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Old 18th August 2003, 02:35 AM   #101
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Default noise output

i want to know how much noise tha amp output is best. i saw netlist's aleph-x output 1.8mvAC is accepted by him, my amp output 2 mvAC but i am unhappy with this value. so anyone can tell me how much noise your diy amp output is accepted by you?
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Old 18th August 2003, 07:42 AM   #102
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Default Re: noise output

Quote:
Originally posted by john-china
how much noise your diy amp output is accepted by you?
The XA200 specs tell us the output noise is about 300V.
That's of course a lot lower than 1800V.
I can live with that because from the moment on the music
is playing it's absolutely inaudible to me.
IMO, the best way to lower that noise is even better filtering.
Look at post#89 here. After every R the noise diminishes a lot.
Others like Till and Edwin also report some output noise but very inaudible.
Of course, a lot depends on the sensitivity of your speakers.
Did you build the AlephX?
From what point of view are you not happy with +/- 2mV?
A practical or a theoretical point?
Greetings

/Hugo
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Old 18th August 2003, 08:14 AM   #103
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Hi,

since I tried building my amp in a enclosure one channel has a slight 50hz humm... You can only hear it within 10-20cm of the speaker but it is there and it was not there before. I get this humm even with the other channel disconnected completely from the mains, power supply and pre-amp. This one channel evens humms without the pre-amp connected. As both channels have the same grounding scheme and wire gauge and wire length and one channel humms and the other does not I do not think I have a ground loop... But...

I will swap powersupply maybe one of my rectifier diodes are bad. hmm...

any ideas?

Edwin
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Old 18th August 2003, 09:21 AM   #104
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I have just been looking at your pics.

Is the driver board still mounted on the heatsink?

If this is the case I doubt if it is the bridge or capacitors and sounds like you have some induced hum into the driver board.

The postion of the high current wiring from the bridge to the capacitors relative the driver board will effect you local hum and also any earth wiring near the power supply.

I had this problem with the Baby X until I move the driver board and hope this is a cure for your slight hum.

regards,

macka


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Old 18th August 2003, 09:23 AM   #105
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it is because xa200 specs said only 300uv noise, i am unhappy with 2mv , i did not build aleph-x but aleph-4, my aleph-4 outputs
2mv hum noise , i am so sensitive to hum noise that when my ears close to speaker, i feel the hum will be louder and louder. of cause i can not hear any hum when i am listening some music.
maybe i am a completist, so i want to reach the spec of pass comercial xa200 amp . how should i do?
ps : does anyone 's amp reach this specs ?
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Old 18th August 2003, 09:30 AM   #106
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Quote:
Originally posted by macka

If this is the case I doubt if it is the bridge or capacitors and sounds like you have some induced hum into the driver board.

The postion of the high current wiring from the bridge to the capacitors relative the driver board will effect you local hum and also any earth wiring near the power supply.

My boards are still on the heatsinks at a distance of about 2cm from the heatsinks. I will remove the heatsink from the chassis and move it away from the wires and transformers to see if the hum level will get lower. The strange thing is still why one channel hums and one does not with the same wiring layout.

Edwin
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Old 18th August 2003, 09:37 AM   #107
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Yeah,

Its a bit odd (but is only one channel in a box)

There could be a dry solder joint somewhere also

macka
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Old 18th August 2003, 09:48 AM   #108
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Quote:
Originally posted by macka
Yeah,

Its a bit odd (but is only one channel in a box)

There could be a dry solder joint somewhere also

macka

Both channels are in the same box! It is a dual mono amplifier. They share the box and the 230V AC inlet... Both have there own powersupply and transformer...

Edwin
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Old 18th August 2003, 10:13 AM   #109
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Quote:
Originally posted by Edwin Dorre

Both have there own powersupply and transformer...
Edwin
Try turning the humming channel's transformer 180 if you can.
Just a thought.
Is it a 50 or 100Hz hum?

/Hugo
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Old 18th August 2003, 10:23 AM   #110
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My,

Its must be quite a box! Lovely and warm in winter though.

I'll bet your pussy (cat) justs love the heat pouring out it.

I would meter out all the earthing wiring and particularly any connectors associated to the metal chassis.

macka
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