B-AKSA 55

Introduction

A few years ago destroyer X (with Hugh Dean's permission) published the conceptual schematic of one of Hugh Dean's commercial AKSA 55 kitset products. Being a conceptual schematic, it is not identical to the commercial AKSA 55, there are a few components that are not shown on the schematic and the values of some of the components are different.

Here is the DIYAudio thread for reference:

• Attention AKSA 55, Hugh is thinking in let us see schematics on forum

I was learning EAGLE at the time so I drew the schematic and designed a PCB as an exercise. At the time the AKSA 55 was still a commercial product, so I didn't think it was appropriate to publish the PCB. But now, the AKSA 55 is no longer for sale, so I sent the PCB files off to a PCB manufacturer and have now built a few of these amplifiers.

Note: My schematic is a little different from the one that was shown in the reference thread in a couple of ways. I changed a couple of values that were obviously wrong, I used BD139 / BD140 as drivers and I used a BD139 for the VAS. When testing the PCBs I used the recommended transistors mentioned in the quote below.

Here is a quote from destroyer X's original thread:

Differential transistors (Q1, Q2) are matched 2N5401 Voltage bias multiplier (Q4) can use BD139 Voltage amplifier (Q3) can not inform, a lot of them works there (I used a KSC3503) Drivers (Q5, Q6) are 2SC4793 and 2SA1837 Output (Q7, Q8) are 2SC5200 and 2SA1943

See the DIYAudio thread Based on Hugh Dean's AKSA 55 for more information and discussions.

More information:

• Schematics
• Printed Circuit Board
• Construction
• Bill of materials
• Adjusting Vbias and checking DC offset
• Test voltages
• Things to try