Sorta OT - What are these tubes?

[Paul Marossy]

I have some tubes which were given to me. They have seven pins, and I have three different types:

12AT6
12BE6
12BA6

Are these mini pentodes?

[Joep]

12AT6 (6AT6)

12BA6 (6BA6)

12BE6 (6BE6)

They all can be found here:
http://home.wxs.nl/~frank.philipse/frank/frank.html

Bye,

Joep

[Arn C.]

12AT6  (miniature button 7-pin) Duo Diode High-Mu Triode  .5watts plate dissipation (suitable for second detector audio amplifier service)

12BE6  (   "     )  Heptode Converter  1 watt plate dissipation

12BA6  (   "     )  Remote Cutoff R F  Pentode (deigned primarily for service as a high gain rf or if  amplifiers

Hope this helps!
Arn C.

[Gringo]

I have those exact ones, plus some 12AV6, they are used in old radios (about the only way for me to get near a tube). Any possible use for them in a tube overdrive/preamp?

[Jim Jones]

Hey guys - for tube data you can't beat Duncan's Amp Pages. The search engine there is fantastic!  //www.duncanamps.com

Jim

[Pedro Freitas]

I have those exact ones, plus some 12AV6, they are used in old radios (about the only way for me to get near a tube). Any possible use for them in a tube overdrive/preamp?

The 12AV6 will make excelent platforms for tube preamps/overdrives.
Just use one biased exactly like one would bias half of a 12AX7 and it'll make a very loud clean boost! (like, 100Kohm on the plate, 1,5K on the cathode, bypass cap on cathode if you will, 100VDC on the plate)
Cascade 2 or more and you'll get distortion.
The 12AT6 will have slightly diferent bias points but will work too.

Pedro

[Gringo]

Great!!

I've never worked with tubes, and i'd like to do something simple first. That clean boost you suggest sounds just fine. Maybe you could explain it a little more foolproof?

I don't mind experimenting on my own, but when high voltages are involved, i become 300% more careful (paranoid), as i've had my share of shocks to last a lifetime . Besides, i only have two of each tube, and i don't want to fry them.

But first things first, i'll go check my tubes are good (not blown).

[Paul Marossy]

Hmmm... sounds like stuff for old tube radios.

I have heard of people using 12AV6 tubes before. I hadn't had of any of these ones, though. Maybe I could do something with the 12AT6...

[Pedro Freitas]

Great!!

I've never worked with tubes, and i'd like to do something simple first. That clean boost you suggest sounds just fine. Maybe you could explain it a little more foolproof?

Here you can see how I turned a 6AV6 into a ultra simple clean booster:
http://www.geocities.com/stompboxworktop/preamp.html
The 6AV6 is a 12AV6 with 6,3V filament. You might have to replace the 33ohm resistor in the filament suply with a smaller value one.
Disregard the centre tap in the filament, it's an error.

And at GEO you can see the Alembic F-2B preamp, just use the first half of the 12AX7. Remove the tone stack if you don't need it.
http://geofex.com/FX_images/alembpre.gif

Tubes are very forgiving, don't be afraid to experiment. Just mind where
you touch with your fingers and try to keep the filaments at their required voltage and the tubes should last for a long time.

[Gringo]

Ok, a couple of questions:

- Are the 160v (B+) critical, or pumping 100v at the plate is the desired effect? (i have a 220-110ac tranny)

- By looking at your preamp, i believe you are feeding 12v to the heater,instead of 6. Is this right?

I was thinking of using two transformers (that's what i got handy right now) independently(ie not in series), one (220-12ac)to get the 12vdc for the heater, and another (220-110ac)to get B+, just for testing this out.

What do you think?

[Pedro Freitas]

Ok, a couple of questions:

- Are the 160v (B+) critical, or pumping 100v at the plate is the desired effect? (i have a 220-110ac tranny)

The desired effect is having the plate at 100V and the grid at -1V.
With a plate resistor of 100K and a cathode resistor 1,5K would expect a gain of about 30.
If the voltage at the plate are way off you can play with 56K resistor coming out of the PS.
Altering the plate resistor will alter the gain factor and bias point.

- By looking at your preamp, i believe you are feeding 12v to the heater,instead of 6. Is this right?

No, I'm feeding it 7VDC, the series resistor is taking the voltage down a bit.

- I was thinking of using two transformers (that's what i got handy right now) independently(ie not in series), one (220-12ac)to get the 12vdc for the heater, and another (220-110ac)to get B+, just for testing this out.

What do you think?

That'll be cool. See if the tranny supplying the filaments can take the 150mA per tube. The plate current is almost neglegible, about 0,5mA.

[Paul Marossy]

OK, all you experts on tubes, I have a question about the 12AT6:
If that tube is a duo-diode hi-mu triode, can I connect it in a circuit so that the triode amplifies the heck out of the signal and then have the two diodes clip the signal? It seems like you would get a nice diode clipping sound compared to Si diodes. I wonder if it would sound more or less like Ge diodes...

Anyhow, is this possible?

[Gringo]

This was asked in a thread not long ago:

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=22821&highlight=tube+diode+clip

BTW, I've assembled something similar to a McTube using the 12ba6 into the 12at6 instead of a single 12ax7 (with a lot of help from people from this forum), and it sounds (amazingly) quite good.

Since you are in a "tube spree", you might want to give that a try (that way we could compare results ). The actual schem right now is:



Next step will be a tonestack, and adding a new gainstage, since it takes my mosfet booster very gracefully.

[Paul Marossy]

Cool! I was just thinking of doing exactly the same thing...
Do you have any sound clips of it?
Also, do you have any details on the pin connections? I know the tube pinouts, just not how they connect to the circuit.

This would work out very well for a sloped front aluminum enclosure that I have been trying to find a use for.

[Gringo]

I updated the picture with the pins numbered. Reloading the page a couple of times should do the trick.

[Paul Marossy]

Thanks gringo.  
Two more questions: On the 12BA6, are pins 2 & 7 connected together? What did you do for the heaters? Seperate transformer?

[Gringo]

Two more questions: On the 12BA6, are pins 2 & 7 connected together? What did you do for the heaters? Seperate transformer?

Yes, pins 2 and 7 are connected.

I'm using a separate transformer for the heaters. When i have the preamp ready, i'll try to add a power stage using the output transformer from the radio (only gripe is that it's a 50c5 - heaters run at 50v).

[Paul Marossy]

Thanks gringo. I just need to get my 7-pin sockets and I think I can build this one just for fun (since I am on a tube binge as of late...).

Say, some pictures of your project would be interesting, if that's possible.  

[Gilles C]

I have some tubes which were given to me. They have seven pins, and I have three different types:

12AT6
12BE6
12BA6

Are these mini pentodes?

I wasn't home when I first saw your post, but I was pretty sure about the 12(6)AT6 tube being inside my Mercury tube tester.

So I checked once home...

It is a 6AT6. So for your info:

http://www.finitesite.com/gtechblues/My_images/Schem.jpg

http://www.finitesite.com/gtechblues/My_images/Parts.jpg

[Paul Marossy]

That's cool, that manual is pretty detailed. More so than the one EICO published for the Model 625. It doesn't have the parts list, but it does include the schematic.