Q17.3 is a continuation of the Q17 class B amplifier based on current dumping principle.
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LTSpice - contain simulation asc file
Click & Order your Q17.3 parts @ digikey https://www.digikey.co.uk/en/mylists/list/O9YXGXU6LF
For STEREO or MULTICHANNEL multiply the order with the same parts.
You may order your PCB at
What is new ?
Operational was changed to OPA828. This is one of the few SiGe devices on the market, with terrific performance and most important, sound quality is exceptional. Current mirror was replaced with NDC7003P (PJS6839 is an alternative). This have 2 matched p-mos transistors on same substrate with same thermal Vgs deviation.
Furthermore, by adding Q7, current mirror was upgraded to a Wilson one. This improve mirror stability and class A stage operation at high frequency. In an atempt to make the amplifier more "popular", I have adopted jellybean parts as IRFP240/IRFP9240, 2N4401/2N4403 and 2N5551/2N5401. These are widely available from various manufacturers. First stage after OPA828 is now a modified "a la" Borbely cascode, made with a well known jfet LSK170B/2SK170B and a depletion mosfet DN2535/DN2540. In addition, R10 and R13 have been reduced to 9R1. In case IRFP's get too hot (over 60Celsius), you may increase R10 and R13 to 10ohm.
With this modifications, Q17 performance was considerably improved, both in measurement and listening.
If you have built this amplifier I would love to see your Q17 implementation. :-)
Enjoy and thank you for reading !