Marantz Model 30 ringing issue in only one channel.

[JohnSnow]

Hey all, I was hoping someone might have some insight into an issue I'm having with a Model 30 I just purchased.

There is an audible ringing/tone from the left channel, and the left channel only, that does not change with volume. I have troubleshooted the basics, swapped speakers, swapped speaker wire, removed all interconnects, plugged it into a line conditioner, etc

Using a spectrum analyzer app on my phone, the frequency of the ringing measured ~6,000Hz on my Klipsch speaker, and ~7,000Hz on a Polk.

This was purchased as a Marantz Factory Refurb, so maybe I'm expecting too much, or maybe I'm being nitpicky...but even as a factory refurb it wasn't an inexpensive purchase.

Anyway, thanks for any and all suggestions.

 

[JohnSnow]

Just wanted to add a little bit more information, including an audio file of the sound.

Not sure if these other things are related or not, but here we go:

1. When I had the right speaker wired to the right channel of the amp, and left with the left channel, music was biased towards the right side. I could correct for this with the balance control, but I had to turn the knob from the 12 o'clock position (balance set to 0) all the way to the 9 o'clock position...which seemed excessive. I decided to see if I wired the left speaker to the right channel if the left speaker would sound biased, but this was not the case. When I wired them up to the opposite channels the balance was perfect, with the balance control set to the 12 o'clock (balance set to 0) position.

Perhaps this really is just a variable of the room?

2. When I turn the volume knob continuously, either increasing or lower the volume, there will be intermittent crackling from the speakers. This also occurs if I hold the volume buttons up or down on the remote..so it isn't isolated to the volume knob itself. Like I said this occurs in both speakers, it's not isolated to the left channel, like the high-pitched tone.

Not really sure if these are related, but thought I'd mention it.

Here is the audio of the noise, any modulation in the sound is from me moving the phone closer and further away from the tweeter...it never changes in pitch:

 

[DVDdoug]

I think you should return it.

The balance problem is "weird". It would normally take two "opposite problems" for it to go-away completely when the speakers/channels are swapped...

"Scratchy" controls is not uncommon on old equipment. It is a defect and they can often be cleaned. That's usually a potentiometer (270 degree rotation) with "mechanical memory". It shouldn't happen with a digital rotary encoder that can be rotated more than 360 degrees.

This was purchased as a Marantz Factory Refurb

Sometimes it's not the original "factory", and it may not be authorized by Marantz. Sometimes it's just a shop/warehouse they call a factory where they do a quick inspection and re-packaging, often in generic packaging.

Sometimes you're lucky and someone returned it for a different reason and there was no problem with it, but it can't be re-sold as "new".

 

[JohnSnow]

I think you should return it.

The balance problem is "weird". It would normally take two "opposite problems" for it to go-away completely when the speakers/channels are swapped...

"Scratchy" controls is not uncommon on old equipment. It is a defect and they can often be cleaned. That's usually a potentiometer (270 degree rotation) with "mechanical memory". It shouldn't happen with a digital rotary encoder that can be rotated more than 360 degrees.


Sometimes it's not the original "factory", and it may not be authorized by Marantz. Sometimes it's just a shop/warehouse they call a factory where they do a quick inspection and re-packaging, often in generic packaging.

Sometimes you're lucky and someone returned it for a different reason and there was no problem with it, but it can't be re-sold as "new".

Thanks for the feedback. I'm leaning toward the same determination, though I didn't really want this to be the solution. I'm currently working on an exchange, so we'll see how that goes.

 

[Extreme_Boky]

You could do some basic troubleshooting. Based on the hum frequency/ringing frequency, the NCore module has been damaged, most likely. I suppose you could ask Marantz to send you one..??

To convince Marantz... see below. You could check the pre-amp section to confirm an equal voltage is present. Feed a 200 mV, 1kHz signal to either channel and measure the signals at the connectors. If equal in value and clean from oscillations, it's the NCore module.

A simpler check would be to physically swap the NCore modules around - see if that can be done from the mechanical/mounting point of view. If the issue persists with the module, email Marantz, explain what you did, and request a spare module.

You could also drive the NCore modules directly from the same point (see the black line) I showed in the photo. Just be careful, as you'll get full-blast amplification of the modules if you do. Nevertheless, this test would undeniably prove an issue with a module.

Shame to return it... the amp looks good, and apparently sounds pretty good.

 

[JohnSnow]

You could do some basic troubleshooting. Based on the hum frequency/ringing frequency, the NCore module has been damaged, most likely. I suppose you could ask Marantz to send you one..??

To convince Marantz... see below. You could check the pre-amp section to confirm an equal voltage is present. Feed a 200 mV, 1kHz signal to either channel and measure the signals at the connectors. If equal in value and clean from oscillations, it's the NCore module.

A simpler check would be to physically swap the NCore modules around - see if that can be done from the mechanical/mounting point of view. If the issue persists with the module, email Marantz, explain what you did, and request a spare module.

You could also drive the NCore modules directly from the same point (see the black line) I showed in the photo. Just be careful, as you'll get full-blast amplification of the modules if you do. Nevertheless, this test would undeniably prove an issue with a module.

Shame to return it... the amp looks good, and apparently sounds pretty good.

View attachment 501827

Appreciate the suggestion. I did all the trouble shooting I was aware of at the time. If something goes south with the seller I'll contact Marantz and provide them with this information. Again, thanks for taking the time.

 

[JohnSnow]

Just wanted to follow up on this. The original seller has agreed to exchange the amp for a another one. I did a bit more trouble shooting today, and discovered that if only the left channel is connected the tone rises to 9,000Hz, but as soon as you connect the right channel it reduces to 6,000Hz...so there is definitely an interaction between the two channels.

May not be worth mentioning for those that have an idea of the root cause, but thought I'd mention it anyway.

 

[JohnSnow]

Updating this post.

I received the replacement amplifier today. Works perfectly.

Thanks to those that offered advice and suggestions. Would like to have confirmation of what was causing the high-pitched tone, but I doubt I'll ever find out.

Happy listening!