Neumann KH80DSP Teardown

[restorer-john]

@restorer-john, anything on this board trigger any alarms? It's the AB tweeter amp from an Adam AX series I found on Adam's site (I own A5Xs.):

https://www.adam-audio.com/content/uploads/2016/09/adam-audio-technologies-tweeter-amp-1400x933.jpg
View attachment 134981

The vent stamps suggest Nippon Chemicon (blue) and Nichicon (brown), but I can't tell. There are plenty of Chinese brands using vent stamps of Japanese manufacturers.

Obviously, having capacitors right up against the heat producing output transistors is not terribly good for reliability. The output transistor I can see appears to be a Renesas 2SA-1302, but the tabs look aluminium, not copper. They may be fake, maybe not most likely.

 

[Ron Texas]

I managed to remove the heatsink. Amp chip is a lonely TAS5613A. This is a stereo chip from Texas Instruments. My uneducated guess is that it is used in a similar fasion to the STA350BW on JBL305p MkII with one channel hooked up to bass and the other linked to the tweeter. View attachment 134974

What kind of SINAD does that chip have in a reference circuit? Probably not so hot. What frequency does the DSP operate at, 48 or 96 Khz?

 

[amirm]

What kind of SINAD does that chip have in a reference circuit? Probably not so hot. What frequency does the DSP operate at, 48 or 96 Khz?

About 75 to 80 dB:

 

[Mountain Goat]

The vent stamps suggest Nippon Chemicon (blue) and Nichicon (brown), but I can't tell. There are plenty of Chinese brands using vent stamps of Japanese manufacturers.

Obviously, having capacitors right up against the heat producing output transistors is not terribly good for reliability. The output transistor I can see appears to be a Renesas 2SA-1302, but the tabs look aluminium, not copper. They may be fake, maybe not most likely.

Yeah, they do run really hot, even at idle. Luckily, 5 year warranty.

How common is it for established brands to use counterfeit parts?

 

[Ron Texas]

About 75 to 80 dB:

View attachment 134986

That's a straight up answer if there ever was one.

 

[voodooless]

No view on the DSP? It’s not the puny STM32 doing that.

 

[Mario Sanchez]

No view on the DSP? It’s not the puny STM32 doing that.

The DSP chip is a tiny ADAU1761BCPZ stuffed between the ADC and the input XLR.

 

[Grotti]

Slightly of topic (sorry: I don't want to derail this very interesting thread), but: if the TI-Chip measures at least mediocre, should this change our view on power amplifiers? I listened to this little speaker (which seems to have a lot of fan boys out there) before i discovered ASR and despite of its limited bass response and max SPL I was surprised about its performance....

When it's abilities are not negatively influenced by this chip (I suppose the whole electronics might even measure worse than than the spec sheet amir has posted) than we shouldn't care about the SINAD and distortion above a certain level, which seems to be easily achievable by most amps, right?
At least when it comes to active speakers, passive crossover seems to be a different ballgame though.

 

[voodooless]

but: if the TI-Chip measures at least mediocre, should this change our view on power amplifiers?

None of the components are anywhere near high end. Cheap woofer and tweeter, puny DSP, low cost DAC, crappy caps.. And it still sounds amazing. Goes to show that engineering is much more important than the quality of the individual components (except for the caps that is )

 

[wwenze]

should this change our view on power amplifiers?

Speakers at less than 0.1% distortion are considered excellent. We just need the amplifier to not bottleneck so we get a amp that is 0.01%

Same goes for the relationship between amp and DAC.

And DAC and storage format / medium.

This is not a new thinking. And designers who have to deal with cost optimization think about this all the time. And they have chosen a -80dB amp to pair with a -60dB speaker.

But for reviews, we are still interested in whether product A perform better than product B and hence if it justifies a higher price. In terms of functionality and diminishing returns, the bar is pretty low for electronics. That's exactly how all the snake oils and tweaks work - You can't tell if it made things better or worse.

 

[amirm]

Slightly of topic (sorry: I don't want to derail this very interesting thread), but: if the TI-Chip measures at least mediocre, should this change our view on power amplifiers?

The median for all amplifiers I have measured is 78 dB. So this is in line with that.

In general, you can do much better with passive speakers and external amplifications. Noise floor will often be lower and you can get far more power.

 

[jhaider]

Slightly of topic (sorry: I don't want to derail this very interesting thread), but: if the TI-Chip measures at least mediocre, should this change our view on power amplifiers?…
… we shouldn't care about the SINAD and distortion above a certain level, which seems to be easily achievable by most amps, right?

If that’s a change in view, then probably yes except in edge cases such as very sensitive speakers (noise floor more important).

 

[DJBonoBobo]

My goodness.

They are using one of the absolute worst tier of capacitors in the world for catastrophic failure. CapXon. I can see 11 of them on the one board.

All to save a few cents. Neuman are taking their customers for fools. Shame.

I don't know anything about this, but reading this, I'm wondering what this means for KH80 owners. What you write sounds like you have to expect that all KH80s will break after 3-5 years at the latest. Was that roughly what you meant (and if so, what is the basis for this assessment) or how can I put this? I can not really determine what such comments mean and do not know if I should now be unsettled or if we need an assuring statement by Neumann about this?
My expectation of Neumann would be that they don't put in parts that any reasonable person would expect to break after a few years.

 

[kipman725]

CapXon are really really bad. Statistically significantly bad not just anecdotally bad, can't give further details.

 

[Matias]

What frequency does the DSP operate at, 48 or 96 Khz?

48 kHz

 

[Matias]

The median for all amplifiers I have measured is 78 dB. So this is in line with that.

In general, you can do much better with passive speakers and external amplifications. Noise floor will often be lower and you can get far more power.

The only active monitors I know of that use Ncore are a lot more expensive: Kii Three and Barefoots (Barefeet?). None use Purifi.

For the price of these Neumanns (and similar priced monitors from other brands), I expected TI or Infineon chip amps. They are OKish, could do a lot worse than TI, so for me this is good news.

BTW: THD+N in 4 ohms is 0.02% = SINAD 74, slightly below average, orange zone.

Most important though: THD+N of the TAS5613A does not shoot up with frequency and power, which is very good. And 125W per channel in 4 ohms.

 

[Moonhead]

Appreciate the effort, thx a bunch!
Do we have any tear down data of
KH120 and/or KH310?

 

[leonroy]

I have seen cheapo Lelon caps in Devialet Phantom Golds and KEF LS50W speakers. The new Sonos Sub has CapXCon as do most of their other speakers although the power stage on their Sonos One is Nichicon (prob varies from manufacturing run though).

Funnily enough it’s Apple who ship high quality caps throughout with Nichicon and Elna only inside their (big) HomePod speaker.

 

[Mario Sanchez]

Appreciate the effort, thx a bunch!
Do we have any tear down data of
KH120 and/or KH310?

I think there is another post out there which gives some quick and simple internal shots of the kh120a.
Link here: https://www.audiosciencereview.com/forum/index.php?threads/neumann-kh120-disassembly-pictures.11975/

 

[pozz]

The port tube is of a curious design - There is a small hole in the middle of it blocked by the same material which stuffs the upper part of the cabinet! I'll leave it to someone savvier in these things to explain this.

Shorter wavelengths/higher frequencies will exit through the hole and be attenuated by that porous/fibrous material. Longer wavelengths will move past it and exit the end of the tube.