Orchard Audio Starkrimson Ultra – Class D Update

All Image Credit: Orchard Audio

Back in September 30, 2019, I introduced several upcoming Class D amplifiers. Orchard Audio of New Jersey had then just released their first offering, the BOSC, named after the pear. That amplifier was well received by many reviewers and Orchard Audio has gone on to release their latest Class D offering, the Starkrimson, named after yet another pear.

The Starkrimson Stereo Ultra is again a Class D design. Most Class D designs use digital modulation techniques created by FPGAs, DSPs, and processors. Not so for this design. According to its designer, Leo Ayzenshtat, this novel design is an analog switching audio power amplifier. It uses his proprietary DC-coupled, fully balanced dual feedback, pulse-width modulation (PWM) technique that is performed completely in the analog domain and is then amplified by the GaN FET power stages. This technique allows the amplifier to be completely balanced from input to output, through the use of bridged GaN power stages.

According to Orchard Audio Gallium Nitride (GaN) field effect transistors (FET’s) have the following advantages over traditional silicon transistors:

• Less harshness
• Cleaner highs
• Better transparency
• Higher detail

These sonic improvements occur because GaN FET’s have improved device characteristics when compared to their silicon counterparts, having:

• Increased slew rate
• Reduced ringing
• Faster switching
• Faster overload recovery

Furthermore, this technology improves amplifier performance due to:

• Decreased noise
• Lower distortion
• Improved transient response
• Higher bandwidth
• Less heat

As can be seen in the attached images this is not a complicated design, employing one or two Hypex switched mode power supplies, a pair of GaN modules and additional boards for added supply storage options.

GaN technology was developed back in the 1980’s and can be found in military RF electronics, blue LED’s and the blu-ray laser pickups in your UHD video players. These devices offer extremely high switching speeds and their semiconductor design creates a very high efficiency switch that dissipates very little power thereby creating very little heat and thermal noise.

GaN Power Module – Single Channel

These GaN power FET’s can switch at speeds above 800KHz which is two to three times faster than silicon devices in similar Class D amplifiers. Such high switching speeds permits the use of a simple LC (inductor/capacitor) output filter that smooths out the PWM waveform. These essential, yet simple L/C filters, offer the advantage of having practically no phase-shift from DC to 30KHz. This filters design directly impacts the sound quality so the Stakrimson uses oversized very high-quality, oxygen-free copper inductors and very high-grade film capacitors.

Rounding off the design all these high quality components are mounted on a 4-layer, gold plated, PCB that uses a custom stack-up and high end dielectric insulation.

Finally for all those DIY’ers out there Orchard Audio sells these GaN modules and supporting hardware as kits with full supporting documentation and DIY YouTube videos. So if you are handy with a screwdriver and a soldering iron you can save yourself a few dollars.

Brief Technical Specifications:

Starkrimson Ultra (500W)

• Fully balanced from input to output (w/ differential input)
• Differential (XLR) or single-ended (RCA) inputs
• Extremely low noise and distortion
• Power output 250/500W into 8/4Ω
• 2-ohm capable
• Size: 45cm (17.72″) x 36cm (14.17″) x 11cm (4.33″) – w/o binding posts
• Weight: 6.5kg (14.33lbs)
• Power Supply Input Voltages:
  • 110/120VAC
  • 220/240VAC

GaN Module

• Gain Balanced Input: 19.05dB
• Gain Single-Ended Input: 25.05dB
• Signal-to-Noise Ratio (SNR): 120dB (A-weighted, 22kHz BW)
• Residual Noise: 44.72uV (A-weighted, 22kHz BW)
• THD* @ 10W: <0.0004% (-108dB) for 1kHz into 8Ω
• THD @ 0.25W: <0.0016% for 20Hz – 20kHz into 8Ω
• THD @ 250W: <0.016% for 20Hz – 20kHz into 8Ω
• THD @ 10W: <0.0005% (-106dB) for 1kHz into 4Ω
• THD @ 0.25W: <0.0021% for 20Hz – 20kHz into 4Ω
• THD @ 500W: <0.08% for 20Hz – 20kHz into 4Ω
• SINAD @ 5W 1kHz: 100dB into 8Ω
• SINAD @ 5W 1kHz: 97dB into 4Ω
• Frequency Response: DC – 80kHz+
• Sensitivity Balanced Input: 5Vin for 250W into 8Ω
• Sensitivity Balanced Input: 5Vin for 500W into 4Ω
• Sensitivity SE Input: 2.5Vin for 250W into 8Ω
• Sensitivity SE Input: 2.5Vin for 500W into 4Ω
• Balanced Input Impedance: 44kΩ
• RCA Input Impedance: 22kΩ
• Output Power (8Ω): 250W_RMS (500W_PEAK)
• Output Power (4Ω): 500W_RMS (1000W_PEAK)
• Damping Factor: >700 @ 1kHz
• Power Supply Input Voltages (rev 3.0 modules):
  • +/-36V (+/-30 to 43.4V)
• Efficiency (stereo amp): ~85%

• Custom Front Panel
  • The panel color can be made silver (brushed aluminum) and/or without any logos/text
  • Can be made to be rack-mountable
• Upgraded Power Rail Capacitance
  • Improves amplifier transient response and distortion at power levels above 50W
  • Helps when driving difficult loads (hard-to-drive speakers)
• Dual Mono Upgrade
  • Two monoblock amps inside a single enclosure. Each amplifier module gets its own power supply.
• Monoblock
  • Two individual monoblock amplifiers each amplifier has its own power supply and an amplifier module.

MSRP:

• Starkrimson Ultra Amp Module x2 (500watts/chl): $1,049.95
• Starkrimson Monoblock Base x2 (150watts/chl.): $1,599.95
• Starkrimson Ultra stereo Base (500watts/chl.): $2,499.99
  • Options (ULTRA):
    • 37,600uF rail capacitance: $400.00
    • Dual mono supply: $550.00
    • Dual mono with 56,400uF rail capacitance per channel: $1,000.00

For the full technical specifications click this link.

For more information on the pre-built and kit version pricing visit Orchard Audio.

For more information on the GaN devices used in this product visit GaN Systems.

Check out my original Class D post.