Class d keeps improving

[direstraitsfan98]

From what I gather the actual Harmon Kardon brand is now a lifestyle brand. They mostly rebadge Bluetooth speakers and headphones now. Is this amp going to be similar to something like the Mark Levinson line of amps? I’m not sure there’s a market for a lifestyle integrated audio amplifier. Unless this thing just turns out to be an AVR. Which Harman Kardon also sells I think.

 

[JohnKay]

The Sonos guts is Qualcomm DDFA. These kinds of amps do have deviation from flat at the high end, a shown in Amir's measurement of the Sonos Amp and also Stereophile measurements of NAD DDFA amps. However, someone posted measurements of Sonos vs another amp that show they overlay exactly, so at least with the right speakers there is no brightness problem.

https://en.community.sonos.com/components-228996/amp-freq-response-sonos-vs-peachtree-6822985

Very interesting indeed and thank you for sharing this link. I had a brief audition of the Sonos Amp about a year ago at my local dealer (paired with Dynaudio M10 speakers) and to my ears the sound was lean, clean and a bit bright... it was not a comfortable sound for my ears. I remember that I immediately reached for the EQ settings and lowered treble by 4 clicks (almost half the scale). That reduced the brightness but the bass was relatively boomy now so I lowered that as well by 4 clicks. A bit more comfortable but quite lifeless after this adjustment. I really really wanted to like the sound as the convenience is sky high. After reading the analysis provided in the sonos forum link I am quite perplexed as I cannot explain why I found the sonos amp to be uncomfortable. I would blame myself for psychological bias but I did and still do envy the Sonos Amp for the convenience. I wish I could like it.

 

[hfavandepas]

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

Yes there is already another product on the market for almost 2 years. Its the: True-blue-Box (https://truebluebox.com). This amplifier is based on the AX5689 digital audio amplifier controller chip developed by Axign (https://www.axign.nl).

A prototype of True Blue Box was first shown and demonstrated by 'Vintage Audio Repair' (https://vintageaudiorepair.nl) at the X-Fi show (Eindhoven) on 30 sept-1 ok 2017. In 2018 the first AX5689 chip based amplifiers were handbuild by mr Abe the Groot. To my knowledge mr Abe de Groot developed the concept and Axign 'materialised' it into the AX5689 digital audio amplifier controller chip.

In december 2019 a friend bought a True-Blue-Box and al I can say: The True-Blue-Box sounds VERY, VERY, GOOD too my ears.

 

[tom_tom]

@hfavandepas thank You for info. This seems like a really interesting unit ( especially wooden version with DAC )! It's really pitty that i can be heard only in Holland.

 

[MrAlexH]

I've had the H/K Citation amp now for a few days and can confirm the heat "issue" along with the fans going on and off for short periods of time.

I think the heat is normal for this product even if it gets hotter than a typical class A/B amp, maybe it's the way H/K designed it that makes is this hot and putting it vertical could help but have no confirmation that this actually helps in the long run and that the components inside likes this as heat goes upwards first and stays there before gently leaving through cabinet vents.

Overall a descent amp that puts out alot of power and has a lot of good features for it's price, only cons I've experienced so far is this heating thing that most certainly can be optimized over time to help this unit live longer.

 

[tvrgeek]

I think a lot of short cuts in heat sinks and ventilation to make them sleek. And cheap. Heat sinks are expensive.
I ran a Behringer on my subs in my last house and one of my mods was much larger heat sinks and a tunnel for the fan. Dropped the cases by 30 C.

 

[MrAlexH]

Gonna try out vertical stand and see if this helps, this amp got a great future for it if not the heat makes it struggle for it's life first.

 

[tvrgeek]

Well, sounds like par for HK. Great sound for the price, but reliability was never their strong suit. So if a small mod can cool it off, you may have found a deal! One can use larger slower fans to be quieter and a diverter or two to make it quiet and cool. I guess what used to be HK AVRs is now sold as a JBL but in China only. Strange. It even kind of looks like an HK.

I dislike fans. Even worse was my old Sanyo Plus 55 MOSFET power amp. It had a heat pipe between the transistors and external heat sink. You could hear it gurgle in quiet passages. Other than that, it was a very sweet amp. Suprise! Sanyo! Of course they dropped them. I went Hafler.

The market of reasonable size integrated amps seems to be alive. Reasonable basic amps seem a little shy.
Harmon: HK, JBL, ML, Infinity, AKG, Revel, Lexicon. Some good stuff n there. Revel I have heard recently and quite livable.

 

[MrAlexH]

Yes after owned several amps like 980,990 and 3770 I've found that H/K is not what it used to be, part of Samsung division they are no longer a proper amplifier manufacturer if i have to be honest.

Been a Rotel fan now I recent years and sold out my RA 1592 transistor amp for a digital version and i actually regret it if this is what class D is being to this day, it's strange that this little Citation amp can put out this amount of heat still bein a 2x125w amp it pretty strange.

Other people have just been pleased with the guts inside this amp and praised it to be a amp to be reckoned with so i think time will tell if this is a bargain or not, remember having Beringer class D amps myself and modding those fans to not be as high pitched as those original fans was, the result was quite good, but I'm not into modified this Citation amp when it is new so gonna see if some other placements can help out for now.

 

[tvrgeek]

Samsung. Well that is a good fit as their reliability is crap too. Shame as Revel is still a decent brand. Cute little amp, but seems a very small cabinet to have any luck in cooling or even a big enough power supply. Form factor designed by marketing, not engineering.

How much heat an old AB puts out depends on the class A region. It may be pretty large. It could also be that it seems hot as the heat sinks are no where near large enough. My 60W MOSFET amp has bigger heat sinks than some of these newer 200W amps. I ran a couple Watts class A though. Heat sinks are expensive.

I was a fan of the RA 800 series when used on mid-fi speakers. Moved to Parasound 2200's when I upgraded to better speakers. Then to my own MOSFET. I too heard the Rotel class D, along with the Peachtree, so have stayed away from them. But I have been told to listen to the Lyngdorf and March as they will change my mind. So said a salesman ( his lips were moving, so maybe a lie) even the NAD C268 is worth a listen. Execution is probably more important than the technology. I have heard class A amps that stink, AB that were wonderful. Of course, I have heard wonderful class A and horrific AB. Class D may be just like transistors were when new, much to learn on implementation. Go back to the Carver "magnetic field" amplifier. I think pretty much a class D concept and not what I called HI-FI. More WAYBACK machine, I would take a good Luxman or even Dynaco tube amp over the 1960 transistor amps, but now, I would take a class D over even a Cary.

One issue with class D is that below the rated output, they are very clean. Most of us would pick in a blind A/B test, an amp with a bit more even low order distortion over one with much less, but higher order and odd. All things equal, which they are not as other factors involving gain and feedback come to play. Simple vs well done CCS on the LTP and VAS, local vs global feedback and dominant pole filter vs. Miller compensation, so what caused the preference may not be as clear as simple non-linear distortion. It is complicated.

 

[NTK]

Here is a link to the HK Citation Amp compliance test report submitted to FCC for approval.

https://fccid.io/APIHKCTAMP

The report includes a number of teardown (internal) pictures. Picture with the top cover removed, showing the outlet side of a small (guessing 40mm x 40mm) fan and the top PCB.

Picture with the bottom cover removed, showing the inlet side of the fan and the L shaped bottom PCB, which looks like it is the switch mode power supply.

L shaped SMPS PCB taken out of the case.

L shaped PCB with the aluminum cover removed, showing a number of heat sinks with power transistors attached.

Underside of the top PCB. Looks like the speaker amp section.

Top side of the top PCB.

 

[tvrgeek]

Yup, package by marketing, not by engineering. Shame. Given 5 more cm, they could have done better. They should talk to high end PC gamers as they have had to deal with tremendous heat loads when over-clocking CPUs. Some rather clever.

Rule of thumb back from my old failure analysis days: Every 10 degrees C on the die is half life. Never exceed 135. 95C a safer target. The die temp is a lot higher than the heat sink.

 

[MrAlexH]

Have now taken the vertical placing for the Citation amp and heat is just minor now, the fans doesn't even come on, hopefully because of the heat is disappearing and not the vertical position that is causing the fans to not come on.

All in all as said by numerous others this is a well designed class D amp for what it is and in it's price class, challenging others like Sonos and Bluesound i think this little champion can compete.

Wish you all a great weekend

 

[MrAlexH]

Have now taken the vertical placing for the Citation amp and heat is just minor now, the fans doesn't even come on, hopefully because of the heat is disappearing and not the vertical position that is causing the fans to not come on.

All in all as said by numerous others this is a well designed class D amp for what it is and in it's price class, challenging others like Sonos and Bluesound i think this little champion can compete.

Wish you all a great weekend

Sooo... after some hours now testing with music and other content playing but also idle with speakers connected and playing content normal and idle without load or content being played I've come to the conclusion that this amp has a lot of heat going on by itself from new state.

That being said i have already been sending email to Harman support for more info about this amp condition along with the fact that you cannot use optical and coaxial while hdmi is being used as these three inputs summed internally, I've already tried it and unfortunately that's the case, why they make it this way is beyond me but hopefully something that maybe is possible to modifying through an update later on if we're lucky.

So my final thoughts about this amp is that it's a sleek designed amp and packs great power through out, but I'm worried about the heat when using this over the years and along with those inputs not being able to be split and used to different devices at a time but only one being prioritized.

For now I'm keeping this and have some Klipsch RP280F that is going with it so time will tell if it's going to keep up.

 

[tom_tom]

What a pity. I really had high hopes for this amp because of Chromecast and hdmi integration in that small box.

 

[MrAlexH]

Despite the heat I fully recommend the Citation amp, the heat is there probably because of the stacking of the components and that makes it hotter than if the layout was as a standard size amp i guess, but other than this little thing I'm quite happy with it and can't wait to see what it sounds like with RP 280F when it powers my current Tangent Spectrum X6 so good even when they are 88db in 6ohm..

I'm fully aware that I have avoided the warranty at this point lol but the holes does make a difference it's still hot but some free air flow never hurts, and this amp is now mine for years as I don't want to sell it when it's been a diy project like it looks like.

 

[MakeMineVinyl]

They mention that it feeds back digitally to the digital input of the amplifier module. No mention was made of an analog input to the module. I would wonder if this technology is applicable to digital input only.

 

[MrAlexH]

They mention that it feeds back digitally to the digital input of the amplifier module. No mention was made of an analog input to the module. I would wonder if this technology is applicable to digital input only.

You talking about that Digital Loop technology? some word about it here just in case.

 

[NTK]

They mention that it feeds back digitally to the digital input of the amplifier module. No mention was made of an analog input to the module. I would wonder if this technology is applicable to digital input only.

The Axign controller chip has 8 channels of ADC. Not all of them are needed for the amplifier feedback, and can be used for analog inputs.

Source:

Amplifier Series: Axign of Things to Come

Continuing audioXpress' Amplifier Series, looking at the latest technologies and Class-D amplification platforms, Ward Maas writes about Axign, a new company from The Netherlands, founded by former Philips and NXP employees who worked on the pioneering Class-D efforts. Established in 2014, their...

audioxpress.com

 

[Sam3]

I’ve just received this Harman Kardon Citation Amp and installed it.

So far initial impressions of setup:
- horrible manual that skips over many information needed
- wont play any sound out of of the box. By design. You must first connect to internet to enable that this amp plays any sound. Says so in the manual. So basically its data sellout.
- You must first connect the amp to either Apple airplay or Google Home. Harman has no control or menu app for it. Again data sellout.
- no way to connect this to wi-fi through pairing. So you must connect it to ethernet, in order to get it to play sound via Airplay. And that still does not get it properly connect it to your home wifi.
- it does not display a menu on your TV or status despite having the HDMI ARC to receive the sound signal
- nothing in the manual about web-based control, but I see on doing some searching on internet that this is possible
- no buttons on the unit or the remote to adjust EQ or sub output or crossover

Having connected it to airplay via ethernet, it will now play sound. But once I remove the ethernet, it is not connected to the wifi still

It runs very hot, even just during 20 mins of setup and no speaker connected to terminals it was already very hot.

Quick superficial impression was the sound was clean and it had no problem powering my fairly power-hungry Sonus Fabre toy Tower speakers, which run around 87 db sensitivity and go down from a nominal 8 ohm to close to 4 in some circumstances.

Will do more listening tonight. But overall am just horrified by the way this product was crippled. I dont mind not having an LCD but being so app dependent makes this a planned obsolesence risk. Will have to try to get access to the web control and determine if this stays or gets sent back for a refund.