Compact Aleph 5 module

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Another work in progress Aleph 5:

This time I fitted everything on one small PCB which also includes the power devices. Two parallel speaker output relais are also on the PCB (I prefer to have them). Yet to do is a PSU PCB with protection circuit. This is a quick project on a lower cost basis, although I used reasonably good components. The first picture shows the board from front, spot the Panasonic FC and silver mica caps. I used MPC71 metal band resistors, they are cheap, non-inductive and do not smoke up that easily. The IRF9610 FETs are not yet bolted to their heatsink, but the amplifier module has been tested and the typical Aleph sound could easily be recognized.
 

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Input section detail. Note that I ran out of 10k resistors, so I temporarily use two 4k99 in series. All electrolytics are bypassed with film type capacitors. The zener of the input pair CCS is capacitor buffered also. At the very left and right of the board there will be two Wima MKP-10 10µF capacitors (which haven't arrived yet).
 

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I took the schematic from Kristijan Kljucaric's site as a basis simply because the quality is better than Nelson Pass' scans:

http://web.vip.hr/pcb-design.vip/aleph-5.gif

The only things I changed were a film bypass cap for the inverting input electrolytic and the CCS zener. I used BC550C instead of MPSA18, simply because they are easier and cheaper to source here. And, as I do in all my projects, the supply is bypassed using Wima MKP-10 right on the amplifier PCB.

PCB layout and silk screen to be posted soon.
 
PCB artwork

Here's the PCB artwork in PDF format for best compatibility. If you print it from Acrobat, make sure to uncheck all the options in the print dialog that stretch or shrink the page to get the original size.

Please be aware that it is a top (component side) view!

I get the best results printing the layout to normal paper on my laserjet and making it transparent using cooking oil.
 

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AMT-freak,
that's an ok first effort, but given the number of Aleph PCB out there I expect new versions to be just about perfect and this ain't. ;)

A quick look reveals the following improvable areas:
the gate resistors should be mounted as close as possible to the mosfet pin, input gnd and bypass capacitor gnd should not travel together but rather meet at the star ground point.
 
It's definitely not my first effort doing a PCB, and not even my first Aleph 5 PCB ;)

I don't think this design is by any means perfect, and surely there are better sounding Alephs than this.

You have valid points here, and they are not even the only things that could be improved on. The reason I did yet another PCB was to construct the circuit around a forced airflow heatsink that I aquired for free and I wanted my components to fit (especially the metal band resistors). You can see that I that I emphasized the look of the board a bit, the equal distance of the output resistors (and my goal to not use wire bridges) dictating some gate resistors being a few mm off the MOSFETs. The grounding scheme to me seems more important, and depending on listening tests and measurements I might decide to cut the V+, V- and input section grounds and wire them separately to the star ground.

Btw, it was just a fun project being started off by the heatsink, and to be honest I don't actually need this amp. It might end up being sold to a friend together with some speakers, a situation in which I prefer to have the amp's internals looking tidy (and the protection circuit comes handy, too).
 
Re: Re: PCB artwork

Cooking Oil?

That's the true DIY spirit. Why bother with expensive chemicals when you can get the same result with readily available everyday products. It doesn't work with all sorts of paper, but most. You have to clean your light box afterwards, though. And increase exposure time. I'm using two sheets as the contrast of just one print isn't very good.

I also use a hydrochloric acid based process for etching which is very fast and clean, but it might not be ok to post this, I don't know.
 
Re: size

MikeW[/i] [B]Very nice. How big is the completed unit going to be?[/B][/QUOTE] That depends on the caps and transformers I'll be using. I'm waiting for a good deal as I'm currently working on a different project. Two of the boards together with the forced airflow heatsink fill a space of approximately 120mm width X 250mm depth X 120mm heigth. [QUOTE][i]Originally posted by HBarske said:
Nice artwork, congrats.
On question: Do the IRF9610 really need a heatsink or is this a kind of safety issue?

They're not actually needed, but help to keep the transistor temperature a bit more constant. Thermal coupling of the differential is a good idea, too.
 
Amt,
mine was intended to be constructive criticism, the comments strictly apply to the layout not your ability as a PCB designer. I cannot even speak for the sound, which may indeed be just fine and at par with all the other designs.

The feel good comments are great for a while, but I rather have some critique that helps me improve the design.
 
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