amp-in-a-tube

[jcgss77]

I am the fortunate recipient of a bunch of vacuum tubes, which come from devices other than those designed for audio. Looking at the datasheets, they are basically triodes, pentodes, and diodes. One of them, a 15BD11, has really gotten my attention. It contains two triodes, which differ in the amount of gain, and a pentode.

If this was a normal pentode, I would have no problem working out a schematic to design a small watt amp. However, the cathode of the pentode is tied to one of the grids. Here is a link to a 6BD11 tube datasheet, which is the same tube just varies in the heater specs:

frank.pocnet.net/sheets/123/6/6BD11.pdf

What does this mean in the designing side of things, to have the cathode tied to a grid?

[s151669]

Is not this business as usual ? Supressor grid is internally tied to cathode in many tubes, eg. EL84, 6V6, etc. Most likely you would tie it to cathode anyway.

[jcgss77]

Thank you for your post. I had never seen the two tied together in a schematic, that is, until after I posted this question. I have a design now, and will post my results once I get to it. The only thing holding me back now is trying to find the proper transformers. I think I will be using a nixie power supply fed by a 15 volt wall wart. I am currently looking for an output transformer that won't break the bank. Will be waiting for the components for a little too.

[thetragichero]

classictone makes some nice iron

[s151669]

Something like this (overkill ?)



or this ?



As maximum plate dissipation is 4W, realistic output should be at around 1...2W.





(EDITed by sumgai to enable direct image viewing.)

[jcgss77]

I think with this tube something with an impedance of 5-10k is what I need, if my research has brought me proper insight. That would likely work-are you offering to ship that to me? I do want a transformer that will handle a 4 ohm load. Looks like I am gonna have to do some math to find the proper impedance for this amp!

Now what it comes down to, like usual, is if my better half will let me shed out some bucks...looks like I can build this for at or under 75 clams, less if I us a SMPS power.

I do have a couple rectifiers too...if I have a suitable PT laying around or find a good deal on one, maybe I can go all tube on this baby!

@tragichero-Hey, those transfos look pretty nice.

Since most OT's are modeled after the vintage ones, what company was known for a warmer sounding OT?