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 and BOM list:- The-Ovation-nx-Amplifier-V2.10 (updated November 2014 to V2.0 PCB’s incorporating all feedback and updates)
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:
(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.