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Chip Amps Amplifiers based on integrated circuits

Hum with Brian 3886 kits
Hum with Brian 3886 kits
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Old 11th April 2005, 06:25 AM   #11
jeff mai is offline jeff mai  Australia
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Quote:
Originally posted by phoneisbusy
The wiring from the amps and the power board is pretty long so it sounds like if I reroute/shorten the lengths, I may be able to eliminate the hum?
Maybe. But maybe not. Mine are pretty short and of similar lengths and I still have a faint hum. I don't worry about it too much as I'm used to SE tube amps that have a lot of hum by any comparison.

If I were going to undo a "done" amp, I'd attack the problem the way Carlos is doing his. I think the results are more certain to be better.
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Old 11th April 2005, 01:48 PM   #12
homer09 is offline homer09  Canada
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jeff,

how would you do things with one transformer and two power supply boards?
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Old 11th April 2005, 06:15 PM   #13
carlosfm is offline carlosfm  Portugal
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I hope this is clearer now.
Two channels with single PSU.

PS: I don't use the on-board CHG connection to the chassis.
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Old 11th April 2005, 06:43 PM   #14
homer09 is offline homer09  Canada
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Quote:
Originally posted by carlosfm
I hope this is clearer now.
Two channels with single PSU.

PS: I don't use the on-board CHG connection to the chassis.

Almost clear, i understand your PSU power ground arrangement now. I imagine you will join the PG+ and PG- on the PSU boards with a rigid copper wire also and join its center to the PSU ground you labelled on your pic, right?

Now, im still unclear about chasis ground. You will be connecting your AC ground to the screw on the top of your heatsink right? What i dont understand, is what you will connect from your PSU to that and how.

obrigado para a clarificação Carlos
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Old 11th April 2005, 07:27 PM   #15
carlosfm is offline carlosfm  Portugal
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Quote:
Originally posted by homer09
Almost clear, i understand your PSU power ground arrangement now. I imagine you will join the PG+ and PG- on the PSU boards with a rigid copper wire also and join its center to the PSU ground you labelled on your pic, right?
Right.

Quote:
Originally posted by homer09
Now, im still unclear about chasis ground. You will be connecting your AC ground to the screw on the top of your heatsink right? What i dont understand, is what you will connect from your PSU to that and how.
This amp will use my own external PSU (snubberized 3x4,700uf per rail, MBR16100 schottky diodes, heatsinked).

I have a big 4-pin Din plug, with two pins for ground (shunted).
The groung that comes from the PSU is only one, but I use two wires. Yes, double or very THICK wires for ground.
Still unfinished but just for you to get an idea.
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Old 11th April 2005, 07:33 PM   #16
carlosfm is offline carlosfm  Portugal
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The back.
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Old 11th April 2005, 07:44 PM   #17
homer09 is offline homer09  Canada
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Thanks, its clear now. i also see you dont kid around when it comes to the power supply

Wire thickness... what happens if your wire isnt thick enough? should your ground wire be thicker than your V+ and V- wires? or is it also important for these to be thick too?
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Old 11th April 2005, 08:34 PM   #18
cjd is offline cjd  United States
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I get a similar hum if I have been an idiot and wire one of the input RCA's backwards. . . (signal and ground reversed).

I also discovered a bad IC this way (an old cheap one but it was part of my junk test-rig, and it had the leads reversed on one RCA - totally surprised me).

C
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Old 11th April 2005, 08:43 PM   #19
carlosfm is offline carlosfm  Portugal
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Quote:
Originally posted by homer09
Thanks, its clear now. i also see you dont kid around when it comes to the power supply
Nah...

Quote:
Originally posted by homer09
Wire thickness... what happens if your wire isnt thick enough? should your ground wire be thicker than your V+ and V- wires? or is it also important for these to be thick too?
I use 2.5mm multi-strand copper wire for power gound, 1.5mm multi-strand copper for the voltage rails.
Of course, PSU wires should not be thin, and more critical is the ground.
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Old 11th April 2005, 09:42 PM   #20
carlosfm is offline carlosfm  Portugal
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Done.
Kimber 4TC for signal and speaker wires (because I have some).
Everything soldered with silver solder (including all the components on the PCBs).

This massive heatsink doesn't get hot, even listening to Talking Heads' "Burning down the house" at half volume.
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