MCH-K38 - a giant killer!

dwaleke · « **Reply #220 on:** 10 Aug 2016, 08:51 pm »

I contacted John Casler on the forum here. He can get an updated unit.

John Casler · « **Reply #221 on:** 11 Aug 2016, 12:02 am »

Quote from: Eric Gustafsson on 9 Aug 2016, 07:25 pm

By coincidence I found this information today.

"Due to the XLR shield and ground pin specification (see https://en.wikipedia.org/wiki/XLR_connector), some manufacturers implement it differently from others, therefore there could be humming noise if a non NuPrime product is connected to MCH-K38 using XLR cables.
XLR Hum Eliminator products from http://www.ebtechaudio.com/hedes.html can be used to completely remove the noise and improve performance."

It seems to me that Nuprime has made some kind of special xlr connection in MCH-K38. It can' t the same as in STA-9. Why? This is not good at all!

I found the information in the FAQ releated to Home Theater and not in the Power Amp section.

Now I have to spend money on one or several "Hum Eliminators".

Initially we discovered this issue with the Yamaha CX A5100 PrePro and it seemed isolated to just that component. The suggestion to use the Ebtech isolator was put up, because the user found that totally took care of the problem.

Apparently the engineers found a "fix" in a snap in replaceable board.

Eric Gustafsson · « **Reply #222 on:** 12 Aug 2016, 05:45 am »

Quote from: John Casler on 11 Aug 2016, 12:02 am

Apparently the engineers found a "fix" in a snap in replaceable board.

Maybe on the drawing board. So far I haven't heard anything more.

Eric Gustafsson · « **Reply #223 on:** 12 Aug 2016, 06:49 am »

Now things are moving a little bit forward.

flat4 · « **Reply #224 on:** 13 Aug 2016, 05:18 pm »

Quote from: Eric Gustafsson on 12 Aug 2016, 06:49 am

Now things are moving a little bit forward.

Good to hear. Please keep us posted. This is on my short list for my next amp purchase down the road.

Eric Gustafsson · « **Reply #225 on:** 21 Aug 2016, 09:09 am »

Waiting...............

Eric Gustafsson · « **Reply #226 on:** 26 Aug 2016, 06:16 am »

New board is on its way!

Eric Gustafsson · « **Reply #227 on:** 31 Aug 2016, 01:01 pm »

The new board has arrived to my office

, but I'm on business trip until friday.

nocrapman · « **Reply #228 on:** 31 Aug 2016, 09:31 pm »

Wonder how they will sound with LX521s. Maybe its time to build a pair.

Eric Gustafsson · « **Reply #229 on:** 2 Sep 2016, 08:21 pm »

This evening I have installed the new board, but there is still a 50 Hz humming noice.

What to do?

Eisener Bart · « **Reply #230 on:** 3 Sep 2016, 10:11 am »

Quote from: Eric Gustafsson on 2 Sep 2016, 08:21 pm

This evening I have installed the new board, but there is still a 50 Hz humming noice.
What to do?

ask dealer to replace it or money back.

Eric Gustafsson · « **Reply #231 on:** 3 Sep 2016, 01:02 pm »

It seems to me that the difference between the boards is that two links has been replaced with two resistors. I couldn't see any other difference.
I have an ongoing dialog with Nuprime, Hattor Audio (the manufactorer of my preamp) and the dealer how to solv the problem.

JimW · « **Reply #232 on:** 5 Sep 2016, 09:19 am »

I'm considering the NuPrime MCH-K38 but on one dealer site SNR is listed as < -80dB, which doesn't seem acceptable to me, but on the NuPrime site it's listad as SNR < -95 dB which isn't that great either, someone want to enlighten me?

Thanks

J

JimW · « **Reply #233 on:** 5 Sep 2016, 01:30 pm »

Only a 1 year warranty

. Most amps are at least 3 years if not 5. Wyred 4 Sound 5 years, Emotiva 5 years.

That is a deal breaker for me.

srb · « **Reply #234 on:** 5 Sep 2016, 03:34 pm »

Quote from: JimW on 5 Sep 2016, 09:19 am

I'm considering the NuPrime MCH-K38 but on one dealer site SNR is listed as < -80dB, which doesn't seem acceptable to me, but on the NuPrime site it's listad as SNR < -95 dB which isn't that great either, someone want to enlighten me?

It's listed as > 80dB in the Specifications section of the downloadable Manual as well.
MCH-K38 Manual

Eric Gustafsson · « **Reply #235 on:** 5 Sep 2016, 03:59 pm »

Quote from: JimW on 5 Sep 2016, 09:19 am

I'm considering the NuPrime MCH-K38 but on one dealer site SNR is listed as < -80dB, which doesn't seem acceptable to me, but on the NuPrime site it's listad as SNR < -95 dB which isn't that great either, someone want to enlighten me?

Thanks

J

My suggestion is that you listen to the amp instead of reading technical data.

Eric Gustafsson · « **Reply #236 on:** 5 Sep 2016, 04:02 pm »

Quote from: JimW on 5 Sep 2016, 01:30 pm

Only a 1 year warranty . Most amps are at least 3 years if not 5. Wyred 4 Sound 5 years, Emotiva 5 years.

That is a deal breaker for me.

Here in Sweden is it 3 years warranty on products from Nuprime.

Eric Gustafsson · « **Reply #237 on:** 5 Sep 2016, 04:06 pm »

Quote from: srb on 5 Sep 2016, 03:34 pm

It's listed as > 80dB in the Specifications section of the downloadable Manual as well.
MCH-K38 Manual

According to this page http://www.nuprimeaudio.com/index.php/products/amplifiers-and-preamps/multi-channel-amps/mch-k38.html is it 95 dB.

rustydoglim · « **Reply #238 on:** 5 Sep 2016, 05:31 pm »

I think MCH-K38 warranty should be 2 years, the manual has an error. In some countries it has 3 year warranty.

rustydoglim · « **Reply #239 on:** 5 Sep 2016, 06:31 pm »

We are waiting for engineering to look into this issue. XLR pins implementation could be different between European and US standards as I showed you on the Wikipedia info. But now you have already tried two preamp boards with different XLR pins implementation and still have the ground noise. That would be very strange.
And your RCA connections do not have noise.
So this points to ground loop problem with MCH and your preamp.