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Swapping out filter caps


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2 hours ago, CECAA850 said:

While your modding, what color power LED do you have on your amp?  Now would be a good time to swap it out.  The red ones sound a little hot, blue ones sound cool. 

 

Power switch is red. The channel LED's only activate with clipping, so probably don't need to worry about them coloring the sound. I'm more concerned about the chassis paint - the front is black, but top case and rear panel are grey - sure that's making the sound too analytical?

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Ha, not yet. Two channels work without issue, so I put the amp back into service after taking pictures and have been running in 2.2 mode for the last couple weeks. I need to just bump everything up to the AVR for power and then pull the amp  back out of the rack and start disassembly, order the smaller caps, and begin replacement.

 

I've also been cleaning out my garage and reorganizing so that I can use my soldering station rather than the kitchen table. And it's ridiculously hot outside still. Soooo.. lots of moving parts.

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  • 1 month later...

Replaced all the caps tonight, put it all back together, and the hum is back - though much more clear and pronounced.

 

So back to troubleshooting - fairly certain it's not a ground loop, but I'll lift the ground on amp and test just to be sure. Otherwise I'll dig back in and see if it's something related to the line level inputs.

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well two channels are consistently staying quiet. the other three keep flip flopping as I power the amp off and on to try different connection combinations. the fact that it happens with nothing but speakers connected still points to it being isolated at the amp.

 

I guess i can start replacing fuses (there's two per amp module)? I did notice that most of the chassis RCA jacks had just the slightest bit of play on the center post.

 

The maddening bit is that I can observe the hum fading out in real time, it's constant and unaffected by input volume, all channels play their input content, and the hum can appear/disappear sometimes by just power cycling or by reseating cables and power cycling, etc.

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On 10/12/2019 at 10:40 PM, Thaddeus Smith said:

I did notice that most of the chassis RCA jacks had just the slightest bit of play on the center post.

I think that the outer portion of the RCA's are all tied together.  They look alright?

 

Tried wiggling the RCA's up and down to see if it makes an audible difference?

 

I wish I could remember Paul Hovenga's forum name.

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I've gotten some static when moving RCA cables around willy nilly, though it's different than the hum and I worry about blowing drivers - which is why now I'm powering off/on every time I try to isolate the cable issue. Unfortunately, this adds another potential variable since that results in a discharge/charge of the power delivery system. I did have Morgan sit and listen while I moved the cables around - fully seated - to see if there was any proximity to power cables causing hum, each other, RCA connectors touching, etc and she did not observe any change.

 

Remember that my gear is in a closet and isolated from the MLP, so it's difficult for me to be fiddling at the back of the rack and see if there's any change in behavior in output. The most noticeable changes I've observed are when I just sit there on the couch out of frustrated resignation and the hum just fades to black.

 

It's literally this scene right here..

 

 

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28 minutes ago, CECAA850 said:

Never shut it off again.

 

That's sorta what I had been doing prior to the cap swap this past weekend. The DB-25 based 12v trigger is a bit wonky and I don't get any sort of noise when turning the AVR on/off while it's still powered on (same for my subwoofer amp). So yeah.. probably will just leave it on.

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  • 6 months later...

With regards to audio v. non audio, this is one manufacturers take on it from their spec sheet:

 

Overview

KEMET's ALC10S Series of capacitors features improvements in general construction of the capacitors to achieve better results in audio, where fidelity of the waveshape is very important. Great attention has been paid to the construction details that can affect performance such as foil type, its connections and mechanical construction. Details of capacitance and case sizes are available in KEMET's slit foil capacitor range.

 

Applications

Modern electrolytic capacitors are designed for use in power supplies, thus, most aspects of their design have been optimized for this application. Some advances in design may not be beneficial in audio applications where the requirements of the capacitors are very different.

 

KEMET has produced the ALC10S slit foil capacitors specifically for audio applications. Its patented design eliminates circulating currents in the aluminium foils. This spurious current flow on the capacitor plates is known to occur but not apparent in most applications.

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