Question re: 6L6 wiring

[JamesO]

My goal for the weekend is to get the 6L6's wired on my Funk build. After looking at things all week, I'm more confused than I was prior.

- Some builds simply have a 1k5 5 watt wirewound going from pins 4 to 6: https://tubeamparchive.com/download/file.php?id=2142

- Some builds simply have a 5 watt 470R or 500R wirewound going from pins 4 to 6. Brandon told me either of these options was good.

- Some builds have the 5 watt wirewound going from pins 4 to 6 AND a 3k3 or 5k1 resistor going from pins 1 to 5: https://tubeamparchive.com/viewtopic.php?t=6240 , https://tubeamparchive.com/viewtopic.php?t=1654

What are the purposes of each variation? I'm building a high plate non-hrm, and I don't know which scheme is appropriate. [/i]

[Bob-I]

- Some builds simply have a 1k5 5 watt wirewound going from pins 4 to 6: https://tubeamparchive.com/download/file.php?id=2142

- Some builds simply have a 5 watt 470R or 500R wirewound going from pins 4 to 6. Brandon told me either of these options was good.

Yes, both are good. The higher value protects the tubes a little more but I like the sound of the lower value. It's a very subtle difference at low volumes.

- Some builds have the 5 watt wirewound going from pins 4 to 6 AND a 3k3 or 5k1 resistor going from pins 1 to 5:

The 3K3 or 5K1 are the grid stoppers. If you're using 6L6's you can use pin 1 as a terminal since it's not connected to the tube at all. If you plan to use EL-34's or KT-77's you might consider using a terminal strip for these resistors as these tubes have this pin connected and pins 1-8 should be connected together.

[JamesO]

Thanks, Bob.

Is the value of the grid stopper consequential? The 3k3 or 5k1?

[Bob-I]

Thanks, Bob.

Is the value of the grid stopper consequential? The 3k3 or 5k1?

I've tried both, plus 1k5 too. I can't really hear a dramatic difference. Some folks say larger for better cleans, but I haven't heard it myself.

[Funkalicousgroove]

The ODS amps I have been in all had 5K1, but the Early one (Overdrive Delux) had 1.5. I like 5.1k, but only because I have a bunch of them-

[JamesO]

After hearing Scott's bluesmaster, I'm convinced that that's the direction I want to go in. I have the bluesmaster schematic and bluesmaster HRM layout.

My powertubes right now are wired per the #124 image below with 5k1 grid stoppers and 470R screens. Plus the 120R's on V4 (not sure what they are).

Looking at the bluesmaster HRM layout, I only see the 5k1 grid stopper, no screen, and pins 8 and 1 tied together.

Is that the way to wire them up? Why no screen?

[Bob-I]

My powertubes right now are wired per the #124 image below with 5k1 grid stoppers and 470R screens. Plus the 120R's on V4 (not sure what they are).

The 120R's are a virtual center tap for the heaters. If your heater windings don't have a center tap, these resistors lift the heaters above ground reference to kill the 120hz AC hum. I forgot those on my last build and it was unplayable, until I remembered.

Looking at the bluesmaster HRM layout, I only see the 5k1 grid stopper, no screen, and pins 8 and 1 tied together.

Is that the way to wire them up? Why no screen?

If there's no screens, the layout is incomplete. There must be screens or you'll kill your power tubes. You can put a terminal strip near the power tubes and mount them from the tube socket pin 4 to the terminal strip then to the screen node on the power supply.

The key is that with a 6L6 there's no connection on pins 1 and 6 so you can use them as a terminal. With an EL-34 pin 1 must be connected to pin 8 for the supressor grid so you can't use pin 1 as a terminal.

What I do it connect the screen from pin 6 to 4, with pin 6 connected to the screen node on the power supply. Then connect the grid stopper resistor standing straight up to pin 5 and heatshrink it to the socket so that it's secure.

I hope that helps.

[JamesO]

Thanks, Bob. That does help a lot. Like always

If my transformer has a center tap, can I remove the 120R's?

[Bob-I]

Thanks, Bob. That does help a lot. Like always

If my transformer has a center tap, can I remove the 120R's?

Yes

[heisthl]

Thanks, Bob. That does help a lot. Like always

If my transformer has a center tap, can I remove the 120R's?

make sure the center tap you're talking about it the heater winding center tap (typically green with yellow stripe).

[JamesO]

Will do.

Thanks guys. This thread has helped me learn a lot.

[JamesO]

I have good news After requesting the transformer's schematic from Mojotone, it looks like my transformer has the center tap. Should I remove the 120R's and wire the center tap to a ground point? There is also a red/yellow with 0v. Should I wire that to a ground point as well?

[heisthl]

The red/yellow grounding is a must, it's the center tap for the B+ and also the ground reference for the bias tap.
The heater center tap is your choice, I like using it because it's easier.

[Structo]

I liked the way Normster laid out the power tubes on the D'Lite.

With the terminal strip with the screen resistors connected to that.

Just seems like a more sturdy design.

This is from the Tweeked Layout with the new values.


BTW this diagram has an error on the standby and OT connection to the board. It should go to the choke resistor.

[JamesO]

Great! Thanks, guys