Overview

In real world audio applications, available power can be limited by long AC power cable runs (extension cords) and affected by the quality of wiring in the wall itself, or by the distance from the breaker or fuse panel to the wall outlet. Available AC power can also be severely limited if multiple amplifiers (or any devices) are forced to run on the same circuit.

Conventional power supply non-power factor corrected amplifiers have to severely limit their output power relative to the available current at the AC source input. In short, less available AC power at the amplifier's input means less audio power at the output. The peak current demands (powering repetitive kick drum hits, playing back long low synth drones) of an audio amplifier exaggerate the problems of line sag in power distribution. This is why it is common to spec amplifiers considerably larger than the ratings on the speakers would suggest.

The power supply characteristics greatly affect the audible differences between amplifiers. Engineers designing the A4.4 knew the importance of the power supply dynamics. These do not show up on conventional bench tests. The burst power measurements indicate a difference, but that specification doesn't tell the whole story. The audio quality of an amplifier appears as differences in apparent power output with real loads, real music and real AC power.

The design goal with the A4.4 was to preserve the dynamics of our successful conventional supply amplifiers while eliminating the undesirable effects of real world AC distribution problems.

Enter the Switching Power Supply

Switching Power Supplies are an alternative technology with greatly reduced weight and improved performance over iron core transformer conventional power supplies. Since they can compensate for AC input voltage sag, they can put out their maximum rated power even if wall voltages are low or fluctuating. As a side benefit, a switch mode power supply is much smaller and lighter than any conventional iron core transformer power supply.

In order to output their maximum power with reduced input voltages, the switch mode power supply must draw more current out of the wall. Where a conventional power supply amplifier would reduce its output power relative to its input current, a switching power supply can and will draw more current, and maintain the audio output at full power.

Add Power Factor Correction

A Power Factor Corrected amplifier can make the most efficient use of its available wall current or ability to create usable output power for a given input current.

When the input voltage sags (Volts), a switch mode power supply must increase the current draw (Amps) to maintain its output power level (Watts). Good power factor correction allows the amplifier to better continue to operate without tripping the AC source circuit breaker, while making maximum watts from the available input voltage.

In short, this means that if you compare the power factor corrected A4.4 with its switch mode power supply against competitive conventional power supply amplifiers, including our own AP4040, the A4.4 will sound louder and consistently deliver more volume in real world audio operations.

The A4.4 Advantage

Combine a switch mode power supply with good power factor correction, and you can make the most efficient use of its available wall current, or ability to create usable output power for a given input current.

If you have an amplifier rated at 1200 watts per channel at a 4-ohm load with conventional supply and no power factor correction, with 120 volts available at the AC source, you can expect to see that 1200 watts per channel. However if the A.C. input line voltage were to sag to 110 volts, that same amplifier's output would drop to 1050 watts per channel into that same 4-ohm load. At 110 volts at the AC source, the AudioPro A4.4 can and would deliver its full 1200 watts per channel.

This becomes even more dramatic when the input line voltage sags as low as 105 volts, which can easily happen at the end of a long AC cable run, or where there are multiple amplifiers on the same AC circuit. - With only 105 volts available at the input, an amplifier with a conventional power supply and no power factor correction will only deliver 950 watts per channel at a 4ohm load, where the A4.4 with a switch mode power supply and power factor correction can and will deliver a full 1200w per channel.

Please note: The terms 'Switching Power Supply' and 'Power Factor Corrected' are not interchangeable. Competitive power amplifiers that advertise the use of Switch Mode Power Supplies are not necessarily also Power Factor Corrected, and will not necessarily perform as well as the A4.4. Yorkville's A4.4 is somewhat unique as it is in fact a 'switch mode power supply' amplifier that is 'power factor corrected'. This is why the A4.4 out performs most of the competition in this class, and in fact does 'sound louder' when compared to a conventional power amplifier.

A-Series amplifiers are not only suitable for use in both heavy duty touring sound reinforcement systems but also when high headroom and low distortion are needed to fully reproduce the dynamic range and clarity of today's digital recordings. They are built to survive grueling road conditions and will drive reactive phase shifted loads with no difficulty - even though they are fully protected from accidental short circuits. Unlike many of our competitors, Yorkville power amplifiers are designed for rock solid performance right down to and below their lowest impedance ratings. This impedance aware strategy deals with the realities of driving typical reactive speaker loads and the associated problems such as thermal shut-down, inductive 'snap-back', and premature current limiting.

All A-Series amplifiers undergo a thorough computer-monitored, temperature-cycled, burn-in period to test for any deviation from design parameters. The designs, while unique, are conservative with regard to the power handling capabilities of the output devices. The computer optimized heat dissipation system ensures that excessive thermal stress will not occur. Cool, clean air is supplied to the amplifier via fan-assisted front-to-rear venting. A user-serviceable filter is incorporated into the front mounted air intake grill, ensuring long-term reliability. Front panel Power, Protect, Activity and Clip LED's are bright and easy to see and all knobs and handles are recessed for safe, easy transportation. All A-Series power amplifiers also feature full DC, load and thermal protection while a user-defeatable limiter maintains full output without audible clipping.

The back panel features Speakon™ and binding post outputs as well as balanced XLR & ¼" TRS inputs. The peak limiter, subsonic filter, mono/stereo/bridge mode and ground lift switches are also mounted on the back panel.

Specifications

Continuous Average Power @ 8 Ohms BCD (Watts)	750(x2)
Continuous Average Power @ 4 Ohms BCD (Watts)	1200(x2)
Continuous Average Power @ 2 Ohms BCD (Watts)	NA
Continuous Average Power Bridged BCD (Watts)	2400 @ 8 Ohms
Burst Average Power @ 8 Ohms BCD(Watts)	1200(x2)
Burst Average Power @ 4 Ohms BCD (Watts)	2175(x2)
Burst Average Power @ 2 Ohms BCD (Watts)	NA
Burst Average Power Bridged BCD (Watts)	4350 @ 8 Ohms
Frequency Response (Hz, +/- 1dB)	20-20,000
Hum and Noise (un / Aweighted -dB)	-103
THD -1kHz- 4 OHMS	less than 0.01%
THD - 20Hz-20kHz, 4 Ohms	less than 0.1%
Slew Rate (V/uS)	25
Slew Rate Bridged (V/uS)	50
Damping Factor (30 Hz - 400 Hz @ 8 Ohms)	greater than 600
Crosstalk (1kHz / 20Hz-20kHz)	-75 / -60 dB
Input Impedance - Bal/Unbal (Ohms)	20,000/10,000
Input Sensitivity (Vrms) For Full Power Out	1.4 V
Max Voltage Gain (dB)	41
CMRR @ 60Hz (min/typ)	48/56 dB
Stereo / Mono / Bridge )S/M/B)	S/M/B
Protection	DC, Load, Thermal
Limiter	User Defeatable Peak Limiter
High Pass Filter	Yes
Cooling	Variable speed DC Fan
Cooling Path	Front to Back
Fan Filter	User Serviceable
Inputs - XLR	2
Inputs - 1/4" Jacks	2
Outputs - Speakon 4-pin	2
Outputs - Binding Post	2
Power Consumption (typ/max)	1800/3000
Rack Spaces	2
Transformer Type	High Frequency Switch Mode
Exterior Finish	Baked, Black Painted
Dimensions (DWH /D fm ears, inches)	17.8 x 19 x 3.5
Dimensions (DWH /D fm ears, cm)	45.2 x 48.2 x 8.9
Weight (lbs / kg)	25 / 11.4

Specifications subject to change without notice

Downloads

• Owner's Manual
• Service Manual