ET7 S2 transformer hum

[Matty]

The issue I have is my ET7 S2 transformer hums.

With all apartments, other circuit breakers turned off and everything else unplugged apart from ET7 S2, and even with that only on standby...it hums.
The kitchen appliances are on a different circuit as is all lighting.
So those circuits are turned off to test this.
It's only lounge, bedrooms, and hall wall sockets on this circuit and breaker.
To test everything is unplugged apart from the ET7 S2.

The hum never increases when ET7 S2 is turned on fully or with any volume increase and it does not transfer or come out of the speakers at all.
It's only from the actual ET7 S2 unit.

It's not loud but in a silent room, I can hear it 2 meters away in a listening position and silent moments within the music.
Not life-threatening but am unsure of the cause or if it can be dealt with.
Is it my apartment's electricity or the ET7 S2s transformer?
I am using Titan NYX power blocks and cables.
Chord clearway Interconnects but if they are unplugged it makes no difference

It's an almost new ET7 S2... a review unit from the UK dealer....so has not been used apart from for the Review.

The equipment list is Martin Logan 13a's, ART SA, ET7 S2, iFi micro idsd blk, iFi Zen Stream, Chord Clearway Interconnects, Titan Nyx Power blocks, and power cables.
However, with everything turned off and disconnected and only the single circuit breaker turned on with only the ET7 S2 plugged in and on standby...
It has the same constant hum...

[AnotherJohnson]

Are you saying it is mechanical hum you hear that’s not electrically induced hum in the speakers?


Why not get advice from the dealer? If there is a problem, the dealer would likely help.

[AnotherJohnson]

If it is mechanical buzzing emanating from the body of the transformer, there may just be a loose screw.

[roberto]

Hola Matty,

If the hum is not volume dependent, and the hum is right in the unit itself, the power transformer is the culprit. All what you have to do is re-tighten the four screws that are securing metal case and the transformer to the chassis of the preamp. This is an unusual problem. My ET7 V2 is totally silence as if the unit is not power on, but it is. Just re-tight those screws and nuts,

[admin]

It sounds like a mechanical hum. This will be the transformer actually vibrating. It needs dampening. As other mentioned, I would tighten the screws. Make sure the unit is off and unplugged when you do this. If that doesn't fix it, then it will probably need to go back to CJO for fixing.

There really shouldn't be any negative influence on the sound quality, but I can see how this can be annoying.

[AnotherJohnson]

There really shouldn't be any negative influence on the sound quality, but I can see how this can be annoying.

To my ears NO EXCUSES FOR THIS ARE ACCEPTABLE. It is not just annoying. In a $12000 preamp, it is disqualifying.

But I do agree that it is rare … I’ve never heard of a similar complaint with the ET7 s2. I think the screw tightening issue is a consensus. A transformer failure at this stage of the ET7s2 life cycle is highly unlikely.

[roberto]

I'm with AJ, there should be no hum or any issues. You should make your warranty to act. Talk to your dealer...it is a very expensive unit and should be free of any defects. On the other hand, perhaps it is a minor problem that you could solve with the help of a screwdriver.

If your problem remains, then talk with your dealer. He should be know what to do and solve your problem right away,

[Big Dog RJ]

G'day maties,

This is a good mate of mine and I'm glad that he has finally reached out to you all for help. I've given feedback based on a few members that I've been in touch with because those members also have the same preamp. As noted by them, the ET7S2 should be dead silent. Or any CJ preamp for that matter unless it was over 30yrs old, even not a CJ.

I believe the unit is under warranty, however easier said than done, this particular CJ dealer is one of those chaps you'd rather want to avoid... very rude, arrogant and careless and has absolutely no compassion for customers. (Check out his google reviews... shocking!) Hence, I'm actually wondering why on earth he still represents CJ in London. This should be brought to Jeff's notice, but then again what's Jeff going do...?

I know this character type of dealer, and I've dealt with quite a few of them here in Melb as well. However, for some good reason the system seems to work here pretty good, such that we have Consuner Advice regulators and the consumer ombudsman. Once shit happens, mind my French, and it goes to the ombudsman, oh boy! All hell breaks loose. Those type of dealers are now shut down, they paid up a fair sum back to their customers whom they treated unfairly.

I'm not sure if the UK/ London town has this kind of support for loyal customers...?

Initially I suspected it was something to do with all those bits & bobs plugged into the same circuit as the Lounge room, which the audio gear is also plugged into. Hence, it's not a dedicated line on a separate CB. I also suspected something else in the house, perhaps another appliance is causing this hum within the apartment grid... and the ET7S2 is picking it up because the ET7 has no bells or whistles, it's a very simple circuit, so it will pick up whatever...

However, now that's clearly not the case and as Matty has described, the preamp seems to hum on its own! So that's a warranty issue, I guess.

Matty, if push comes to shove, can't you approach that goose and see what he says? Or do you need to send in the mob...

I feel really annoyed with this whole hum saga, and it shouldn't be happening especially at this level! If this happened to me and the dealer treated me this way, I would have burned his shop down. It's pretty common from where I come from... other than that we're generally a peaceful bunch!

I truly hope you can sort this out because you're a very deserving chap, who's worked extremely hard to get here, plus had the sheer patience for several years to be able to afford such gear. By now, you should be sitting back and enjoying those fine tunes! Clearly not the case, and if the CJ dealer was a bit more caring, you'd have peace of mind.

There has to be better way... the other thing is you can send the ET7S2 directly to CJ to check but they won't honor warranty because you bought it from a UK dealer, so that warranty is taken care of by them... is my understanding.

In the good old days, CJ direct would take care of it, that was over 20yrs ago but not now. Any other ideas maties, we must help Matty!

Best, RJ

[AnotherJohnson]

Has he actually tried the screw idea? That seems like really low hanging fruit. Of course if it’s not mechanical hum, then it could be rf or a ground loop. Try a home made aluminum foil shield.

JF would point out that if it hums by itself with nothing plugged in, that could still be rf coming in via the rca input jacks.

Does it hum at a friends house? Or back at the dealer ? If no, it’s the house.

[AnotherJohnson]

Bypass the dealer and go straight to the importer. Unless the importer is the dealer, this might work.

I used to trade quite a bit with Peter Swain at Cymbiosis in Leicestershire. Although naturally he would promote Linn, Naim, NAD etc, he had heard CJ. In those days my sense was that CJ wasn’t well supported in the UK. Of course Linn was not well supported in the US either.

These days, with the exception of the LP12s, I’m trying hard to source the big ticket items in the US.

[Matty]

Are you saying it is mechanical hum you hear that’s not electrically induced hum in the speakers?


Why not get advice from the dealer? If there is a problem, the dealer would likely help.

Its an electrical hum. Sounds like from the transformer of the amp.
Not from the speaker.

[Matty]

If it is mechanical buzzing emanating from the body of the transformer, there may just be a loose screw.

It's not a buzzing.
It's an electrical hum.

[Matty]

Hola Matty,

If the hum is not volume dependent, and the hum is right in the unit itself, the power transformer is the culprit. All what you have to do is re-tighten the four screws that are securing metal case and the transformer to the chassis of the preamp. This is an unusual problem. My ET7 V2 is totally silence as if the unit is not powered on, but it is. Just re-tight those screws and nuts,

Thanks, Roberto,
I will try that.
Might wait till tomorrow morning.
It's definitely transformer hum.
Not volume dependant and not from speakers

[Matty]

It sounds like a mechanical hum. This will be the transformer actually vibrating. It needs dampening. As others mentioned, I would tighten the screws. Make sure the unit is off and unplugged when you do this. If that doesn't fix it, then it will probably need to go back to CJO for fixing.

There really shouldn't be any negative influence on the sound quality, but I can see how this can be annoying.

Thanks, Admin.
That's clear advice.
Will try that tomorrow.
Carefully
With it all unplugged

[Matty]

There really shouldn't be any negative influence on the sound quality, but I can see how this can be annoying.

To my ears NO EXCUSES FOR THIS ARE ACCEPTABLE. It is not just annoying. In a $12000 preamp, it is disqualifying.

But I do agree that it is rare … I’ve never heard of a similar complaint with the ET7 s2. I think the screw-tightening issue is a consensus. A transformer failure at this stage of the ET7s2 life cycle is highly unlikely.

Thanks, AJ.
Very good to hear it's not normal or acceptable.
Will look tomorrow.
Then I also have a technician coming to check a Martin Logan 13a panel next week so might wait to ask them before contacting the UK CJ dealer.
Let's see.

[Matty]

Has he tried the screw idea? That seems like really low-hanging fruit. Of course, if it’s not mechanical hum, then it could be off or a ground loop. Try a homemade aluminum foil shield.

JF would point out that if it hums by itself with nothing plugged in, that could still be of coming in via the RCA input jacks.

Does it hum at a friend's house? Or back at the dealer? If not, it’s the house.

Thanks, AJ.
Have tested with all RCA interconnects out.
Be good to test at another house...
Don't know any local audiophiles and no car being as being in central London.
Be good to check that.
The Martin Logan shop/Technician might let me take it over there to check if I ask.
Very nice guys so it's worth an ask next week.
I have 1 local friend who lives in central London but no idea of his electrics.
Would be best to test it on a confirmed silent electrical circuit.

[Matty]

G'day maties,

This is a good mate of mine and I'm glad that he has finally reached out to you all for help. I've given feedback based on a few members that I've been in touch with because those members also have the same preamp. As noted by them, the ET7S2 should be dead silent. Or any CJ preamp for that matter unless it was over 30yrs old, even not a CJ.

I believe the unit is under warranty, however easier said than done, this particular CJ dealer is one of those chaps you'd rather want to avoid... very rude, arrogant and careless and has absolutely no compassion for customers. (Check out his google reviews... shocking!) Hence, I'm actually wondering why on earth he still represents CJ in London. This should be brought to Jeff's notice, but then again what's Jeff going do...?

I know this character type of dealer, and I've dealt with quite a few of them here in Melb as well. However, for some good reason the system seems to work here pretty good, such that we have Consuner Advice regulators and the consumer ombudsman. Once shit happens, mind my French, and it goes to the ombudsman, oh boy! All hell breaks loose. Those type of dealers are now shut down, they paid up a fair sum back to their customers whom they treated unfairly.

I'm not sure if the UK/ London town has this kind of support for loyal customers...?

Initially I suspected it was something to do with all those bits & bobs plugged into the same circuit as the Lounge room, which the audio gear is also plugged into. Hence, it's not a dedicated line on a separate CB. I also suspected something else in the house, perhaps another appliance is causing this hum within the apartment grid... and the ET7S2 is picking it up because the ET7 has no bells or whistles, it's a very simple circuit, so it will pick up whatever...

However, now that's clearly not the case and as Matty has described, the preamp seems to hum on its own! So that's a warranty issue, I guess.

Matty, if push comes to shove, can't you approach that goose and see what he says? Or do you need to send in the mob...

I feel really annoyed with this whole hum saga, and it shouldn't be happening especially at this level! If this happened to me and the dealer treated me this way, I would have burned his shop down. It's pretty common from where I come from... other than that we're generally a peaceful bunch!

I truly hope you can sort this out because you're a very deserving chap, who's worked extremely hard to get here, plus had the sheer patience for several years to be able to afford such gear. By now, you should be sitting back and enjoying those fine tunes! Clearly not the case, and if the CJ dealer was a bit more caring, you'd have peace of mind.

There has to be better way... the other thing is you can send the ET7S2 directly to CJ to check but they won't honor warranty because you bought it from a UK dealer, so that warranty is taken care of by them... is my understanding.

In the good old days, CJ direct would take care of it, that was over 20yrs ago but not now. Any other ideas maties, we must help Matty!

Best, RJ

Your a good mate RJ.
Thank you.
Look forward to seeing you in London some time in the future.

[AnotherJohnson]

If it is not manifesting through the speakers, then it is mechanical hum. It is induced by the emf in the transformer.

There are two possible reasons.

1. The laminated core has separated and the plates are jiggling against each other as a consequence. THIS IS HIGHLY UNLIKELY given the age of the unit, though it is not impossible.

2. The transformer is not secured and its mounting screws need tightening. I suggested it, Roberto suggested it, admin suggested it … maybe even RJ suggested it. This is the most likely issue, especially since it was a review sample, hence shipped around more than normal.

It is a very easy fix. UNPLUG the unit. Half hour later, pull the cover. Stay away from the caps (big white buggars). Check the transformer mounting screws. Tighten as needed. Just get them a quarter turn past good and snug.

[Matty]

Thank you, AJ.
Just got back home from a night out at the National Theatre in London,
for a play set in Harlem New York during prohibition.
Will get to this in the morning with a fresh and clear head and then report back.
Thank you all so much.

[roberto]

Sometimes the transformer vibration is transfer to the furniture and this furniture does resonate with this 50 Hz from the AC line. I had that problem with a customer. It was a wooden furniture...I put two pine logs 2X3X14 inches under the chassis and solve the problem. The lugs should touch the chassis only, not the rubber feet.