more heater current. But they sure do sound nice! I'm partial to 6W6Gs & 6Y6s are nice too.

Jusrin

[Justin Thomas]

A lot of these TV tubes, may not have worked perfectly.

I wish I could advertise to buy everyone's "bad" or "microphonic" tubes they pull from their amps & trash. Them: "I tapped it & it made a noise so I tossed it." Me: [SMH]

Jusrin

[patlaw]

I wish I could advertise to buy everyone's "bad" or "microphonic" tubes they pull from their amps & trash. Them: "I tapped it & it made a noise so I tossed it." Me: [SMH]

What is it that you like about microphonic tubes?

[Justin Thomas]

patlaw because a tube making a noise when you tap it isn't really a problem. It's when you tap it and it CONTINUES to make a noise that it's a problem. Or if it makes noise under playing conditions. I see a hundred times a day where guys poke theor tubes with a pencil or screwdriver or whatever & it "makes a noise" so under the advisement of internet gurus, they throw it away & buy new ones.

They might also work perfectly fine in a phase inverter or tremolo oscillator slot. Nobody (well, almost nobody) tells them to try that firsr before trashing it.

Jusrin

[g1]

If you turn all the controls up full and tap on tubes you are going to hear something. Some people think this means the tubes are microphonic. By this logic, all tubes are microphonic.
So, agree with Justin's assessment, if it starts ringing on it's own (or keeps ringing), and under normal playing conditions, that is a reasonable standard of microphonic.

[Helmholtz]

If you turn all the controls up full and tap on tubes you are going to hear something. Some people think this means the tubes are microphonic. By this logic, all tubes are microphonic.
So, agree with Justin's assessment, if it starts ringing on it's own (or keeps ringing), and under normal playing conditions, that is a reasonable standard of microphonic.

When I tap a tube with the tip of my finger and it makes a loud noise at a normal amp setting, I consider it microphonic and replace it. Doesn't need to keep ringing. Of course I make sure it's not a socket contact problem.
It's very likely that such tube spoils the sound when excited at stage volume.
Especially the power tubes in a combo amp like to get microphonic over time because internal elements become loose.