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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Jun 2017, 13:30 
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Can you show how grounding should be on a photo or a diagram? It would be much more clear for us this way.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Jun 2017, 15:22 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Here is a really crude diagram I'm actually embarrassed as to how cruddy it is. I put lines etc on a schematic. Hope it helps.

Good listening
Bruce
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grounds.jpg


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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Jun 2017, 16:33 
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Main ground bus does not directly go to the earth ground, right? Main ground bus is connected to chassis through resistor and capacitor in parallel. Chassis is directly connected to the earth ground.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Jun 2017, 17:19 
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correct

Good listening
Bruce

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PostPosted: 10 Jun 2017, 21:07 
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wats the big deal bout how the pre amp is connected to power amp, that is a futile
subject, not only so, but it is mostly discouraging to the simple diyer. everyone
knows, there must be a ref point, put the darn pre amp gnd, to bus gnd,
and be done with it. wats the big deal


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PostPosted: 03 Sep 2017, 09:21 
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Where should I ground the cable shields inside amplifier ?
One side of the shield is grounded
- directly on chassis ground
OR
- on main ground bus.


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PostPosted: 03 Sep 2017, 20:07 
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Sorry Steakhead, it matters contrary to "what everyone knows". Read up on the subject as it is not nearly as simple as it would appear.

The cable shields inside the amp should go to a signal ground which in most cases with my designs is the buss ground. I typically place that at or very near the input jacks. Going directly to the chassis is likely to create a ground loop and will degrade the S/N.

Good listening
Bruce

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PostPosted: 04 Sep 2017, 02:38 
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How about power supplying cables inside a preamplifier? Can I benefit from shielding them too? Where should they be grounded? Chassis ground makes more sense to me just not to put interference noise to signal path. I'm going to terminate only one end of the shield. So I don't think ground loop will be a case here.

Is shielding that important? Hell yeah!
Half year ago, I built an rca interconnect cable. It was not shielded. In the first try, It sounded good to me. But, after a long session, my ears were almost bleeding because the sound was ultra bright. I then shielded the cable and tried it again. It was like night and day. Sound had more body. Mids were back again. Treble was sweety. It was the same cable, but just shielded with an aluminium tape.

I believe grounding and shielding is the holy grail of this thing.


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PostPosted: 04 Sep 2017, 10:13 
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Hi, Somewhere on the site I just recently covered that...but here goes again. There are three grounds in any of my projects. The earth ground which by most electrical codes is connected to any external metal parts (think chassis in diy). The signal ground and the internal power supply ground. The signal ground usually has a buss that connects the ground terminals on the input and output jacks. I like to use something like 14gage or heavier copper wire for this. Then I separate (electrically) the signal sections of the item from the power supply portions. Each will have a singe connection to the ground buss. Similar to a star configuration, but think more like separate power and signal busses connected to a main input buss. The chassis will have a type X2 capacitor of around 0.1uf and a parallel resistor of approximately 150 ohms between it and the input buss. What this all does is reduce noise contamination of the signal ground. The case is still both an EMI shield and a safety protective cover. If something inside fails the case will keep you from getting hurt. To be true there will be some small amount of power going through the signal ground. The cathode currents of the tubes need to go somewhere. The thing to do is to make sure that most of it takes a rather direct route to the buss. In preamps I like to have the signal ground go from the input stage area to the buss as there are minimal cathode currents. In power amps it can pretty much be either at the input side or output end of the signal circuitry. This is because the actual signal strength is quite high. Ideally you want to design a circuit and build it so that the least amount of power goes through any signal path. Like I said not really possible to completely eliminate it.

My designs tend to use a modular design. This is quite noticeable in preamps. The PS is on one board (or on a separate section of a large one) and the active circuitry on another. If there is control circuitry then it would be on a third section or board. The only connections between them are ones needed to power them. There is no direct ground connection between them. As most folks know by now, I hate hum and noise. Any is too much so I place extreme emphasis on getting it to the lowest levels possible. The grounding arrangements I use do this. Built properly my designs are really quiet. There is no magic involved, just care in layout and connections.

Good listening
Bruce

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PostPosted: 24 Sep 2017, 12:42 
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So far so good. But how about the shields? I plan to connect shields directly to earth ground. I don't want it to input some noise to signal ground. Is this o.k.?


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