How many connections to chassis ground?

[chuckulaa]

When you build an amp, how many connections do you make to chassis ground?

I would guess, maybe two? one for the earth ground power outlet, and one for the circuit ground.

I could also see three or four?

Do you connect the center tap for the HV to the circuit ground?

What about the center tap for the 6.3VAC heaters?

[ampgeek]

Here is a well respected reference for grounding tube amps.
I have followed this guidance on a number of occasions and have made very quiet amps. Many others here have done the same.

http://www.valvewizard.co.uk/Grounding.html

As always, there are many ways to correctly "skin a cat" so this shouldn't be viewed as the only way to set up a grounding scheme.

Cheers,
Dave O.

[vibratoking]

The total number depends. There isn't one correct way.

Earth by the power outlet...yes.

Center tap for HV...yes

Center tap for heaters...yes or artificial tap if none.

Look in the Dumble and Trainwreck file sections. There are good layouts for those detailing the ground scheme. Also, Hoffman Amps has layouts for Fender type stuff with grounding schemes.

[chuckulaa]

I have seen that valvewizard article. I feel that I could benefit from reading it a dozen times.

It leaves me with one question about the generic "leads from rectifier."

Would that be the +HV from the rectifier and the center tap of the HV on the transformer?

EDIT: Because for my champ, the rectifier only has one lead!

[Andy Le Blanc]

One... star point...

[ampdoc1]

In developing their Classic series of amps, Peavey had some noise problems. They devised a plan that is common to all that series, and uses 2 or 3 grounds (depending on the amp) separated by 47 Ohm resistors. Check a schematic of any of those amps. It's pretty simple and easy to understand.

a'doc1

[Gaz]

In developing their Classic series of amps, Peavey had some noise problems. They devised a plan that is common to all that series, and uses 2 or 3 grounds (depending on the amp) separated by 47 Ohm resistors. Check a schematic of any of those amps. It's pretty simple and easy to understand.

a'doc1

I've seen that on a new orange too, and maybe a newer Marshall of some kind.

[tubeswell]

Besides Merlin Blencowe, RG Keen has also written a little article on Star Grounding

[10thTx]

There are probably numerous ways to do this that are successful.

My amps are very quiet and I use this method:

http://www.el34world.com/charts/grounds.htm

With respect, 10thtx

[Ken Moon]

I use 3:

- Earth safety ground, close to power inlet
- Circuit star ground, very close to input jack
- Output transformer ground, near speaker jack(s)

Merlin's website and books get into the details of every possible current loop, and have the most complete technical explanation of grounding I've ever read, but as others have said, quiet amps have been built with many grounding schemes.

I've had success with a straight buss ground across one side of the turret board, but only if the preamp is pretty low gain.

The Trainwreck circuit seems to be very sensitive to grounding differences, and I've even gone as far as using a separate heater transformer on these amps.

And the "headphone trick" is one of the best ways to reduce overall noise, and I use it every time I come up with a new layout.

[briane]

I use 2 - 1 for all power connections, and other, at other end of amp - for signal ground.

the power connection is right next to the power, includes CT & power cap grnd.

works greatl - no loops to worry about!

[Firestorm]

I use 2 - 1 for all power connections, and other, at other end of amp - for signal ground.

the power connection is right next to the power, includes CT & power cap grnd.

works greatl - no loops to worry about!

Me too (although it's really 3, because the safety ground should be separate). My dilemma is always where to put the PI; it's technically part of the PA, but...

[Phil_S]

It depends on which ones count
One circuit ground. That's the one that counts. Some people use two. I'm not debating it, but I don't get it, and never have.
Other that don't count:
Artificial CT for heaters.
Mains ground.

[chuckulaa]

I used the Hoffman layout with the greatest success on my 5F1.

My 5F1 has been wired similar to the Hoffman/classic grounding scheme with three grounding points. It has always had a small baseline hum. The hum is independent of where the volume is set, and therefore is not in my preamp.

I experimented and converted my wiring to the "approximate multiple star ground" that the valve wizard talks about in his article. He gives an illustration of this scheme in figure 15.10.b. This involves only using ONE connection to chassis ground at the input of the amp. Doing this conversion actually increased the noise in my circuit. The noise also increased with the volume knob indicating that it was better to keep my resevoir capacitors connected to a separate ground point by at one of the power transformer lugs. Granted, the layout is not perfect, but the leads dress was pretty neat. (This is about the 4th time I rewired th amp as it was my first build.) I actually have quite a few components wired point to point, and all ground loops are minimized.

The Hoffman/classic grounding scheme worked best for me. It was less noisey, but there is still a baseline hum.

For my 5E3 I will use the hoffman/classic style grounding scheme with a bus bar for the preamp.