Drip Dual-STA build - dual 6BA6 option

[morls]

Hi,
Does anyone have experience with using dual-6BA6 or 6BJ6 instead of 6386 in this build? I'm looking into going this way due to the scarcity of 6386s.
I'm interested to know whether the main board needs to be modified, or if it's just a matter of fitting an adapter board into the 6386 socket.
Stephen

 

[FarisElek]

This technique can be used in any sta-level type build, or anything with a 6386 in general. You don't need to look at this in a drip sta-level exclusive point-of-view. Chances are no one has tried it on the drip yet. I got the tubes for doing this same thing but ended up finding a good price on 6386 not long after so I abandoned the project until the 6386 die out and I don't feel like buying some again.

You're going to have to build your own adapter boards. Bowie sent me this information at some point that he gathered from somewhere. Look at the Manley T-Bar for inspiration on what it may look like.

 

[morls]

That's great, thank you!

 

[schrobbelbop]

I've made my own t-bar boards from turret and a tube socket extender (socket saver)
I've cut open the extender and soldered wires to the 6ba6 sockets. added the
68R and is works like a charm.

I've matched the 6BA6 to have equal voltages at pin 7 at 6BA6. on some different
compression levels injected with 100hz sine. The 6386 balance trimmer can help
to find the sweet spot.

Planning on making some decent boards for my fairchild when it needs replacement
tubes. way cheaper then the overpriced 6386's and works just as good.

 

[TLRT]

You need many 6BA6 to find really matching pairs, needs a good curve tracer or measure anode/grid voltages at different compression points and measure with a good DC emission tester like Neubergers. If the tubes are really matched well it sounds very good.

 

[Sc]

You need many 6BA6 to find really matching pairs, needs a good curve tracer or measure anode/grid voltages at different compression points and measure with a good DC emission tester like Neubergers. If the tubes are really matched well it sounds very good.

Yes very difficult to find good matched pairs - I ended up using the 9003 t-bar, price is about the same and imho easier to find matched ones. Testing done with a roetest. One main advantage is half heater current also (esp. for 670 designs). Any other experience with these ?

 

[Walrus]

Where did you find the 9003 t-bar? A quick search does not reveal anything.

 

[Sc]

Sorry - missed your question. The circuit that Faris-Elek uploaded above is (as indicated in the text) originally the one for a 9003 t-bar (9003 data attached). Same pinout as the other valves -, but internal connection cathode / shield on Pin 7, so you don't need to have this link on the T-bar.