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Old 13th June 2013, 04:50 PM   #2031
Rixsta is offline Rixsta  United Kingdom
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Everything is fine when one channel is attached only (both are on but only one channel connected up), as soon as both channels attached then hum, confusing as hell ;-)
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Old 13th June 2013, 05:00 PM   #2032
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you have a groundloop. solder a short fat wire between the GND points on each ch.
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Old 13th June 2013, 05:16 PM   #2033
Rixsta is offline Rixsta  United Kingdom
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Thanks, shall go sort this
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Old 15th June 2013, 09:46 AM   #2034
WalterW is offline WalterW  Netherlands
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Making some progress...
I thought posting some pictures will be nice.
I'm rebuilding my F5Tv2 to a v3.
One channel is done, think I test it first, before buiding the next channel. Curious if it will be stable with the larger output stage.
I'll test it today, hope I don't destroy it

Made some improvements too.
-Used Kerafol 86/82 red for the outputs and diodes. On the first pic you can see it's rather fragile, can't be used twice. I mounted the outputs for a test with M4 bolds with washer, as tight as possible, and it gives too much pressure in the area of the M4 so it destroys the Kerafol.
So I decided to make a clamping bar of 4 mm steel just for the outputs. See pictures.
Hope the thermal coupling gets better. Will post the results.

- Coupled the Jfets with some copper and thermal glue.
- I glued the new (better) thermistors to the outputs. I have good experience with that, with my standard F5.
- Replaced the 10 Ohm JFet source resistors for Dale CMF55's.
- made the connection to the PSU with faston connectors, so it's easier to disassemble.
- Upgraded the outputs source resistors to 10 Watt with two paralled MPC74 0.47 Ohm resistors. Looks nicer when the whole PCB is filled with components...
- upgraded some cabling with thicker 6mm cable. And for the input no more fragile coax, but twisted signalwire. Like Pa does...

Oh, and I build a DC-filter ( schematic of Rod Elliot) for the mains, see picture, and now all mechanical hum of the big toroids is gone !
Attached Images
File Type: jpg Kerafol used with to much pressure.jpg (184.7 KB, 271 views)
File Type: jpg v2 vs v3.jpg (406.3 KB, 293 views)
File Type: jpg nice.jpg (297.6 KB, 283 views)
File Type: jpg Clamp bar.jpg (375.0 KB, 265 views)
File Type: jpg better position of NTC.jpg (448.2 KB, 259 views)
File Type: jpg JFETs coupled with thermal glue and copper.jpg (418.3 KB, 165 views)
File Type: jpg DC-filter.jpg (329.3 KB, 158 views)
File Type: jpg PSU connectors.jpg (231.8 KB, 156 views)
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Old 15th June 2013, 10:45 AM   #2035
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Quote:
Originally Posted by WalterW View Post
Oh, and I build a DC-filter ( schematic of Rod Elliot) for the mains, see picture, and now all mechanical hum of the big toroids is gone !
Which projectnumber is that?
(I guess I'm a bit tired today, just can't find it...)
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Old 15th June 2013, 10:57 AM   #2036
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Great job Walter. Very clean and well thought build. Any hum issues from seperating the boards?
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Old 15th June 2013, 11:46 AM   #2037
WalterW is offline WalterW  Netherlands
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Quote:
Originally Posted by ijscobar View Post
Which projectnumber is that?
(I guess I'm a bit tired today, just can't find it...)
Mains DC and Transformers

I used figure 8

Walter
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Old 15th June 2013, 11:50 AM   #2038
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Thanks, dankjewel, vielen dank!
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Old 15th June 2013, 11:56 AM   #2039
WalterW is offline WalterW  Netherlands
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Quote:
Originally Posted by buzzforb View Post
Any hum issues from seperating the boards?
Thanks Buzz!

No, not at all.
You can't really see it on the pics, but I connected the two grounds with 4 x 1,5 mm wires under the PCB. Thought it should be thicker, but like you said earlyer " point of diminishing returns"...

Walter
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Old 15th June 2013, 05:08 PM   #2040
Rixsta is offline Rixsta  United Kingdom
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P1060024.jpg


P1050990.JPG


P1060027.jpg
Check out the single ground point
The earth wire is interlaced with the inputs ground

P1060028.jpg


P1060030.jpg

Learnt a Lesson with the Diyaudio F5T boards, make sure the solder connections are realy good filling both sides of the board, some connections on the PCB are the top side only, I had a problem where I couldn't Bias up the let channel but fixed it now.

anyway Ive sorted out most of the issues now and Ive redone the power supply with thicker solid wire, there is no hum on either channel if only one channel has the Mp3 player connected. as soon as I connect to both channels RCA's I get loads of hum still. I find it rather odd that having only one channels RCA connected and its ok. so still wondering what the hell is going on lol

So I need help to understand how this can happen somehow both channels are interacting in a wierd way.
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Last edited by Rixsta; 15th June 2013 at 05:32 PM.
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