Issue with MF M3i

Filipedine

Hi All,

I’ve recently added a 2nd hand Musical Fidelity M3i to my AV system that has a Marantz SR8012. The MF amp sounds great, but I am having some concerns related with:
- pop sound when I turn the amp on
- shhh sound when not playing music.

According to stereophile this amp should be dead quiet, Which was the reason why I bought it. Using the Marantz has a reference, I can say that the Marantz does not make a problematic pop nor a very excessive shhh sound. In fact from me hear the shhh sound I need to turn the volume to max and get my ear really near the speaker.

I know that no Amp is free of shh sound and that some do more than others, but this shhhhh sound is really annoying because I can hear it even at low volumes. Does anyone have a M3i that has the same issues or should I get it serviced?

Many thanks in advance

Filipe

gibbsy

Disconnect and power down all your other equipment and just have the MF turned on and have a listen if the sounds are still there, especially the shhhh.

Filipedine

Hi Gibbsy,

Yes the shhhh, is still there, and I can hear it like from 1 to 2 meters from the speaker and normal volume.

Hixs

It's either ground loop or transformer buzz I'd have thought.

Worth just reseating cables etc just to rule that out though.

noiseboy72

This sounds like a gain mis-match issue somewhere in terms of the white noise and the pop suggests the amp has a fault with the power on muting. The power amp should mute for 6 seconds and the mute light illuminate during this time.

I assume you are running out of the Marantz into the MF and then to the speakers using the HT / Aux1 input set to HT? In this scenario, you are bypassing the pre-amp stage and volume control, which contributes most to the hiss, as this is where the voltage rather than current amplification will happen.

I would not expect there to be much in the way of audible hiss in this setup. If you are using the volume control and hence, the pre-amp, this will contribute to the noise floor and should be avoided using the digital trim controls on the Marantz to balance out any differences between the speaker levels. The auto setup should do this for you.

Filipedine

Hi,

Just to clear out some points, so we can have a base line of understanding:
1. the MF amp does the the 6 second mute and the come up. when it comes up the speakers pop.
2. the "shhh" sound comes from any source I select and even with out any source connected to it
3. All my devices are currently connected to a Power conditioner (Keces BP-2600) that does check the ground connection.
4. Disconnecting the Marantz I also have the same "shhhh" sound
5. I have a Moon 280D connected to the CD in of the MF M3i, and on quite music passages i can hear the "shhh" up to some level.

@noiseboy72 when you say:
"I assume you are running out of the Marantz into the MF and then to the speakers using the HT / Aux1 input set to HT? In this scenario, you are bypassing the pre-amp stage and volume control, which contributes most to the hiss, as this is where the voltage rather than current amplification will happen."

I have not tested the amp with the "HT/AUX1" set to "AUX1", but would assume this issue would be unrelated with it. Do you know if just by setting the "HT/AUX1" to "HT" is a condition that in general introduces noise in to Amp?

Many thanks for your help

Filipe

noiseboy72

HT should REDUCE noise, as it by-passes the preamp and you have just the input buffer and power amp. In HT mode / input, the volume control should not do anything. If it alters the volume or hiss level, something is amiss.

My thought based upon the conditions you report is that there is a fault in the amplifier. The pop suggests that DC is getting through from the preamp into the power amp and that causes the pop. It could be the switching circuit, as this is the only thing common to the inputs, but equally it could be power supply related. Without it in bits on the bench it's very difficult to diagnose.

The only thing I would consider is to remove the power conditioner and see if that changes things. I've known these to make things worse with some amplifiers that have inductive coupling between mains earth and audio ground.

Filipedine

Hi @noiseboy72,

Thanks for your feedback, I normally leave my amps/ equipment turned on during the night, and I was thinking this issue could be causing issues on my speakers. If there is an issue, can see it can cause harm to the other components. I will see if i can get it serviced.

Many thanks

Filipe

SickSquirrel

The speaker pop is probably a faulty / dirty speaker relay.

Have a word with Henley Audio, they will help you out if your in the UK,  but if it was me I would return the unit to the seller, it is faulty...

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