• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Audiophonics MPA-M400ET hum

vco1

Active Member
Joined
Jun 9, 2021
Messages
102
Likes
68
All of a sudden I noticed that one of my 2 Audiophonics MPA-M400ET Purifi amps is emitting a quite loud hum/buzz from the unit when it's switched on. The other one is dead quiet.

I tried several power cables, put the amp in different outlets, in different places in the house, but the hum/buzz remains. Also, there's no difference if a source or speaker is connected. The hum/buzz is constant.

What could be the cause? And more importantly, should I consider this to be normal and/or acceptable or should I contact Audiophonics for a repair?
 

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
1,714
Likes
2,651
Location
Germany
These devices should be silent at all times. I would open it and take a look around, hoping for a loose cable or something. But there is high voltage involved and you might not be comfortable with it.

Audiophonics has an excellent service and they will sort it out quickly.
 
OP
V

vco1

Active Member
Joined
Jun 9, 2021
Messages
102
Likes
68
I opened up the amp. No loose cables. Everything looks nice and tidy. I tried to locate the source of the humming (or buzzing) and I think it’s coming from the power supply. But it’s hard to tell all components are next to each other.

I created a service request at Audiophonics. Let’s see what they think of it.

B.t.w. The humming can be heard from about 30cm or 1 ft distance.
 

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
1,714
Likes
2,651
Location
Germany
Sounds serious. Are you in Europe? The EU?
 

Shazb0t

Addicted to Fun and Learning
Joined
May 1, 2018
Messages
606
Likes
1,138
Location
NJ
Hopefully it's still under warranty. I would contact whomever you purchased it from for return/replacement.
 

Doodski

Grand Contributor
Forum Donor
Joined
Dec 9, 2019
Messages
12,790
Likes
12,598
Location
Canada
If from the power supply it might be the transformer and it is under load meaning something is drawing power from the power supply. It is rare for a PWM/SMPS to have a noisy transformer at idle. The transformers may hiss, emit a high pitched whine or outright buzz and hiss and whine all simultaneously. Sometimes it is a factory defect in the transformer and other times it is a shorted amp driver or similar in that it draws enough power to stress the transformer but not enough to kick in the protection ccty. Does it produce proper sound out of both channels?
 
OP
V

vco1

Active Member
Joined
Jun 9, 2021
Messages
102
Likes
68
Hopefully it's still under warranty. I would contact whomever you purchased it from for return/replacement.
It has been returned. Let's see what they think of it.

I do like the amp. But not the buzz from this unit. So hoping for a solution.
 
Top Bottom