According the the data sheet info (copied/pasted below):
https://www.anthemav.com/downloads/str_integrated_amplifier_datasheet.pdf
Amplifier uses 8 bipolar output devices per channel, a toroidal transformer power supply, and Advanced Load Monitoring for 200W at 8 ohms, 400W at 4 ohms,
550W at 2 ohms,
all continuous
Output (
per channel, continuous, 20 Hz - 20 kHz, <1% THD) . . . . . . . . . . . . . . . 200 W (8Ω), 400 W (4Ω),
550 W (2Ω)
Impressive, double down into 4 ohm and 2 ohm stable, and continuous?
Then look at the "Power Consumption" section:
Idle . . . . . . . . . . . . . . . . . . . 40 W
Typical Use . . . . . . . . . . . . . 250 W
High Output . . . . . . . . . . . . 500 W
and the fact that:
1. The enclosure looks to be made of steel, definitely not plastic, may be some AL?
2. No fans at all.
3. Including the build in preamp and DAC,
weight: 40 lbs soak and wet.
4. Class AB amp's efficiency typically<<100%
You can see why I have serious doubt about their power output into 2 ohms specs, I hope..
My estimate of the VA rating of the transformer is purely based on visual, it appears to be very similar in physical size to that of the Halo A23 that has an exceptionally large transformer for a 125 WPC. That amp is fitted with a 850 VA transformer, website claimed 1kVA that was an error (I have confirmation). I have 3 power amps that have transformers rated 1,200 VA and much more storage capacitance than the STR; and none claimed 550 W into 2 ohms continuous, in dynamic rating yes, but not continuous.
https://www.google.ca/search?q=halo...AhUmwYMKHcRFB1AQ9QEIKTAA#imgrc=JQpYDc7Zf1rNhM:
To be fair, aside from the power output rating that I don't believe (unless it was for one channel driven), the STR does have very impressive THD, IMD, SNR, slew rate, and decent DF. Among integrated amps, I would think the STR would rank among the top in terms of specs that count, just wish it has a larger transformer and more capacitance, not necessarily for SQ as such, but for bragging right. I won't pay C$5,500 for it, but if I am in the market for an integrated amp, I wouldn't mind getting it for a deep discount.