Hello everyone, I just finished a new NAP 250 clone.
I had already made two other versions of the NAP 250, but as a hobbyist, I made mistakes and learned along the way how to correct them and tune this amplifier, thanks in part to other members of the diyAudio community.
My previous clone can be seen here:
So, I'll present my new version here. I can provide my files for those who wish to build one and/or conduct further tests and delve deeper into the design of a NAP250 clone.
This time, it's not a truly original clone; the objectives were as follows:
- Find other transistor references that could be used for the NAP
that were both of better quality to improve audio quality and more robust.
- Switch to plastic transistors for simpler and less expensive construction.
- Make the amplifier more stable and able to handle low loads (1 ohm for a musical signal).
- Integrate the NAP and NAPS on the same PCB, with full alignment of the power transistors and drivers to place them on the same heatsink.
-Place the VBE on the heatsink for better control of the output stage bias.
-Improve the ground plane, which was done with the help of jpk73.
-Make an effort to minimize the design and reduce the final cost.
-Add a regulator for the amplifier's input stages, which was done thanks to the work of jpk73. I used his schematic. The goal was to improve sound quality.
-Add speaker protection, which was made possible thanks to Bigun's TGM10 design. This protection was modified by jpk73 based on suggestions from various forum members; mine is based on jpk73's schematic.
-After simulating in Ltspice, I slightly modified some values to achieve a slight improvement in the phase and gain margin while maintaining the same THD. These are the values Naim has used on some NAP140s.
Once finished, I encountered a NAPS stability issue with the modifications I had made. I was able to resolve this issue with the help of as_audio:
I added a Hypex module that does softstart/standby mode and thermal protection.
the main PCB with NAP/NAPS :
the front regulator base on LM317/337 :
The HP protection PCB TGM 10 :
square wave signal 100 mv 10 Khz in on a capacitive load of 1uF with 6,8 ohms with a NAPS rail (up trace is the output signal, down trace is the NAPS rail)
square wave signal 100 mv 10 Khz in on a capacitive load of 1uF with 6,8 ohms with a front regulator rail
square wave signal 1 Volt 10 Khz in on a load of 6,8 ohms with a NAPS rail
Sinusoidale wave 2,6 volts 1 kHz load 6,8 ohms with a NAPS rail :
I had already made two other versions of the NAP 250, but as a hobbyist, I made mistakes and learned along the way how to correct them and tune this amplifier, thanks in part to other members of the diyAudio community.
My previous clone can be seen here:
So, I'll present my new version here. I can provide my files for those who wish to build one and/or conduct further tests and delve deeper into the design of a NAP250 clone.
This time, it's not a truly original clone; the objectives were as follows:
- Find other transistor references that could be used for the NAP
that were both of better quality to improve audio quality and more robust.
- Switch to plastic transistors for simpler and less expensive construction.
- Make the amplifier more stable and able to handle low loads (1 ohm for a musical signal).
- Integrate the NAP and NAPS on the same PCB, with full alignment of the power transistors and drivers to place them on the same heatsink.
-Place the VBE on the heatsink for better control of the output stage bias.
-Improve the ground plane, which was done with the help of jpk73.
-Make an effort to minimize the design and reduce the final cost.
-Add a regulator for the amplifier's input stages, which was done thanks to the work of jpk73. I used his schematic. The goal was to improve sound quality.
-Add speaker protection, which was made possible thanks to Bigun's TGM10 design. This protection was modified by jpk73 based on suggestions from various forum members; mine is based on jpk73's schematic.
-After simulating in Ltspice, I slightly modified some values to achieve a slight improvement in the phase and gain margin while maintaining the same THD. These are the values Naim has used on some NAP140s.
Once finished, I encountered a NAPS stability issue with the modifications I had made. I was able to resolve this issue with the help of as_audio:
I added a Hypex module that does softstart/standby mode and thermal protection.
the main PCB with NAP/NAPS :
the front regulator base on LM317/337 :
The HP protection PCB TGM 10 :
square wave signal 100 mv 10 Khz in on a capacitive load of 1uF with 6,8 ohms with a NAPS rail (up trace is the output signal, down trace is the NAPS rail)
square wave signal 100 mv 10 Khz in on a capacitive load of 1uF with 6,8 ohms with a front regulator rail
square wave signal 1 Volt 10 Khz in on a load of 6,8 ohms with a NAPS rail
Sinusoidale wave 2,6 volts 1 kHz load 6,8 ohms with a NAPS rail :
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