Ovation nx-Amplifier

Ovation nx-Amplifier: A High Performance 100 W class AB Current Feedback Amplifier

This power amp design is based on the sx-Amplifier topology, but with the TIS and output stage re-configured for class AB operation, enabling it to deliver 100 W into 8 Ohms. I have kept the design very simple, retaining the CFA topology, providing a very wide -3 dB bandwidth of 570 kHz, high slew rates (140 V/us) and low distortion.

Amplifier write up with circuit description, wiring diagram and construction details:- The-Ovation-nx-Amplifier-V2.10  (updated November 2014 to V2.0 PCB’s incorporating all feedback and updates).  Please IGNORE the BOM in the build document and instead use this latest BOM, released in December 2021 that uses currently available semiconductors  nx-Amp BOM December 2021

You can get a complete set of  double sided THP Gold Plated V2.0 PCB’s for the above from Jim’s Audio on ebay here:

nx-Amplifier PCB Set

(2 off nx-Amplifier boards + 1 off  PSU +Protect for about $26 excl. shipping).

If you are having problems wiring up your nx-Amp, please email me for assistance at


or simply ask in the comments section.  Good luck with your builds!

1. The nx&sx-Amp PSU board is a simple unregulated PSU board with no muting, output short circuit or DC offset  protection. The only protection is the amplifier module fuses

2. .  The nx-Amp_PSU+Protection board option  couples an unregulated PSU with speaker muting, output short circuit protection  and DC offset detection protection.

See the nx-Amplifier article above for details.  If you have any questions, feel free to post your questions up here.

If you are a manufacturer, kit supplier or DIY shop, and you want to use the designs (circuit or PCBs) you need to contact me.

I’d be happy to hear your comments/feedback.

Notes and Addendums

1. Please note, there in no R2 on the PSU +Protect PCB or on the schematic although the BOM calls for it.