Question Marantz PM KI Ruby amp hiss and hum

mark1811

Novice Member
I recently bought the Marantz PM KI ruby amplifier and noticed when plugging in a pair of Sennheiser HD 599 headphones there is some hiss and hum in the background. It doesn't matter what source I select it's the same. The hum is faint and doesn't appear to increase when volume increases.

Without the headphones is if I put my ear up to the speaker (with no music playing) I can just hear it.
I have the matching sa ruby CD player and when I plug in the headphones into its jack, no noise.

Anyone else have this amp and experienced this?
 

gibbsy

Moderator
The amp will have a higher output than that of the player which is more likely just 30mW, same as my sa8005. With the higher output you're getting floor noise with the 300 ohm(?) Senns. May just be a failing with Marantz headphone circuits. Does it impact on your listening?
 

Mark.Yudkin

Distinguished Member
Since the hum is independent of volume, I'd guess it's an earth loop. What else is connected, and how?
 

xmb

Well-known Member
Try unplugging all connections to the Marantz amplifier and then listen with the headphones. If the noise is gone you know the amplifier is OK, if not then start to connect items one at a time to see which is causing the issue.
 

LampPost

Banned
I just tried plugging in my HD650's to my Ruby and there is no hiss. Also with speakers I can turn the volume to the max and the background is completely silent with my ear to the tweeter as a class D amp should be.

Have you had a chat with your dealer?
 

mark1811

Novice Member
Thanks for the replies. I tried disconnecting all other devices from the amp and hiss / hum still remain from the speakers and from headphones. I think I'll contact Marantz and see what they say
 

mark1811

Novice Member
I contacted the dealer and they told me to send it in for repair. It went in last week so waiting to hear back
 

mark1811

Novice Member
Update on this. I received the amp back yesterday (after 5.5 weeks in for repair) with a fix applied only to find.....it's exactly the same as it was before.
Contacted dealer (Peter Tyson) who contacted Marantz and I need to send back again!
They have said they will look at as a priority.
I'm losing faith with Marantz considering this is supposed to be part of their Premium Series.
 

mark1811

Novice Member
Yes, I spoke to the service company and they said they couldn't replicate the fault. They put the amp on the scope and noise levels were in specifications. They think it is something in my set up. The amp has been returned to me. I guess I will have to live with it. It's not noticeable when listening at normal volumes through the speakers so not going to lose sleep over it
 

Couto

Standard Member
Thanks for your answer. I was asking this because I‘ve noticed there was a huge price drop on this amp in many UK retailers and I was wondering if the price drop was a consequence of some reliability issues..
 

Mark.Yudkin

Distinguished Member
Yes, I spoke to the service company and they said they couldn't replicate the fault. They put the amp on the scope and noise levels were in specifications. They think it is something in my set up. The amp has been returned to me. I guess I will have to live with it. It's not noticeable when listening at normal volumes through the speakers so not going to lose sleep over it
Just to confirm: the hum can be heard through the headphones when the sole connections to the Marantz PM KI Ruby are the Sennheiser HD 599 and the supplied power cord, whose other end is plugged directly into the wall socket?
 

matthewpiano78

Active Member
Thanks for your answer. I was asking this because I‘ve noticed there was a huge price drop on this amp in many UK retailers and I was wondering if the price drop was a consequence of some reliability issues..

I think the price drops are more to do with the launch of the of the Model 30 amplifier. According to Andrew Everard's review the two amps are very difficult to differentiate from one another in sound or overall specification.
 

Couto

Standard Member
Hi. I ended up purchasing the PM-KI Ruby amplifier. I am very pleased with the sound. I wonder if any of you know of a way to change from/to power amp mode using the remote. I could find a remote control key combination to activate this in the Model 30 user manual, but can’t find the same for the Ruby :(.
 

gibbsy

Moderator
Connecting a pre-amplifier
If you use a pre-amplifier, connect it as shown below, and then you can use this unit as a power amplifier.
Conne Preamp PMKIRUBY

Turn INPUT SELECTOR on the main unit to select the input source to “PWR AMP”.


You cannot use the input source switching buttons on the remote control unit to select “PWR AMP”.
Volume adjustment, muting and adjustments to the volume balance (LEVEL) and sound quality (BASS/TREBLE) are not possible when the input source is “PWR AMP”. Adjust these via the pre-amplifier connected to this unit.
When the input source is set to “PWR AMP”, you cannot use the remote control unit to select the input source.

NOTE
When the input source is “PWR AMP”, the main unit outputs at maximum volume. Check the output level on the input device before playing it and adjust the volume accordingly.


back to top

Integrated Amplifier
 

Couto

Standard Member
Thanks for the reply. I had already read this part of the manual but I am still hopping there could be an undocumented way do do it anyway. Maybe I’ll contact Marantz support.
 

gibbsy

Moderator
Thanks for the reply. I had already read this part of the manual but I am still hopping there could be an undocumented way do do it anyway. Maybe I’ll contact Marantz support.
The access is from the remote. Most of the Marantz are the same. The pm8005 has a button on the fascia that has to be pushed in and held for three second to go to by-pass, it takes a further three second push and hold to come out of by-pass. That's the Marantz way and there is no workaround at all. A small price to pay for such a good amp as the Ruby.
 

Couto

Standard Member
The access is from the remote. Most of the Marantz are the same. The pm8005 has a button on the fascia that has to be pushed in and held for three second to go to by-pass, it
The access is from the remote. Most of the Marantz are the same. The pm8005 has a button on the fascia that has to be pushed in and held for three second to go to by-pass, it takes a further three second push and hold to come out of by-pass. That's the Marantz way and there is no workaround at all. A small price to pay for such a good amp as the Ruby.
On the Marantz Model 30 this can be achieved by changing the remote control to “AMP 2” as stated on the unit manual. I have some expectations that a similar functionality my exist for the Ruby. It is not uncommon that certain devices have this kind of hidden functions.
54127739-4D8C-4EDB-914B-8D4749972BF2.jpeg
 

gibbsy

Moderator
The Model 30 is a brand new product. Things move on and Marantz may have taken onboard complaints about the lack of convenience functions. I don't know why it can't be accomplished on the remote, even my Rega amp's few remote functions includes an easy change to the direct function needed for the power amp. Still have to get up and turn it on manually from a fascia button though.
 

mudan

Active Member
At closer inspection, the Model 30 inside looks noticeably different from the PM-KI Ruby. The more expensive PM-12SE however looks like the Ruby without the copper chassis. Not sure if individual components are different though.
 

Couto

Standard Member
I listen to both PM-12SE and PM-KI Ruby and I could not tell any difference soundwise. But besides the copper chassis, the ventilation openings in the top of the PM-KI look much nicer than the ones in PM-12SE
 

nicoladinisio

Novice Member
I recently bought the Marantz PM KI ruby amplifier and noticed when plugging in a pair of Sennheiser HD 599 headphones there is some hiss and hum in the background. It doesn't matter what source I select it's the same. The hum is faint and doesn't appear to increase when volume increases.

Without the headphones is if I put my ear up to the speaker (with no music playing) I can just hear it.
I have the matching sa ruby CD player and when I plug in the headphones into its jack, no noise.

Anyone else have this amp and experienced this?
Mark, I have your same couple, PM-KI Ruby and the SA-KI Ruby.
After your post I have checked and I confirm it is exactly the same by me.
I have the Grado GW 100, wired through a QED precision Jack-to-Jack cable.
I could hear a feeble hiss from the PM-KI headphone output, not dependant on the volume level. No audible hiss when using the headphone output of the SA-KI.
The hum disappeared when I switched off the "video" devices (TV, DVD player, Nintendo switch), unplugging them from the power outlet (I have them on a dedicated power strip with a switch). I have also unplugged the cable TV cable from its socket (even though I have put a high pass filter there, because it was causing hums with the turntable).
So, no hum, just some feeble hiss. And I noted that I like the output of the SA-KI slightly more, at least with my Grado headphones. The SA-KI is connected to the PM-KI though a 60 cm Audioquest Golden Gate, the longer signal path is of course putting the PM-KI at disadvantage, but I am not sure the difference (hiss aside) can be explained only by this fact.
 
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Helix Hifi

Well-known Member
Mark, I have your same couple, PM-KI Ruby and the SA-KI Ruby.
After your post I have checked and I confirm it is exactly the same by me.
I have the Grado GW 100, wired through a QED precision Jack-to-Jack cable.
I could hear a flebile hiss from the PM-KI headphone output, not dependant from the volume level. No audible hiss when using the headphone output of the SA-KI.
The hum disappeared when I switched off the "video" devices (TV, DVD player, Nintendo switch), unplugging them from the power outlet (I have them on a dedicated power strip with a switch). I have also unplugged the cable TV cable from its socket (even though I have put a high pass filter there, because it was causing hums with the turntable).
So, no hum, just some flebile hiss. And I noted that I like the output of the SA-KI slightly more, at least with my Grado headphones. The SA-KI is connected to the PM-KI though a 60 cm Audioquest Golden Gate, the longer signal path is of course putting the PM-KI at disadvantage, but I am not sure the difference (hiss aside) can be explained only by this fact.
I can only give you my answer. Others well perhaps not agree. But if you google speaker hiss, you’ll se that it is perfectly normal. It is short the amplifier noise floor you hear. Hum can be dc related, or it may not be. Some amplifiers just hum, but it should only be noticeable if your ears are located directly by your amplifier. If you hear it 3 meters away, then there is most likely a problem going on. The tv can make noice because it is not using an isolated antenna cable.
 

mudan

Active Member
On my Ruby I can hear an extremely feint or low level hum that's barely noticeable through the headphone socket but it's certainly a great headphone stage! Yes I would prefer it not to be there but some odd interference that's being picked up, despite very minor. Unfortunately it seems even amps like this aren't immune.

In comparison my Audiolab M-DAC+ is dead silent but doesn't sound as good.

I don't hear any hiss or hum through my speakers at all - dead silent.
 
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