Hello Webmaster at Pass DIY - here is a short summary and some pictures of my recently completed Aleph 5 project.

The project was started on the basis of my two ZEN stereo amps that I built in 1997 to bi-amp my speakers. Picture 1 shows one of the old stereo ZENs (left) and one already completed Aleph5 mono amplifier (right).

For the ZEN amps I did the PCBs myself - for the Aleph 5 I used the boards available from Kristijan Kljucarcic. The quality of the boards is very good and delivery was fast and without any problems. As you can see in the picture, I used the same basic layout - two sides made from heatsink profiles that are mounted to a aluminum bar (40x12 mm) that runs the entire length of the housing. The heatsink profile is Fischer SK71 which is rated at .9 K/W for a 100mm lenght. Since my heatsinks are 150mm each, I felt that I am on the safe side.

In picture -1- each of the 6 FETs are mounted to an individual heatsink for optimal cooling - this was changed and now (as in all of the rest of the pictures) the FETs are mounted to the aluminum bar next to the PCB. Overall temperature was not as critical after all and I decided to better temperature-couple the FETs by mounting them together to the bar. Temperature after several hours is max. 45C measured at the mounting bar between two of the FETs. The 9610s measure max. 60C and were therefore left without extra heatsinks.

These pictures show the grounding of the amps - on the bottom is the grounding point for all the safety related (protective ground), above is the signal ground. Both are connected via a 5W 10Ohm resistor to avoid any grounding related hum. The amps are very quiet, you need to get very near (within less then 10cm) to the speakers to hear any noise (mostly white (?) noise from the tweeter)

The front of the housing is 10mm aluminum, holes and slot were done with a vertical mill. Mat finish was done with 'satinating' mesh and liquid aluminum cleaner.

The last pictures show some details and the rest of the system that I use to listen.

The amps drive Beck BK3 speakers - two way D'Appolito designs that are efficient (>91 dB/W) and very neutral. Preamp currently is an old Classe DR5 that has symmetric inputs and outputs, CD is a Rega Planet and turntable is a ProJect 6.1. All wiring is done with homemade cables a la Allan Wright's cable cook book (braided wire wrap).

Compared to the ZENs the sound improved significantly - there is much more authority, it feels as if the speakers are much tighter controlled and the bass has much more (clean) punch. I enjoy my partly new system tremendously and detect a lot of new details in what I thought was well known music.

Thanks to Nelson Pass for his willingness to share his designs and his patience to discuss with us. Thanks to the DIY community, especially to the contributors of the 'DIYaudio' forum for the open-minded discussions and the know-how that is made available.

Best regards from Moosburg/Bavaria

Andreas

questions and contact : arad.home@t-online.de