light noise from MFB speakers when idle

hi

welcome to this forum specalized in mfb speakers and audio
from the past .

if er is noise comming from both your mfb 544 there are possible couses
which are : set them to a normal amp ouput in too low setting
on the back of te speaker , couses it too make a light noise when idle .
an a power amp setting is : 19 v on a light amp 7,5 v
and on a preamplifier 1 v .

another problem is the connection cable , when passing a light dimmer
it will give a light buzzing sound , best is shielded cable as axample
tv coax .

and another thing could be the switches on the back , are polluted
with the years , simply put some contactspray into them , and use them a 15 times , but if you have this from both speakers in the same volume
it is probably the first one of these problems .

if its a buzzing sound , it also could be bad grounding of the amp- mfb cable , some jiggeling with the connectors must make a difference .

greetings from mattie

thank you mattie! I did spray the switch and now it is much much better. I wish I knew how to get rid of or reduce the humming coming from the transformer and the active components, but I guess this "humming" is part of the design.

again, thank You !
Ted

hi

some mfb's have a bit humming noise from the transformer .
altough i never had it .
what voltage do you have in your country ?
on most type's mfb's er is a rotationswitch on the back for the
input voltage from the mains , in the usa is this 110 volt
but in the uk or netherlands this is 240 volts .
when this is set too low , the humming noise can be becouse of this .
most times is settable to : 110 , 127 , 220 , 240 volt .
if its not that , you can test with the backplate open , switched off
when you pull out the connector going into the speakercompartiment .
them power on , if its then gone , the amp is cousing this , also try to pull out the cable
going in to the box , if its goane , probably you set the speakervoltage
( on back ) too low on a regular power amp

greets mattie

hi mattie,

thank you for your note! I have a few MFBs and they all seem to have this humming noise. I did notice that if I set the sensitivity voltage too low the noise is significantly higher. i am not sure if I can expect the mfb to be totally silent or some humming will always be there...?

I like the idea to switch the speakers to 240V - I live in Germany and despite that fact that we have 220V - switching to 240V may put the amplifier in a "less performing" mode and reduce the humming because of the lowered transformer output voltage. Having said, that if Philips has a voltage regulator it may compensate to a certain degree.

Once I have some time I will look at the diagram and will test the speakers with 240V setting in the back.

again thanks for helping !!

hello

if they all make noise , what do they if you switch off the amp ?
if its then goan , it comes becouse of the amp . setting treble
too high makes also noise . but i understand you have a regular power amp connected to the mfb's . in that case you have more chance to get this problem . and if so the knob on the back off the mfb must be set all to the right or 19 v .

also , if you have a flatscreen connected to your stereosystem en that's also connected to a antennacable on the tv or seperate fmtuner . you get a humming noise . caused bij a earthloop . simply put de powerplug
off the tv in a unearted outlet . but this problem must then also be by the internal speakers of the tv .

mattie