PCB and schematic differences on Aleph 5.

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Hello All,

I am building an Aleph 5 using the circuit boards available at


I don't have the boards yet but I am slightly troubled by an apparent discrepency.

There seem to be differences between this version of the circuit and the one published in the Aleph 5 service manual at the Pass website.


It looks to me like the pcb-design PCB has a couple of extra resistors and a couple less zeners.

Are these apparent differences for ease of manufacture of the boards or am I not interpreting the circuit correctly?

Thanks for any information that anyone can supply.

Tony D.
Retired diyAudio Moderator
Joined 2002
The circuit schematic on the site you mentioned is correct. It is the same exact expanded form of the circuit shown in the service manual. The service manual just keeps the devices as X3, instead of expanding them.

I see no extra resistors or diodes. If you look at the the pcb, there is a diode labeled D6, which is just the LED that connects to the 10k resistor (R1 on the aleph5 schematic, R25 on his)

It is a little confusing because of the different numbering scheme on the board, but the schematic seems functionally correct.

If you are still confused, point out the resistors and diodes that are confusing you.

Hi BrianGT and thanks for replying to my post.

What has me confused is that on the PassLabs PC board I see 8 large resistors (.47?) R22-R25 etc.

On the pcb design PCB I see 10 large resistors R20-24 etc.

Also on the Pass PCB I see 8 9.1v zeners and on the pcb design PCB I see 5 diodes only.

Am I misinterpreting things here?

Tony D.

The layout for the boards you ordered apears to match the schematic correctly. The board is for one channel. The Passlabs Service manual PBC appears to have parts for two channels on the main board and there are likely some other smaller PCBs that are not shown. Stop worrying, the PCBs you ordered look fine to me and the schematics match.

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