Bridgeable Stereo Power Amplifier with 1M Ohm Input Impedance
The AMG STA comprises of several state-of-the-art innovations in power amp design. Its class-leading features include 1M Ohm input impedance, high instantaneous current for power delivery, 700kHz switching frequency, and Single-Ended Non-Negative Class A module coupled with Double Feedback Class D module for 300W mono amp power.
The AMG series front panel embodies its spirit. It is milled from a 15mm harden aerospace aluminum alloy using a four-axis CNC machine with a diamond cutter through a 48 steps process. Design elements such as the 3D “floating” logo, the curved surface around the front panel switch, and diamond-cut edge bring the quality of ultra-high-end audio products to the affordable range of the AMG series.
AMG STA PCB integrates ground wire shielding to isolate external interference. The 300 Mhz bandwidth JFET provides ultra-high input impedance and wide-band fast response. The dynamics of the design and the single-ended Class A circuit enriches the natural second harmonic.
This design allows the most delicate details in the audio signal to carry through the chain. The level of transparency in sound reproduction is genuinely astonishing in this class of equipment, with a deft in creating a highly detailed sonic imagery.
The AMG-STA uses the “Single-Ended, Non-Negative Feedback” Class-A module partners with a new “Double feedback” Class D circuitry. The Class D oscillating frequency has increased to 700kHz, which is 1.4 times that of the STA-9.
 |
 |
 |
 |
| The power supply uses a 380W special winding power transformer, which has 30% more peak power output of a similar volume transformer. | The AC power input from the Inlet Connector to the power transformer utilizes a high current welding line to provide maximum power transmission. |
Besides, high-frequency 3rd-order AC power filter reduces external noise. The main current path, adopting a large-capacity current design, uses a low-impedance copper plate to maximize power delivery to the amplifier circuits. |
A 20A lock wire terminal block connects the transformer to the motherboard, in parallel with two10A peak current rectifiers. |
Listening Impression
With improvements to every area, the bar has been raised for what is achievable with audio performance in small form factor.
The AMG STA has a flavor of its own, so it is hard to compare it with the Evolution One, which derives some of its design from or the similarly priced ST-10. AMG STA sounded smooth and relaxing. Detail, resolution, dynamics, and speed are in the ST-10 ballpark, yet the sound is quite different.
Drawing comparison with the Evolution One, they shared a trait of ease in reproducing the details of the recording comes afore. However, AMG STA does things differently. While the Evolution One has that inviting warmth, the AMG STA wants to allure the listener. Hence, instead of glitz and glamor, which pulls you in quickly into the performance, the AMG STA has a demeanor that slowly brings you into the music.
Tonal qualities of the AMG STA leans toward being full and rich, so instruments and vocals seem to gain extra body, weight, and harmonic richness. It may not be the most accurate reproduction but does make Jazz and Vocal pieces highly addictive. It may take away the raw edge of Rock and Electronic music and sounds less exciting for some.
The sound stage has an attractive characteristic. A linear presentation is like having floodlights shining on all the performers such that everyone can be seen equally well. The AMG STA, however, has more of a spotlighting effect, where performers are focused on getting your attention.
It is tough to put the sound of the AMG STA into measurable attributes as the presentation is quite different from the other series. You’ll need to try it and hear for yourself.
Specifications:
- Stereo Power: 2 X 130W @ 8 Ohm & 2 X 200W @ 4 Ohm
- Mono Power: 300W @ 8 Ohm & 320W @ 4 Ohm
- Gain : 26 (stereo) & 52 (mono)
- Signal to Noise Ratio : 100 dB @ 10W
- THD+N : 0.006
- Frequency Response : 10Hz~50K Hz +-0.2dB @ 8 Ohm. 58K Hz @ -3dB
- Input Impedance: 1M Ohm
- Sensitivity: 1.2 Vrms @ Stereo; 0.95 Vrms @ Mono