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Old 18th December 2001, 08:36 PM   #21
Freddie is offline Freddie  Sweden
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Default Aleph 30 Output board

Here comes the Aleph 30 output board.
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Old 18th December 2001, 08:37 PM   #22
Freddie is offline Freddie  Sweden
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Here comes the stuffing diagram
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Old 6th January 2002, 09:41 PM   #23
Freddie is offline Freddie  Sweden
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Default Stuffing diagram

Here comes the stuffing diagram.
Remember to scale the layout to correct size!

/Freddie
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Old 9th January 2002, 06:29 PM   #24
Freddie is offline Freddie  Sweden
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Default Aleph 30 back end

Here comes layout for the Aleph 30 output stage. Use this one if you have mosfets with TOP3 (TO247) package for example IRFP240. The layout posted above is for TO-220.

/Freddie

(I just did some changes to the layout, the holes were too big)
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Old 13th January 2002, 11:41 PM   #25
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Grey,

I just finished making the layout for my Aleph 5 using yours as a starting point (thank you very much). I opted for double sided prints with a ground plane (saves etching fluid.........), using one eurocard (100x160mm) for two front end boards and one eurocard for four output boards. The advantage with euroboards is that you can get them with a thicker copper layer (70 mu).

Thereīs one thing I didnīt understand in your layout, the "from output devices (CS sence)" is used twice. Why didnīt you connect the emitter from Q5 with "from output devices" on the print itself?

And another question: Whatīs the advantage of R0? Itīs used with the 60 but not with the Aleph 5 or 4.

william
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Old 14th January 2002, 12:53 AM   #26
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William,
Since you're using a double-sided board, you can run the emitter of Q5 on the other side of the board. I set myself the task of making a single-sided Aleph board. I have nothing against double-sided PC boards, and in fact usually keep some around, but I found that I didn't really need it for this project.
If you think you see a way to sneak a trace from the emitter of Q5 around to the top of the resistor array, by all means do so. However, if you're using a double-sided board, a larger board, or run a connection to the interior of the board (instead of connecting at the edge), you've changed the rules of the game.
To me, doing a PCB layout is like assembling a jigsaw puzzle. I don't have any fancy software; I do the layouts by hand, trying several different versions, then keeping the best portions of each. It's a nice mental challenge. My goals are:
--No interior connections.
--Keep connections to as few edges of the board as possible. This isn't really strictly necessary, but it makes service easier if you can unbolt the board and get underneath while it's still connected. In this case, I managed to keep connections down to three sides, one side exclusively inputs, with no high current wires nearby.
--Keep signal traces as short as possible.
--Keep the overall board as compact as possible, while allowing for heat dissipation. I cut my boards to size on a band saw. If you want to use a larger board, then other options might present themselves.
--Use as few layers as possible.
--No jumpers allowed.
--To the extent possible, keep components lined up. This is purely esthetic--it makes my eyes happy to see nice orderly rows like that. I was particularly smug when I managed to get that long row together across the middle of the board. Not that it matters to anyone but me. Bear in mind that at the time that I did the layout, I hadn't really considered that anyone else would ever see the layout but me. As far as I knew, there were only two homebrew Alephs in the world, mine and Mark Finnis's. It never entered my mind that there would be so many other folks who would take on the building of an Aleph, or that I would be posting my layout online. I just did as neat a layout as I could imagine and went on from there.
Note that large regulated power supplies generally run an output and a separate voltage sense. The sense connection is connected to the load with a light gauge wire, as there's no current draw to speak of and hence no voltage drop across the wire. In this manner the sense/feedback circuit within the power supply is able to get an accurate reading of what's going on at the load without having to worry about heavy losses across the output cable.
That's similar to what I did with the Aleph layout. A fairly heavy wire (I forget what I used, 12 ga. maybe? doesn't really matter, it's only about 2" long) for the actual output, and a much smaller wire (about 20 or 22 ga.) for the sense.
The purpose of R0 (along with R1 & R8, which I opted not to use) has been covered before. R0 is there to keep ground loops from forming. You can omit it and jumper straight to ground if you like.

Grey
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Old 14th January 2002, 03:39 AM   #27
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First off, I would like to thank everyone who has contributed to this forum. I recently joined and have enjoyed reading everyone's posts. I was wondering if anyone could lead me to the schematic for the board layout that is posted on this thread. I have all the schematics from the passdiy website (aleph 2, 3, 4, 5) but can't seem to get all the reference designators to match with the layout that is posted. I see mentions of the volksamp schematics, are those available?? I and a co-worker of mine are in the process of planning the construction of two aleph4 amplifiers and may be interested in using this layout. Also, I missed the explaination of why R0 (R1, R8?) helps with ground loops. Can anyone help me with this? I do not see how an additional resistor from R4 and R5 to ground can help. aren't they already tied to ground? Thanks for your help.

Jake
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Old 14th January 2002, 04:09 AM   #28
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Jake,
The Aleph amplifiers began life as a product in the Pass Labs lineup, lived a long (by audio standards) and fruitful life, then passed into the great listening room in the sky.
But...
The stereo gods had mercy and, due to the great diligence and valor shown during their first life, granted the Alephs a second life under the moniker Volksamp (www.volksamp.com). Two circuits were chosen for this special priviledge, the Aleph 2 and the Aleph 3.
However, both were returned to life with some differences. Lower bias current in the output stages--this so that the smaller heatsinks would not be overburdened--and a bit of a re-fiddled front end.
After rolling the bones and swirling tea leaves, I decided to use portions of the newer front end design, but mostly the older circuit of the Aleph 2. After adding the resistors for the front end, the resistor numbering became problematic, so I simply defaulted to the Volksamp numbering scheme for the rest of the parts. This should all become somewhat clearer when you look at the Aleph 60 schematic.
There's a thread somewhere back in the Pass Labs forum where Nelson addressed the R0, R1, and R8 issue. None of them are necessary. R0, as stated above, is for ground loop prevention. R1 & R8 are for DC balance and CMRR, and are selected to match the transistors that are actually in the circuit.

Grey
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Old 14th January 2002, 07:07 AM   #29
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Default zener current

Hi folks, I'm the new guy. An Aleph 4 is my first and only electronics project. I'd like to participate in this forum by shareing my subjective conclusions as they relate to the value of R13.

When I first completed my Aleph the sound albiet good was not quite the warm and romantic sound I was expecting. I trusted my subjective conclusions enough to decide an some aspect(s) of my version was not up to factory par.

I read the A75 articles on the Passlabs site and drew the conclusion the 1 watt zener I was using for Z9 should have been a 1/2 watt type and perhaps 4 ma of current through it wasn't enough to keep it quiet. I didn't have any 1/2 watt zeners around so I played with the value of R1. With R1 changed from 10K to 6.8K the sound was now darker and less hard, a decided improvement.

I bought some 1/2 zeners and replaced the 1 watt types at the same time returning R13 to it's orginal 10K value. The sound is better yet, now possessing a wounderful black ambience. For the purposes of experimentation I retried the 6.8K resistors and found I prefered this over the original configuration, yet another small step in the warm/romantic direction. I suggest you try it for your self.

I should also mention I am using tantalum caps on the neg input and maybe they contribute some hardness to the sound. I haven't tried anything else and will gladly entertain suggestions!

I don't want to come across arogent by deviating from Nelson's fantastic design. I don't claim this slight change to be a general improvement, I simply found a way to satisfy my own subjective taste within my given stereo set up . In other words be nice to the new guy!

Brett
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Old 14th January 2002, 07:24 PM   #30
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Just a postscript on the fate of the Aleph design. We
have re-acquired the Aleph for the purpose of integrating
it into the XA products at Pass Labs, and I intend to put
newer Alephs onto the market in something resembling
the original and current circuit.

The Volksamp Alephs are terrific products; in my opinion
better performing than the originals, but they have only
enjoyed lackluster sales, and that is, of course, not
acceptable.
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