Class d keeps improving

[Prutser]

https://bits-chips.nl/artikel/axign-chips-at-the-heart-of-harman-kardons-beat/

 

[JonP]

Wow... sounds like it shoud have great potential! Wonder how much it adds to the cost of an amp, though. Sure would like to see a test of this....

 

[Matias]

This Axign looks like it is cutting edge tech and is just begging to be tested by for @amirm. Very interesting!

About the AX5689 chip:

• Performance with a typical output stage:
▪ 115 dB dynamic range A-weighted (up to 124
dB with parallel ADCs)
▪ 0.001% THD @ 10W / 4 Ω / 20 – 20 kHz

 

[mhardy6647]

Is that Beat as in thumpa-thumpa-thumpa or Beat as in plumb tuckered out?

Besides, doesn't some other tech company have a product called Beats already?

I do hope that Samsung didn't actually pay anyone to come up with that moniker.

Maybe NAD will come out with one in a dark red enclosure and call it Beet.

 

[Matias]

It is called Citation Amp. The beat thing is from the headline.

 

[mhardy6647]

It is called Citation Amp. The beat thing is from the headline.

whoops! sorry

The funny thing is -- I read through it (OK, skimmed through it). And I plumb missed that.
It does indeed say Citation myriad times... it's been a long day (workin' out in the yard), I guess!

 

[Matias]

More info here:
https://audioxpress.com/news/harman...ring-axign-ax5689-class-d-controller-solution

 

[technoian]

A very interesting development in the amplifier world. A combined DAC and amp that uses an ADC to feedback from the output of the power amp into a DSP module prior to the DAC.
The team who have invented this technology appear to have come from Philips class D division so would likely to have been colleagues of Bruno Putzeys who's work with Hypex and Purifi has been so well received.
A claimed THD+N of 0.001% with the Citation Amp would certainly make it worthy of being tested by Amir.

 

[tom_tom]

I am pretty amped for this amp ! Is there any other product already on the market that uses AX5689 chip ?

 

[andreasmaaan]

Very interesting. I had read about earlier attempts at similar digital feedback loops, but had always thought the limiting factor was latency. I wonder how they've got around that in this case.

 

[Matias]

I am pretty amped for this amp ! Is there any other product already on the market that uses AX5689 chip ?

What's most interesting to me is that the business model of selling the chip, instead of an entire amp board, opens up possibilities for chi-fi companies like Topping, SMSL, Gustard, etc to implement it in their designs. Like they do with ESS and AKM DAC chips.

Fingers crossed here!

 

[restorer-john]

It looks very cute and would be a perfect match for my HTPCs.

We've all heard this before : “The result is a Class A audio performance at Class D efficiency, size and cost,”

They say this "As the feedback is taken from the loudspeaker terminals, the damping factor is also very high". They mean the amplifier terminals. The loudspeaker terminals are on the loudspeakers, at the end of a whole length of resistance wire and putting that successfully in the loop is a challenge. Clearly not something they wanted to do.

Remember this was done in the analog domain in the very early 1980s by Kenwood with their Sigma Drive. They also trumpeted their super high damping factors (>1000) and elimination of the effects of the speaker wire. Low distortion and wide bandwidth. They took feedback from the actual speaker terminals.

Let's see how this "Citation" performs in the real world, connected to real loudspeakers, not dummy loads. Let's see what its power bandwidth, FR and transient performance is like. THD numbers are just one part of it.

But it does look interesting.

 

[tvrgeek]

Now, if HK can just get on the ball with their reliability. I have owned two. Both preformed top of their class, both failed prematurely. Only other brand I won't touch is Sony. Same experience.

Hearing is believing. Maybe they have the clout to get it into big-box stores so I can hear one. Around here, they think Pyle is hi-fi.

Yes, latency is always an issue, but processors have gotten a LOT faster.

Feedback sensing including the speaker wires is just too much cool-aid. It also introduces it's own issues do the reactive components of the sense lines. It is not like doing 4 terminal dc measurements.

 

[boXem]

Very interesting. I had read about earlier attempts at similar digital feedback loops, but had always thought the limiting factor was latency. I wonder how they've got around that in this case.

My understanding is that all attempts have been made with of the shelf ADCs that are fast and inaccurate or slow and accurate. Developing their own chip may have allowed to have the right compromise.

What's most interesting to me is that the business model of selling the chip, instead of an entire amp board, opens up possibilities for chi-fi companies like Topping, SMSL, Gustard, etc to implement it in their designs. Like they do with ESS and AKM DAC chips.

Fingers crossed here!

I don't think so: the chip needs to be programmed with proper parameters for the control loop. This needs serious control engineering qualifications that the companies you mentioned don't have. So unless they subcontract the engineering, it's certainly out of their reach for the moment. Ihmo.

 

[hhkg34]

This amp looks very attractive to me... if it comes with parametric EQ. I'm sick of expensive streaming dacs not allowing PEQ.

 

[Matias]

0.001% THD @ 10W / 4 Ω / 20 – 20 kHz

By the way, THD+N 0.001% is SINAD 100, should be in the same performance ballpark as Hypex NCore.

 

[ahofer]

The currently advertised Citation series appears to be quite...sold out.

https://www.harmankardon.com/citation-series/

 

[Alexanderc]

By the way, THD+N 0.001% is SINAD 100, should be in the same performance ballpark as Hypex NCore.

That was my thought as well. The ones measured here are at 5 watts into 4 ohms, so probably SINAD in the mid 90s if the specs are accurate?

 

[peanuts]

Now, if HK can just get on the ball with their reliability. I have owned two. Both preformed top of their class, both failed prematurely.

same here, a dvd player and receiver from HK. both crapped out

 

[Sharpi31]

This amp looks very attractive to me... if it comes with parametric EQ. I'm sick of expensive streaming dacs not allowing PEQ.

I’d be much more excited if it had Dirac too..... Then you have a very interesting one box solution