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Old 4th January 2017, 11:15 AM   #2561
wuffwaff is offline wuffwaff  Netherlands
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Default DC Servo for the AlephJ-X

Hi,

some people asked for information on the dc-servo I put in my Aleph-X a while ago. I finally managed to write it all up.

The parts values will probably not fit any other amp as they will vary with supply voltage, cooling, McMillan resistor values, JFet or Fet input etc. etc. but it will help getting started.

Main motivation for doing this was the possibility to raise the values of the McMillan resistors above 30k. I think these have quite an influence on sound quality. This would not have been possible otherwise as mains voltage fluctuations are just too big where I live.

I put it all together in a pdf. This made it a lot simpler for me to write down. The pics are a bit small but I can post them separately if needed.

Hope this helps,

William
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File Type: pdf Aleph-X DC Servo.pages Kopie 2.pdf (283.3 KB, 236 views)
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Old 13th January 2017, 11:43 AM   #2562
esprit is offline esprit  Europe
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Default Aleph X for 2017

Hello
For a member of Pink Fish, I have made the following purchase.
4x Aleph X boards (2 surplus)
3x Soft start boards (1 surplus)
3x discrete regulators (need 1)
5x 1000va transformers, with 18v18 x4 secondaries (3 surplus)
12 x copper bus bars to mount the transistors directly to this with no isolators the copper bar then insulated with Sil-Pad.
4x Heat Sink = 400x150x50
14x capacitors 50v 68000uf
Pack of components for the amp boards and soft start.
All good, however, I need two more power caps to make up the 16 required, they are United Chemi-Con U32D, 68,000uf 50v. Can anyone advise where to purchase these caps, or advise on inserting alternatives (I guess it would require 4 off).
So far, done some top level reading and gathering of information regarding the Aleph X. (Gulp) !. I am beginning to understand that, the Aleph X, is a quite a different amp to the F5 's I have constructed so far, (I hope that I haven't bitten of my than I can chew!).
(I am currently part way through building a stero F5t, with twin power supplies, completed and tested).
The Aleph X will be mono's.
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Old 13th January 2017, 11:53 AM   #2563
Eric is offline Eric  United States
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Aleph-X builder's thread.
William - thank you for the writeup. I've been adjusting my amps every few months to account for the change of season and the accompanying change in ambient temperature in the semi-unfinished portion of my basement where the amps live. It is surprising how much the offset changes - this will remove a seasonal chore!

Esprit - have a look through my Aleph-X web page, it will probably answer most of your questions. I am wondering why you are bothering with copper bus bars for mosfet mounting. If you don't insulate each transistor from the copper bar, then you can only put one transistor on each bar, so you're not likely to be doing much spreading of heat across your sinks and will only be introducing another thermal junction which will decrease your cooling efficiency. Best in this case to just mount the mosfets directly to your sink with an electrical insulator. Finding good caps is always a treasure hunt. I don't have ready made sources for these, you just have to poke around. I advise against using old/surplus parts - go with new parts.
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Old 31st January 2017, 02:59 PM   #2564
kropf is offline kropf
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William,

If I may offer one tweak to your DC servo circuit, you could use the balanced output of the amp to good advantage by summing the outputs at the input of your DC servo. The music signal sums to nearly zero and wouldn't need to be filtered, leaving only the common mode signal that is mostly the DC you want to use, along with any 50Hz/60Hz power supply noise and harmonics.

Jeremy
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Old 15th March 2017, 10:18 PM   #2565
Zen Mod is online now Zen Mod  Serbia
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Aleph-X builder's thread.
Eric , is it possible to find anywhere pdf or even gerbers for those green AX pcbs ?

I need them for deciphering purpose
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Old 16th March 2017, 08:46 PM   #2566
Eric is offline Eric  United States
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Aleph-X builder's thread.
Zen: I don't have either a PDF or Gerbers. The only thing I have are digital images of the front and back of the bare PCB. Lower resolutions ones are on my website - I can provide higher resolution if you think they'll help.

Edit: Someone here has got to have the original files - I think they were a "design by committee" so there should be multiple sources...
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Old 16th March 2017, 09:03 PM   #2567
Zen Mod is online now Zen Mod  Serbia
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Aleph-X builder's thread.
tnx Eric , I already got those from your site

as photos , they're good enough
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Old 17th March 2017, 01:41 PM   #2568
Eric is offline Eric  United States
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Aleph-X builder's thread.
Maybe send a PM to Chad (hifizen) as he was one of the main players in the development of the board. He is likely to have an old document laying around somewhere...
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Old 17th March 2017, 01:43 PM   #2569
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Aleph-X builder's thread.
tnx
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Old 24th April 2017, 08:07 AM   #2570
Rodeodave is offline Rodeodave  Austria
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Aleph-X builder's thread.
Sneak preview of my upcoming AJXH build...
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File Type: jpg IMG_20170423_213730.jpg (815.8 KB, 235 views)
File Type: jpg IMG_20170423_213738.jpg (830.6 KB, 230 views)
File Type: jpg IMG_20170423_213810.jpg (854.3 KB, 227 views)
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