• PCB view

    PCB view

  • FFT at 1kHZ

    FFT at 1kHZ

  • FFT at 5kHz

    FFT at 5kHz

  • FFT - IMD test

    FFT - IMD test

  • Bolt SMD - Bode plot

    Bolt SMD - Bode plot

SMD version of the BOLT IPS was made to proof myself that surface mount components have their place in DIY audio world. I have soldered the boards, adjusted the amplifier and started some basic measurements. Turned out that from technical point of view the SMD version outperformed THT version by a tiny fraction of % (it could be the measurement tolerance too in my DIY lab enviroment). If SMD IPS board measures a bit better than THT board it can not be worse for sure. Connected a pair of speakers and after few hours of listening I can not point any difference in between SMD vs THT. Schematic of the both BOLT version is nearly identical (just VAS transistos are MPSA92 MPSA42). The key to the success is to use right kind of SMD components at the right place:

-Thick film resistors - use them in DC bias places where AC component is very small, do not use them in audio path if possible

-Thin film or minimelf resistors - use them where AC component is present and in audio path

-MLCC X7R capacitors - use them as DC decoupling capacitors, where exact capacitance value is not so extremely important

-MLCC C0G capacitors - this guys are great where high AC swing is present, recommended as a compensation capacitors, just remember to get ones with correct voltage rating.


 How does it sound ? Sounds as typical CFA, very detailed top octave, rather bright with exposed background, quick punchy bass, not as heavy as some other amplifiers. I like it a lot.

Script logo