Pcb For Aleph 5


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2002-01-31 5:48 pm
The preamplifier is Balanced Zen Line Stage and it is installed in well modified enclousure of Technics preamplifier SU-C 1000 mark2.
Balanced outputs are not in use because it is still under construction (input/output selector without tape monitor switches).
Sigma 6 is printed because it have 6 inputs.

Sony minidisc is also well facelifted for more audiophile look.
As you know, I'm planning on building Aleph 2. The circuit diagram shown on Kristijan's web link caught my attention because I want to compare the differences between Aleph 2 and Aleph 5.
I've check out the circuit diagram of Aleph 5 on the Pass Labs web site and it sure looks very similar to Aleph 2, especially at the outputs stage. If what was shown on Kristijan's web link is correct, does it mean that the resistors at the source of the output transistors for Aleph 2 should NOT be tied together either? I wanted to know because I'm going to be building the Aleph 2 in the near future.
There are a couple of difference for Aleph5 that I can see. Example, C7, C10 are connected differently. There are four 0.47 ohms at the output for Aleph 5 while there are six 1 ohm for Aleph 2. And then there are also some other different values of capacitors and resistors for Aleph 5. I'm assuming that X3 IRF244 for Aleph 5 is correct. I read that the X3 for Aleph 4 is not correct initially as reported on Mark's web site.
PCBs for ALEPH 2 amplifier will also be available on my website:
( http://web.vip.hr/pcb-design.vip ), and it will have 6 output devices with their current sources, like Mr.Pass used his original
ALEPH 2 amplifiers.
PCBs will be available after 22.IV.2002 and they use similar layout like Aleph 5 amplifier on my website, but dimensions are a little bigger and all parts are also located on one PCB.

Kristijan Kljucaric
Bear in mind that the output line is at ground potential when there's no signal. Thus, for all intents and purposes, the LED sees one rail's worth of voltage (assuming no signal).
Note that I chose to run the LED on my Aleph from rail-to-rail with two current-limiting resistors. Yes, I could do one with twice the value. I just liked the visual symmetry of having one resistor per rail. It bleeds both rails down equally at shutoff.



diyAudio Moderator Emeritus
2002-01-21 2:42 pm
near Atlanta, GA
Kristijan have shown -ve of C9 (220uf) connected to +ve output as per spec from the Pass Labs service manual. You have shown yours connected to the emitter of transistor MPSA18 as documented in the other thread. I have been meaning to ask you .... or anybody ...... how the circuit would operate differently from the 2 different ways of connections ..... heat wise, sound wise, speaker sensitivity wise, etc .... I'm trying to understand this circuit a lttle bit more.
promitheus said:
I was always wondering why this led is connected there. Does it have any purpose ?
As opposed to Wuffwaff's helpful comment re the amp being on (I think promitheus got that one!) I wondered this myself.

This is the reason that I installed a LED for each channel in my Aleph4. Not being an EE I could not guarantee Nelson hadn't used it in some subtle way as a part of the current source .... which is what I suspect promitheus was really asking, and I would like to ask as well.

Can anyone clarify this?

Otherwise I would go for Grey's approach and have just 1 LED for the power supply rails ...... I only need 1 to know the amp is on, I'm quick like that ;)

cheers, mark