Build start- grounding Q

[The Captain]

Hi- Ive all bits, & starting a (scratch) 5E3 using the Weber layout. As its clearer if I can ask here as I'm still not 100% sure on this grounding plan(there's just so much www. info!)- sorry if its all been heard before:

1) Im NOT using the brass plate & going for using a few(?) ground points: the PT cts + mains earth to one PT bolt seems simple; but the others from board, pots and (plastic) jacks.. all to one spot perhaps ALL these to an OT bolt, or maybe best to divide them to * other points?

2) Ive seen the 2 filter caps grounds tied separately, to an OT bolt (I think) in keeping with simplicity as it were so caught my eye: should any other grounds go here also, or is it best to leave to just these 2?

Thanks for any help. Pic of the 'Tweed Tiddler II' to follow- Captain.

[stokes]

I've found that grounding the main filter the power tube cathode resistors and heater CT or 100ohm resistors,OT,and the ground wire from your power cord to the same spot,one of the PT's mounting bolts is good.These are the higher current components and should be kept together.Everything else can be grounded at the other end of the chassis at one or two points,just keep them away from the high curent grounds.Some people like to isolate the input jacks and ground them with the rest of the pre grounds,I have never had a problem grounding the inputs right where they sit,but it could be a source of hum,I just never had the problem yet.

[The Captain]

Muchos gratias Mr. Stokes- that's a plan sorted then. Having done 'star' grounding with hifi amps it was a bit daunting thinking of tying the lot to one bolt, so Ill go for your method. I presume that with 'std' metal jacks the body would be grounded to the chassis where they sit; with the plastic ones I have they seem to have both tip and sleeve with 2 'sides'/ ie one side switched out when jack inserted-
3) should I ignore this side and just use one tip and one sleeve?

On a slightly different point, as Im using a 1x12 cab and squeezing the lot in, one thing crosses my mind: the speaker is not offset to the right as per 5E3 'std' and tho all goes (phew!) the top half of magnet will be close to the Ts, and an inch or so right behind the power tubes (its a shallower spkr than weber for eg, but a larger diameter magnet)-
4) Is there likely to be any interference between magnet and amp so close, or any other nasties to consider?

Thanks for the help, Captain.

[stokes]

As for the jack if you are describing a shorting jack,you should use the shorting jack connected to ground,it keeps the input quiet when not plugged into.As long as the speaker isnt touching the components,you shouldnt have a problem,I just installed an EVM 12L into a clone and it has a very large magnet,which is less than an inch from the trannies and tubes and it wasnt a problem.

[The Captain]

Great help thanks.

And another Q.. (I have a feeling there will be a few as the build comes on)-

I ordered 2x 6v6GT (EH) without asking specifically for a 'matched pair'(?): is this my 1st cock-up? thanks, Capt.

[stokes]

I would imagine it depends on where you ordered them from,most suppliers should know that if you order a pair,you need a matched pair.If they havent been delivered,contact the supplier just to be sure.

[The Captain]

Assuming they are not matched (order from TAD germany on its way) should I return them, or can they be used ok? thanks Capt

[MWJB]

TAD grade their tubes by plate current (PC) & transconductance (TC) so check the numbers on the tubes when they arrive. Up to +/- 5mA difference (measured) may be considered a matched set.

You say you are not using a brass plate, will you be using a wire grounding buss soldered to the backs of the pots & to the input jacks?

[stokes]

Like MWJB says +/- 5ma's is fine.After a while they may even drift further than that and it wont make a big difference.Just call the supplier and ask what they shipped to you,you are just starting this build so if you have to return them it wont make a big difference,since you wont need them imediately.

[The Captain]

TAD grade their tubes by plate current (PC) & transconductance (TC) so check the numbers on the tubes when they arrive. Up to +/- 5mA difference (measured) may be considered a matched set.

You say you are not using a brass plate, will you be using a wire grounding buss soldered to the backs of the pots & to the input jacks?

Thanks, Ill have a look at them tmrw and see: as i ordered ~£120 worth of bits clearly for a 5E3 build I hope they'll come up trumps on the 2 tubes matching: thats kind of complicated things though...

MJWB I'll have 2 chassis bolts/ gnd points near the pots/ board for these gnds. I cant clearly see the bus bar's terminal point or clear pics as to which uses it, which confused me- it seems way simpler to just have 2 or 3 bolts and divide appropriate bits to them.

[stokes]

As long as you keep those higher current grounds away from the others you should be fine without the bus bar.

[The Captain]

Ok so I tie all these to a PT bolt:

1. Gnd from the '3rd' 16uf HV filter cap from board
2. Gnd from the 25uf/ 50uf (bypassed with the 270 5w) from the board
3. PT green heater 6.3v CT
4. PT High Voltage red CT
4. Gnd from the mains lead
5. *OT? (it shows to the spkr jack on the Weber layout)..

Then the pots, jacks (&*OT?) to a separate one t'other side of chassis. I think thats the lot. Here's the 'Tweed Tiddler II' ready to be stuffed..



Much great help so far- rgds Capt.

[hasserl]

I didn't read the whole thread, might have missed something. But IMO, you are best served by using the brass grounding plate and grounding the amp as indicated in the Weber layout diagram. The amp will be nice and quiet. Get fancy and try to do your own grounding scheme and be prepared for a noisy amp. I speak from personal experience. The 5E3 was not my first build, or my first attempt at correcting poor grounding schemes on other amps and quieting noisy amps. I thought I was smarter than Fender, and I thought using the often bandied about star grounding schemes would give me a quieter amp. Wrong. It wasn't bad, but there was definately more noise than there should have been. As a good faith gesture I went ahead and used the grounding scheme in the layout, and my noise issues disappeared.

It may seem low tech and/or crude, but it flat works. I've since built a 5E5A, this time I went with the layout to begin with, I didn't try to get fancy (I did use shielded wires on the input though) and the amp is very nice and quiet.

Just save yourself the hassle, use the brass ground plate and the layout. It works. Period.

[The Captain]

But I don't have one, and havn't seen them sold on their own- defo not at TAD.

[Bruce / Mission Amps]

If you are not using the brass plate because you do not have it, use a solid copper wire soldered to the back of the three 1m pots as a common ground point and make sure you also run a jumper over to any one of the grounded lugs on the input jacks per channel. Also connect your cathode bias and bypass ground there too.
DO NOT use the same ground point of the green wire in a three wire power cord as a ground point for the preamp, power amp, well, any part of the amp circuitry....in some countries it is even illegal to do so as that ground point is just to ground the chassis to the mains earth ground point.
You can connect your HI-V CT and filament CT to the same point (not at the mains ground) if you wish, as long as it is at chassis ground and keep it very close to the same place the first main filter cap is grounded.

Don't waste a bunch of time trying to reinvent the wheel... use the standard 5E3 audio and power supply ground scheme. This is a fairly simple amp design and quite quiet if you follow standard procedures.
I speak from being invloved with well over a thousand tweed 5E3 amps.