In this blog post I test the Rogers Sound Labs IA255.1 Integrated Amplifier. I purchased the amplifier for $110 USD with $27.75 shipping into Canada. With HST the total came to $137.50 USD ($185 CAD).
I will provide my listening impressions as well as objective test data on its overall performance in terms of distortion in various use cases.
Why test the Rogers IA255.1?
RSA publishes their own Audio Precision test data for harmonic distortion. I wanted to see how the amplifier did with intermodulation distortion, particularly in the high frequencies. I also wanted to measure Gedlee distortion as a function of frequency using a custom test sequence in my Virtins Multi-Instrument software. I can then overlay and compare against my Hypex amplifier’s result which stands as a my current reference for low distortion.
I will test the amplifier’s performance in three use cases.
1) Powering a pair of medium sensitivity speakers to 85dB at 1m using a 2V output voltage from the amplifier. (0.5watt)
2) Powering high sensitivity speakers to 85dB at 1m using a 1V output voltage from the amplifier (1/8 watt)
3) Powering a compression driver to 85dB at 1m using a 130 milli-volt output voltage from the amplifier. (2 milli-watts Mw)
Features
- True 55 watts per channel (x 2)
- Easy Hi-Fi 2.1 audio in any room
- Line-in, Bluetooth, USB Audio
- Selectable 90Hz high-pass filter
- Stereo pre-out / subwoofer-out
Contents
- IA255.1 amplifier x 1
- 24VDC/7A External Power Supply (5.4”x1.25”x2.4”) x 1
- 3.5ft. USB-A to USB-C cable x 1
- 1ft. 3.5mm Stereo to Female RCA cable adapter x 1
- Micro Bluetooth Antenna x 1
Specification
- Power: 55 Watts RMS/Channel <1%THD @ 4ohm
- Type: Proprietary audiophile pre-amp stage, Class D output using MA12070 IC by Infineon
- S/N Ratio: 106dB
- Channel Separation: 100dB
- THD+N: <0.006 % 1000 Hz ~10W
- Internal High-pass Filter: 12dB/octave @ 90Hz, by passable via rear toggle switch
- Efficiency: >92% efficient
- Input Sensitivity: 185mV
- Input Impedance: 40k ohm
- Inputs: Stereo RCA (Line level), USB Audio (Type-C), Bluetooth 5.0 (APTx)
- Speaker Outputs: Gold-plated fully-insulated Clear banana jacks (chassis mounted)
- Pre-Outs: 3.5mm Stereo full-range signal output (standard line level)
- Bluetooth: Up to ~30ft. wireless range with detachable compact antenna
- Reset: Recessed button to forget and unpair BT device
- USB Audio: 16 bit, 48khz*(pending device interoperability)
- Power Consumption: 30W TYP. 168W MAX
- Bass: +-9dB @ ~100 Hz Varying shelf compensation
- Treble: +-9dB @ ~5000 Hz Varying shelf compensation
- Chassis: 6061 Extruded Aluminum Housing and CNC machined panels
- Product Dimensions: 5.48″ x 1.46″ x 5″
- Packaging Dimensions: 13″ x 3″ x 8″
- Product Weight: 0.87lbs
- Shipping Weight: 2.2lbs
- Warranty: 2 years
As you can see from above, the IA255.1 uses the MA12070 IC by Infineon chip. I searched through the chip specification and found some performance graphs. 
We can see the distortion profile for the chip depending on the configuration, either PMP0 or PMP1. We do see improved performance at 5w vs 1w, however things get congested in the upper treble especially with the PMP0 configuration. I am not sure which configuration the IA255.1 uses.
My Own Distortion Measurement
I began by measuring the intermodulation distortion at 0.13V, 1V, and 2V.
Below is the intermodulation distortion with an output voltage of 0.13V. This is a very low output which would be typical for connection to a compression driver. We see 65dB dynamic range for the 10kHz region.
Increasing the output voltage to 1.00V is shown below. Dynamic range improves to -73dB for the 10kHz region. This represents 1/8w output.
Increasing the output voltage to 2.00V is shown below. We see dynamic range decrease to -68dB in the 10kHz region. This represents 1/2w output.
If we compare this to the Hypex FA123 (Channel 3) under the same test, we can see that we get a dynamic range of 84dB in comparison (see below).
I then measured the Gedlee Distortion (Gm) which is shown in red below. I also measured the Hypex FA123 which is shown as an overlay in green. The Hypex serves as a reference amplifier for comparison's sake. (click below to enlarge)
Measuring Harmonic distortion at 2.00V is shown below. We see H3 at -48dB with H4 at -51dB for the 10kHz region.
Comparing this with the Hypex FA123 we see distortion is so low I will need to increase the vertical scale.
Increasing the vertical scale from 100dB to 140dB is shown below. Distortion for 10kHz is H3 is 81dB with H4 being at 83dB.
Testing Line-Out Distortion
The IA255.1 features an USB input which allows use as a DAC with volume control. I tested the distortion performance for the variable line-out and depending on the output voltage I was able to at best get around 60dB dynamic range using a multitone intermodulation distortion test.
Subjective Listening Impressions
Smoothness --- 8/10
Sense of dynamic range --- 7/10
Detail and soundstage depth --- 7/10
Conclusion
The Rogers Sound Labs IA255.1 is suitable for background music, television listening, and gaming. It has an overall pleasing sound character that is more relaxed and competent for non-critical listening applications.
Can the unit serve as a USB DAC with volume control in a hifi setup? In this configuration IMD was only -62dB which puts it out of contention for this use.
Overall, the RSA IA255.1 is feature packed and built nicely. It is a competitive product for this price category. I did not find it suitable for critical home hifi listening, but otherwise is a very flexible and useful product for around the house.