Author Topic: qsxm3  (Read 20879 times)

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Offline peranders

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Re: qsxm3
« Reply #30 on: October 18, 2013, 08:53:02 AM »
A normal EI-core transformer has a magnetic leakage field but either has less. You can get rid of the hum if you have shielded wires inside and you can also insert a steal shield between the transformer and the rest.
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Offline yiancar

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Re: qsxm3
« Reply #31 on: October 18, 2013, 09:23:22 AM »
I have shielded wires and that reduced the ham a lot , at the volume i hear it i never use the amp, its intolerable. using a steel sheet the hum gets redued even more . but there is still some there i guess the amplifier is just too sensitive at that point?

Offline yiancar

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Re: qsxm3
« Reply #32 on: October 19, 2013, 06:07:22 PM »
I belive that something is wrong with one of the channels lt1115. when i mesure the opamps out one of them gives me a stable voltage where the other suddenly drops to a -ve voltage. any chance that the answer?  Also the output of the lt1010 on the side with the hum is 0.002v where on the silent side is ~0.6v

Edit:
I am usign a single transformer so i tried moving it from one channel to the other and guess what the hum passed to the other channel. So does this mean that i need an ac line filter or something?
« Last Edit: October 19, 2013, 08:54:30 PM by yiancar »

Offline peranders

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Re: qsxm3
« Reply #33 on: October 19, 2013, 09:38:47 PM »
Is the sound quality good?
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Offline yiancar

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Re: qsxm3
« Reply #34 on: October 19, 2013, 09:49:56 PM »
when playing music its excelent. so the ics are ok right?

maybe i should use an emi filter on the mains ?

Offline peranders

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Re: qsxm3
« Reply #35 on: October 19, 2013, 10:30:46 PM »
What is the problem right now?
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Offline yiancar

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Re: qsxm3
« Reply #36 on: October 19, 2013, 11:10:11 PM »
hum , to the channel the transformer is connected to ( the bridged channel also has hum but lots less)

Offline peranders

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Re: qsxm3
« Reply #37 on: October 19, 2013, 11:31:27 PM »
Is the transformer feeding two channels? How does this connection look like?
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Offline yiancar

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Re: qsxm3
« Reply #38 on: October 20, 2013, 12:29:11 AM »
here:)

Offline peranders

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Re: qsxm3
« Reply #39 on: October 20, 2013, 08:42:50 AM »
The green wire, what is that for?
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Offline yiancar

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Re: qsxm3
« Reply #40 on: October 20, 2013, 09:42:37 AM »
i use it ad a ground when i probe

Offline peranders

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Re: qsxm3
« Reply #41 on: October 20, 2013, 10:25:56 AM »
Are you getting hum when nothing is connected at the input? Is the hum audible or do you see the hum on your oscilloscope only?
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Offline yiancar

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Re: qsxm3
« Reply #42 on: October 20, 2013, 02:43:02 PM »
with nothing connecred on the input i het noise which u explained is from the high gain. the hum is audible only at about 3/4 and above of the volume of my amp. and its louder on the channel that the transformer is connected to

Offline peranders

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Re: qsxm3
« Reply #43 on: October 20, 2013, 03:29:13 PM »
Is it 50/60 Hz hum or 100/120 Hz? If it is 50 Hz, then you have a ground loop or magnetic coupling from the transformer. 100 Hz and harmonics comes from the smoothing caps.

How high is the hum compared to the normal music level?

Does the hum go away if you locate the transformer further away?
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Offline yiancar

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Re: qsxm3
« Reply #44 on: October 20, 2013, 03:51:52 PM »
i thing ot is 100/120 hz . the hum is very low compaired to music level. if i take the transformer further away it seems to decrease but not complitly. btw if i move my input cable over the caps it gets very loud so maybe harmonics?