Starke Sound AD4.320 Power Amplifier Review

The AD4.320 amplifier is also unique, in my experience, in using a conventional, but very heavy-duty analog power supply with dual 30-amp transformers to power the output modules. Starke Sound claims that the AD4.320 combines the high efficiency of Class D circuitry with the warmer and more accurate sound of Class AB designs. Have they succeeded? Read on!

Four-channel power amplifiers are somewhat unusual. Most audiophile amps are one or two channels per chassis. Home theater amps have three, five, seven, or more channels to match the number of available channels on the movie soundtrack. In this review, I decided to strongly test the Starke Sound claim of audiophile performance in stereo from their Class D modules. All other manufacturers that I’m familiar with purchase their Class D amplification modules from other companies (B&O ICE modules are common, as are Hypex NCore modules) and then build their product around that company’s pre-selected, modular output cards. Starke Sound doesn’t do this. Their NS-600 Class D modules are designed and built in-house.

This would be academic if the NS-600 modules sounded like everyone else’s – but they don’t. The Starke AD4.320 sounds very much like a tube amplifier in the midrange, but with the speed, detail, and control of a high-powered Class A/AB amplifier in the treble and bass.

Having used Class D amplification products before: Crown XLS series, primarily, but also the excellent Emotiva PA-1; I was honestly just not expecting much from the Starke Sound AD4.320 power amplifier. But from the moment I turned it on, I knew it was something special. The manufacturer has voiced this amplifier in such a way as to enhance detail, emphasize speed, and extend bass.

The Starke Sound company was founded in California in 2009 to “combine state of the art technology with an elegant, contemporary design aesthetic.” And although design aesthetics may improve the spouse acceptance factor for speakers, amplifiers are generally immune to such considerations. Amplifiers are “out of sight and out of mind” from a visual standpoint and ONLY their sound and durability matters. And the sound is where Starke has staked their claim for the AD4.320. See the “In Use” section for details.

The Starke AD4.320 Power Amplifier is an unusual product. Multi-channel amplifiers are normally offered without bridging capabilities but the AD4.320 takes a different approach. The four available channels can be configured as two, three, or four discrete channels via bridge switches on the back panel. This makes the amplifier more flexible than the usual multi-channel amp, and offers (highly unusually) two-Ohm stability, even in bridged mode!

To make the AD4.320 so flexible, Starke Sound uses not one but two toroidal transformers and two stereo Class D modules in the same chassis. Conventional audiophile wisdom is that Class D amplification, while offering the benefits of cool operation and high power efficiency, is just not good-enough sounding for home audio use. And up until recently, pro amplifiers from such manufacturers as Crown and others proved the conventional wisdom. However, newer Class D amplification units like Hypex’s NCore and Emotiva’s PA-1 amplifiers have shown that the best of Class D amplification CAN indeed compete with Class A and AB amplifiers on the basis of audiophile sound quality.

Since I had previously thought of Starke Sound as a loudspeaker manufacturer, the high quality of this power amplifier is an even greater surprise.

The Starke AD4.320 Power Amplifier comes well packed, in a protective sleeve; and with a spec-sheet, owner’s manual, and warranty card. The owner’s manual clearly describes how to configure the amplifier, and users (as always) should review the manual.

Most of the power amplifiers I have owned that offered bridged operation required that a bridging switch be activated and that the speaker load be connected between the two positive (red) speaker terminals for the two bridged channels. In other words, no connection to the negative (black) speaker terminals was normally used.

But the Starke amplifier, by contrast, uses internal switching such that bridged operation requires speaker connection to the positive AND negative terminals of the single bridged channel. The adjacent channel terminals are not used at all. This is unique, in my experience, although I understand it is very common for car audio. In any case, Starke Sound has dummy-proofed this amplifier by disconnecting the terminals of companion channels in bridged mode, so that even if the user mis-wires the outputs, the amplifier will not be damaged.

The amplifier internals show a clean layout, high-quality parts, and heavy-duty transformers for power supply independence. The high parts quality should contribute to long-term durability.

The AD4.320 can be run as a two, three, or four-channel device. The options are as follows:

In four-channel mode, one can run up to four different speakers.

In three-channel mode, a high-power bridged channel can be used to drive a center speaker, and the remaining two independent channels can run the right and left front, side, or rear speaker pairs.

In two-channel mode, a pair of speakers can be powered with:

• Two of the four available channels with the other two idle.
• Vertical loudspeaker bi-amplification with all four channels used – a channel apiece for the low and high-frequency sections of each speaker (this assumes four terminals on each speaker and removal of the speakers’ terminal jumpers).
• High-power bridged operation with two of the four channels contributing to the other bridged pair.

What is unique, to my experience, about the Starke Sound AD4.320 amp is that no matter how you configure it (bridged or not) the voicing remains the same! All previous amplifiers that I’ve owned or reviewed changed their sound significantly in bridged mode. But with the Starke AD4.320, I could not tell by listening whether the amplifier was bridged or not.

Setup for the Starke Sound AD4.320 was simple. The 28-pound chassis was light enough to lift, the dimensions fit my equipment racks with room to spare, and the small amount of heat produced by the amplifier was negligible. I also took the option of connecting my DAC to the unbalanced inputs of each channel and my Blu-ray player to the XLR inputs of each channel. By doing so, I could effectively use the power amplifier for source switching and eliminate a preamplifier from the signal chain completely. Of course, to do this, both sources were required to control their own volume.

The AD4.320 amplifier uses but 14 watts at idle, and when turned to standby mode (only the 12VDC trigger monitored), the power consumption drops to 8 watts.

• Mac Mini running Roon server software from HDD library
• Audioquest Dragonfly Black DAC (unbalanced output & variable volume)
• Audio-gd HE-1 solid-state preamplifier (balanced output mode)
• Audio-gd HE-1 Vacuum XLR tube preamplifier (balanced output mode)
• Yamaha Blu-ray player (with either of the two above preamplifiers)
• Emotiva T2 loudspeakers
• Tekton Design Double Impact loudspeakers*
  *to be reviewed as an addendum to this review

Note: All listening notes were compiled using Emotiva T2 loudspeakers.

In two-channel vertically-bi-amplified mode (4 channels used, speakers vertically bi-amplified):

In two-channel bridged mode (all 4 channels used, but in high-power, bridged mode):

The Starke Sound AD4.320 four-channel power amplifier is not only reasonably priced but also competes with the best amplifiers I’ve heard at any price.

THE STARKE SOUND AD4.320 POWER AMPLIFIER WITH THIEL 5i SPEAKERS:

Really?

REALLY?!?

Well, the bottom line is: The Starke AD4.320 held its own and sounded good doing it!

So how did the AD4.320 sound with the Thiels? After the first few seconds, and even with the amplifier stone cold, the speakers’ owner spontaneously commented, “this is a really good-sounding amplifier!” He normally plays his speakers with either the big Krell or, more frequently, a highly modified Crown PSA-2.

The system has been equalized and tweaked to sound its best with the Crown, and some of those tweaks that benefitted the Crown likely worked against the Starke amplifier. You wouldn’t expect the Starke to do its best under such circumstances, yet here was the consistent voicing of the AD4.320 despite the handicaps. Overall, it sounded very good with the big Thiel 5i speakers!

• The image depth and width of the Thiel speakers was amazing with the Starke
• The dynamics of the Thiels were as good or better with the Starke as with the Crown
• Bass clarity, slam, and bass harmonics were stunning
• Despite the brutal impedance load, the Starke amp never got hot or changed voicing

The consistent voicing of the Starke, regardless of load, is a highly unusual characteristic in a power amplifier. With a very slight touch of equalization or maybe even a different cable, the Starke might have matched the performance of the Thiel owner’s house amps. But such tweaking takes time, and I didn’t want to spend significant time inside listening (despite wearing a mask) for fear of COVID.

What went wrong? Very little. I’m deliberately picking microscopic nits here to find something to criticize, but these few flaws were not the defining characteristics of the pairing, and may well have been caused by the owner’s tweaks intended to maximize the sound quality with his Crown amplifier:

• Occasional slightly over prominent bass
• A very slight touch of lower treble glare
• Slightly less airy presentation in the high treble (also lacking with the Emotivas)
• Slight harmonic leanness in the midrange

And that’s it! Again – these issues were very minor and did not in any way diminish the pleasure of hearing the Starke Sound AD4.320 drive the Thiel speakers.

The conclusion of the Starke Sound AD4.320 vs Thiel 5i experiment proves that this amplifier is no flash-in-the-pan. Nor is it just a synergistic fluke with my Emotiva T2 speakers that makes me like the amp so much. Despite the Thiels’ incredibly complex crossover and low impedance dips, the Starke amplifier controlled the 5i speakers really well and sounded good while doing it.

–Glenn Young–