Legacy, D-Sonic & Orchard Class D Amps

The Basics of a Class D Power Amplifier

Introduction

The age of Class D amplification is here to stay with the introduction of  the Legacy, D-Sonic & Orchard Class D Amps. If correctly designed they have advantages over traditional linear amplifiers in terms of efficiency, power delivery, size and weight. The latest generation of Class D amplifiers (modules) from companies like; ICE, Pascal, Hypex and Anaview are claimed to be amongst the most powerful and reliable Class D designs currently available. A quick review of the data sheet confirms these designs are stable down to low impedance, have a high damping factor, low distortion and a low noise floor. Besides the three new power amplifier models listed below many other high end audiophile, professional studio and virtually all active subs and speakers now use this class of amplifier; to include: Genelec, Integra, Pioneer and SVS to name but a few.

It is NOT that Class D amplifiers sound any better than conventional Class A or Class AB, they do not, and if not designed well, sound a lot worse. Their real advantage is in their efficiency, design simplicity and lower cost than conventional amplifiers. Their extremely high efficiency can be greater than 90%, causing very little heat to be generated, even from a 1000 watt Class D amplifier at full power, meaning they require very little space and only minimal air ventilation. This makes them ideal for inclusion inside speaker cabinets and small spaces. However, their high speed switching generates a lot of RF interference and noise so excellent screening, filtering and grounding is required to prevent this noise from being radiated and/or getting into the signal path or other equipment.

Class D amplifiers like many other amplifier classes are broken down into a number of sub classes, each one is a different design approach using different circuitry techniques to create the same effect.

Three new Class D(x) power amplifiers are in the process of being released:

1. Legacy I.V7 600 watts per channel – 7 channels
2. D-Sonic M3a 400 to 1500 watts per channel
3. Orchard monoblock 150 watts per channel

Legacy Audio

Legacy’s claims their new I.V7 is the most powerful home theater amplifier in consumer audio to date. Featuring state of the art ICEedge technology, the elegant amplifier operates at nearly 80% efficiency at rated output and is said to deliver  more than 600 watts into 4 ohms (all channels driven) and remains stable driving impedances as low as 2.7 ohms with 1kwatt of peak power per channel.

Based upon ICE’s Class D designs this latest module is said to be load invariant, in that the frequency response does NOT change with a varying load impedance. This was a problem with many earlier Class D designs making their sound inconsistent depending what speaker it was driving.

The amp is well protected against thermal overload or short circuit and also includes inrush limiting to eliminate any on/off popping sounds.

These huge powers, especially if requested from all channels simultaneously, requires a very capable high voltage AC power supply. In this case either dual 120volt 20 amp or a single 230volt 20amp supply is required.

The I.V7 amplifier has 4 power supplies, each shared by up to two channels.

This new multi-channel power amplifier tops out their range of Class D amplifiers in their Powerbloc series that support both 2 and 4 channel designs.

Image Credit: Legacy Audio – I.V7

Specifications:

• 660 watts per channel @ 4ohms, all channels driven
• 600 watts per channel @ 8ohms, all channels driven

Each channel driven individually:

• Peak output                   1000 watts peak 4ohm/1Khz with less than 1% distortion
• Distortion                       0.005% at rated output into 4 or 8 ohms, 1kHz
• Dynamic Range           127 dB, A-weighted
• Voltage gain                 25.8 dB
• Inputs                              Fully balanced XLR ,single-end RCA
• Input Sensitivity           5.0 Vp @ 1000 watts/4 Ohm
• Input impedance       38 kOhm for both pin 2+ and pin3-
• Damping factor          750 from 20 Hz to 1kHz
• Channel separation  120 dB at 1kHz
• Weight  31 lbs.

Features:

• Short circuit protection
• Thermal protection
• Triggered on/off
• Standby switch
• Front panel status indicator with bi-color LED
• Rear panel reset switch defends against accidents

At an anticiptaed price of under $8k, this amplifier is not cheap, but must be one of the most powerful multi-channel power amplifiers currently available for the home Hi-Fi market.

D-Sonic

Dennis Deacon’s D-Sonic M3a Class D amplifiers produce 400, 800, or 1500 watts into 8 ohms and are based upon the Pascal X-PRO Class D module. They are sold in mono and stereo configurations, in addition to 3, 5 and 7 channel amplifiers for home theater or professional sound applications. The D-Sonic amplifiers are modular allowing custom amplifier builds with any combination of one to seven channels with power from 400 to 1500 watts per channel.

They run cool with a claimed 88+% efficiency, featuring silver/teflon wiring to military specifications and medical grade filters to remove RFI/EMI from the AC power and signal circuits. Balanced and unbalanced inputs are provided. All channels are true mono, sharing only grounding and AC line power. There’s also a 12V trigger input for a very low power standby mode.

The D-Sonic M3a-600M amplifiers feature extensive protection circuitry. The amplifier and your system are safe from shorting, over/under current conditions and thermal overheating. A D-Sonic amplifier will automatically power itself down and reactivate after it finds a short circuit or a current/thermal problem. And, to make it even safer, it will activate graceful, rounded wave forming if it clips, to prevent damage to your speaker drivers.

Image Credit: D-Sonic

Specifications:

Image Credit: D-Sonic

D-Sonic is offering an extendable 30-day trial period . If you don’t like them, just send them back and pay a 10% restocking fee (all shipping is on you).

List Price $1075.00 each, with a three year warranty.

Orchard Audio

This offering is still in the starting blocks. It has been designed by Orchard Audio who launched in 2017 and are based in New Jersey. They are currently actively seeking funding for the development of this class of amplifiers, see here for further technical and financial details.

The BOSC Class D power amplifier (named after the pear) is very compact, provides very low distortion, is DC coupled for a flat frequency and phase response down to 0Hz (DC) and offers a high damping ratio. The amplifier is based upon Gallium Nitride (GaN) technology resulting in a very energy efficient design which is fully balanced from input to output.

BOSC’s very small size allows it to be placed next to or behind the speaker eliminating long and costly speaker cables while increasing sound quality. Its separate power supply is contained in a slightly larger chassis.

Image Credit: Orchard Audio

Preliminary Specifications:

• Gain: 16.8dB or 6.92 (Recommended for 6 to 8Ω speakers)
• Gain: 13.8dB or 4.89 (Recommended for 3 to 4Ω speakers)
• Signal to Noise Ratio (SNR): 121dB (A-weighted)
• Total Harmonic Distortion (THD) @ 10W: <0.0003% (-110dB) for 1kHz into 8Ω
• Total Harmonic Distortion (THD) @ 0.25W: <0.0030% for 20Hz – 20kHz into 8Ω
• Total Harmonic Distortion (THD) @ 10W: <0.0013% for 20Hz – 20kHz into 8Ω
• Total Harmonic Distortion (THD) @ 75W: <0.0050% for 20Hz – 20kHz into 8Ω
• Total Harmonic Distortion (THD) @ 150W: <0.015% for 20Hz – 20kHz into 8Ω
• Total Harmonic Distortion (THD) @ 10W: <0.0004% (-108dB) for 1kHz into 4Ω
• Total Harmonic Distortion (THD) @ 0.25W: <0.0030% for 20Hz – 20kHz into 4Ω
• Total Harmonic Distortion (THD) @ 10W: <0.0025% for 20Hz – 20kHz into 4Ω
• Total Harmonic Distortion (THD) @ 75W: <0.0092% for 20Hz – 20kHz into 4Ω
• Total Harmonic Distortion (THD) @ 150W: <0.015% for 20Hz – 20kHz into 4Ω
• Frequency Response: DC – 60kHz+
• Sensitivity: 2.5Vin for 37.5W
• Input Impedance: 5kΩ fully balanced for 16.8dB gain amp
• Input Impedance: 7.1kΩ fully balanced for 13.8dB gain amp
• Output Power: 150W
• Damping Factor: >550 @ 1kHz
• BOSC Size:  5.5″ (14cm) x 4.8″ (12.2cm) x 1.9″ (4.8cm) – not including binding posts
• Power Supply Size: 8″ (20.4cm) x 3.7″ (9.4cm) x 1.72″ (4.35cm) – not including cables

Image Credit: Orchard Audio

In order to raise funds for development, a Kickstarter campaign has been started for its development and manufacture. Contributors can pre-order the monoblocks to secure low, ‘early-bird’. pricing.

List pricing starts from $1,500.00 each.

UPDATE 7/23/2022:

For information on their latest Starkrimson Ultra 500W Class D stereo amplifier read this post.