Grounding Qn on 5G9

[tubeswell]

Has anyone got any views on whether its better to ground the PI tail with the pre-amp grounds of with the output stage grounds, when contemplating a split grounding scheme? (i.e. preamp grounded at one of the input sockets - everything else grounded at one of the PT bolts)

Also, figuring that the trem and bias hook into the signal path at the output grid load resistor(s), I was planning to ground the bias ground with the Trem ground and the output stage ground altogether (along with the mains ground)

[tubeswell]

Where I got to so far...

Well today I worked feverishly doing and undoing and redoing bits.

I will put the pre-amp filter, cathodes for V1, Vol and tone grounds to one of the input grounds (should I have an input ground for each pair of input jacks, or should I just have one ground for all four? (all speculation and good advice welcome please )

I did a mains tag board (behind the pilot lamp) . At this stage everything else will go to this board (PT, Filter caps, trem, PI cathodes, bias ground, heater CT, HT CT and AC Mains ground). The tag board has one wire coing off it with a solder lug screwed to a PT chassis bolt.

[tubeswell]

Well, finally got it completed (see pics in the tweed builders forum)

In the end I have grounded the PI with the preamp and pre-amp filter ground, at one of the input sockets. All the input socket grounds are hooked up together.

I grounded the trem cathode grounds and speed grounds at the trem footswitch socket ground

I grounded everything else, (Mains AC ground, heater CT, Output cathode ground, High Voltage winding CT, Bias ground) at one of the PT bolts)

So far, so quiet - no hum issues at all. A little concerned about a blown fuse after switching it off (probably a few too many times to soon?) (see 'nother post in the debugging forum)

[Jester]

Well, finally got it completed (see pics in the tweed builders forum)

In the end I have grounded the PI with the preamp and pre-amp filter ground, at one of the input sockets. All the input socket grounds are hooked up together.

I grounded the trem cathode grounds and speed grounds at the trem footswitch socket ground

I grounded everything else, (Mains AC ground, heater CT, Output cathode ground, High Voltage winding CT, Bias ground) at one of the PT bolts)

So far, so quiet - no hum issues at all. A little concerned about a blown fuse after switching it off (probably a few too many times to soon?) (see 'nother post in the debugging forum)

Hi Tubeswell,

I often read with interest what people are doing with grounding as it appears to be a bit of an art. I am worried that one of my amps will have a problem with this, and it will take an age to work out how to solve it, so I read what ever I can and try and understand what is best.

So far my understanding pretty much lines up with what your saying re: putting Mains AC ground, heater CT, Output cathode ground, High Voltage winding CT, Bias ground at one of the PT bolts and then the pre amp grounds, including there power supply filters are grounded at another position on the chassis. For your information I have several chassis grounds for the pre-amp ccts (ie I use the screw that holds in the tube sockets for the grounds of each of the pre-amps / phase inverter tubes, and I use the back of the pots for grounding of the tone ccts and volume controls. In one of my early amps I used a copper strip to create one of the star points for all the pre-amp and tone cct. But in my latest, and quietest champ clone, I tried it without this, and it works very well. I must add that I'm using aluminium chassis, so they are good conductors and I guess this helps.

Cheers
Jester

[tubeswell]

Yep I use Aluminum for my chassis as well.

I understand that keeping the 'low current' grounding points together and the 'high current' grounds together but keeping the low current ones away from the high current grounding points is an important ingredient.

Also, the voltage difference between grounding points has an impact on hum