Marantz PM6005 Help please! :)

keaton86

Novice Member
Hi everyone! This is my first post on this forum, so thanks for having me. Hopefully this is kind of thread is allowed.

I recently bought a second hand Marantz PM6005. Every so often (between every 10 seconds to 2 minutes) it sends a quick burst of static through my speakers. When no audio is playing there is also a slightly audible hissing noise coming through both speakers too. The speakers are brand new (Triangle Borea BR03s) and I've changed the cables and banana plugs to check everything is working. I've also unplugged everything else in the room, turned wifi off and moved the amp and speakers to a different room to test and the hissing still prevails. I've also cleaned the inside of the amp with canned air. Does anyone have any idea what could be wrong with the amp? I want to take it to a repair shop but the wait time is 6 weeks. Thanks in advance :)
 

dobrykamil

Well-known Member
What about direct mode, do you still hear static sounds?
 

rccarguy2

Well-known Member
Audible hiss is normal but static is not. Possibly dac chips are faulty or the fets
 

dobrykamil

Well-known Member
Is this happening on all analog and digital inputs? If so, then I don't think there is an issue with amplifier circuit. If I had your amp in my workshop, I would rather focus on the pre-amp section. Analog signal goes through input selector chip and then through few OPs (operational amplifiers)
Those ICs require symmetrical DC, +15V and -15V in your case. Many times one of those two DC regulators or its smoothing capacitors can fail, causing voltage unbalance which OPs really don't like.
 

ShanePJ

Well-known Member
AVForums Sponsor
Sounds like an amp issue, but as you have just changed the cables and speakers, do you have your old kit to ensure you haven't been unlucky with your new speakers or cables picking up unwanted frequencies and reconnect them. Sometimes you can hear a hiss if the volume is high, but what you are saying seems like its pointing to the amp for sure
 

keaton86

Novice Member
Audible hiss is normal but static is not. Possibly dac chips are faulty or the fets
Sorry, I'm a bit of a noob with this stuff, what is FETS?
Is this happening on all analog and digital inputs? If so, then I don't think there is an issue with amplifier circuit. If I had your amp in my workshop, I would rather focus on the pre-amp section. Analog signal goes through input selector chip and then through few OPs (operational amplifiers)
Those ICs require symmetrical DC, +15V and -15V in your case. Many times one of those two DC regulators or its smoothing capacitors can fail, causing voltage unbalance which OPs really don't like.
Yep, it does it on network/cd and also on the phono inputs when i play records. It doesn't matter what channel is selected.
Sounds like an amp issue, but as you have just changed the cables and speakers, do you have your old kit to ensure you haven't been unlucky with your new speakers or cables picking up unwanted frequencies and reconnect them. Sometimes you can hear a hiss if the volume is high, but what you are saying seems like its pointing to the amp for sure
Unfortunately I don't have any other gear to test it with. All my other stuff is in New Zealand and I'm in Germany now. The hiss is audible all the time and weirdly doesn't get louder when the volume does.
 

ShanePJ

Well-known Member
AVForums Sponsor
That’s very strange that the his doesn’t louder when you turn the volume up, if you know anyone with different speakers, try the amp. But that’s weird and I suspect it’s interference with what you have said from something in the room as the basic of an amp is when you turn is to make things louder and if that isn’t happening. Then have you a microwave or a boiler nearby
 

hifidanne

Novice Member
Hi.
Bought a second hand PM6005 and I have to say it sounds great!!. However,
I also have problem with noise on my amp. Quite audible when placing ear close to the L&R speakers with no music playing. I think its more noisy compared to other amps I had previously. I can hear it in a quiet room 2m from the speakers. Increase to 3m I cannot hear the noise.

My findings:
  • noise is present in L&R both analog and digital inputs.
  • direct in and loudness doesnt matter.
-doesn’t matter which volume level Im at, however, at max volume I think it’s less noise..how now that is possible?

So. I will try to
1. Change the +15V &-15V 220uF smooting caps. And also check the voltages+grounding.
2. Bypass the HDAM curcuit in the pre amp after the volume control to see if it improoves.
3. If not any of above works, bypass the whole pre amp section..

Is there anyone else have this amp who could test and compare it to some other amps?
would be interesting to see if its a “Marantz design feature” a la SR6014 models..maybe its just designed as intended..

I will do some tests, i will keep you posted..

/Daniel
 

rccarguy2

Well-known Member
Hi.
Bought a second hand PM6005 and I have to say it sounds great!!. However,
I also have problem with noise on my amp. Quite audible when placing ear close to the L&R speakers with no music playing. I think its more noisy compared to other amps I had previously. I can hear it in a quiet room 2m from the speakers. Increase to 3m I cannot hear the noise.

My findings:
  • noise is present in L&R both analog and digital inputs.
  • direct in and loudness doesnt matter.
-doesn’t matter which volume level Im at, however, at max volume I think it’s less noise..how now that is possible?

So. I will try to
1. Change the +15V &-15V 220uF smooting caps. And also check the voltages+grounding.
2. Bypass the HDAM curcuit in the pre amp after the volume control to see if it improoves.
3. If not any of above works, bypass the whole pre amp section..

Is there anyone else have this amp who could test and compare it to some other amps?
would be interesting to see if its a “Marantz design feature” a la SR6014 models..maybe its just designed as intended..

I will do some tests, i will keep you posted..

/Daniel

Hdam introduce distortion and noise into the signal.
Some hiss is normal, when I switch on my power amplifiers only thre is some hiss (pre amp off)
 

hifidanne

Novice Member
So. I have now repaired my amp.

Turned out it the -15V stab (UB8102, 7915) was broken. Sitting on the main PCB.
It was outputting -14.3V making the noise floor too high. Changed it and now its completely silent 😊.
The 7815 +15V was ok.

Another thing to note is that it seems this amp suffering from really poor solder joints, found poor solderings on main, volume and front PCB. So it can be worth checking..
 

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