Marantz PM6006 UK (and other Marantz models) buzzing noise digital inputs

[jmz]

Did anyone here investigated the problem?

Marantz PM6006 UK (and other models) buzzing noise digital inputs. This is also happening with PM6006 and PM6007.

Some amplifiers are more affected and some less.

My PM6006 UK Edition have the problem but... I can hear this buzzing noise on any digital input only when volume is set above 9 hour position. Is easier to spot it when using headphones. But is hard to hear it when using speakers.

I got second PM6006 UK today from ebay and this one is much worse regarding this problem. The buzzing is easy to hear even if volume is set to ZERO level and is very loud when using headphones.

I can also hear it when using speakers.


Some links for people who didn't know about the problem

https://www.avforums.com/threads/marantz-pm6006-uk-buzzing-on-digital-inputs-solved.2210949/

Marantz PM6006 - Digital Input Noise — tdcat.com

My reasons for returning the Marantz PM6006 twice.

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[AnalogSteph]

If you have basic soldering skills, we may be able to investigate this as a joint effort.

Does the eBay unit have any typical shipping damage? I would look for dislodged connection cables and cracked PCBs, as well as anything else that seems suspicious.

 

[jmz]

If you have basic soldering skills, we may be able to investigate this as a joint effort.

Does the eBay unit have any typical shipping damage? I would look for dislodged connection cables and cracked PCBs, as well as anything else that seems suspicious.

Hi and thank you for the answer.

Yes, I know how to solder and have good soldering station (Weller). I have some basic electronic knowledge.

The amp that arrived from ebay yesterday arrived with dent on the right side. It happened during delivery. I'm still not 100% sure that I will keep it. Negotiations with seller are still in progress regarding large part refund.

So at this moment I don't want to open it. But this may change later today.

But the second unit is my and I could take a look without a problem.

 

[jmz]

I decided to open return on ebay for this amplifier.

Just discovered another problem.

Analogue inputs, tested on CD input. When listening classic music over headphones at lower levels (when volume is set below 9 hour position) delicate sounds are played with distortion and I can hear some cracks. All of this will disappear when volume set above 10 hour position.


One more thing... in one situation with headphones connected to amp and speakers turned off with volume set to zero I was able to hear some very distorted music from CD input. The problem disappear as I changed the sound source a few times.

So... we will not be able to investigate this one as I will return it.

But my own PM6006 UK Edition have some buzzing noise on digital inputs and we could try with this one if you want.

 

[AnalogSteph]

Sure.

For starters, I would mute the audio path in various spots end see whether the buzz is still there. The idea is to do one item, log what changed, then undo what you did and move on.
-1. Touch the 3-pin audio cable going from N8302 on the main board to BN301 on the digital board.
0. (If possible) If you have a linear or switching power supply that you could wave around over the boards while it's supplying a decent load current, that may tell us something.
1. N8302 on main board - connect pins 1-2-3 together. I rather assume that'll kill the buzz.
2. Moving on to the digital board, connect collector and emitter on Q307 and/or Q315 (with the middle pin facing up on this SOT-23, that's the collector and the bottom right pin is the emitter). Should be equivalent to connecting all 3 pins of BN301, which may be easier to reach as the Qs appear to be between some electrolytics.
3. Short C308 and/or C324. You can use some pads of unpopulated R307/R329 and R348/R361 for this if need be, just be sure that you're either connecting the two pads that connect to the cap or the two pads facing away from it (and going to C309/C320, C325/C328) instead. Results may actually differ. I reckon the highest-impedance nodes are after R312/340 and R353/365, at the gates of double JFETs Q305/321. The entire area from C308/324 to there may potentially benefit from electrostatic shielding. (The problem still smells more like some sort of ground loop to me though.)

That should keep you busy for a while, I reckon.

 

[Haider]

It's an earthing issue. Connect a wire to ground terminal/screw on the back panel of the amp and the electrical ground terminal of the plug. I just used the plug the unit came with but you can use a different wall plug and remove the live and neutral pins...