power tube 1 ohm to ground confusion

[joesatch]

I have seen two different variations of this and don't know which one to implement (using EL34 or KT77). What are the differences here?

[jordan86]

I can’t see where pin 1 goes to in the 2nd image, but I will assume to ground. In which case these are functionally the same. Tying pins 8 and 1 together, and to ground. I imagine someone would do #2 scenario if they had a long run to a power amp ground further away. Allows you to neatly tuck the 1 ohm resistor on the socket and do a long wire run to a different ground point.

[joesatch]

yes the black runs to ground. so i guess there is no difference in running the resistor between pin 1 and 8 vs running it off one of the pins with pin 1 and 8 tied together?

[glass54]

Joe
Can be done either way depends on the circumstances.
Have a look at Hoffman AB763_2 (https://el34world.com/Hoffman/files/Hoffman_AB763_2.pdf)
With the Long (turret) board, the 1R are placed "onboard" and wired as indicated
However with the Short board, the option is a suitable earth point, eg fit 1R from pin 8 to lug on Octal socket.
Regards
Mirek

[joesatch]

i've gone with the second option. seems like a more solid ground than depending on the resistor lead

[Latole]

The best way to do it

[pdf64]

The best way to do it

That kinda implies using the chassis as a conductor for circuit 0V, so not really, but each to their own 
However, in the case of EL34, it’s inappropriate; note that pin1 is assigned to g3.

[Latole]

The best way to do it

That kinda implies using the chassis as a conductor for circuit 0V, so not really, but each to their own 

Chassis or ground or common......name it .

[HotBluePlates]

The best way to do it

Chassis or ground or common......name it .

You're ignoring the only point of the original question was the connection from Pin 8 (cathode) to Pin 1 (Suppressor Grid) for EL34.

Your diagram shows Pin 1 being used as a mounting point for the screen resistor, which then runs to Pin 4 and has high positive voltage present on Pin 1.  That's a complete non-starter for EL34.

There are also times where the amp manufacturer does not use the chassis for ground connection/circuit common, and adding circuit common connections to the chassis will create a ground loop and hum (old Ampeg amps are notorious for this).

[Latole]

All of these are easy to mods.

[pdf64]

‘Easy to’ mods are still easy to feck up 

[joesatch]

Still confusion about this. Normally the ground pin is Pin 8. Running this 1 ohm resistor like this is bypassing that ground how should this be wired?

[sluckey]

#1 is correct. #2 does nothing.

[joesatch]

fabulous. i dont have to unsolder anything.   

[sluckey]

fabulous. i dont have to unsolder anything.   

Of course my reply depends on my assumption that the black wire on pin 1 is connected to ground.

[joesatch]

indeed 

[Dyerseve726]

The idea is to put the 1 ohm resistor between the cathode and ground (in a fixed bias amp). The other pin is just being used as a support for the resistor. I just run a wire off pin 8 to some banana plugs and hang the resistor between them, see the photo.