Aleph J for Universal Mounting Spec - Page 31 - diyAudio
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Old 29th April 2013, 08:18 PM   #301
henryve is offline henryve  South Africa
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Fellas

One potentially stupid query. I have for this amp's PSU one Amplimo 650VA trafo with 2 18V secondaries and 2 of the black BrianGT CCRC PSU boards, each stuffed with 6 33000uF caps.

Do I use 4 bridges so that I have 2 per board and 2 per secondary, or do I use 2 bridges giving 1 bridge per secondary and then split from there to the 2 PSU boards?
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Old 29th April 2013, 09:08 PM   #302
Zen Mod is offline Zen Mod  Serbia
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4 bridges

that way you're having at least some isolation between C banks
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Old 29th April 2013, 09:12 PM   #303
henryve is offline henryve  South Africa
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Thx ZM.
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Old 6th May 2013, 09:30 PM   #304
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Default Follow-through and follow-up

As I mentioned before my available time to work on audio projects is very limited, which sometimes causes delays in completing a build. Here are the final steps I took to resolve the remaining issues with the DIY Aleph J clone using the boards designed by Didiet.

After I determined that both the Ultrafast Recovery and Soft Recovery diodes caused mechanical hum in the transformers, I removed them from the boards and attached Fairchild bridges to the chassis perforated insert.

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The two transformers are stacked in the center of the chassis. The top one is upside-down (yes, you can do that) just because of the limited length of the wires. What is not visible in the picture is that the bottom transformer has its own top plate, lock washer and nut installed. Using the oscilloscope attached to the output I started one channel and carefully rotated the transformer until no noise was induced into the output. I then locked it in place so rotating the top one would not disturb it.

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I first tried to return the PSU ground to AC ground with wires and thermistors. Dropping the CL-60s straight to the chassis floor gave me the best results.

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Below you can see the AC connections including the ground connection close to where it enters the chassis.

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This is how the back panel looks from inside the case.

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And this is the view from the outside.

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Attached Images
File Type: jpg DiodesRemoved.JPG (160.5 KB, 381 views)
File Type: jpg Bridges1.JPG (175.1 KB, 374 views)
File Type: jpg Bridges2.JPG (169.9 KB, 373 views)
File Type: jpg StackedTrafos.JPG (207.6 KB, 375 views)
File Type: jpg PSUGround.JPG (220.3 KB, 375 views)
File Type: jpg ACConnections1.JPG (238.3 KB, 374 views)
File Type: jpg ACConnections2.JPG (272.0 KB, 373 views)
File Type: jpg ACConnections3.JPG (228.6 KB, 371 views)
File Type: jpg BackPanelInterior.JPG (258.8 KB, 376 views)
File Type: jpg BackPanelExterior.JPG (137.9 KB, 372 views)
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Old 6th May 2013, 09:38 PM   #305
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Default Final words...

The amplifier sounds fantastic! As for the noise issues, pausing the music and getting the ear close to the speaker I still could not hear any noise.

Things I have learned:

1) Didiet's boards are good
2) MUR and MSR diodes are not well suited for this application
3) Stacking transformers is a non-issue
4) Flipping one of them upside-down is not an issue either
5) Sometimes a wire connecting PSU ground to earth can be noisier than no wire at all

Last edited by grimberg; 6th May 2013 at 10:07 PM.
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Old 7th May 2013, 01:58 AM   #306
biju55 is offline biju55  India
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what is the VA rating of the each of these transformers ? I have got the same power supply boards . planing to build A30.
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Old 7th May 2013, 02:10 AM   #307
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The transformers are Avel Lindberg 115V+115V/18V+18V @ 250VA.
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Old 7th May 2013, 02:41 AM   #308
6L6 is offline 6L6  United States
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grimberg - What a fantastic journey! You have done a couple of things that I would never have thought of, but very simple when shown - specifically where you put the thermistors and the rotating of the transformers.

Well done!
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Old 8th May 2013, 05:51 AM   #309
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Jim,

I am really glad to have purchased the perforated insert as it was very helpful in experimenting with the different setups. It went in and out of the case so many times we became good friends. It even stopped biting my fingertips after a while. Either that or I learned how to hold it properly.

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Old 8th May 2013, 07:52 AM   #310
henryve is offline henryve  South Africa
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I pity I can't buy those cases because of shipping cost. That perforated plate is really nice for the floor. Saves a lot of drilling. I can now drill and tap M3, M4 and M5 holes with my eyes closed.
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