12v heater wires

[andrew]

My transformer has 6.3v and 12v heater wires each having a center tap. How could I use the 12v to run 6.3v DC to a 6sl7 and a 12ax7? It is either this method or buy a 6v wall wart. Thanks for any help.

[David Root]

You need a small bridge rectifier, I would use a BR34 (3A at 400V), which is overkill, or a smaller packaged bridge rectifier, these are pretty cheap, not less than 2A rating and 50V DC, two 1000uF/25VDC caps, and a 7806 regulator or modern equivalent. These usually come in a TO-220 package which you mount to the chassis with a 4-40 bolt & nut and an insulating shoulder washer and a mica insulating pad between the back of the piece and the chassis. Thermal grease is a good idea too on both sides of the mica insulator. Thermal grease improves the thermal capacity of the mica so the regulator doesn't overheat.

Try www.apexjr.com he should have all above for about $2.50 or so.

This will give you solid regulated 6.0VDC at up to 1.0A, which is safe because you only need 0.6A.

If anyone has a ready made schematic please post it, otherwise I can draw something up for you.

[Structo]

As an FYI, Apex has a $20 minimum order so if you do buy there it's a good time to stock up on hookup wire, pots, etc.

[tubeswell]

Hi Andrew

You could use the 6.3V for the 6SL7 and run the 12AX7 off the 12V supply - just wire one side to pin4 and the other side to pin 5 - leave pin 9 unconnected. That way you can elevate the heaters separately.

[David Root]

In my experience using 6V3 AC on a 6SL7 in a high gain circuit results in loud hummmmmmmm, because the filament design is not humbucking. You need DC heaters on a 6SL7, that's why Andrew is looking for 6V3 DC.

[andrew]

Yes. I could sure use a layout. Thanks!!

[dehughes]

In my experience using 6V3 AC on a 6SL7 in a high gain circuit results in loud hummmmmmmm, because the filament design is not humbucking. You need DC heaters on a 6SL7, that's why Andrew is looking for 6V3 DC.

I had loud hum even in a low-gain 6.3vac circuit when using a 6S*7 tube. DC was (and is) the way to go, IMHO.

[andrew]

Hi, here is a neat idea for a DC heater and I read a post where Alessandro uses this method also. https://tubeamparchive.com/download/file.php?id=8159
I have a question though. How do I wire a 6sl7? The diagram shows a 6v out and a cap to ground. Thanks.