sckott, Steve, toob doods - what's a 6B4G???

[indy mike]

I was bad and steered the naughty bits/suspension thread over in the music department; toob dood sckott mentioned a tube I wasn't familiar with, the 6B4G - what in the name of Mullard is a 6B4G???

[Steve Hoffman]

Beats me. Probably a TV tube. What's it used in?

[Sckott]

A fairly inexpensive push-pull directly heated triode.

http://www.arrakis.es/~igapop/6b4g_push_pull_amp.htm

The one I'm building on parts for:

http://www.pmillett.addr.com/6B4G%20push-pull%20amp.htm

If you look at the shape and size of a 6B4G, it looks like the tube on my Avitar, which I THINK should be a 2A3.

The tube is actually a great performer, but demands quite a bit in the capacitor dept. I've seen a lot of 6SN7's used for inputs (or types) and not only these....

It'll be fun.

[indy mike]

Ahhh, not a well known tube about town - been reading audioXpress on the side, sckott???

[Steve Hoffman]

I'm giving you a hard time, Mikey

It's an obscure 6A3 6-volt version. It has an octal base instead of the old four pin base of the 2A3...I have NO idea what it sounds like.....

Sometimes people design tube stuff using a certain tube just because it is "unknown" and still cheap to buy...

[Sckott]

Right. I have all ceramic octals for the base. All tubes in that Pete Millett receipe are one type, and use fairly easy-to-git transformers. It IS obscure, as many popular tube sites don't carry it. Angela does though, as is the trannys.

Pete wrote a few articles for AudioXpress. I would recommend that mag for DIY'ers. Lots of neat stuff in those rags. I haven't been very excited about a mag since this one. Very thoughtful.

I'm building it to follow a schem for the 1st time unattended, and I only know the amp is a solid performer. I don't know if it will kill alything else I have, but that's also in the fun.

[ferric]

nice looking layout and execution on the links!

I'd like to hear it.

[Sckott]

If the LCR caps are stil available in the spring, I'll let everyone know.


If it sounds good, I'll be happy. Tis mostly a mountain I want to climb and say, "I did that all by myself! Goo goo...."

;)

[Drew]

A 6B4G triode is the exact same tube as a 2A3 triode (used in my Bottlehead Paramours and some other SET amps) except it needs a 6.3 volts (with 1 amp of current) on the filament instead of a 2.5 volts and 2.5 amps like a 2A3.

Since the 6B4G has a higher filament voltage than a 2A3 its very difficult to control hum in single ended applications, so its used in push-pull where the hum usually cancels.

[indy mike]

Glass-lovers, thanx for the info!

[Drew]

Sckott:

Have you ever thought about an interstage coupled push-pull like this?

http://www.meta-gizmo.com/Tri/interstage.html

I've been slowly getting together the parts to build a 2A3 push-pull. Since I already have 2A3's for the Paramours it makes more sense than going to a 6B4G.

Here's an interstage coupled 300B push pull for anyone who's interested:

http://www.meta-gizmo.com/Tri/RRM/sun.html

Steve:

Are the VAC amps that you used in the past interstage coupled or do they use some kind of Mullard phase splitter like the old McInstosh/Dynaco/Eico equipment. I don't think the VAC web page goes into that kind of detail.