Virtual/Artificial 6.3 Center Tap

[LearnEverything]

Apologize if this is the wrong forum to post this.
No 6.3v center tap on my transformer, Rob Robinette and Terry @D-Labs have different methods of creating these. Rob's site has the resistors solders on the tube socket pins, Terry uses a 3 tab center grounded terminal strip. Thoughts, recommendations? Thank you.

 

[King Fan]

What amp are you building? It makes a difference; Rob's is for the cathode-biased 5E3, IIRC. Just as a start, it may help to read about the difference between an artificial CT, an elevated CT, and one like Rob's that’s both. See the 3rd, 4th, and 6th headings here. Let us know what doesn’t make sense.

The Valve Wizard

 

[printer2]

I would not put them on the output sockets as things get busy there. Usually we have the grid stoppers and screen resistors on the sockets to keep the lead length between the resistor and the tube short. This reduces the chance of RF getting in the elements.

 

[King Fan]

I would not put them on the output sockets as things get busy there. Usually we have the grid stoppers and screen resistors on the sockets to keep the lead length between the resistor and the tube short. This reduces the chance of RF getting in the elements.

Good point. Still, it's possible to do it Rob's way (for elevation) and still run grid stoppers and screen resistors. In fact, I'll argue you can do it more neatly than the tag strip picture above. Heh, I admit that's a low bar. This is for a 5E3.

 

[clydethecat]

Dumble used to tack them onto the pilot light:

 

[printer2]

Good point. Still, it's possible to do it Rob's way (for elevation) and still run grid stoppers and screen resistors. In fact, I'll argue you can do it more neatly than the tag strip picture above. Heh, I admit that's a low bar. This is for a 5E3.

View attachment 1215099

Sure you can fit stuff on the sockets, more so with a octal socket. Really all depends if you can easily to get in to make measurements if needed.

 

[LearnEverything]

What amp are you building? It makes a difference; Rob's is for the cathode-biased 5E3, IIRC. Just as a start, it may help to read about the difference between an artificial CT, an elevated CT, and one like Rob's that’s both. See the 3rd, 4th, and 6th headings here. Let us know what doesn’t make sense.

The Valve Wizard

KF, building Rob's Champ Micro.

 

[LearnEverything]

Dumble used to tack them onto the pilot light:

View attachment 1215102View attachment 1215103

DB, have to say I like this.

 

[King Fan]

KF, building Rob's Champ Micro.

So that makes a difference. Are you building the 12AU7 or EF80 version? Those smaller tubes may not provide enough cathode voltage to provide useful elevation, plus that socket is small, so the fit concerns mentioned by @printer2 matter more.

If you read the Merlin article I linked above, you'll see that DC elevation is optional. It may be easiest to mount somewhere else along the heater chain, like the lamp as @David Barnett says.

 

[LearnEverything]

What amp are you building? It makes a difference; Rob's is for the cathode-biased 5E3, IIRC. Just as a start, it may help to read about the difference between an artificial CT, an elevated CT, and one like Rob's that’s both. See the 3rd, 4th, and 6th headings here. Let us know what doesn’t make sense.

The Valve Wizard

Thanks for

So that makes a difference. Are you building the 12AU7 or EF80 version? Those smaller tubes may not provide enough cathode voltage to provide useful elevation, plus that socket is small, so the fit concerns mentioned by @printer2 matter more.

If you read the Merlin article I linked above, you'll see that DC elevation is optional. It may be easiest to mount somewhere else along the heater chain, like the lamp as @David Barnett says.

The 12AU7 version, so DB’s suggestion looks clean and simple and I need simple. Thanks so much for the Valve Wizard link, looks like a great resource. Appreciate how helpful the folks are here.

 

[Arry]

Here's how it's done on my Victoria 5112:

 

[Glen W]

Fender did it at the pilot light as well...

 

[LearnEverything]

Here's how it's done on my Victoria 5112:

View attachment 1215276

Thanks Arry, another good example/reason to go this way.

 

[LearnEverything]

Fender did it at the pilot light as well...

View attachment 1215292

Appreciate the info Glen.

 

[akulikow42]

The D-lab pic is a little too cramped with wires for my tastes, might be annoying if you want to change anything, not to mention the extra hole in the side of the chassis. It looks like the pilot on the micro champ is close to the upper right PT bolt. I'd add a solder lug and put it there, or solder to chassis ala vintage Fenders if you have a higher wattage iron. The dumble way is pretty cool too...

 

[gusfinley]

Another suggestion: Use 1% resistors.

I've had 5% resistors still allow a little hum. I opted for 1% once, because that was all I could find and now that is all i will use for this purpose.

 

[LearnEverything]

The D-lab pic is a little too cramped with wires for my tastes, might be annoying if you want to change anything, not to mention the extra hole in the side of the chassis. It looks like the pilot on the micro champ is close to the upper right PT bolt. I'd add a solder lug and put it there, or solder to chassis ala vintage Fenders if you have a higher wattage iron. The dumble way is pretty cool too...

The D-Lab pic is actually a kit someone built that was sent to him for repair, had a bad ground, so he added the tag strip to fix it. Would guess if he'd scratch built it, it would've looked cleaner. Solder lug is a good idea as well. Thanks

 

[LearnEverything]

Another suggestion: Use 1% resistors.

I've had 5% resistors still allow a little hum. I opted for 1% once, because that was all I could find and now that is all i will use for this purpose.

Checked and mine are 1%, should be good to go. Appreciate the suggestion!