Grounding - alternative grounding schemes - any difference?

[novosibir]

is this better? Or should i move point 4 more to the "north-west" of the chassis (oriented by this photo)?

Might work ok, but IMO too close to #3 - I'd move it more east, no matter whether south-east or nord-east, only keep space to the PT!

The other question is on potentiometer case grounding. I'm planning on going with PEC pots, but since they have long shafts, i have to put spacers - i'm not gonna install plastic spacers, but use additional nuts. Is that going to provide proper case grounding or should i try to connect a bus along the back of the pots and ground it?

You can't solder the back of PEC's w/o special chemics, because they're VA (stainless steel), but the additional nuts will ground it properly.

Is there any rule on which cables should or should not be close to each other along the chassis (not counting on cables from the board to the sockets)? Grid leads as short as possible and to have nice distance between them and the plate wires - well just as shown in the George's manual.

There are a lot of rules and I could write a book with about 50 pages or even more only about this, but don't expect this from me in a forum - I have a full time business w/ 70-90 hours a week running

What about the Choke wires and OT CT. I was thinking of twisting all 3 of them?

To stabilize each to the other on its long way - ok! But no electrical benefit, cos they contain DC

Any suggestions on the layout of the wire going to the potentiometers (apart from the presence pot wire going as far away as possible from the other tone stack wires)?

Run it close along the chassis (shielding effect) to the front chassis' edge and then therein along - not through free air.

EDIT: OH MAN, WILL I HAVE TO TREAT YOU WITH SOME HIGH QUALITY CLIPS WHEN I GET MY AMP DONE - AS A THANK YOU FOR BEARING ALL OF MY BORING QUESTIONS AND PROVIDING HELP

We're waiting

Larry

[bulatovic]

Thanks for the answer Larry!

Don't worry, i wasn't gonna ask you to do so, first of all i wouldn't probably understand a thing out of these 70 pages until the conclusion which would say ...so you should run it like this:..
So, sticking with the manual layout there, right?

What about the PT wires - AC and the DC from the stdby switch? Any benefits/disadvantages if i run them close together?

Oh, and i do have just the person for the job of recording clips! He's been awarded for the best guitarist from the Ex-Yugoslavia for the year 2006, and is one of the best known guitarists over there for his work with the group "YU Grupa". So expect some nice playing as well

[mwm523]

is this better? Or should i move point 4 more to the "north-west" of the chassis (oriented by this photo)?

Might work ok, but IMO too close to #3 - I'd move it more east, no matter whether south-east or nord-east, only keep space to the PT!

How about if you put #4 on the board mounting bolt between the bias caps, right below V4?

[novosibir]

How about if you put #4 on the board mounting bolt between the bias caps, right below V4?

Still better and more comfortable is the board mounting bolt under the bias trim pot, but the ground solder lug must be placed between the stand-off & chassis, not between stand-off & board.

Larry

[mwm523]

How about if you put #4 on the board mounting bolt between the bias caps, right below V4?

Still better and more comfortable is the board mounting bolt under the bias trim pot, but the ground solder lug must be placed between the stand-off & chassis, not between stand-off & board.

Larry

??? I don't have a board mounting bolt there... The closest one to there is between the 220K resistors, which is where bulatovic had referenced #4 in his last image.

And yes, I would of course put it down against the chassis, not floating up by the board...

Maybe a good idea to drill a new hole in the chassis in that area (below bias trim pot) for #4...

[bulatovic]

Well i was concerned that you won't be able to do so because of the OT which sits just above. But maybe there's some space if the bolt's head is flush enough. I'll drill it just a bit "south" of the hole where you feed the OT primaries through. (where the ground bus wire is on the picture in between of the back of the bass and mid pots)

Or - in other ways of describing it

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[mwm523]

I'm going to ground my current build in a similar fashion, with a couple of small changes.

I think I'm going to use an OT bolt for #4 (the top-left bolt, which you can't see in this pic since it's under the board).

I'm also going to ground the V4 and V5 cathodes to local ground lugs on their respective sockets instead of running wires to #5.

And I will move #5 to the rear bolt of the mains/screens filter cap. I think I'll turn that cap around so the - terminal is close to the rear bolt.

[Roe]

I'm going to ground my current build in a similar fashion, with a couple of small changes.

I think I'm going to use an OT bolt for #4 (the top-left bolt, which you can't see in this pic since it's under the board).

I'm also going to ground the V4 and V5 cathodes to local ground lugs on their respective sockets instead of running wires to #5.

And I will move #5 to the rear bolt of the mains/screens filter cap. I think I'll turn that cap around so the - terminal is close to the rear bolt.

that's almost what I've done. But I attatched #4 to OT bolt near the purple NFB wire

[mwm523]

Hey Roe, did you do this on a new build? Or was it an existing build that was originally grounded differently? How are your results?

I thought about using that OT bolt, but thought it might be too close to the PT...

[Roe]

Hey Roe, did you do this on a new build? Or was it an existing build that was originally grounded differently? How are your results?

I thought about using that OT bolt, but thought it might be too close to the PT...

Hi, this was on my jmp50. I will try my other plexis later.
yes it may be a little to close to the PT. I wasn't aware of this when I did it. she sounds dirty good, so I'll keep it like it is. this amp was never noisy, but I believe she sounds better and is a little more quiet now.

[Roe]

I just implemented Larry grounding on my early 67 jtm45/100 with el34s and the 1202-119 OT.the difference was more noticeable in this amp than the jmp50, express and champ. much less ghosting and less noise. sounds real good. With a little eq adjustment I'm capable of getting a real thick and dirty malcolm young tone (with the otherwise twangy sounding tvclassic pickups).

thanks Larry!

[novosibir]

I just implemented Larry grounding on my early 67 jtm45/100 with el34s and the 1202-119 OT.the difference was more noticeable in this amp than the jmp50, express and champ. much less ghosting and less noise. sounds real good. With a little eq adjustment I'm capable of getting a real thick and dirty malcolm young tone (with the otherwise twangy sounding tvclassic pickups).

thanks Larry!

I'm happy with you, that it performs so good in your amps!

Larry

[krusty]

And what about the grounding of a tube FX loop?
All the grounding concerning the loop toghether (send, return jacks, filter cap for loop) in a different point (let me call it #7).
Where it should be located? in front of the chassis? or in the rear part?
If the loop is between tone stack and phase inverter circuit,
will it be the ground point put before "phase inverter" ground point?
Thanks a lot.
Krusty

[arledgsc]

I think you are on the right track Krusty. The SEND is driven by the cathode follower so this part of the effects loop ground current wants to get back to the V2 circuits. RTN is capacitively coupled to the PI input so the ground current follows the PI circuit but you don't have the option of splitting the grounds so stick with the V2 ground. V2 ground should be quieter than the PI ground anyway. Scott

[krusty]

Ok, you said:
SEND jack is grounded to V2.
and RETURN jack is grounded V2 too!
So what about cathoode(s) of the FX loop tube?
They will be grounded at the filter cap that filter B+ for the loop tube right?
I thought that SEND and RETURN should be grounded on the same point as the tube,
so a let's say "new ground point" between V2 and PI ground!
Anything wrong in doing this?
Krusty