Strange Audio Problem

[Capndad]

Hi,
This is my first post, so if it's in the wrong place, don't hesitate to let me know. My 2 channel system is a McIntosh MA6300 running 2 Focal Chorus 720 loudspeakers. I listen to CD's, (Rotel) Vinyl (Linn)and stream music from the web via an Audio Engine Sender/Receiver.

About 1 year ago I started to notice that every so often, (not every time I listen) one of the channels (the issue doesn't seem to favor left or right) would start cutting in and out, or producing static like noise. I checked banana plugs and connections on the back of the Mac and the Focals, tightened everything up, moved the wireless receiver away from the rest of the system,and things seemed to get better.

But it wasn't fixed. The problem continued to happen off and on, but without any rhyme or reason. Then it would just go away.

I took the MA6300 in for repair, and of course they ran the system for 4 days straight with no issue. Brought it home, and it ran without the issue for about 7-8 months. then last week it started again.

I'm now thinking I'll start eliminating gear from the system so that I only run bare bones CD's and Vinyl. The problem is that if that doesn't help, the system could still run for months and then show up sometime down the road.

If anyone has suggestions of any kind I'd appreciate it. My brain is fried with just trying to figure this out.

Cheers,

Cap

 

[KenM10759]

With the MA6300 do you happen to notice any deviation between the two VU meters as this intermittent problem happens? When it does happen are you running off of your turntable, CD player or streaming device every time or does it happen with any or all of the input devices? Are all the devices direct into amp inputs?

Any chance you might have another integrated amp kicking around to substitute for the McIntosh temporarily?

 

[Capndad]

Thanks for the reply. I've checked the meters when I've had the problem but no difference between the two. Also, the problem has occurred on all sources, TT, CD, external Tuner, and wireless. All the devices are direct into the Amp except the Audio Engine which goes from my PC in the basement to its receiver and then onto the Mac.

And no, I do wish I could test with another amp, but all my "kickarounds" have been used to their death.

I just changed the power cord at the suggestion of another reply, so I'll try that for a while.

The new power cord is 14 gauge whereas the stock one was 18 gauge. (strange) Hope that's not an issue to have done that.

Cheers

Cap

 

[WaynePflughaupt]

If it happens with any source, it has to be something that’s always in the signal chain. The first thing that comes to mind is a dirty volume control pot, but that would be noticeable anytime you adjusted the volume. Along the same lines the balance control could be a more likely culprit, as it seldom gets moved. Note, I can’t find anything to tell me if this unit has electronic volume and balance controls or not, so obviously if it does the problem can’t be a dirty pot.

Next I’d cast my vote with defective pre-out/mains in jumpers. If this is it, giving them a wiggle would probably make the problem manifest immediately.

Regards,
Wayne A. Pflughaupt

 

[Capndad]

If it happens with any source, it has to be something that’s always in the signal chain. The first thing that comes to mind is a dirty volume control pot, but that would be noticeable anytime you adjusted the volume. Along the same lines the balance control could be a more likely culprit, as it seldom gets moved. Note, I can’t find anything to tell me if this unit has electronic volume and balance controls or not, so obviously if it does the problem can’t be a dirty pot.

Next I’d cast my vote with defective pre-out/mains in jumpers. If this is it, giving them a wiggle would probably make the problem manifest immediately.

Regards,
Wayne A. Pflughaupt

Thanks for the reply. I agree it has to be something common to all sources. I'll try the balance control pot first of all.

Re defective pre-outs/mains in jumpers, I have to embarrassingly now admit I don't know what you mean and what I should wiggle. Where would I look for these on the MA6300?

 

[WaynePflughaupt]

Typically on the back panel, but the 6300 doesn’t appear to have any. When I searched before I must have found a picture of a different model. Sorry about that...

Regards,
Wayne A. Pflughaupt

 

[Capndad]

No problem. I'm open to any "wiggling" solutions.

 

[PENG]

Typically on the back panel, but the 6300 doesn’t appear to have any. When I searched before I must have found a picture of a different model. Sorry about that...

Regards,
Wayne A. Pflughaupt

The MA6300 does have a pair of jumper plugs to connect the preamp output to the bult-in power amp output.

 

[PENG]

No problem. I'm open to any "wiggling" solutions.

Before you wiggle any connection, turn the volume down first to avoid damaging your speakers.

Since the issue could happen to either channel, the chance for the jumper plugs being the cause is very low. It is possible that you have a bad relay somewhere that could affect either channel.

Try to borrow a power amp so you can at least find out if the trouble is originated from the preamp or the power amp section. Or conversely you can also borrow a preamp, or AVR, same logic.

 

[highfigh]

Did the service shop do anything to it, other than connect and find no problems? Did they include any info about what they did, like connect one source device to all inputs, vary all of the controls, use all of the switches?

Typically, intermittent audio or noise when adjusting controls/engaging switches comes from some kind of contamination on the contacts and the friction from changing control settings/engaging switches removes enough to make it work, for awhile. If this is the case, the controls and switches should be cleaned and lubed with the appropriate chemicals. If that isn't the kind of sound you're hearing, can you post a sample of the sound? (with or without video)

If it's similar to the sound you hear when tuning a radio and you're between stations, it could be a faulty part. Resistors sometimes make that sound. If so, the part needs to be replaced.

If you remove the jumpers, make sure the power is off- the volume control will do nothing to keep the signal from reaching your speakers.

Is this in all source input jacks or only only a few? Which inputs are you using? Is anything sitting on top of the cover or is it in a cabinet with little space over it? Heat isn't good for amplifiers.

 

[Capndad]

Thanks Highfigh,

Not sure what the service shop did, but they didn't include any info about what it was. As far as I know ,they plugged it in and left it on waiting to hear the problem.

This morning it happened again, and I took advice and turned the balance knob back and forth. While I was doing that the problem got worse, and eventually cut out altogether, so I'm now looking for some DeoxIT or similar product to give the pots a good cleaning, then we'll see.

 

[highfigh]

Thanks Highfigh,

Not sure what the service shop did, but they didn't include any info about what it was. As far as I know ,they plugged it in and left it on waiting to hear the problem.

This morning it happened again, and I took advice and turned the balance knob back and forth. While I was doing that the problem got worse, and eventually cut out altogether, so I'm now looking for some DeoxIT or similar product to give the pots a good cleaning, then we'll see.

Where are you? If you have a Radio Shack nearby, they sell it. Otherwise, Parts Express and other places sell it and I think Caig has a dealer locator on their site. Antique Electronic Supply sells it, too.

I think the balance control is the cause and I would think McIntosh's controls are good enough that they wouldn't fail completely within a normal person's lifetime.

 

[slipperybidness]

Thanks Highfigh,

Not sure what the service shop did, but they didn't include any info about what it was. As far as I know ,they plugged it in and left it on waiting to hear the problem.

This morning it happened again, and I took advice and turned the balance knob back and forth. While I was doing that the problem got worse, and eventually cut out altogether, so I'm now looking for some DeoxIT or similar product to give the pots a good cleaning, then we'll see.

This is a fine kit from PE
http://www.parts-express.com/caig-sk-av35-deoxit-audio-video-survival-kit--341-275

Personally, if I'm in there cleaning the balance pot, then I would do the volume pot and others too. May as well clean them all while I have it open.

 

[Capndad]

So I finally got a can of contact cleaner and took a shot at cleaning the balance pot today. But after listening for about an hour, the problem came back. I'm gonna take another crack at the cleaning since the pot doesn't look like I expected it to. (i.e. no holes in which to spray the cleaner.)

Anyone know what kind of pot McIntosh used in the MA6300. If I knew that, I could find out how to clean it properly.

Here's another clue. When I recycle the power (Turn it off and on) the problem is gone, and stays gone!!

Thanks to all for the great replies.

Cap

 

[MJAB]

So I finally got a can of contact cleaner and took a shot at cleaning the balance pot today. But after listening for about an hour, the problem came back. I'm gonna take another crack at the cleaning since the pot doesn't look like I expected it to. (i.e. no holes in which to spray the cleaner.)

Anyone know what kind of pot McIntosh used in the MA6300. If I knew that, I could find out how to clean it properly.

Here's another clue. When I recycle the power (Turn it off and on) the problem is gone, and stays gone!!

Thanks to all for the great replies.

Cap

Hi there. I am new here but I was reading about your problem. Did you solved it? I have a pair of McIntosh MA6300 and though that my story would help you or anybody else that have this integrated amplifier too.

 

[Capndad]

Hi there. I am new here but I was reading about your problem. Did you solved it? I have a pair of McIntosh MA6300 and though that my story would help you or anybody else that have this integrated amplifier too.

Hi,

I have not yet solved the issue, although it seems that others have had the problem too and have suggested it may be a relay issue. I'd be interested in hearing your story.....please help!

 

[TLS Guy]

Hi,

I have not yet solved the issue, although it seems that others have had the problem too and have suggested it may be a relay issue. I'd be interested in hearing your story.....please help!

I took a good look at the service manual for that unit. It is horribly complicated design. A classic design by committee and just thrown together. It is just the sort of unit I would run a mile from and expect to go wrong.

Switching is NAND CMOS logic and I suspect is the root of the problem as it involves both channels but at different times. There are relays galore which is never a good sign.

I would contact MAC and see if they will take a look at it. Even so the chance of fixing it is remote unless it progresses to total failure. Finding an intermittent fault like that is worse than finding a needle in the proverbial haystack.

The unit does not have error codes. Basically unless complex units like this have a memory for defined error codes that can be interrogated they are not fixable.

The unit does not have pots by the way. Hardly any units made in the last 20 years have them. Spraying cleaner around is not a good idea and can do damage.

If MAC won't take a look at it, I would get rid of it and buy something else.

I know a lot of people lust after MAC gear. I don't and their products would be far down my list.

 

[MJAB]

I took a good look at the service manual for that unit. It is horribly complicated design. A classic design by committee and just thrown together. It is just the sort of unit I would run a mile from and expect to go wrong.

Switching is NAND CMOS logic and I suspect is the root of the problem as it involves both channels but at different times. There are relays galore which is never a good sign.

I would contact MAC and see if they will take a look at it. Even so the chance of fixing it is remote unless it progresses to total failure. Finding an intermittent fault like that is worse than finding a needle in the proverbial haystack.

The unit does not have error codes. Basically unless complex units like this have a memory for defined error codes that can be interrogated they are not fixable.

The unit does not have pots by the way. Hardly any units made in the last 20 years have them. Spraying cleaner around is not a good idea and can do damage.

If MAC won't take a look at it, I would get rid of it and buy something else.

I know a lot of people lust after MAC gear. I don't and their products would be far down my list.

Hi! I hope you had fix the MA6300 problem. I have two of them and both had exactly the same issue: A very poor quality relay that got broken. My tech man replaced it with a high grade Omron relay and guess what: Problem solved on the two MA6300! My best regards and...spread the news!