Hypex nCore vs Class A amps

[restorer-john]

That is news to me. Can you please explain how that works?

Residual or no signal noise in a power amplifier is relatively constant.

Signal to noise is referenced to the residual noise in V (hopefully uV) and to to the maximum undistorted (usually .1% or 1%) voltage swing. It is described in dB.

An amplifier with a 40V RMS swing (200W@8R) and an amplifier with a 10V RMS swing (12.5W@8R) with the same residual noise of 20uV will have S/N ratios of 126dB and 113.9dB respectively. A difference of over 12dB.

Basically, high power amplifiers get S/N numbers for free, all other things being equal.

 

[Julf]

Residual or no signal noise in a power amplifier is relatively constant.

Yes. Generated mostly by the input stages, and seen as noise *In the input stages*.

Signal to noise is referenced to the residual noise in V (hopefully uV) and to to the maximum undistorted (usually .1% or 1%) voltage swing. It is described in dB.

Indeed.

An amplifier with a 40V RMS swing (200W@8R) and an amplifier with a 10V RMS swing (12.5W@8R) with the same residual noise of 20uV will have S/N ratios of 126dB and 113.9dB respectively. A difference of over 12dB.

This is where I disagree. The 200W amp will have 12 dB more voltage gain, so it will amplify the residual noise from the input circuits by 12 dB, and the SNR will stay the same.

Where you are right is that the contribution from the noise of the output stage will be lower, but that is usually pretty insignificant.

 

[pma]

This is where I disagree. The 200W amp will have 12 dB more voltage gain, so it will amplify the residual noise from the input circuits by 12 dB, and the SNR will stay the same.

It is good not to define SNR with regards to full output power only, but also to some defined output level. It is a good practice of J.A. in Stereophile to define S/N with regards to 2.83V output voltage. And tell what is the measuring BW or is it A weighted. You may then really compare how noisy are the amplifiers. If you have 96dB/2.83V/m sensitive speakers, you do not care much about S/N at 800W, you want the amplifier to be quiet and you do not need more than some 50W. Purely technocratic approach does not work well for listening evaluation. The point of @restorer-john was well expressed.

 

[Julf]

Purely technocratic approach does not work well for listening evaluation.

Curious about what you mean by "purely technocratic approach".

 

[Stonetown]

Speaking about class A "in general" only, makes absolutely no sense. The implementation can be very good or awkward, regardless operational class of the output stage. If implemented properly, class A avoids the only issue of a good linear amplifier - crossover distortion. At the expense of heat, so going above some 30W in a pure class A is almost impossible. So, the class A has no future if we do not use extremely sensitive speakers.

How about Technics vintage "New Class A" and Denons Optical Class A from same era? Two different systems running class A at lower power levels and seamlessly switching to AB at higher levels. Would be interesting to see the curves for those vintage class A-patent amplifiers. Has anyone done that? For example I've recently got my hands on a pair of Denon POA-6600A which sounds promising. I can't find these types of measurements of those. Is it possible they are good as pure class A? Or why not?

Maybe those vintage patents Hybrid Class A-AB can compete with today's class D?

 

[Julf]

How about Technics vintage "New Class A" and Denons Optical Class A from same era? Two different systems running class A at lower power levels and seamlessly switching to AB at higher levels.

That is basically how A/B works. A class A/B amp is biased between class A and B, so that the behavior at small signal levels is like a class A amp, and at larger signal levels like B.

 

[pma]

Class A plus, AB amp + floating PSU class A. Avoid extreme heat.

 

[Julf]

Class A plus, AB amp + floating PSU class A. Avoid extreme heat.

For a suitable definition of "extreme".

 

[pma]

2 x 10V PSU for the class A. Swing defined by class AB that makes the class A float. I am not going into details.

 

[Julf]

2 x 10V PSU for the class A. Swing defined by class AB that makes the class A float. I am not going into details.

Can you comment on efficiency?

 

[ahofer]

Dan D'agostino's new monoblock is allegedly class A to 100 watts and 6000 watts into 2 ohms. Is that even possible with normal mains?

https://www.stereonet.co.uk/news/dan-dagostino-relentless-mono-amplifier-unveiled-at-munich

At 500 pounds each and costing $250k the pair, there's a lot of impossible going on here.

 

[tomtoo]

This thing looks like a steampunk amp.

 

[ahofer]

It's super ugly, IMO, reflecting the current over-the-top wristwatch aesthetic with its oversized, somewhat..erect, tourbillon.

And wouldn't you love to blind test a $250k set of monoblocks against a purifi?

Once on Audiogon I compared high end amps to high end wristwatches. I got a dozen or so reactions of complete outrage but no explanation of why it was an inappropriate analogy. "I can't believe you just compared high end audio equipment to expensive wristwatches!"

 

[RayDunzl]

Dan D'agostino's new monoblock is allegedly class A to 100 watts and 6000 watts into 2 ohms. Is that even possible with normal mains?

6000W into 2ohms is 110V @ 55A at the speaker terminals.

Momentary? Maybe.

Continuous?

If "normal" means 120Vac @15A, no. (U.S. common outlet spec)

If "normal" means 240Vac @ (at least) 25A, yes.

 

[ahofer]

So all you need is two separate 220V circuits for your audio room. Indeed not a big deal for the individual who shells out $250k for a pair of monoblocks.

Each one drawing 480 watts at idle. Remember folks, at least a continuous year of burn-in required!

 

[DonH56]

It has "bolt type" power connections to attach (up to) a 30-A, 220 V (240 V?) cable. Not sure exactly how the cables attach; leaving bare wires exposed seems unsafe so guessing there's a cover or something. Idle power is 480 W, max 10 kW, so plan on adding a couple of dedicated 30 or 50 A, 220 V circuits in your listening room.

https://cdn.dandagostino.com/documents/brochures/DDMAS_Relentless Brochure.pdf

IIRC one of his earlier (similar) models had some "hiccups" during Stereophile's testing.

 

[tomtoo]

"..Is that even possible with normal mains?.."

Not in Germany. With normal AC=220v*16A=ca.3600W. Maybe it uses 3 phases than 11kW would be possible. So if it would be class A at 6kW (it is not and it dont says so) you would need 12kW if it would be perfectly efficient. And you would have also a 6kW heater for your room. Didnt @armir told his Garage is cold?

 

[RayDunzl]

It has "bolt type" power connections to attach (up to) a 30-A, 220 V (240 V?) cable. Not sure exactly how the cables attach; leaving bare wires exposed seems unsafe so guessing there's a cover or something.

My little baby Krells have a 15 foot "non-detachable" Carol Cable 10AWG SOOW power cord, terminated internally to the breaker/power switch to the left of the cord. They're set up for 120Vac@15A, and are rated 350/700/1400W into 8/4/2 ohms.

Since the whole rack, the PC stuff across the room, and part of the kitchen are all on a single breaker, I can't run them "full power" (not that it is needed). The breaker in the garage will pop.

 

[restorer-john]

2 x 10V PSU for the class A. Swing defined by class AB that makes the class A float. I am not going into details.

Yamaha produced a similar design in 1986. The B2x. Here's part of the original brochure from my library.

 

[Julf]

Yamaha produced a similar design in 1986.

Two pretty standard architectures - Continuously variable supply rail voltage is class H, supply rail switching is class G.