Gareth Magennis wrote in message
...
"N_Cook" wrote in message
...
spamtrap1888 wrote in message
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On Jun 18, 8:03 am, "N_Cook" wrote:
Hearing it again I would say its more open looped amp motorboating.
Cant
analyse for frequency etc until tomorrow. Needless to say have not been
able
to induce any noise like this.
Further info from the owner
" It's whenever there isn't a signal that the buzz persists. I first
noticed
it when i stopped playing in the middle if a song and i heard this
murmur"
140K MP3 , 5 second file, is (theoretically ) now on/off this host
sitehttp://www.diverse.4mg.com/ampbuzz.htm
(minimal htm page to get round "forbidden" remote linking stuff )
Your search - buzz site:www.diverse.4mg.com/amp - did not match any
documents.
+++++
unfortunately owner's choice of file name, i convert spaces to
undescore,
I
should have changed it to _.
There is a space between buzz and amp in the file name
I don't know how fidele this recording is, phone - email - MP3
player -DSO
but I make that a principal repeat of 103 Hz and next most observable
repeat
of 475 Hz.
So is it mains initiated ?
103100 , I will assume that is twice mains frequency as principal
component
By ear, I make that 100Hz and 500Hz.
But my ears are a bit old.
Gareth.
With this amp and the Return Effects bypass switch to ground. If it breaks
it does not kill the amp but is highly sussceptible to injecting hum into
the amp. There are 6 chances of a break in that line.
That switch
a simple .1 in space 2 of 3 pin jumper in series with it
4x IDC ribbon headers, on two ribbons, links to the PA
Although , as received , the headers and ribbons were made, there was very
little force required to separate them (as well as no glue across them). I
will go with opening of this line somewhere as the fault and something to do
with none of the PREA is directly grounded to chassis, with or withoud
Ground-Lift
Perhaps just replacing input and EFF-Ret socket and a set to these header
pins plus glue spots.
Will try a heavy throughput with amp in the chassis this afternoon , in case
a more electronic type fault.
I don't like the way its consistenetly half-hour in and no amount of kicking
or tugging will change the buxx once it starts/