Integrated Amp Reviews

I really appreciate your personal insights on this as well as SET Tube-based amplification.

But what about single-ended transistor-based amps?

I've had my eye on the Audio By Van Alstine DVA-225 monos (SET), and I'd really like to put my ear on them sometime. Given their direct, custom order business model, it takes a bit more courage to audition.

I'm also searching out the Rogue hybrid power amps to feel them out as well.

I'd really like to see the market put out a GaN-based power amplifier for under $5k as well. I'm sure one day that will happen, given their burgeoning presence in the market now.

Very nice column as usual; I always feel like we know your brain and soul a bit more with every month's writing.

Happy Holidays to Herb and the rest of the Stereophile staff!

JA:"The Pharaoh II's reproduction of a 10kHz squarewave (fig.2) showed only the slightest hint of overshoot, with no ringing."

Is this the reason there is no hint of overshoot, because you can't see it when it's measured at low level + - 1v output, with the AUX-0025 bench testing filter installed on the amps output?

Cheers George

I enjoyed Herb's ruminations on Class A and D (which he's discussed in other reviews). I have both types of amps, as well as a 12AU7 based preamp, so this review really spoke to me. I imagine that a NOS tube would sound even nicer in the Rogue than the JJ tubes. As long as you're spending a few grand, spring for some Siemens or Telefunken or bugle boys.

Now that the weather has gotten a bit chilly where I live, I brought my "winter amp" (Class A) out to the living room where the wasted heat is welcome for 3 months.

A technical question: does it really matter for an ncore unit if it's a switching power supply or a toroidal? I've heard that switchers might have more EMI, but a regular transformer has ripple that needs to be tamed by caps and chokes. I think we can stipulate that linear is simpler and thus more reliable.

Yes it does to my ear, as I have the NC500's in mono-block form (used with no buffers) because my discrete R2R MSB dac (with volume control)and can put out enough bal volts direct into the NC500's for the loudest that I would ever listen to on my 89db speakers

And with Hypex's own SMP (switching supply) they had, while good, it could not equal the Linear Toroidal power supplies I substituted for them. Much less sterility and more body to the sound, the only place the SMP's equaled the linear supplies was in the bass slam, but again not for body detail. EG: double bass being bowed, both as taught as each other, but the gut of the bow comes through far better on the Linear Supply.
I'm all behind Rogue etc for using linear supplies for their Class-D Intergrated and power-amps, while much more expensive and using far more real estate they sound far better, if designed correctly.

Cheers George

Finally! A rave review of a Class D that does not ignore the elephant in the room--Class A. I love my tubes too much to switch, but it's great to see the new tech emerge. Thanks

Hmmm! Please don't delete, comments are for debating + & -'s also.

Sorry JA,I have these NC500 modules here, and they vhf ring (just like this at only 1khz!! https://ibb.co/R2NPzHQ ) with (switching noise) with even 1khz let alone 10khz square wave on the scope without using a low power external AP AUX-9925 type filter or similar, as will/do any other amp that uses the NC500 modules.

Cheers George

Submitted by Jack L: "Any SMPS emits RF noises airborne & thru hardwiring into any powerlines associated with it."

So true, all they achieve is more profit, as they are cheaper and take up less real estate than good Linear Supplies.

Cheap Test:
With an old portable transistor AM radio (that doesn't auto mute off channel)
Tune it down low 600khz-700khz off channel with the volume up and go near any smps with it, and hear what's bombarding your audio signal.

Cheers George

Benchmark Audio offers the contrary view:
google for full version:
AUDIO MYTH - "SWITCHING POWER SUPPLIES ARE NOISY"

THIS MYTH GOES SOMETHING LIKE THIS:
"Switching supplies are noisy."

"Linear power supplies are best for audio."

We disagree!

About 5 years ago, Benchmark stopped putting linear power supplies into our new products, and we replaced them with switching power supplies. We did this because linear supplies are too noisy. Yes, you read that correctly, linear supplies are noisy! A well-designed switching power supply can be much quieter than a linear supply.

LINEAR POWER SUPPLIES CAUSE HUM
The noise problem is due to the fact that linear power supplies have large transformers and other magnetic components that operate at the AC line frequency (50 Hz to 60 Hz). These line frequencies are audible, and we are all too familiar with the hum and buzz that audio products can produce. It is no secret that this noise is caused by the power supply, but few people understand why it can be so hard to eliminate. Most people think that hum is caused by conducted interference (AC ripple on the power supply rails), but this is rarely the case. Most AC hum is caused by magnetic interference, and this can be very hard to eliminate.

HUM IS USUALLY CAUSED BY MAGNETIC INTERFERENCE
Transformers are magnetic devices. Power is magnetically transmitted between a transformer's input and output windings. In a linear supply, power is transmitted from the AC line side of a transformer to the low-voltage secondary side using an AC line-frequency magnetic field. Unfortunately, transformers are never perfect, and some energy always escapes through stray magnetic fields. These stray fields can interfere with virtually every electrical conductor in an audio product. Magnetic shielding is expensive and it has limited effectiveness when sensitive circuits are located in close proximity to a strong field.

POWER AMPLIFIERS ARE THE WORST OFFENDERS
The power supplies in high power devices, such as audio power amplifiers, can emit very strong magnetic fields. These strong fields tend to limit the noise performance (SNR) of power amplifiers. These magnetic fields can also cause interference with audio products that happen to be too near the amplifier. Audio cables that enter, exit, or pass near the amplifier may also pick up unwanted hum and buzz. For this reason, it is usually very important to keep the power amplifier well separated from cables and other components in the audio system.

BREAKING ALL THE RULES!
Benchmark's new AHB2 power amplifier breaks the rules. It can even be located adjacent to sensitive audio components without causing interference! The AHB2 is a high-power device, but it emits almost no magnetic interference. What makes it different?

The secret inside the AHB2 is the switching power supply. This power supply has several high-power transformers, but they are very small, and their stray magnetic fields are correspondingly small. The reason for this is that the magnetics operate at 200 kHz to 500 kHz. For a given power rating, transformer size decreases as the operating frequency increases. High-frequency transformers have smaller cores and fewer turns of wire. As the physical size decreases, there is a corresponding reduction in stray magnetic field strength.

SIZE MATTERS
When transformers are physically small, there are more options for magnetic shielding. For example, the small transformers used in the AHB2 are completely encased in a ferrite material which helps to contain stray magnetics. These techniques are so effective that the AHB2 achieves a SNR of 130 to 135 dB. No power amplifier is quieter than the AHB2. Even more amazing is the fact that the switching power supply board is less than an inch above the amplifier board. This product proves that switching power supplies can be very quiet! The AHB2 could not achieve this level of performance with a linear supply unless the supply were housed in a completely separate box a couple of feet away.

OUT-OF-BAND NOISE
One major advantage of switching supplies is that the operating frequency is above the range of human hearing. If interference occurs, it will not cause audible interference. This interference can even be removed with a filter without infringing on the audio band. But, the power supply in the AHB2 is so quiet that we do not need to filter the audio output. The AHB2 delivers a 200 kHz bandwidth without evidence of any significant switching noise, to a measurement limit of 500 kHz.

LINEAR AMPLIFICATION WITH SWITCHING SUPPLIES
Please note that the AHB2 is not a class-D switching amplifier. The AHB2 is a linear class-AB amplifier. It is only the power supplies that operate in a switched mode. The power supplies simply provide steady and constant regulated DC voltages for the linear audio amplifier.

... particularly compared to the Sphinx v3. Wondering if that's because the Sphinx moved HR more in absolute terms, or if it is the combo of Sphinx sound and its value quotient that make it the more exciting product.

The $64,000 question - How does the Pharaoh II sound compared to the original Pharaoh? In looking for the correct amp for my KEF LS-50's, I was surprised and blown-away when the dealer hooked-up the original Pharaoh. I always thought of it as a well-kept secret. Unlike his other products, Mark never tweaked or offered upgrades to the original since the introduction in 2015. Pretty good first effort. The model II is so different, that he doesn't offer an upgrade path. This review doesn't make me want to run out and buy the new version.

Thanks Herb for the as-always excellent review! I am a happy Sphinx V3 owner but I am having "impure thoughts" now about the Pharaoh II. BTW I share your enthusiasm for Television's "Marquee Moon" - a great, life-changing record that I have also loved since it came out. Nerd alert! Elektra Records is not spelled "Electra," but has a "k" in the name. Thanks for listening!