Marantz amp problem, sudden "gargly" sound

[Scott Dolan]

None of this makes any sense.

At all. 

[Kevin Bresnahan]

3 hours ago, Larry Kart said:

Audio Consultants suggests that their tech, for a price, could come out to the house, listen, and perhaps detect something that everyone has missed, or they could lend me an amp and see if that makes a difference. I'm thinking of an exorcism.

Your Marantz has pre-amp outputs. Take them up on the offer of an amp. Use the pre-amp outputs to drive the external amp amp, hook your speakers to that amp's speaker terminals and see if the problem goes away.

https://mans.io/images/1056106/1116983.jpg

The preamp output is PRE OUT

[Larry Kart]

I'm fairly dense in these areas, Kevin, so please bear with me. Why would what you've suggested (use the pre-amp outputs to drive the external amp amp) be different diagnostically than just hooking up their loaner amp to my speakers? If the problem doesn't go away when I do that, and it does go away when I do what you suggest, what does that tell me about what's wrong equipment-wise? In particular, what part of my system do I then need to get repaired and in what way, or what part of my system do I probably need to replace altogether? And what if the problem goes away in both cases or in neither case?

[Scott Dolan]

10 hours ago, Kevin Bresnahan said:

Your Marantz has pre-amp outputs. Take them up on the offer of an amp. Use the pre-amp outputs to drive the external amp amp, hook your speakers to that amp's speaker terminals and see if the problem goes away.

https://mans.io/images/1056106/1116983.jpg

The preamp output is PRE OUT

I'm not seeing the need for this particular exercise, Kevin. The actual signal processing is fine, since Larry said the signal out to his headphone output is fine. 

The problem seems to lie somewhere between the processing, and the speaker level output. 

[Kevin Bresnahan]

15 hours ago, Larry Kart said:

I'm fairly dense in these areas, Kevin, so please bear with me. Why would what you've suggested (use the pre-amp outputs to drive the external amp amp) be different diagnostically than just hooking up their loaner amp to my speakers? If the problem doesn't go away when I do that, and it does go away when I do what you suggest, what does that tell me about what's wrong equipment-wise? In particular, what part of my system do I then need to get repaired and in what way, or what part of my system do I probably need to replace altogether? And what if the problem goes away in both cases or in neither case?

If you hook an external amp to your PRE OUT connections and the sound is fine, then you have determined that it is the amplifier circuit of your Marantz that is mucked up. If it's still gargly, then it's something in the preamp section of your Marantz. If it's gargly both ways, it's probably your speakers.

To Scott's point about headphones sounding fine, your Maranz integrated amp has a headphone amp that is separate from the amp that drives the speakers. Headphones have a different load impedance than speakers, hence the need for a different circuit to drive them. It's possible to have a good preamp and headphone amp but a bad speaker amp.

And to clarify, what you want to borrow is a pure audio amplifier, not another integrated amplifier.

[Scott Dolan]

Thanks, Kevin. We're saying the same things, I just misinterpreted your previous post a little. 

[Larry Kart]

1 hour ago, Kevin Bresnahan said:

If you hook an external amp to your PRE OUT connections and the sound is fine, then you have determined that it is the amplifier circuit of your Marantz that is mucked up. If it's still gargly, then it's something in the preamp section of your Marantz. If it's gargly both ways, it's probably your speakers.

To Scott's point about headphones sounding fine, your Maranz integrated amp has a headphone amp that is separate from the amp that drives the speakers. Headphones have a different load impedance than speakers, hence the need for a different circuit to drive them. It's possible to have a good preamp and headphone amp but a bad speaker amp.

And to clarify, what you want to borrow is a pure audio amplifier, not another integrated amplifier.

Many thanks, Kevin. Now I get it.

[Kevin Bresnahan]

I just had an "Ah Ha" moment here...

Many years ago, I had a receiver that had a muddy audio problem at certain lower volumes. It would have been a bitch to debug on a bench because it was a dirty volume pot but it only happened during a very small part of the volume rotation.

Before you go through the amp experiment, see if the gargly sound changes with volume. Also, with the amp off, move the volume knob back & forth from no volume to full volume a bunch of times and see if the gargly sound changes after you turn it back on (make sure that the volume is not all the way up when you turn it back on!!).

I also once had a noisy balance pot but that only affected one channel.

[Stefan Wood]

This.  Sounds like the connections are dirty.  Could be at the speaker ports to the amp, or just the volume knob.

[Larry Kart]

Kevin and Stefan -- I think that's it! I worked the volume knob back and forth a number of times, and things sound fine now. If the problem should return, I'll take the unit in and they can remove the volume knob and clean underneath. Thinking back, the unit has been sitting in my basement since 2009, and no basement is free from dirt/grit, etc. Thank you and everyone else who has weighed in over the life of this thread. And cancel the exorcism.

[JSngry]

Just curious, don't have hi-end equipment, but I have had dusty/dirty knobs and stuff, but it's never sounded gargly, it's been more like static/fuzzy. Does the better stuff have a different interaction with dusty/dirty?

And hell, get the exorcism anyway. One cannot be too careful these days!

[Kevin Bresnahan]

1 hour ago, Larry Kart said:

Kevin and Stefan -- I think that's it! I worked the volume knob back and forth a number of times, and things sound fine now. If the problem should return, I'll take the unit in and they can remove the volume knob and clean underneath. Thinking back, the unit has been sitting in my basement since 2009, and no basement is free from dirt/grit, etc. Thank you and everyone else who has weighed in over the life of this thread. And cancel the exorcism.

A dirty pot can't be cleaned from the outside of the unit. I am editing this because I am finding that your Marantz integrated amp likely has a mostly sealed volume pot. The best way to fix this is to bring it into a shop because they may have to remove it and replace it or take it apart to clean it.

I guess the days of a quick spray of Deoxit are over.

Edited September 29, 2017 by Kevin Bresnahan

[Kevin Bresnahan]

From looking at the service manual, I believe that this is your volume pot: http://www.mouser.com/ProductDetail/ALPS/EC12E2430804/?qs=PoKhxlfUXjKf1hIerO3GPQ%3D%3D. It's a ALPS volume control pot, a fairly well-respected volume pot manufacturer.

It looks like it's part number EC12E2430804. I checked a 3D drawing of it ( http://www.alps.com/prod/info/E/HTML/Encoder/Incremental/EC12E/EC12E2430804_3dcad.html) and I think it is mostly sealed so cleaning it likely requires disassembly.

[Larry Kart]

Well, for better or for worse, I did spray some Deoxit into the narrow inner and outer openings around the volume knob. Then I took a folded strip of typing paper, poked it into those openings and ran it around. The paper came away black at first.