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Old 11th March 2013, 04:46 PM   #3831
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Originally Posted by buzzforb View Post
Might not be worth circuit board it is printed on. Easy enough to try once parts come in.
Your designs are meticulous. To me, the proper phase of the signals in the guts of the circuit is the most important criterion for it to work or not. Synchronicity!
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Old 12th March 2013, 09:19 AM   #3832
cjkpkg is offline cjkpkg  United States
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Originally Posted by Tea-Bag View Post
Here is my approach to FW amps.
I believe ZM taught me this.

Take all ground wires from Speakers , line signal and and solder all to PS ground at back end, In the middle of the V+ and V- outputs. In that same area, take CL60 and tie that to chassis ground with bolt, and from there, bolt wire to IEC power cord ground.
So a CL60 seperates everything from direct chassis or IEC ground.

From here, shorting the inputs should lead to a quite amp. If not. Twist toriod, or cover toriod and or the Jensen's with MU-Metal (careful not to short).

Is your setup different?
So are you saying not to use any of the in/out ground points on the amp PCB?

I also assume then to only run one gnd wire from amp board to PSU ground and run input /output ground wires only directly to PSU board gnd? Then PSU board gnd to cl60 to star gnd?
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Old 12th March 2013, 09:38 AM   #3833
generg is offline generg  Germany
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Hi cjkpkg,

Still the hum it seems....one idea got in my mind some days ago....

The current through the F6 circuit goes up very quick turning the pot....
Is it possible that you have more than 1.5A let's say 2A ore even more...
Happened sometimes to me......
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Old 12th March 2013, 10:15 AM   #3834
Tea-Bag is offline Tea-Bag  United States
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Quote:
Originally Posted by cjkpkg View Post
So are you saying not to use any of the in/out ground points on the amp PCB?

I also assume then to only run one gnd wire from amp board to PSU ground and run input /output ground wires only directly to PSU board gnd? Then PSU board gnd to cl60 to star gnd?
Yes, although I realize the board is designed to handle a direct ground, and then one wire ground to PS ground. Usually there is no problem either way, and I tested both. I wonder if you can uncouple a channels heatsink and stretch the wires out if you will, if the hum is redunced. This may tell us if it is coming from another components, or is just a ground loop.
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Old 12th March 2013, 10:28 AM   #3835
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My amp builds are generally dual mono. Their central star grounding points where all ground connections meet, is always the ground rails of the capacitors banks, irrespective of passive or regulated power supplies. The chassis ground is connected via NTCs.

There is one exception yet. The signal grounds from the input terminals lead directly to the amp boards.

It is always dead silent and absolutely hum free.
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Old 15th March 2013, 10:23 AM   #3836
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Single transformer.
Attached Images
File Type: jpg F6.jpg (233.4 KB, 179 views)
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Old 15th March 2013, 10:56 AM   #3837
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Single transformer.
buzzforb. You show an interesting schematic.
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Old 15th March 2013, 10:59 AM   #3838
flg is offline flg  United States
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Yes, quite. Simplified of coarse
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Old 15th March 2013, 11:06 AM   #3839
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The big question is the modulation of the second stage. I believe this or the first circuit could be operated with no local feedback and achieve very respectable numbers. In my very short stint in audio, there is something very alluring about minimalist circuts that perform well. There is simply more information and space conveyed in the playback. I was quite shocked when listening to the original F6 how much removing the source resistors seemed to open things up. Sure we have feedback, but it does not seem to be causing any nasties that come through. I am going to be trying both the firs circuit and this one, as I am unsure if either holds an advantage. FE on this one will be cascoded with LEd rferemce so I can run Jfets at miminal degeneration. All options and configurations will be included for playing. I am even trying prganic polymer as coupling cap in output as I am interested to see how these perform/sound vs standard electrolytics.
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Old 15th March 2013, 11:07 AM   #3840
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buzzforb. You show an interesting schematic.
Little spin on your suggestion.
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