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Old 19th January 2014, 02:41 PM   #1
cowneko is offline cowneko  France
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Question Beginner to build an Aleph30 needs some help

Hello and happy new year to all of you.
I'm new here and quite new to the DIY amp world, but I've already built two different amps (one TA2022, a dual lm3886 (following the optimizations given by Aguilabrava, AndrewT, Pemo...etc on the thread Bought a XY LM3886 Kit. thanks a lot to all of them for sharing )
Both sounds really good (especially the Dual Lm3886, although it misses a little power for my rig).

Now I really want to try something witch should be called audiophile....a class A Aleph 30.
I've read a lot about the Aleph and Zen amplifier series (on those forums as well as on the Nelson Pass website...... thank you Mr Pass for sharing your passion and discovers, this is really what knowledge transmission is) But as I am quite new to diy amps and electronics in general, all those information tend to be a little confusing.

To begin, here is my current rig:

AMP:

-Stereo XY Lm3886, XY psu with 4x10000 uf 50v nover capa (20000uf per channels), a 300Va 2x24v/2x15v on 230VAC transformer .
-Two Analog metric speaker protection cards (fed by the 15V secondaries)
-A 10KOhm stepped attenuator (vishay Dale resistors)

Speakers:

-Davis MatisseHD floor-standers; 80W (120W peak) 91db 4 to 8 ohms

Sources:

-Project XpressionIII turntable with Ortofon Red stylus and a speedbox
-Diy scph-1002 (playstation) with modified output stage / psu
-Dynavox TPR-2 Phono and line tube preamp

Now, a list of what I've already on hand for my Aleph 30 project:

- two BrianGT Mini Aleph board (the black one with golden contacts)
- One BrianGT Aleph PSU board (black one with golden contacts)
- A set of paired transistors bought on ebay (12x VISHAY IRFP240, 4+2 VISHAY IRF9610, 4 ZETEX ZTX450)
- Two Hifi2000 300x210x40mm heatsinks given for 0.20 C°/W modushop.biz
- TO220 Ceramic insulator pads (0.3C°/W)
- One 600VA 2X24V 12.5A toroïdal transformer (on 230VAC as I live in Europe)

I'm already on the process of designing the enclosure of my future amp under 3Dsmax (I'm a 3D graphist IRL), witch will be full aluminum (I'll post some pics in the upcoming posts)

Now I have to find out the best settings for the bias/resistors, this is where I need some help from the Aleph experts.
I've used the Aleph-Power.xls by wuffwaff spreadsheet to do my calculations, can you tell me if it makes some sense

Click the image to open in full size.

I've read that to know the secondaries voltage under load with rectifier losses I shall take the secondaries voltage minus 0.5 to 0.7v (rectifier losses) witch leads me to 24-0.5= 23.5, the nearest settings (23.1V secondaries standard) in the spreadsheet gives me 32V DC at rails (23.1V x 1.41 from the capacitor filtering if I'm not wrong)

So I would have to change the 0.47 Ohm resistor from the original BOM by 1 Ohm resistor (3W) to reach the 1.6A Bias (for a 41W under 8 Ohm) right?

However, when i try to simulate the PSU in PSUdesigner I cant reach the specified 32V (with 0.47 Ohm resistor).... Did I made a big mistake here?

Click the image to open in full size.

Witch resistor(s) shall i solder between the two capacitor stages on the psu to obtain the expected rail voltage?, how to calculate them?

I think it' enough for a first post, sorry for it's length, I hope it's not too confusing, but I'm really beginning in this hobby and even if I'm curious and I think a quick learner, the multiplicity of information are a little overwhelming, that's why i'm searching for help here.

Thanks for reading and please excuse me for my English.

Last edited by cowneko; 19th January 2014 at 07:52 PM. Reason: cleaning up / rectifying errors
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Old 19th January 2014, 03:23 PM   #2
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Hi,

there will me some much knowledgable guys chiming in to answer your questions.

That being said, I think you are mixing up the bias and the rail voltage somewhere.

Aleph 3 (or 30) runs on 25 DC rails (something like 18V secondaries), so having 32 Rails (from your 24V secondaries) can give you an aleph without any doubt, but not a 3 or 30.

I suggest you use the search function and look for the algar_emi spreadsheet and schematics.

No way you can drop your rails from 32 to 25 V using the resistor in your CRC filter - no use either to do so

Hope that helped a bit!

Last edited by coolnose; 19th January 2014 at 03:27 PM.
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Old 19th January 2014, 03:51 PM   #3
cowneko is offline cowneko  France
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You're totally right, my project shall better be called Aleph 40

I'll take a look at this spreadsheet, thank you

EDIT: I think I've found the schematic http://www.diyaudio.com/forums/attac...-algar_emi.pdf
But I was not able to find the spreadsheet, however, next to the AXE-1-2.xls i've used to make my calculations, I have another one witch is called Aleph-Power.xls (Aleph-X calculations)

Last edited by cowneko; 19th January 2014 at 04:15 PM.
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Old 19th January 2014, 05:25 PM   #4
cowneko is offline cowneko  France
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Sorry I've mixed the spreadsheets.
I've used the Aleph-Power.xls to do the calculation and I have another one called AXE-1-2.xls (ALEPH-X calculations)

I don't understand why those two spreadsheets gives me different settings and results with what I think are the same datas

Aleph-Power.XLS
Click the image to open in full size.

AXE-1-2.xls
Click the image to open in full size.

I'm a bit lost here....

Last edited by cowneko; 19th January 2014 at 05:46 PM.
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Old 19th January 2014, 06:10 PM   #5
Zen Mod is offline Zen Mod  Serbia
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X is Aleph bridged
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Old 19th January 2014, 06:19 PM   #6
cowneko is offline cowneko  France
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Quote:
Originally Posted by Zen Mod View Post
X is Aleph bridged
God, I feel dumb right now I should have read more carefully what was this "X" (I naively thought that it meant Aleph "whatever you want it to be" ), the result makes sense knowing that.
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Old 19th January 2014, 08:28 PM   #7
cowneko is offline cowneko  France
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Another question, do I have to oversize the capacitors of the PSU (22000uf for Aleph 30) to adapt to my power source (24vac per channels)?

Maybe this post should be a sort of guide for the beginners (like myself), with your help and advices.

Last edited by cowneko; 19th January 2014 at 08:34 PM.
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Old 19th January 2014, 09:16 PM   #8
Zen Mod is offline Zen Mod  Serbia
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more is merrier

but only if you're having adequately sized each part of chain

so - proper xformer , bridges , caps

looking at your PSUD sim - it's beter to put 22mF after the bridge and 44mF as final

less burden to xformer
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Old 20th January 2014, 11:43 AM   #9
cowneko is offline cowneko  France
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For the diodes I plan on using 4 MUR2020CTPBF-ND Invalid Request
as listed in the BOM http://www.chipamp.com/beta1/wp-cont.../03/mini-A.xls

I understand your advice to put 22000uf after the rectifier and 44000uf (2X 22000uf) after the resistance, but the layout of BrianGT PSU board calls for the inverse

Click the image to open in full size.

Shall I bridge C5 and C6 with a strap, soldering 22000uf capa on C7 and C8 then 22000uf on C3-C4 with two additionnal 22000uf in parallel (wiring them on the underside of the board)?

As for the results from PSUdesigner witch doesn't gave me the expected 32Vdc at rails, I've just realized I leaved the default 5A for the load, I changed it to 1.6A (Aleph Bias) then I get 31.216 mean voltage (witch seems better)

Click the image to open in full size.
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Old 20th January 2014, 12:15 PM   #10
6L6 is online now 6L6  United States
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The resistor in your PSU simulation is much too big - the PCB has place for up to five resistors in parallel, making the resistor valuw much smaller than just one resistor. If you were to use the "normal" Pass-style CRC filter you would have (4) 0.47ohm resistors, giving a value of 0.12ohm.

Anyway, don't worry about the simulation - use your parts, assemble the PSU and know that under load your rails will be something close to +/- 32V

You are using 35V capacitors (or better)?
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