Nelson Pass Aleph P, Class A preamplifier.

My brother and I have build two Nelson Pass Aleph P Class A preamplifiers, and we are very pleased with the sound. The preamp is controlled by a PIC18F4620 micro controller. You can find much more information on Nelson Pass's website. Below you can see some photos of our design (click on the picture to enlarge it).

We have made a new volume attenuator, which can be mounted directly in the amplifier existing relays sockets. This is the attenuator the preamplifier should have had from the start. We have also made a record out modification pcb, with an OPA2134 to feed PGA2311 from a signal source with a low output impedance.

Note that you have to use a Sony compatible remote control with the Nelson Pass Aleph P preamplifier.

The new attenuator pcb, with 5 relays giving approx. 1.7 dB pr step. The new attenuator is originally designed by a Dutch engineer: Jos Vaneijndhoven.
Graph of the new attenuator, step versus dB. The dB indicates the three final amplification factors you can choose in the preamp.
The new attenuator pcb bottom side. Please note that the photo is showing version 2. We had to multiply all component values by 10 to reduce the load on the Aleph P preamp.		Pcb files updated 2007.01.20
Record out modification pcb, with an OPA2134 to feed PGA2311 from a signal source with a low output impedance. Picture of the top pcb.		Pcb files updated 2007.01.20
Picture of the bottom PGA2311 modification pcb.
Aleph P 1.7 amp PCB. Remember to match the Mos Fet's, here is an article describing how to do it: Matching Mos Fet's		Pcb files updated 2007.01.20
Input/output relay PCB		Pcb files updated 2005.01.20
PIC control board PCB. We have changed the PIC to a new bigger model PIC18F4620 to implement new functionality. Note! This is version 30 with the old jog wheel.		Pcb files updated 2007.01.20
Updated! PIC control board software, version 31 with the new Grayhill jog wheel.		Pic files updated 2009.05.20
Menu structure of the Aleph P preamplifier.
Power supply PCB		Pcb files updated 2006.01.08
The control button PCB	Ups no picture ;-)	Pcb files updated 2006.01.08
Updated! We have changed the jog wheel to a Grayhill optical encoder model, a considerable improvement with much better response. The zip contains two PCB file versions: a modified old control button PCB and a new control button PCB.		Pcb files updated 2009.05.20
Overview drawing showing the cable interconnections between the pcbs.
LCD display during software test
Front of my Aleph P 1.7 preamp
Back of my Aleph P 1.7 preamp
The whole Aleph P 1.7 preamp
Front of my brothers Aleph P 1.7 preamp
CAD files for the cabinet.		CAD files updated 2007.06.18

This page was last updated 2009-09-13.