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Old 13th September 2012, 06:04 PM   #431
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post 417 !!!!!! For 4.7ohm signal ground!!!

"To allow this to happen the sig gnd must be separate from the amp Power Gnd. Many amplifier layouts maintain this separation"
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Old 13th September 2012, 06:09 PM   #432
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not the F5.
or any other pass diy board i have seen.
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Old 13th September 2012, 06:15 PM   #433
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Last question!
Is there any difference between starground on the pcb and the one after the pcb?
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Old 13th September 2012, 06:17 PM   #434
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not that i know. so if you can have it on the PCB, why not
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Old 14th September 2012, 08:38 AM   #435
AndrewT is offline AndrewT  Scotland
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If the Signal Ground is connected to the Power Ground, then that connection becomes the Main Audio Ground. All other Ground References must come to the same meeting point. 6L6 shows this arrangement in post401.

For a monoblock amplifier, this arrangement is perfect.

But if you use what is effectively a monoblock PCB and use two or more of them inside a common Chassis then the combined Signal+Power Grounds creates a Ground Loop.

I can understand a High Dissipation amplifier PCB having that combined Sig+Pow. It perfectly suits a monoblock.

Now back to post429.
That pic is the Leach alternative for a multichannel amplifier. It almost works. I have found that it is not perfect, there are some interconnecting arrangements that hum slightly. But I have not found any arrangements that have the zero hum that a monoblock can have.

If the PCB can be modified to separate the Sig G from the Power G then the post429 wiring arrangement should give the best chance of avoiding hum in a two channel amplifier.
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Last edited by AndrewT; 14th September 2012 at 08:46 AM.
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Old 14th September 2012, 08:50 AM   #436
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by prooptiki View Post
.......................Is there any difference between starground on the pcb and the one after the pcb?
The Star Ground or Main Audio Ground (MAG) can go anywhere in the space inside the Chassis.
It must not be attached to the Chassis. It must not be attached to the link between the smoothing capacitors. It can be anywhere else.

I try to place the amp PCB and the Output terminals in a close grouping. Then I place the MAG in between these two. That gives me shortish cable pairs for all the interconnections between the modules.

I have not done it yet, but I think the Speaker Return Terminal would be a good location for the MAG. Maybe it's time for me to experiment and report.
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Old 14th September 2012, 12:25 PM   #437
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6L6, Do you have a picture shot straight down into your amp so we can see the full wiring setup.





Quote:
Originally Posted by 6L6 View Post
Trying this has been in the queue for a bit longer than I was hoping. Sorry.

Long story made short, Andrew is quite correct -- placing the speaker Negative at the point where the input and the PSU all connect has made it quieter by an order of magnitude.

Even the transformer even has less mechanical hummm.

So, the scheme is -

PSU GND to circuit board GND. Input and speaker negative all attach at that point.

In the photo;
PSU GND (white)
Speaker Negative (black)
Speaker Positive (red)
V+ (green)
V- (blue)

Click the image to open in full size.

Click the image to open in full size.

It looks a bit kludgey, but remember that the PCB is quite small (2x3 inches)
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Old 14th September 2012, 12:48 PM   #438
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like this dont know if it is dual mono or common PSU. but i guess its dual mono.
Attached Images
File Type: png wiring.png (26.1 KB, 354 views)
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Old 14th September 2012, 02:16 PM   #439
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Speaker terminal is a good option for MAG, but the powerground need also to follow V+ & V- cables!

After a MAG we use a thermistor and then to the Chassis, can we put them anywhere to the Chassis (dual mono 2 MAG) or all of them must be again in star earth ground?

Last edited by prooptiki; 14th September 2012 at 02:18 PM.
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Old 14th September 2012, 02:37 PM   #440
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let the MAG's meet at a commen earth ground.
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