Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ocean7 on March 09, 2015, 05:29:54 am

Title: Do I need to ground this ground bus?
Post by: Ocean7 on March 09, 2015, 05:29:54 am: Newbie question here but I am still missing a few episodes on proper grounding...

So I started to build a 5E3 with the Hoffman layout (by the way many thanks Doug for making this public!).

I've got my ground bus running at the back of the potentiometers and I am wandering if at the end of the ground bus I have to run a wire to the chassis main ground? Where it says "ground buss" on the layout.

It looks like everything is already grounded through input jacks ground tips and chassis.

Also if I am doing things correctly there will be 4 wires going to the chassis main ground?
- PT heater center tap.
- Output jack ground.
- Board ground (power section).
- Potentiometer ground bus?

Thanks very much for your help :worthy1:
Title: Re: Do I need to ground this ground bus?
Post by: sluckey on March 09, 2015, 07:14:10 am: Don't connect the pot buss to the chassis main ground. It's connected to ground thru the input jacks and the body of all the pots.

http://el34world.com/charts/grounds.htm (http://el34world.com/charts/grounds.htm)
Title: Re: Do I need to ground this ground bus?
Post by: Ocean7 on March 09, 2015, 08:06:30 am: Quote from: sluckey on March 09, 2015, 07:14:10 am
Don't connect the pot buss to the chassis main ground. It's connected to ground thru the input jacks and the body of all the pots.

http://el34world.com/charts/grounds.htm (http://el34world.com/charts/grounds.htm)

Thanks a lot Steve.

Just curious why the speaker jack grounds need to be connected to chassis main ground then since they are also in contact with the chassis.

Grounding is a mysterious thing!
Title: Re: Do I need to ground this ground bus?
Post by: EL34 on March 09, 2015, 07:08:33 pm: You don't have to run a ground wire from the speaker jacks either.
Just make sure they are clamped down good
Title: Re: Do I need to ground this ground bus?
Post by: lego4040 on March 10, 2015, 02:56:14 pm: i was schooled again, I ground my buss bar to chassis as well. I always thought it wasn't necessary since pots are self grounding
Title: Re: Do I need to ground this ground bus?
Post by: sluckey on March 10, 2015, 03:24:22 pm: I ground my buss bar to chassis near the input jacks. But it's because my buss bar floats in the air above the pots, not soldered to the pot bodies. In fact, my current project has a split buss bar. IOW, I have two buss bars floating above the pots. One will be grounded to chassis near the input jack and the other will be grounded at the power ground lugs.
Title: Re: Do I need to ground this ground bus?
Post by: Ocean7 on March 10, 2015, 03:49:38 pm: Quote from: sluckey on March 10, 2015, 03:24:22 pm
I ground my buss bar to chassis near the input jacks. But it's because my buss bar floats in the air above the pots, not soldered to the pot bodies. In fact, my current project has a split buss bar. IOW, I have two buss bars floating above the pots. One will be grounded to chassis near the input jack and the other will be grounded at the power ground lugs.

Sounds interesting! Would you share a quick picture please?

I am not sure I will do the buss bar soldered to the back of the pots again. It was quite a pain to get a clean looking solder with my cheap soldering iron. And if I need to remove one pot it's not too practical either (like I just realised that I forgot locking washers on my build... Oh well).
Title: Re: Do I need to ground this ground bus?
Post by: sluckey on March 10, 2015, 04:08:00 pm: Here are a couple pics that show my buss bar...

http://home.comcast.net/~seluckey/amps/dual_lite/big_guts.jpg (http://home.comcast.net/~seluckey/amps/dual_lite/big_guts.jpg)

http://home.comcast.net/~seluckey/amps/6v6plexi/P-6V6_05_big.jpg (http://home.comcast.net/~seluckey/amps/6v6plexi/P-6V6_05_big.jpg)
Title: Re: Do I need to ground this ground bus?
Post by: lego4040 on March 10, 2015, 05:13:23 pm: Hey Steve,
Since grounding is a huge thing, one mainly being noisy ground loops, whats up with not twisting the heater wires in your 6v6 build there?
Title: Re: Do I need to ground this ground bus?
Post by: sluckey on March 10, 2015, 06:29:41 pm: I discussed that in my 6V6Plexi thread. I didn't twist them in my Dual Lite amp either, and may not twist them in my Maggie project.
Title: Re: Do I need to ground this ground bus?
Post by: lego4040 on March 10, 2015, 07:05:23 pm: I will reread that Steve
Title: Re: Do I need to ground this ground bus?
Post by: Ocean7 on March 10, 2015, 07:09:02 pm: Quote from: sluckey on March 10, 2015, 04:08:00 pm
Here are a couple pics that show my buss bar...

http://home.comcast.net/~seluckey/amps/dual_lite/big_guts.jpg (http://home.comcast.net/~seluckey/amps/dual_lite/big_guts.jpg)

http://home.comcast.net/~seluckey/amps/6v6plexi/P-6V6_05_big.jpg (http://home.comcast.net/~seluckey/amps/6v6plexi/P-6V6_05_big.jpg)

Awesome. Thanks! I will try that floating buss bar on my next project.

And your builds are so clean... wow... most impressed!
Title: Re: Do I need to ground this ground bus?
Post by: Ed_Chambley on March 11, 2015, 02:20:17 pm: Quote from: sluckey on March 10, 2015, 06:29:41 pm
I discussed that in my 6V6Plexi thread. I didn't twist them in my Dual Lite amp either, and may not twist them in my Maggie project.
I missed something. You building a Maggie? Which one are you working on. You restored a 10A didn't you?
Title: Re: Do I need to ground this ground bus?
Post by: sluckey on March 11, 2015, 02:30:41 pm: I'm building a M2. I'm 50% there. My little Peewee has become a donor! :icon_biggrin:
Title: Re: Do I need to ground this ground bus?
Post by: Ed_Chambley on March 11, 2015, 02:40:38 pm: Quote from: sluckey on March 11, 2015, 02:30:41 pm
I'm building a M2. I'm 50% there. My little Peewee has become a donor! :icon_biggrin:
That is a very cool little amp. You building it using 6GW8 tubes and FM modulation?

I never cared for the 8" speaker in them, but yours will be a head I assume.
Title: Re: Do I need to ground this ground bus?
Post by: kl2mcbride on March 11, 2015, 03:18:10 pm: Carefull, I never create a ground bus connecting the back of pot's, There gronded by being mounted on the metal chassis, Ground bussing the pots can create ground loops (HUMM). I also never use the chassis as a giant ground buss. The chassis should be treated as a shield from external rfi/emi noise. The Circuit should be grounded to the chassis at 1 point only. the center tap of the power xfmr should go directly to the - side of the rectifier (whatever kind it is) then connected to the "to be grounded" (-) pathe of amplifier to the single point ground. Isolate all input and output Jacks. on long signal runs I will also use shielded cable with to signal wires and the shield 1 signal wire is for the signal the other is the ground reference lead to the portion of the circuit involved, the shield is only grounded on 1 end the end that's being driven.