Ground Question

[J Rindt]

http://www.el34world.com/charts/Schematics/files/ampeg/m12_6v6.pdf

I am building an amp similar to above. Space is hard to come by, so the layout suffers to need.
I usually try to ground each circuit with (or very near to) its corresponding B+ ground.
Do you guys think it might be a problem if I grounded the Pot for the Trem Speed with the B+ ground for the Phase Inverter.?
Thank You

[HotBluePlates]

Probably won't be a problem. The very low frequency trem signal should be filtered effectively regardless.

But you can't connect that trem circuit stuff to its own little eyelet/turret/terminal strip lug, and run a wire to the appropriate filter cap ground?

[J Rindt]

Probably won't be a problem. The very low frequency trem signal should be filtered effectively regardless.

But you can't connect that trem circuit stuff to its own little eyelet/turret/terminal strip lug, and run a wire to the appropriate filter cap ground?

Hey -
Yes I can.
This is a long and narrow chassis. Before you know it, a potentiometer is a Long Way from its family. My ground lug for the phase inverter is right below the Speed Pot.
I thought it -might be- worse to run a ground wire for the pot Over/On Top of a bunch of lead dress, just so I could keep that circuit ground in one place.
THAT might be my "real" question.....I am not sure how bad an idea it is to run ground wires for a long distance. I suppose it depends what current (if any) it carries, and what that ground wire might have to run over or next to.
Thank You

[Tom_Hull]

hi

 can we get a peek of your project .


tom

[J Rindt]

hi

 can we get a peek of your project .


tom

Yes -
I would be happy to post some pics.
I pretty much have all the grounds and lead dress in place and am ready to go.
I am really starting to wonder if I am trying to put 7 pounds of crap into a 5 pound bag.
At some point (soon) I am going to have to wire the board into the chassis. If there is lead dress issues, poor layout (on my part) or just some problems in general.....it will be hard to deal with after the board is wired.
Pics ASAP
Thank You

The amp has dual bias pots. That circuit is by itself, on the transformer side of the chassis

http://s111.photobucket.com/user/zzmoore/library/proto%206k6

[John]

.I am not sure how bad an idea it is to run ground wires for a long distance. I suppose it depends what current (if any) it carries, and what that ground wire might have to run over or next to.

I was hoping someone would chime in and answer that, as I've often wondered myself. It seems like it shouldn't matter... but does it?

[Tom_Hull]

hi
my ampegs are
 a long ground wire,,,from the input jack ground  to the pt ground ,isolate the input jack from chassi......
the ot speaker grounds at the far end,,away ,,,,,,,,, from the pt ,,

I believe that
steve has the intensity pot and the speed pot grounded,,,,,,,, to the  power tubes and phase ground ..

[HotBluePlates]

Probably won't be a problem. The very low frequency trem signal should be filtered effectively regardless.

But you can't connect that trem circuit stuff to its own little eyelet/turret/terminal strip lug, and run a wire to the appropriate filter cap ground?

I thought it -might be- worse to run a ground wire for the pot Over/On Top of a bunch of lead dress, just so I could keep that circuit ground in one place.
THAT might be my "real" question.....I am not sure how bad an idea it is to run ground wires for a long distance. I suppose it depends what current (if any) it carries, and what that ground wire might have to run over or next to.

Exactly right!

If the wire were carrying amperes of current, then the resistance of the wire (albeit low) creates a non-trivial voltage drop between the real 0v ground point and the other end of the wire you wanted to be 0v ground. Same issue if the ground wire were 4,000ft long. Now a thin-gauge wire because a significant resistance.

Additionally, if the wire were carrying a very large current, there would be a significant magnetic field set up around the wire. That might induce spurious voltages in any high-impedance circuits the wire passes by on it's way between the two ground points.

However, you are unlikely to have either of these situations. Current will be pretty low, and the wire isn't a half-mile long. I think you'll be fine connecting the circuit to the ground point you really want to use.

[J Rindt]

10-4...
That is kind of what I thought, but was not sure.
I run the long ground like I would any other lead dress I guess. Try to avoid parallel as much as I can, and cross at 90 degrees if possible.
Thanks Guys
I just hope this works out. It will be hard to deal with if there is "trouble".
This is basically a Black Face input, LTP phase inverter, 2x6K6 power amp, fixed bias with dual bias pots, and an Ampeg bias vary Trem.
I kind of wish I had just used the Fender bias wiggle circuit, but Ampeg has/had a circuit that was set up with a 6SL7, and I am using those tubes.
Thanks Again

[jojokeo]

HBP is correct - you have to have significant current in a ground wire to present probs - but not in your low powered amp. Most critical grounds are your primary/VAC, B+ resevoir caps, speaker output, and heaters.

[J Rindt]

So anyway.....
I have this wired in now. I have to double check everything, but this is basically it.
I am more use to working on a BF/SF Fender type chassis...where there is a lot of room to make changes if necessary. With this chassis, there is not much room to even push a wire around, to check if lead dress Might Be a problem. I was forced (at least I think I was) to cram a lot of wires Together/On To Of each other. I did the best I could.
What do you guys do in a situation like this.? Can I make it "better" somehow.?
Thank You

[jojokeo]

That looks really good! Fire it up and test but you look to be fine. At this point all you can really do is just play it and see where you are then if necessary go from there. Hopefully you don't have to do anything more.

[J Rindt]

Yeah -
I hooked it up with all tubes. and no signal..... Voltages are "normal".
Guess it is time to put a guitar into and see what happens. 
What a mess in there. Although I have worked on a few old stereos and other things that were 10x the rats nest that this is. But those companies know what to pile up and what not to.
Thanks