Aleph X strange behaviour - Page 3

JBL4435 · 25th May 2008, 01:02 PM

Good Amp input

JBL4435 · 25th May 2008, 01:04 PM

Good Amp PS

Zen Mod · 25th May 2008, 01:08 PM

what is bias in these amps ?

are these chokes air wound ?

JBL4435 · 25th May 2008, 01:27 PM

Quote:

Originally posted by Zen Mod
what is bias in these amps ?

are these chokes air wound ?

app. 18.5 V
app. 4.3 Amps bias

Power supply ripple
good Amp, app24 mV peak to peak
bad Amp, app24 mV peak to peak

These chokes are ferrite core bobbin types rated for >15 Amps
They reach app. 70°C

JBL4435 · 25th May 2008, 04:48 PM

Maybe this helps not only me but all plagued by hum.

It comes from the transformer! Turn the transformer till the amp is quiet.
When the transormer outlets are on 3, 6, 9, 12 o'clock there is hum.
If they are at 1:30, 4:30, 7:30 or 10:30 there is no hum.

Mine where at 12. Seems to be in realtion to the chassis walls.

Try it!

Zen Mod · 25th May 2008, 06:11 PM

Quote:

Originally posted by JBL4435
Maybe this helps not only me but all plagued by hum.

It comes from the transformer! Turn the transformer till the amp is quiet.
When the transormer outlets are on 3, 6, 9, 12 o'clock there is hum.
If they are at 1:30, 4:30, 7:30 or 10:30 there is no hum.

Mine where at 12. Seems to be in realtion to the chassis walls.

Try it!

certainly worth trying ;

Papa wrote (few ?) times about same issue

macka · 25th May 2008, 10:28 PM

Guido,

Do not dispair,

I also have had that problem with another product......

Please bare in mind its still being picked up by the amps and some thing is acting as a antanna.

Check that all aluminium panels are at ground potential.

What is the bottom panel made of?

Ground the input stage earth with 3 ohms to chassis ground.(A must do)

Also, try to shield all the input wiring. I would suggest splicing the coupling caps into external the cable if it helps reduce the hum.

Re-route those wiring coming over the transformer. That is full of noise! They should be all twisted in a spiral together and be attached to the chassis.

If all that fails put a 4-6 mm plate steel partition across the chassis in front of the board isolating it from the rest of the interior

I just had a look at my X Aleph, no hum no matter what I do.

Ian

25th May 2008, 01:08 PM	#23
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	what is bias in these amps ? are these chokes air wound ? __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

25th May 2008, 04:48 PM	#25
JBL4435 diyAudio Member Join Date: Oct 2006	Solution Maybe this helps not only me but all plagued by hum. It comes from the transformer! Turn the transformer till the amp is quiet. When the transormer outlets are on 3, 6, 9, 12 o'clock there is hum. If they are at 1:30, 4:30, 7:30 or 10:30 there is no hum. Mine where at 12. Seems to be in realtion to the chassis walls. Try it!

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25th May 2008, 10:28 PM	#27
macka diyAudio Member Join Date: Dec 2001 Location: Australia	Guido, Do not dispair, I also have had that problem with another product...... Please bare in mind its still being picked up by the amps and some thing is acting as a antanna. Check that all aluminium panels are at ground potential. What is the bottom panel made of? Ground the input stage earth with 3 ohms to chassis ground.(A must do) Also, try to shield all the input wiring. I would suggest splicing the coupling caps into external the cable if it helps reduce the hum. Re-route those wiring coming over the transformer. That is full of noise! They should be all twisted in a spiral together and be attached to the chassis. If all that fails put a 4-6 mm plate steel partition across the chassis in front of the board isolating it from the rest of the interior I just had a look at my X Aleph, no hum no matter what I do. Ian

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