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September 24, 2022, 08:07:57 PM

Author Topic: Freshly completed build - questions re: hum and blown fuses in power amp  (Read 582 times)

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Offline pboser

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Can you try another interconnect?  I've had some of those Monoprice interconnects with RCA plugs that are so tight that it seems like a choice between a good connection and breaking something.  It's always a good idea to rule out the simple things in these frustrating troubleshooting situations.
Best of luck with it!
Peter Boser

Offline cacofonix

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@Paul
- Yes, there is still noise with Moreplay driving the Krell amp
- I find it odd that the noise persists with volume all the way down and even with Moreplay powered off!

i.e.
- If I connect the Krell amp to the peachtree = no noise
- If I connect the Krell amp to nothing = no noise

If I connect the Krell amp to the Moreplay = I get noise

Note: I also get this to reproduce with my main systems which is using an MC462 Power amp - but im not using that to test regularly.

Thankfully - no fuses have blown now - I am being a lot more careful about powering things down and starting up with volume pots all the way down. Any guesses for what was causing that short?

Any thoughts on what to do or try next?

@pboser - I just bought new interconnects from WBC to try that theory as well but the noise persists across interconnects. You are right about the monoprice ones being rather tight

Offline Paul Birkeland

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- I find it odd that the noise persists with volume all the way down and even with Moreplay powered off!
Try this again, then slip the power cord out of the Moreplay while it's off.  I would bet the noise goes away.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline cacofonix

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You are correct / win the bet @Paul - your drink of choice on me

With the moreplay powered down, but connected to the Krell, I still got hum

Then when i slip the power cord out of the Moreplay - the hum is gone

note: both devices are using 3 prong plugs plugged into adjacent plugs on a power strip I've been using here for a bit

So, what that tell you? and/or what can I try to do next?

Offline Paul Birkeland

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The Moreplay will probably be perfectly quiet on a cheater plug.  We don't typically recommend/like doing this, but it may be a good option in your case.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline cacofonix

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So, are you thinking that this is a ground loop thats being created between the moreplay and krell/mcintosh ?

1. What do you recommend I do with that jumper wire i have in temporarily?

Should I
- leave that in there as-is
- solder it in place
- remove


That did not effect noise in any way, but might have positively impacted the blown fuses or is that something else you think?

Offline Paul Birkeland

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You could try with and without the jumper.

There was a stretch in the time back in the day where what was/wasn't earthed in audio components was a little more loosey goosey than it is today, and perhaps the Krell is from that time period (roughly 1990-2005 or thereabouts). 

Leaving the jumper in won't hurt anything if you end up putting the Moreplay on a cheater plug. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline cacofonix

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Thanks for all your help Paul (and others on the forum)