I've been reading the other recent discussion on here related to chassis grounding and just wanted to be sure I'm understanding this schematic correctly and that it seems like a legitimate way to do this. The kit I'm building is an el-cheapo 180 dollar Chinese speaker amp kit... I have built a Bottlehead Crack (which of course had excellent instructions) and also some other solid-state projects, but this is my first foray into working just off a schematic-- and of course the notation is in Chinese and the English is horrible.
As I understand it, all ground points indicated on the drawing should be connected to the cathode side of the 330uf cap. There is a central grounding point that the cap connects to which is screwed to the chassis. I'm a bit confused on the "shield connecting the ground" notation on the pot to the left-- it appears a wire just runs from the terminal to the common chassis ground? But it also looks like there's another line running off to the left which I figure means nothing?
Then, does it appear in this schematic that the earth ground is connected at all? It looks to me like neutral and hot are, but not earth? That seems odd to me. And then there is the poorly written text talking about the ground points represented in the picture and to "remind to connect it". Anyway, just wanted someone knowledgeable to comment and make sure I'm making sense of this. Any other advice or tips would be appreciated-- I've noticed others have really struggled with this kit and I seem to have much better drawings than they had to work with after scouring the internet and translating some Chinese (YIKES that's hard to believe), so I hope others might find them helpful anyway.
Also, could someone explain what the little circular looking loops are in the first drawing, schematic 1-- you can see one right above the power switch. I assume these are twisted pairs to reduce the field for tube heating but wanted to verify-- they are obviously not a standard schematic symbol I'm aware of and the transformers are clearly marked (which they somewhat look like). Thanks!
As I understand it, all ground points indicated on the drawing should be connected to the cathode side of the 330uf cap. There is a central grounding point that the cap connects to which is screwed to the chassis. I'm a bit confused on the "shield connecting the ground" notation on the pot to the left-- it appears a wire just runs from the terminal to the common chassis ground? But it also looks like there's another line running off to the left which I figure means nothing?
Then, does it appear in this schematic that the earth ground is connected at all? It looks to me like neutral and hot are, but not earth? That seems odd to me. And then there is the poorly written text talking about the ground points represented in the picture and to "remind to connect it". Anyway, just wanted someone knowledgeable to comment and make sure I'm making sense of this. Any other advice or tips would be appreciated-- I've noticed others have really struggled with this kit and I seem to have much better drawings than they had to work with after scouring the internet and translating some Chinese (YIKES that's hard to believe), so I hope others might find them helpful anyway.
Also, could someone explain what the little circular looking loops are in the first drawing, schematic 1-- you can see one right above the power switch. I assume these are twisted pairs to reduce the field for tube heating but wanted to verify-- they are obviously not a standard schematic symbol I'm aware of and the transformers are clearly marked (which they somewhat look like). Thanks!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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I don't understand your question about the grounding, perhaps you could explain that a bit clearer.
The loopy things on the diagram, means twisted wires for heater supplies ( I'm pretty sure).
The loopy things on the diagram, means twisted wires for heater supplies ( I'm pretty sure).
I guess I understand that all the marked grounding points (7 of them) connect back to the cathode side of the cap-- where it is grounded to the chassis. I don't see them showing a connection from the Earth ground of the power plug to the chassis--- that must be done as well, correct? Also, I guess my original question was focused on the whole "shield connecting the ground"-- I should just connect the ground of the pot to the common ground, correct?
Thanks for verifying the little loops-- I suspected they represented twisted pairs.
Thanks for verifying the little loops-- I suspected they represented twisted pairs.
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I built one of these a year or so back.
The "Shield connecting the ground" just refers to the cable connecting the inputs through to the pot. It is a two core cable with a braided shield around it. The braided shield should be connected to chassis ground at one end only to provide shielding of the inputs from interference
Yes connect the Safety earth to chassis
The "Shield connecting the ground" just refers to the cable connecting the inputs through to the pot. It is a two core cable with a braided shield around it. The braided shield should be connected to chassis ground at one end only to provide shielding of the inputs from interference
Yes connect the Safety earth to chassis
Star earthing is the best earthing!
Yes you could and should connect the power-plug earth to your common ground for safety sake only! some people find out that this sometimes causes earth loops, and have to lift the ground.
In some countries power-plugs may not have an earth (China I assume) that's probably why you don't see that connection.
I would connect all grounds to one point, meaning as well as the input shielded cable, there should be a single wire from input sockets earth (without the sockets being bolted to the case) to the common ground, and the shield not connected to the sockets, but the common ground.
This being an SE design, means you gonna need very good & quality smoothing caps for eliminating hum and sound quality. the smoothing caps, act as signal caps too in this design.
Yes you could and should connect the power-plug earth to your common ground for safety sake only! some people find out that this sometimes causes earth loops, and have to lift the ground.
In some countries power-plugs may not have an earth (China I assume) that's probably why you don't see that connection.
I would connect all grounds to one point, meaning as well as the input shielded cable, there should be a single wire from input sockets earth (without the sockets being bolted to the case) to the common ground, and the shield not connected to the sockets, but the common ground.
This being an SE design, means you gonna need very good & quality smoothing caps for eliminating hum and sound quality. the smoothing caps, act as signal caps too in this design.
Well thanks for the excellent tips guys-- I feel like I am ready to start screwing some components in and begin soldering at this point. I did purchase the entire thing as a kit so I will use the (probably low quality) caps that came with it to start anyway.
And, I know this is noob but I'm a very technical guy and just want to be sure--- the layout on this schematic is what is laid out as "star grounding", correct? My understanding is that star grounding allows a run from each ground point back to the chassis/earth ground, right? Thanks again guys this forum is awesome!
Oh and FYI, very neat that you pointed out the lack of a ground in other countries-- that makes perfect sense as to why it isn't shown in the schematic-- I was thinking "WTF?" lol
And, I know this is noob but I'm a very technical guy and just want to be sure--- the layout on this schematic is what is laid out as "star grounding", correct? My understanding is that star grounding allows a run from each ground point back to the chassis/earth ground, right? Thanks again guys this forum is awesome!
Oh and FYI, very neat that you pointed out the lack of a ground in other countries-- that makes perfect sense as to why it isn't shown in the schematic-- I was thinking "WTF?" lol
Just as a side note, the paralleled 6n9p at the input is probably not the best choice. Crazy miller cap will roll off treble, and 120 plate volts are not the finest choice either...
This schemo can be vastly improved at the input section. Great for tinkering, probably not so great for noobs to build straight away, since the sonics might disappoint..
This schemo can be vastly improved at the input section. Great for tinkering, probably not so great for noobs to build straight away, since the sonics might disappoint..
Star Earthing means, picking one point , probably the negative side of your smoothing cap, run a short thick bare wire to the chassis, and then connect all grounds, with a separate wire, to this bare wire.
hence the name star!
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The important thing (from the point of view of hum) is that the transformer high voltage winding centre tap should not be connected directly to ground. Instead, connect it to the negative of the 47uF reservoir cap. Then run a wire to the negative of the 300uF smoothing cap. From here you can run other ground connections.
A star ground is all (or almost all - not the transformer CT) ground connections meeting at a point. One point. Difficult to achieve in practice. Having grounds spread along an inch or so of wire is a (short) ground bus.
A star ground is all (or almost all - not the transformer CT) ground connections meeting at a point. One point. Difficult to achieve in practice. Having grounds spread along an inch or so of wire is a (short) ground bus.
Thanks for all the comments once again-- I am learning more everyday. The plan is to begin soldering today after work. Golden beer, being my first build off of a schematic I will probably leave it as is- I could alter things after, I suppose. Is anyone interested in detailed pics of the kit? I document everything and have lots of pics of how it was packed and everything you get for 180 bucks.
Sure I am interested, but mostly after you put it together, and how it sounds.
Good luck
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