budget aleph 5

Hello

About a half a year ago I discovered this forum and started reading about class A amplifiers from Nelson Pass. I got very interested and quickly decided to build one of his designs. I had never build any audio before. The main constraint for this project would be the price because as a student I can’t afford costly parts. So it took me quite a bit of time for sourcing all the parts at a reasonable price.

I first found 4 broken automatic car battery chargers, from wich I used the heatsinks and the transformers. In each charger were two 200VA (estimated) EI transformers with 14 V secondary’s. Four of those with secondary’s in series became the power supply of my aleph 5. The secondary’s of the other 4 I used as inductor in a CLC filter. The speaker connections also came from those chargers.

I also dismantled a broken electronic welder from wich I used the rectifier bridges and wiring. Also used wiring and NTC’s from broken computer supply’s. The boards I made myself at school.

The only costly things which I coulden’t recycle were the transistors and the power supply capacitors. I bought those online with reichelt electronic. The price was very reasonable irfp240 => 1.30 euro, irf9610 => 0.5 euro BC 47000uF =>13 euro. I heard rumours that the irfp240 from reichelt were afaik but they were genuine from ir and were very close in tollerance while matching.

So after some weekends diy I ended up with an aleph 5 at a very reasonable price of 150 euros total. The only thing I didn’t cut back on was the blue led J. I mounted the transistors on a copper bar 3cm*1cm which came from a electrical power substation and clamped the transistors with an aluminium profile. DC offset is 10 mV left and 25 mV right. It runs the standard 2 A bias and after an hour it reaches 52° C . It's quite heavy weighing 25 kg. It plays very good and detailed and I can only hear a bit of hum with my ear close to the speaker

I wish to thank Nelson for sharing his wonderfull designs and al the people on this forum who posted a lot of usefull information.

My next project would be building a pair of speakers to go with the aleph. So far I’ve been looking at proac 2.5 clones and peerless pipes and I think I will go for the pipes because the drivers are cheaper. Also a preamp (bosoz) is still on the todo list, now I’m driving the aleph passive with a pot. But that will be for the summer because I now have to start concentrating on exams.

Have a look at the pictures and feel free to comment or ask questions.

Andries

system on test run

transformers placed in chasis

CLC filter on top of transformers and heatsinks partialy mounted

finisched amplifier with boards mounted

close up

overview

Thanks for all your comments. I submitted the pictures to passdiy gallery.

I like the sound very much. For now I have only my dad's Sony A/V amplifier to compare it to, the aleph plays a lot cleaner and warmer than the sony. Strings and voices sound more natural and the bass is more controlled.

About the humm in the speakers is not such a big deal. The transformers themself also slightly hum a bit. Maybe later I will exchange them for a toroidal and with proper inductance in psu. But for now its more than ok.

Andries