McIntosh Transformer causing noise in speakers while disconnected.

[ClassG33]

It is normal, for a short duration only, could be as long as 100 ms, though normally shorter. This amp has inrush current limiter anyway so it really wouldn't make much of a noise even for that short duration.

It is louder then I am used to hearing in Mac amps.

I have a call today with them, I'll post answers. It's with a rep, not exactly a service tech but it's where I'm starting. I'll be replacing it regardless, however as I've only had it a couple days.

 

[radix]

It is louder then I am used to hearing in Mac amps.

I have a call today with them, I'll post answers. It's with a rep, not exactly a service tech but it's where I'm starting. I'll be replacing it regardless, however as I've only had it a couple days.

Good to hear. I'm sure McIntosh will try to make it right. That price tag on the thing is not just for the weight . So you are calling your dealer/distributor? I'm not sure how much a rep can help versus a tech. How did you hookup with the rep, from the main McIntosh number? I've never had to contact McIntosh, so I'm curious about the process.

I'm interested to hear about your experience and what they say.

 

[ClassG33]

Good to hear. I'm sure McIntosh will try to make it right. That price tag on the thing is not just for the weight . So you are calling your dealer/distributor? I'm not sure how much a rep can help versus a tech. How did you hookup with the rep, from the main McIntosh number? I've never had to contact McIntosh, so I'm curious about the process.

I'm interested to hear about your experience and what they say.

I am calling the Mac rep for the Dealer who I was set up with - he may be able to get me in touch with a tech. the dealer has a return/exchange window so I don't need to send it into warranty service or anything, it's only a few days opened. Normally though there is a number you call on their site, or a form.

I always try to learn about the "scientific version" of what is happening, making sure whether a problem can be solved/ determined, and like to think about it intelligently before I go causing problems and being an annoying customer. I find dealers appreciate when you've gone through extensive troubleshooting with an open mind.

 

[peng]

It is louder then I am used to hearing in Mac amps.

I have a call today with them, I'll post answers. It's with a rep, not exactly a service tech but it's where I'm starting. I'll be replacing it regardless, however as I've only had it a couple days.

The highest transformer inrush current typically occurs under the following conditions (probably not limited to):

1) When turned on right at the time the incoming supply (wall outlet) voltage is at 0 V.
2) When the remnant flux is at the magnitude and polarity that exaggerate the inrush current to the maximum.

So every time you turn power on, the inrush current value can be different.

 

[peng]

I am calling the Mac rep for the Dealer who I was set up with - he may be able to get me in touch with a tech. the dealer has a return/exchange window so I don't need to send it into warranty service or anything, it's only a few days opened. Normally though there is a number you call on their site, or a form.

I always try to learn about the "scientific version" of what is happening, making sure whether a problem can be solved/ determined, and like to think about it intelligently before I go causing problems and being an annoying customer. I find dealers appreciate when you've gone through extensive troubleshooting with an open mind.

Do you actually prefer this model because (or partly because) it does not have autoformers? I don't think they make too many of those anymore, and that's too bad imo.

 

[ClassG33]

Do you actually prefer this model because (or partly because) it does not have autoformers? I don't think they make too many of those anymore, and that's too bad imo.

That's a bonus for me haha!! But yeah, partly. If it had auto former, it would not prevent me from buying it. IMO autoformer is for ppl with money to spennnnd who "marry the amp/date their speakers" and makes a lot of sense in that regard. But I plan on riding these speakers for many years, I'll for sure be their only owner.

I don't see how autoformer cannot introduce noise and it's just another variable I do not need.

 

[Blumlein 88]

OK. Thank you very much. Is a inrush current limiter a single component or a assembly of components making a circuit. I'm very curious because this device has such a high capability for inrush.

On early Mark Levinson amps which were quite large, they had something like a 22 ohm or 47 ohm resistor. Upon turn on everything going to the power supply went that route. In parallel was a circuit with a fair sized electrolytic cap with a resistor which was all setup so it took about that 3 seconds to charge up. When it reached a certain level of charge voltage where upon it switched a relay (a zener diode triggered this) which turns on the front LED and bypassed that resistor. A basic RC timing circuit. I've seen other old large amps use an NTC thermistor with a relay sort of the reverse of what old CRT TVs did. Others used a 555 timer on a relay with some extra resistance on turn on.

Here is an article on one using series/parallel thermistors to accomplish the task.

https://connexelectronic.com/wp-content/uploads/2017/11/Power_SoftStart.pdf

Here is another description of a couple methods.

The Ultimate Guide to Soft Start Design

The toroidal power transformers in audio amplifiers draw large currents on start-up, which reduces their lifespan. This guide presents how to design and make a soft start using inrush limiters. I explore the limitations of power resistors, NTCs, TRIACs, and MOSFETs when used in a soft-start for...

neurochrome.com

 

[ClassG33]

The highest transformer inrush current typically occurs under the following conditions (probably not limited to):

1) When turned on right at the time the incoming supply (wall outlet) voltage is at 0 V.
2) When the remnant flux is at the magnitude and polarity that exaggerate the inrush current to the maximum.

So every time you turn power on, the inrush current value can be different.

That makes sense. It is not noticeably different in loudness, now that I listen again I can hear it for a good full second at least.

 

[Doodski]

@Blumlein 88. Thanks for the literature. It makes good sense to me. I like the relay(s) bypass method for something like this McIntosh.

 

[Blumlein 88]

@Blumlein 88. Thanks for the literature. It makes good sense to me. I like the relay(s) bypass method for something like this McIntosh.

Well when you had tube amps, and used a tube rectifier you didn't have these problems. One of my DIY buddies built up an amp once, and used a small tube rectifier feeding a relay on his MOSFET amp. It slowly came up and turned on the relay. It had no other purpose, but he liked tubes and liked seeing it on top.

 

[RKV1]

Good to hear. I'm sure McIntosh will try to make it right. That price tag on the thing is not just for the weight . So you are calling your dealer/distributor? I'm not sure how much a rep can help versus a tech. How did you hookup with the rep, from the main McIntosh number? I've never had to contact McIntosh, so I'm curious about the process.

I'm interested to hear about your experience and what they say.

ClassG33 wants it replaced so calling the dealer/distributor is the best route. A tech would not have the authority to do that.

 

[ClassG33]

ClassG33 wants it replaced so calling the dealer/distributor is the best route. A tech would not have the authority to do that.

I've got it figured out I really wanted to investigate and make sure I'm not jumping to conclusions. The resources and knowledge this thread has provided has been enlightening on so many levels.

 

[Doodski]

I've got it figured out I really wanted to investigate and make sure I'm not jumping to conclusions. The resources and knowledge this thread has provided has been enlightening on so many levels.

I'm happy you brought this to ASR's attention. It's a one of a kind issue and resultant thread.

 

[mhardy6647]

It's a one of a kind issue

(like the last line in one of those cheezy sci-fi movies of the '50s)

Or is it? Hmm... I wonder...

Ominous music swells.
"THE END?"
<fadeout>

 

[Doodski]

(like the last line in one of those cheezy sci-fi movies of the '50s)


Ominous music swells.
"THE END?"
<fadeout>

Hehe.
Waiting for @restorer-john to post his spectrum analyzer test results so this is simple entertainment to pass the time away.
I remember the first time that I saw this movie, "THEM" on a Sunday afternoon before "The World at War" came on TV and it was glorious!
I watched on TV Sundays "Creature Features" and The World at War for a bunch of years before I was old enough to contribute to working on the farm.
It was my thang to do.

 

[OldHvyMec]

If you have the same thing, and do not have this issue, that is telling.

I'm implying that no one else is saying or has reported this. That is telling, to me. I've never seen or heard of this with any of my
gear or several people with/mac gear. Again Mac equipment is known to be dead quiet. If there is noise it's the valves or cable
routing in most of the noise cases. Routers and Laptops are known to introduce noise. Dirty plugs (different leg) or GL stopper
for 6-11.00 dollars.

In the 70s (and still do) we had to be careful with big amp, placement. It wasn't a nightmare but gear placement was VERY critical.
Most Mac guys are rack mounted or close to the floor. My cables can get pretty hefty, I'm an on the ground guy for that reason.

You'll figure it out, but you'll still have to move it, it's broke. :-(

It's new? SWAP it, and don't look back!

30 days swap on the spot is pretty common with most dealers IF you buy there. A loaner is usually available too, if you ask.

 

[ClassG33]

*Update*

Mcintosh rep told me that the amp has no business making such a loud internal noise upon startup, and he thinks it's defective for that reason alone. That is aside from the speaker noise issue, which he has never heard of happening.

So, my exchange is still set up, and if it happens again with the replacement, he would be interested in the feedback. It sounds like everyone is on the same page with the fact that speakers can make noise while even if disconnected, but also, that mine should not be nearly as severe as it is. I just flipped on some mc1.2k mono blocks today, dead silent.

 

[ClassG33]

*Update*

Mcintosh rep told me that the amp has no business making such a loud internal noise upon startup, and he thinks it's defective for that reason alone. That is aside from the speaker noise issue, which he has never heard of happening.

So, my exchange is still set up, and if it happens again with the replacement, he would be interested in the feedback. It sounds like everyone is on the same page with the fact that speakers can make noise while even if disconnected, but also, that mine should not be nearly as severe as it is. I just flipped on some mc1.2k mono blocks today, dead silent.

I should have a new one set up in a week and a half. I'll update this thread, rain or shine

 

[pma]

It is the electromagnetic induction from amplifier to crossover coils in the speaker, through magnetic field coupling. As others have already said, you need to increase the distance between the amplifier and the speakers. I have experienced the same issue in case of some speakers with large coils in crossovers.

 

[Golf]

I should have a new one set up in a week and a half.

Just curious ... What will the exchange procedure look like? Is McIntosh going to send someone to your home, picking your MC255 up and bringing a new one? I mean, that model is some 40 kilograms ...