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Old 19th October 2013, 04:17 PM   #531
Salas is offline Salas  Greece
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Quote:
Originally Posted by ivanlukic View Post
you take NFB point from loudspeaker terminal with separate wire to amp. There is much about it in some Serbian DIY forums. There are several project currently using it.
Are they doing something similar to Kenwood's Sigma Drive?
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Old 19th October 2013, 04:24 PM   #532
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Quote:
Originally Posted by Salas View Post
Are they doing something similar to Kenwood's Sigma Drive?
I don't know if it is similar to Kenwood's Sigma Drive, but I would not be surprised if it is. The idea is, if I understand it, to eliminate distortions and anomalies present in loudspeaker cables simultaneously with amp distortions.
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Old 19th October 2013, 04:33 PM   #533
PMI is offline PMI  United States
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Quote:
Originally Posted by ivanlukic View Post
I don't know if it is similar to Kenwood's Sigma Drive, but I would not be surprised if it is. The idea is, if I understand it, to eliminate distortions and anomalies present in loudspeaker cables simultaneously with amp distortions.
How do you keep that feedback wire free of EMI/RFI and any other interference, shielded cable?
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Old 19th October 2013, 07:08 PM   #534
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Originally Posted by PMI View Post
How do you keep that feedback wire free of EMI/RFI and any other interference, shielded cable?
To be honest I do not follow those threads seriously (because these threads are epic in length) and do not know the answer to your question. I would have to read some of it to see. Here you have schematic of one such amp designed by the legendary Dragoljub Aleksijević - Macola that uses LM3886 power ICs.
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Old 19th October 2013, 07:41 PM   #535
Mr Evil is offline Mr Evil  United Kingdom
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Originally Posted by PMI View Post
How do you keep that feedback wire free of EMI/RFI and any other interference, shielded cable?
I'm not sure that you would need to do much. For instance ATX power supplies use a simple unshielded wire for 3.3V remote sensing. While the wire is not very long compared to a speaker cable, the inside of a PC is full of RF. This might be a good use of a spare pair in a Cat5 cable.
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Old 19th October 2013, 08:15 PM   #536
BYRTT is online now BYRTT  Denmark
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Pete i have 4 of our nice PCBs and will use when i get there, thanks for that (lots of good reviews from members so look forward), and documented measurements are top class.

For routing/layout concerns started by member "AndrewT" i have little input. First i say that nothing of my input is to make shipped PCB's better without documented measurements or listening tests. It is what i have learned from this site and books and i only post for getting knowledge out and feedback back so everybody can learn. Think it is same boat as members "AndrewT" and "Jameshillj" mention. This routing/layout are very audible in sensitive preamps for audio/musical instrument, and best it is no cost in bits and pieces.

First Picture:
LM317 example with same schematic but different routing/layout. In a simulating program this will give same result but real world as seen is very different. The plots i downloaded somewhere from this site couble of years ago and as i remember was taken with 16bit soundcard. The schematic layout underneath i made myself tonight before posting for understanding of routing seen in plots.

Second Picture:
Taking on SMALL shoes, little routing improvement can be made for C9/C10, see text in Picture.

Third Picture:
Example of one (or make your own) easy way to amend PCB for maybe better routing.

Fourth Picture:
Example routing/layout by member "Metallicus69" taken from #post490.
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File Type: png RemoteSence.png (40.0 KB, 264 views)
File Type: png C9-C10.PNG (20.4 KB, 248 views)
File Type: png CM-PCB.PNG (463.9 KB, 257 views)
File Type: png Post490.png (938.2 KB, 240 views)
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Old 20th October 2013, 06:20 AM   #537
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Now I know why my LM317/337 regulator for phono stage has some noise (BYRTT first picture). My P2P routing was not optimized for lowest noise. If adjustment pin cap is used with LM317/337, do we still need adjustment pin ground to be connected at the load?
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Old 20th October 2013, 09:23 AM   #538
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by ivanlukic View Post
Now I know why my LM317/337 regulator for phono stage has some noise (BYRTT first picture)............ do we still need adjustment pin ground to be connected at the load?
YES !!!!!
At the load connection, i.e the output side.
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Last edited by AndrewT; 20th October 2013 at 09:39 AM.
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Old 20th October 2013, 06:50 PM   #539
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Quote:
Originally Posted by AndrewT View Post
R11 connect direct to Q11 source.
C3 to R3
R9 to Q11 trace
R3 to Q11 trace
Q11 trace to output, AT THE OUTPUT.
...
With regard to the discussion a couple pages back, here is another possible component placement. (The current one was really aiming at a different ground scheme, so, not so easily converted)

R11 relocated and connected directly to Q11 source
C3 relocated and connected to the junction of R1 and R3
R9 and VR1 relocated to make more room for R9 ground connection
R3 and R11 moved to allow common connection

The different filter nodes connected to ground are left unrouted and highlighted.
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Old 20th October 2013, 07:02 PM   #540
AndrewT is offline AndrewT  Scotland
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That looks very much better.
Now repeat for lower half.
Then change the main (across the middle) ground link back to it's original width (where possible or waist it where not possible).

I would look at using a wire link to connect the measuring ground to the middle of the T between the two middle terminals of the output connectors.
If anyone makes a two sided board, then the wire link can be replaced with a top side trace.
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