MA2275 Phono Stage Interference Help - Stumped!

[Matt The Cat]

1 it was quiet in this position in your home at one time (ground at the outlet is probably good)
2 it was worse after a repair (might not be the tech - could be the travel causing loose connection)
3 brought it back to the tech and he found no problem (travel again and not heard at the shop but still there at home)
4 took it apart and still the same
5 found oily substance and took to a different tech - heard no sound at the shop
6 brought it home and the sound is back

This is blowing my mind!
Do you have a different TT to try. I thought my C-26 had phono noise and it turned out to be the wiring on my Technics I know you said you tried a shorting cables at first but not sure if you tried them again. I would try some shorting plugs instead of cables.

Hey Refugee,

Thanks for the reply. That is a real concise and accurate representation of what's been going on that you put together.

I do have a different turntable and it's def not the TT as when everything is unplugged, the amp still has phono noise. I've also tried shorting plugs and they make no difference. Nothing seems to make a difference anymore. Even touching the AX7s doesn't increase the noise like it used to. I used to have slightly less noise when attaching the cage, but that doesn't really happen anymore. The noise is just really annoying as I can hear it from my listening position. If it were just lower, I could and did totally live with it. It was nice to hear NO NOISE at the shop, but so frustrating to get it home and hear an increase in the noise.

Any advice for trying to ground the steel chassis to see if that has an affect?

The tech advised I turn the tube cage around so that the open part faces the back to possibly let more air flow. I keep the amp on for 10 hours a day sometimes, but always shut it off overnight and whenever I leave the house. I work from home and feel that if I'm listening in the morning and then go downstairs for lunch, it's not wise to shut the amp off if I'll be back up in an hour. I'm thinking less wear on the tubes and amp to just leave them on. BUT, the power transformer is pretty hot by the end of the day and that might be what cause the potting material to melt and ooze out (see above pics).

So to help with audio anxiety, I've thought about buying a phono preamp and running it through a line level input, but it kills me to think about wasting the nice phono stage that McIntosh has on this piece AND the money it would take to replicate that using on outboard unit. Also, how do I know if the new phone stage won't pick up the noise. I've had one pick it up and then I've had my NAD not pick up the noise.

One more thing...I produce a weekly radio program in the same room and my Shure SM7b microphone is running through an outboard preamp. That preamp does pick up a fainter version of the same sounds the Mac is picking up. So this interference is definitely coming from outside. I don't have any routers near this room. The wi-fi routers in the house are 2 floor below. I've shut my cell phone off and that didn't make any audible difference.

Has anyone tried ferrite beads and had any luck? If I tried those, what would I even apply them to? We know it's not a turntable shielding issue? It doesn't appear to be the power cable as they only appear on the phono stage.

Anything else I could try?

Thanks again!

Matt

 

[Refugee]

As far as the transformer leaking goes, I hope Mc has figured that problem out. I leave my system on all weekend and we should all be able to do that. Maybe there were some changes to the potting material due to availability or epa rules that made Mc try something new during that particular production run.

As for the grounding, the outlet should be tested for a good ground. In residential building the ground is tied to the neutral inside the main panel so things still work if the ground to the box is compromised. Check that the ground rod is connected well in the panel - those connections can get loose. If the unit is on a first floor outside wall you could drive a ground rod outside and run a ground wire inside to the chassis but that really should not be necessary.

** Perhaps the paint on the tube cage is keeping the shield from making a good connection to the chassis below. See if you have good continuity from the tube shield to the chassis. I'm not sure how it is mounted but you might need to scrape off a tiny bit of paint where the connection is made to the main chassis to have the chassis ground electrically connected to the shield/cage. You would think that the cage would have a good Faraday cage effect when it is in place. I have painted a cover before - had problems - and then scraped the paint off where a couple of screws connect the cover to the chassis and had the noise go away.

Ferrite beads would probably only effect frequencies that are above what you can hear and I would not know exactly which wires to put them on. In my book that would be a change to the original circuit - which you should not have to do.

Man, that is such a beautiful unit! I hate to see you having problems with it.
Check your house grounds and check the ground on the cage.

 

[Matt The Cat]

As far as the transformer leaking goes, I hope Mc has figured that problem out. I leave my system on all weekend and we should all be able to do that. Maybe there were some changes to the potting material due to availability or epa rules that made Mc try something new during that particular production run.

Yeah, so I should mention that the tech who has been working on McIntosh amps since the '60s said that the lady who used to seal the transformers to the chassis left work before 2005 when my unit was made. He said that he has noticed over the year, a different in how the transformers are potted since her departure. How crazy is THAT!!!! This tech is very serious about what he does and he couldn't figure out how I was having such a noise problem. He kept blaming my turntable, but changed his tune when I finally got through to him that it makes the noise when NOTHING is collected, when the inputs are shorted with plugs and that the noise has come up on other phono stages.

Regarding grounding, I've tested the plug with one of those ground testers and it came up fine, but I'll check the socket. I'm not on the first floor but up in the attic (3rd floor) of an 1846 home, so anything's possible, but remember, the NAD had no noise on the phono stage.

Thanks again for all your insight, Refugee.

Matt

 

[Refugee]

Check that cage to chassis continuity. The cage should keep all that s%^& out.

 

[Matt The Cat]

I just discovered something connected and interesting that only makes this case more of a head-scratcher. I haven't messed around with my 1967 Akai reel to reel deck in a long time. I have the output hooked up to the "DVD" input of my MA2275. As soon as I turned it on, I hear a pop and the interference that the phono stage has been picking up for the past 7 years is now on THIS input too. However, unlike the phono stage, when I shut the power off on the reel to reel, the interference goes away. So it's like the reel to reel is acting like an antenna or something when turned on. I mean, first though is always, "is this thing grounded?" To recap, the phono preamp interference occurs if the TT is plugged in, unplugged, if the phono input has short plug, etc. It's always there...except when I pull the phono stage 12AX7s. Then, the channel dies and with it, the interference. You would say, "Oh, it's got to be the tubes," but I have the same results with NOS 1960s-70s Teles and RCAs as well as new production Gold Lion and Tung Sols. AND when I hooked up another phono preamp and to connected it to a line-level input, THE INTERFERENCE was still there and this was a solid state pre. However, when I hook up my NAD 312 integrated, no interference on the phono stage. ARRRGH! No interference on CD, CD2, Tuner, etc. Only other time interference appears is when the reel to reel deck is turned on.

Can anyone think of a correlation between the phono stage and a vintage reel to reel deck and the picking up of some kind of frequencies?

The interference is loud enough to be a real buzz kill when listening to records. In quiet sections of songs, I hear it loud and clear, more on the right channel than left channel.

Ugh! Thanks. I just thought I'd provide all the info here, just in case someone has any ideas.

Thanks so much!

Matt

 

[Bill Ferris]

I just discovered something connected and interesting that only makes this case more of a head-scratcher. I haven't messed around with my 1967 Akai reel to reel deck in a long time. I have the output hooked up to the "DVD" input of my MA2275. As soon as I turned it on, I hear a pop and the interference that the phono stage has been picking up for the past 7 years is now on THIS input too. However, unlike the phono stage, when I shut the power off on the reel to reel, the interference goes away. So it's like the reel to reel is acting like an antenna or something when turned on. I mean, first though is always, "is this thing grounded?" To recap, the phono preamp interference occurs if the TT is plugged in, unplugged, if the phono input has short plug, etc. It's always there...except when I pull the phono stage 12AX7s. Then, the channel dies and with it, the interference. You would say, "Oh, it's got to be the tubes," but I have the same results with NOS 1960s-70s Teles and RCAs as well as new production Gold Lion and Tung Sols. AND when I hooked up another phono preamp and to connected it to a line-level input, THE INTERFERENCE was still there and this was a solid state pre. However, when I hook up my NAD 312 integrated, no interference on the phono stage. ARRRGH! No interference on CD, CD2, Tuner, etc. Only other time interference appears is when the reel to reel deck is turned on.

Can anyone think of a correlation between the phono stage and a vintage reel to reel deck and the picking up of some kind of frequencies?

The interference is loud enough to be a real buzz kill when listening to records. In quiet sections of songs, I hear it loud and clear, more on the right channel than left channel.

Ugh! Thanks. I just thought I'd provide all the info here, just in case someone has any ideas.

Thanks so much!

Matt

FWIW, has "any" recent, going back to your first interference experience some yrs. back, "any" RF/EM digital type device been purchased and powered up and in use anywhere near where the Mc. is installed, either upstairs or down ?

Some dirty digital based house powered devices, and their digital power supplies can back feed into the wiring as well, re-radiating via the house wiring, even the neighbor`s dirty digital devices share your electrical provider`s drop transformer, and can back feed interference into your wiring that can radiate back into your equipment
Like new cell phone, computer, wireless thermometer, new LED bulb(s) installed, etc.

Some yrs. back, as an example of totally unexpected RFI issue was experience by me to my surprise, and initial consternation, was when my Mc. MA-6100 integrated in use in my workshop that was playing HQ hard wire fed music started making a major loud digital noise like racket sound (like it might be blowing up !) when the wireless temperature outside senser`s new batteries were installed 10 ft. from the Mc. and it promptly started transmitting its digital info. to it`s battery powered receiver !

I, of course, initially freaked out, until my housekeeper took the wireless outside temperature sensor outside to reinstall it at its normal location ~50 ft away and the Digital noise RFI kept reducing as she carried it further away, until there was no noise heard when she reinstalled it at it`s location.

I would have not thought that such low RF power transmitter would somehow get into the MA-6100, which was plugged into a well grounded HQ Panamax surge/spike power conditioner, but it somehow did, even though the Mc. integrated is only used with one line level input connected.

Just a suggestive thought to consider.

 

[Refugee]

The low output from a tape head is heavily amplified like a phono output, albeit without RIAA compensation. maybe that is why the tape machine is presenting your local interference like your phono section.

Maybe this could help:


Paint the room with this and pray.

 

[Matt The Cat]

FWIW, has "any" recent, going back to your first interference experience some yrs. back, "any" RF/EM digital type device been purchased and powered up and in use anywhere near where the Mc. is installed, either upstairs or down ?

Some dirty digital based house powered devices, and their digital power supplies can back feed into the wiring as well, re-radiating via the house wiring, even the neighbor`s dirty digital devices share your electrical provider`s drop transformer, and can back feed interference into your wiring that can radiate back into your equipment
Like new cell phone, computer, wireless thermometer, new LED bulb(s) installed, etc.

Some yrs. back, as an example of totally unexpected RFI issue was experience by me to my surprise, and initial consternation, was when my Mc. MA-6100 integrated in use in my workshop that was playing HQ hard wire fed music started making a major loud digital noise like racket sound (like it might be blowing up !) when the wireless temperature outside senser`s new batteries were installed 10 ft. from the Mc. and it promptly started transmitting its digital info. to it`s battery powered receiver !

I, of course, initially freaked out, until my housekeeper took the wireless outside temperature sensor outside to reinstall it at its normal location ~50 ft away and the Digital noise RFI kept reducing as she carried it further away, until there was no noise heard when she reinstalled it at it`s location.

I would have not thought that such low RF power transmitter would somehow get into the MA-6100, which was plugged into a well grounded HQ Panamax surge/spike power conditioner, but it somehow did, even though the Mc. integrated is only used with one line level input connected.

Just a suggestive thought to consider.

Hey Bill,
Thanks for relating the experience. That's given me some food for thought. Over the past 7 years, I have plugged it into other house circuits, unplugged everything in the house, etc, but I need to rethink all of that too.

Any idea what this little tower is? Is it a cell repeater? It's RIGHT across the street from my record room.

 

[Matt The Cat]

The low output from a tape head is heavily amplified like a phono output, albeit without RIAA compensation. maybe that is why the tape machine is presenting your local interference like your phono section.

Maybe this could help:
View attachment 3692197

Paint the room with this and pray.

Ha ha!
Yeah, I'll paint the entire house and hope for the best! I didn't realize a tape head was amplified as much as a phono preamp, so thanks for that, Refugee.

I've lived with this for so long that I got used to it, BUT when I came back from taking it to Hartford for the oil leak, the interference noise was worse and that's what's killing me now. I've put up with it for so long and I just want it to go back to the way it was, if I can't have it go away. Ugh! I could start buying phono pre-amps to see if they work, but how much would I have to spend to equal the quality of the McIntosh tube phono that's built in here? I'd have to buy from somewhere that would let me return any that still pick up this interference.

Matt

 

[Bill Ferris]

Hey Bill,
Thanks for relating the experience. That's given me some food for thought. Over the past 7 years, I have plugged it into other house circuits, unplugged everything in the house, etc, but I need to rethink all of that too.

Any idea what this little tower is? Is it a cell repeater? It's RIGHT across the street from my record room.

Don`t know if it`s a supplemental Cell repeater, but that share services pole is very busy with multiple RF antenna looking and their transmitting like devices and a electrical power use meter tied to it feeding them !

Quite possibly the source of your interference, I have not ever recalling seeing a busy cluster of similar looking wideband microwave frequency looking antennas and connected boxes on any type of common shared services (electrical, cable TV trunk, telephone lines/multipair trunk cable) on a standalone wooden pole in NE. FL.

FCC regulations/resolutions about audio equipment being interfered with legit and properly operating licensed transmitter systems don`t exist, as it has deemed many, many decades back, that unthought of, faulty and possibly cheapening of the design in the affected audio equipment as the cause, as their not considered "intentional" receivers of RF signals.

Contact Mc. to see if they can offer any engineering circuit modifications suggestions for that model to deal with your phono input RF interference problems, or live with it.