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Old 11th September 2017, 11:53 AM   #341
Burnedfingers is offline Burnedfingers  United States
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If its quiet with the preamp connected I'd leave it alone. One thing you might try is inserting a 10 ohm resistor from the RCA ground on each RCA to the circuit board trace where your getting your ground now. Make sure your RCA's are issolated from the chassis.
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Old 11th September 2017, 01:51 PM   #342
ViperZ is offline ViperZ  Canada
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Quote:
Originally Posted by Burnedfingers View Post
If its quiet with the preamp connected I'd leave it alone. One thing you might try is inserting a 10 ohm resistor from the RCA ground on each RCA to the circuit board trace where your getting your ground now. Make sure your RCA's are issolated from the chassis.
The manual says "The input jack chassis ground is the ONLY chassis ground in the amplifier". So they specifically mean that that one screw connecting negative end of RCA connectors to the chassis is the only ground connection.

What worries me is that right channel buzzes much louder than left when not connected. If the screw connection between chassis and the board/RCA is disconnected, both channels buzz loudly and evenly. When the screw is connected, left channel buzz is barely audible, but right channel buzzing is exactly the same as if there was no screw connected to chassis.
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Old 13th September 2017, 10:41 AM   #343
Burnedfingers is offline Burnedfingers  United States
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Originally Posted by ViperZ View Post
The manual says "The input jack chassis ground is the ONLY chassis ground in the amplifier". So they specifically mean that that one screw connecting negative end of RCA connectors to the chassis is the only ground connection.

What worries me is that right channel buzzes much louder than left when not connected. If the screw connection between chassis and the board/RCA is disconnected, both channels buzz loudly and evenly. When the screw is connected, left channel buzz is barely audible, but right channel buzzing is exactly the same as if there was no screw connected to chassis.
I'm sorry its been 20+ years since I saw a Apt power amp. I don't believe I even have a schematic for one anymore. Are the RCA jacks a molded one piece assembly or are they individual jacks that are insulated from the chassis?

There seems to be a slight ground problem in my opinion. I've seen this same problem with Gas Son of Ampzilla's. I can remember one years ago that I ended up insulating the RCA's from the chassis and soldering a 10 ohm resistor from the RCA jack to ground. The problem was solved and I had a amp that was 100% quiet.

The fact that there is no noise with the input of the amp is terminated to the output of a preamp makes me say simply leave it alone unless you have the experience and gear to check out the problem.
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Old 13th September 2017, 02:06 PM   #344
ViperZ is offline ViperZ  Canada
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It's a single piece, which has a negative portion all around the block (soldered into the board and to the mounting bracket - mounting bracket is in turn connected to the chassis with a mounting screw.

I have gear and experience, but at this point I don't think it's an actual problem. It looks like it's the way the wires are laid out inside the amplifier.

Most wires come out on the 'left' side of power board, so they are much closer to the left channel. All right channel wires are longer and have to go right beside transformer.

There is no real way to readjust those wires. The chassis is packed when the boards and heatsinks are screwed up in their final positions. I tried moving wires around with a wooden pick, and I can hear the change in buzzing for sure when the wires are being moved. There is just not much space to reroute those wires.

Ideally I may have to take out the right channel assembly, the power supply board, and reroute the wires as from the transformer as possible, which will move them by a few mm at most.
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Old 13th September 2017, 03:46 PM   #345
ViperZ is offline ViperZ  Canada
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This is what it looks like inside between right channel, transformer, power board, and filter caps under the power board.
Attached Images
File Type: jpg IMG_20170911_223719.jpg (179.4 KB, 49 views)
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Old 13th September 2017, 09:20 PM   #346
Burnedfingers is offline Burnedfingers  United States
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Did you try changing the input wire with a shielded wire and attach one end of the shielded wire to ground and float the other end?
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Old 13th September 2017, 09:55 PM   #347
ViperZ is offline ViperZ  Canada
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Originally Posted by Burnedfingers View Post
Did you try changing the input wire with a shielded wire and attach one end of the shielded wire to ground and float the other end?
That probably should work, I can try that I guess.
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