ADCOM GFA-545(II) Power Amplifier


Audio upgrading of the classic ADCOM GFA-545(II) stereo power amplifier is available.  This robust amplifier is capable of operating into very low impedance or difficult speaker loads due in part to its high current design.  It is based on a triple Darlington configuration and uses no protection or current limiting circuitry other than the fuses used in the DC power supply voltage rails.  For highest performance sound, it is essential that the highest quality audio grade parts be used otherwise ultimate sound quality will be compromised. We offer what we feel is the most comprehensive and sensible upgrade available today.

As part of our upgrade modification process, we will: 

  •  Install high quality audio grade capacitors and low noise metal film resistors in working driver, output stage, and power supply circuits for greater musical clarity.  Areas targeted for improvement include the input circuitry, feedback loop, output stage biasing, output stage & power supply bypassing. The main power supply receives soft recovery bridge rectifiers for drastically reduced switching noise for a quieter background.     
  • Check DC offset, check and adjust bias, before/after modification extended listening tests.



  IEC rear AC power connector installation is available $129


  Non-working amplifiers sent in for modification will incur additional repair charges. 


Manufacturer’s specifications: 100 watts RMS minimum per channel into 8 ohms or 150 watts RMS into 4 ohms at less than .04% THD; Frequency response: 1.7 Hz ~ 100 kHz +0/-3dB; S/N ratio: >110dB (A-weighted); Dynamic headroom: 2.1dB; Damping factor: >400. 



ADCOM GFA-545 Series II Amplifier Improvements Over Original Version:


  • Larger potted AC power transformer provides better overall regulation and greater peak-current capability.
  • No electrolytic capacitors in the signal path or feedback-loop path - only non-polarized capacitors are used. 
  • Addition of a servo circuit minimizes DC offset voltage at the speaker output terminals.
  • Larger rear heatsinks for greater heat dissipation, better temperature and dynamic bias tracking insuring greater thermal stability.
  • Additional cooling vents on top cover and chassis for greater cooling efficiency and cooler operation into lower or difficult impedances.
  • High-quality gold plated brass RCA phono input jacks with teflon insulators.
  • Upgraded 5-way binding posts for speaker terminals.
  • Thermal overload LED indicator on front panel.


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