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Old 17th April 2003, 04:43 AM   #16
Philo is offline Philo  United States
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Matt,
If your hum stops when you disconnect your input interconnects you might have a ground loop though your source if it is grounded as well. Does it have an IEC power cable? Try opening your source (ie CDP) and disconnect the ground at the case socket and see if the hum goes away. Or try a source with a two-wire cord. You might try some different interconnects too.
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Old 17th April 2003, 05:52 AM   #17
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Quote:
Originally posted by Philo
...Or try a source with a two-wire cord...
The easiest way to tell if you have a ground loop is to use something like a portable cd player as your source(battery powered of course)
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Old 17th April 2003, 06:22 AM   #18
Jean is offline Jean  United States
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try lifting one rca ground wire
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Old 17th April 2003, 07:34 AM   #19
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The fact that the hum disappears when you disconnect the source is indicative of the fact that is indeed a ground loop.

By the way, have you used shielded wire for the input connections?

Tie Input, Output, PSU ground and 0volts of transformer to one point and isolate all of these from chassis earth. Use braided earthing strap to electrically connect RCA ground to chassis earth. This should solve your hum problem.

If the torroidal transformer is buzzing, either the windings are loose (should be re-wound) or the mains voltage is slightly higher than what the primary was designed to handle. Check out which is true.

All the best!!
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Old 17th April 2003, 08:50 AM   #20
moamps is offline moamps  Croatia
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Quote:
Originally posted by Mattyo5


FRUSTRATED

Hi,
On pic 1 is your wiring diagram. When small AC ripple current on DC power rail flow from wire A thru CAP1, wire B and C make Vripple (dashed line). This is your problem. When you shortening input RCA, this V appear on input of your amp. Solution is to rearrange ground star according pic 2. IMHO

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Old 17th April 2003, 08:53 AM   #21
moamps is offline moamps  Croatia
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and pic 2
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Old 17th April 2003, 11:46 AM   #22
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Thanks guys for the help. I'm off to school now...when I get back I'll try some of those things. I have tried a discman ....seems like anything I plug into the inputs creates this buzz. I have test RCA connectors that are shorted....they short RCA input to ground...and even those things buzz.

MOAMPS...I'll try what you say...seems like a good way to do it.

Later guys!

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Old 17th April 2003, 11:57 AM   #23
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Quote:
....they short RCA input to ground...and even those things buzz
That sounds as if you'd have a ground loop WITHIN your amp.

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Charles
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Old 17th April 2003, 02:24 PM   #24
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Are we talking about a mechanical buzz from the amplifier here, or an (electrical) buzz in the output signal to the speakers?

If it's an electrical buzz, is it still there if you put a short between input and ground of your RCA connector, with nothing else (only the speakers!) connected?

If so, there's probably a grounding fault somewhere within the amp. Can you point me at the circuit you're using?

If not, does the buzz come back when you touch the ground of your CD to the RCA ground (even with shorting plug)? If so, it's an earth loop (which will need some grounding
mods to CD or amplifier to sort out).

Cheers
IH
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Old 17th April 2003, 04:31 PM   #25
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MOAMPS!!! YEAH BABY YEAH!!! THAT WAS IT!!!! I attached all ground points to the amp caps...then to the power supply ground at the chassis. WORKS BEAUTIFUL!!!! CLEAN AND NICE.....ROCK ON!!!

-Matthew K. Olson
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Old 17th April 2003, 04:46 PM   #26
moamps is offline moamps  Croatia
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Nice
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Old 18th April 2003, 03:54 AM   #27
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Well here it is....finished. LOOKS AND SOUNDS SMOOTH!!! Hope ya'll like it!! The guy I'm building it for didn't want any LED on the faceplate or anything...so I kept it simple. Looks way cool. The paint is the new Rustoleum Metalic. Looks very very good. Later all!

-Matthew K. Olson
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Old 18th April 2003, 09:06 AM   #28
trwh is offline trwh  United Kingdom
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Looks great Matt. How wide are those chassis?
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Old 18th April 2003, 10:43 AM   #29
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I made the faceplates oh 12" wide or so. But the chassis on the bottom is really only 12" deep and 8" wide. The chassis on the top w/o heatsinks is like 4-5" wide plus 3" sinks on either side. It really came out pretty well. I'm not a great painter....so the paintjob isn't terrific...except for the faceplates. They are 3/16" aluminum and came out just great

-Matthew K. Olson
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Old 18th April 2003, 11:16 AM   #30
2Bak is offline 2Bak  Denmark
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Looks really cool !
Do you have some more pics from the side and inside?
/Jan
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