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Old 24th January 2013, 01:00 PM   #501
dazed2 is offline dazed2  Canada
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Quote:
Originally Posted by AndrewT View Post
What is SLB that you and Davenport refer to?
My impression of the SLB in the diagram I posted is what is referred to "ground break circuit". I assume Davenport is referring to the same thing.

However, realistically I'm planning to implement the system Nelson Pass uses in the F5T
Click the image to open in full size.

Last edited by dazed2; 24th January 2013 at 01:03 PM.
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Old 24th January 2013, 06:38 PM   #502
ctrlx is offline ctrlx  United Kingdom
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Quote:
Originally Posted by Bensen View Post
Hi there,

I have gone quickly through this thread and tried some proposals, but sofar no succes.



Please have a look at the wiring sheme below. What should I do to get rid of the hum?


Greetz
read posts 1 to 10.
in post 7 it is shown how to wire the input sockets, which must be isolated from the casework.
if this dont work, i would rewire your whole amp using a central star bolt, because in your picture and diagram this does not seem to be the case, connect up the ov's in order of the magnetude of the currents ie main tx ov, main caps ov, pa hi current ov, speaker ov, pa low current ov, input socket ov.
if you decide to rewire, consider to re-arrange the mains tx to be far from the pa pcbs, dont mount pcbs on the txmr.
good luck.
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Old 20th March 2014, 09:55 AM   #503
basi is offline basi  Croatia
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Hi to all!!!

Here is my latest project and i have some questions.

Click the image to open in full size.


Do i need to separate signal ground on Lm3886 on second star ground?Or is just ok to have two star ground?

This is 2.1 system with one transformer and one diode bridge.


This is bottom side.
Click the image to open in full size.
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Last edited by basi; 20th March 2014 at 10:03 AM.
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Old 21st March 2014, 10:29 PM   #504
TNT is offline TNT  Sweden
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AndrewT - saving lives in a thread near You!

Thanks for being persistent.

//
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Old 22nd March 2014, 09:16 AM   #505
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Quote:
Originally Posted by gainphile View Post
Interesting. I am currently fighting this ground hum. If I put a pair of amp (L+R) no hum. But once I put additional pair (to make it 4-channel) I hear hum.

At the end I had "all grounds connected everywhere" to obtain minimal hum - still audible on very quiet night.

What is the correct grounding for stereo amps then ?
it is all about current loops. You must understand where is the loop for particular signal and try to make it short as possible. All this STAR nonsense only confuses people. They are looking for "stars" , try this and that and at the end of the day connect it somehow just to get minimum noise =)

But, if you understand where high current loop goes, and low current loop goes, you can make them separate physically or placing coupling HF and LF capacitors =) But you have to look into the drawing.
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Old 23rd March 2014, 03:53 PM   #506
basi is offline basi  Croatia
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Quote:
Originally Posted by basi View Post
Hi to all!!!

Here is my latest project and i have some questions.

Click the image to open in full size.


Do i need to separate signal ground on Lm3886 on second star ground?Or is just ok to have two star ground?

Nobody comment my post above.Is this mean that Layout is ok,Can i etch my board now?
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Old 23rd March 2014, 06:57 PM   #507
AndrewT is offline AndrewT  Scotland
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In my case the "no response" means I don't understand.
I can't speak for other Members.
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Old 23rd March 2014, 07:59 PM   #508
basi is offline basi  Croatia
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Quote:
Originally Posted by AndrewT View Post
In my case the "no response" means I don't understand.
I can't speak for other Members.
All black lines are grounding on top(component side) of board,red circles are capacitor positions.Right on picture are lm3886 amplifier circuit.
Question is do i need to separate signal gorunding line of lm3886 from MF,HF,speaker ground point and make a new route to the main star ground or to leave just the way it is?
Click the image to open in full size.

Thanks for replay!!!
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Last edited by basi; 23rd March 2014 at 08:02 PM.
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Old 25th March 2014, 06:45 PM   #509
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Quote:
Originally Posted by tangmonster View Post
I Had problems finding a isolated panel mount rca connector for my projects , But this really is a very most important thing.

I built a 5 channel surround amp with each channel in its own enclosure and one enclosure for my powersupply , so basically i have a small star ground in each of the 5 amplifier enclosures. Luckily i have now hum.

tang
In the past i have isolated rca from the chassis by using teflon plumbers doping tape. It is a very very thin white teflon ribbon that is used to wrap around threads in plumbing, but it is also electrically isolating and ive warpped it around threads of rca jacks to effectilvley isolate them from chassis.

I did that for my pearl 2.

Best is the neutrik rcas. They are isolated.
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Old 25th March 2014, 07:25 PM   #510
andyr is offline andyr  Australia
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Quote:
Originally Posted by FormosaWest View Post
In the past i have isolated rca from the chassis by using teflon plumbers doping tape.
Can't understand why you needed to use teflon tape - every single RCA socket I've ever bought has come with a couple of washers made from teflon/nylon which isolate the RCA metal from the case metal?

The outer washer has a small circular ridge around the hole which locates the RCA socket into the middle of the drilled hole in the case, so that the RCA barrel is not touching the case. The inner washer simply isolates the nut from the case.


Regards,

Andy
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