layout: earth?

[mattpocket]

where are the earth symbols on the following layout going to? do they connect together or what?

http://www.getlofi.com/wp-content/uploads/2006/10/atarilayout.gif

sorry, I'm a noob?

thanks

Matt

[MikeH]

They all get connected to the same place, usually the ground lug, or "sleeve" of the input jack.  Of course, this design has not input jack, so I'd go with the output jack, or the - side of your power supply

[choklitlove]

if i were you, i would use this instead: http://geocities.com/worthekik/atari.html

it's my layout still, but it's better to go to the actual original file on the original page.  in case i update it, or in case you have any questions or anything.  then when you're done, use the feedback form on the page, and i'll post a picture of yours on the page.


it bothers me that they uploaded a copy on the blog instead of linking to the file...



anyway, good luck!

[scaesic]

theres actually 5 vacant holes on the bottom left which are all earths, attach them to any of those.

[GibsonGM]

Just to be 'noob helpful':  usually ground is the - terminal of your battery (not always, some FF"s etc use the + as a common point).  Most circuits have an "earth", or ground (also "common"), connection at 1 place on the circuit board.  That then goes to your stereo input jack...the - side of your battery goes the other unused tab on the jack.  The Atari punk schem above is doing this.   Inserting a plug into the jack makes the connection, and turns the effect on.  The switch just lets you bypass the effect.
Doing it this way ensures all board components have 1 place on the board to go to, and that the - side of your battery does, too.  This is very close to star grounding...search "ground" or "star ground" in the forum for more information. Keeps noise down.  Hope this was helpful! Good luck, good building.   

[mattpocket]

that was unbelievably helpful!

and to choklitlove: I was going to link to your layout, I could not remember your web address, I was about to leave work and wanted to get the question answered for when I got home, I knew there was a link to your site on getlofi so I looked on there for the blog about you apc, while I was looking I noticed a pic of the schem there and when I clicked it it just happened that it was on their site. No offence to you, I was just in a rush, I actually expected it to link to your site. Hope that clears it up for you.

So: to any other builders of the APC, use the link supplied by choklitlove, not mine!

Thanks for the help guys! Well done... again!

Matt

[choklitlove]

that was unbelievably helpful!

and to choklitlove: I was going to link to your layout, I could not remember your web address, I was about to leave work and wanted to get the question answered for when I got home, I knew there was a link to your site on getlofi so I looked on there for the blog about you apc, while I was looking I noticed a pic of the schem there and when I clicked it it just happened that it was on their site. No offence to you, I was just in a rush, I actually expected it to link to your site. Hope that clears it up for you.

So: to any other builders of the APC, use the link supplied by choklitlove, not mine!

Thanks for the help guys! Well done... again!

Matt

no no, i wasn't talking about you.  it's just those blog sites that write about it.  they upload copies of the file instead of link to them.  it's not a big deal at all.  good luck with the project though.

[$uperpuma]

your layout is getting used quite a bit, Chok lots of guys over at Electro-music are trying it as well...

[choklitlove]

your layout is getting used quite a bit, Chok lots of guys over at Electro-music are trying it as well...

yeah, did you see that on ebay?  there's a thread on electro-music.

[brett]

They all get connected to the same place, usually the ground lug, or "sleeve" of the input jack.

Actually, that's not a very good idea.  Search to find out the details.  "RG earth" should get you close.

I'd go with the output jack, or the - side of your power supply

These are better ideas, but don't ground the input or output jacks via the chassis.  Ground them via heavy wire to the common ground.
cheers

[scaesic]

They all get connected to the same place, usually the ground lug, or "sleeve" of the input jack.

Actually, that's not a very good idea.  Search to find out the details.  "RG earth" should get you close.

I'd go with the output jack, or the - side of your power supply

These are better ideas, but don't ground the input or output jacks via the chassis.  Ground them via heavy wire to the common ground.
cheers

when you hear someone say "dont ground the output jacks" etc i find it's often confusing.

what makes more sense to me is, "make sure all ground connections are connected, but make sure you havnt grounded anything 'twice'".

ie it is necessary to ground both input and output jacks, but if you're using a metal box then you only need to connect the negative side of the power supply to one jack, which then in turn earths the box. If you earthed both input and output jacks you'd then get an earth loop, where both jacks are connected directly and indirectly (through the box to the other jack's earth connection) to the "ground" at the power supply. Earth loops cause eddy currents on the earth line (i think...) which in turn causes noise/hum (because you dont have a good reference line).

star grounding is a good way to make sure you ground everything only once, it's the same as tree grouding if you think in nodes. If you do this then you have to isolate your input/output/dc jacks from a metal case, and take one earth wire from every earth point to a common place. The easiest way to do this is take the negative side of the power and run it to a track on the pcb, then have a hole for each earth connection.

in short "ground all grounds, but dont ground them twice", which takes a little bit of thought to understand. i think its only really something you need to watch for is you use a metal enclosure and dont isolate your jacks.

[$uperpuma]

your layout is getting used quite a bit, Chok lots of guys over at Electro-music are trying it as well...

yeah, did you see that on ebay?  there's a thread on electro-music.

I didn't see anything on ebay... someone selling a bunch?

[brett]

Hi

These are better ideas, but don't ground the input or output jacks via the chassis.  Ground them via heavy wire to the common ground.

Maybe it was unclear, but the point is to not use the chassis as part of a ground connection for the input.
It can potentiallly cause greater problems than using anywhere else. 
RG has explained this, and most other common issues concerning grounding, quite a few times in the forum.
cheers

[mattpocket]

Hi,

I had a good read up on earthing from some RG stuff, damn that man's a genius! It makes me sick with envy!

1. There was some mention of isolating my jacks from my enclosure?
2. Is this the same to any pots, switches, or anything else that is housed by drilling the enclosure?
3. Do I do this by using rubber washers or have I misunderstood, or I should be using a different kind of jack isolated from ground?
4. Do I need to solder a wire from the board to a physical point on the enclosure?

Also, my LofoMofo screams with feedback if I turn the volume more than a quarter of a turn upwards, would this be down to bad earthing? I.e. I have not isolated my jacks with washers, nor soldered a wire from the board to enclosure.

I think I understood about not grounding things twice... What you were trying to say is that grounding the input also grounds the output, because they are directed via the circuit, or am I wrong...... again?! haha

Thanks, and try to dumb things down for me. I dont have a heap of electronics knowledge yet?

Matt

[brett]

Hi
yeah RG is a genius.  It's so great to have him and a few other gurus helping us mortals out.

RE:

Also, my LofoMofo screams with feedback if I turn the volume more than a quarter of a turn upwards,

That seems strange.  My LofoMofo was a lowish gain circuit that didn't seem prone to oscillation.  However, oscillations are usually due to close proximity or inadvertant elctonic connection between the outputs (or some amplifed version of the signal) and the input.  What happens is that a small input makes a large output, and a little bit "leaks" back to the input.  If this "leakage" adds more than a tiny amount to the input, it creates extra output, which increases the leakage even more, and so on until it "snowballs" out of control.  This desciption also explain why an output that is "in phase" and adds to the input is so much more likely to cause oscillation than an "out of phase" output, which will cancel some of the input.

About earthing, I should point out that low gain and low power stompboxes are not devices that have lots of problems with earthing.  Where power supplies and/or high gain circuits are involved, the chances of problems increases a lot.

Here's some non-expert answers to your questions:
1. There was some mention of isolating my jacks from my enclosure?

Yes, that's a good strategy for all but the simplest circuits.

2. Is this the same to any pots, switches, or anything else that is housed by drilling the enclosure?

No, these components don't connect either the signal or the "circuit ground" to the enclosure.  Some layouts will show connecting a lug of a pot to the body of a pot (e.g. lug 1 of a volume pot).  This uses the chassis as a path to ground, which isn't a good idea.  Use a 1c piece of wire to connect the lug back to the circuit ground.

3. Do I do this by using rubber washers or have I misunderstood, or I should be using a different kind of jack isolated from ground?

Insulated jacks are readily available.  I use them for about half of my builds.  Basically anything with a power supply or high power consumption or high gain.

4. Do I need to solder a wire from the board to a physical point on the enclosure?

One of the most popular grounding systems is to use a single point on the chassis as the one true ground.  This is "star grounding".  Everything gets its own wire to connect to this point (the input socket, the output socket, the pre-amp, the power amp, the whatever).  This stops high-current, filthy earth lines (like the power supply) from contaminating sensitive low-current, clean earths like a pre-amp.

cheers 

[mattpocket]

My lofomofo was my first pedal and I made the layout myself, its not perfect and could be a lot more compact. But it helped me understand the circuit, and was more logical for me to follow in the need for debugging (it worked first time though, apart from this screaming!)

Here it is. I might have screwed up somewhere.



Thanks for the help with grounding, and does this mean that I need to connect the symbols for ground (see link to schem in my first post) to the five holes at the bottom left of the board as previously indicated by someone, or should I connect them to the enclosure? Or both?

Thanks

[brett]

Hi
You're right, the LofoMofo has that 2N2222A working flat out.  I probably put a small resistor on the emitter (between 220 ohms and 1k) to reduce the gain a bit and stabilize the bias point.
cheers

[JonFrum]

Every part of the schematic that is marked as ground needs to be in continuity with every other such part. If you touch your meter probes at any two ground points, you should get 0 ohms resistance - just like two different points of the same wire. The pattern in which you connect them can make a difference, but the idea is to connect them all together somehow. Once you understand that, you get to the art of wiring ground without causing noise. The recommendations of R.G. and others start after you get continuity among components that need to be grounded.