The more I know.......need help with speaker hum

ukcolin99

I know I can rely on you guys to confirm I am master of my Audio domain or....not, usually with wit & wisdom.
Regular readers know I recently put my Parasound P5 Preamp between my Cambridge 851D (operating as a DAC) & Parasound A21 (operating as an Amp (haha)) sounds great.

Noticed this weekend a week after I replaced my Better Cables RCA Cables - 1.64 feet (1/2 meter) - Silver Serpent Anniversary Edition Audio Interconnect Cable with Silnote Audio Morpheus Reference Series II RCA 1m 24k Gold/Silver Interconnects I have a hum out of both speakers. (It is possible hum was present after install of the new RCA's, I did not notice (volume low, singling loudly, dog barking etc).

I do know the hum is significantly louder with the Silnotes in place. When I replace with the Better Cables hum is lower. I figure Silnotes provide louder (clearer?) signal. Hum increases and decreases with volume changes on the P5.

No other cables changed, I use AudioQuest Cinnamon USB Cable out of my MacPro, Better Cables Silver Serpent II Balanced XLR Audio Cable - 1 meter (3.28 feet) between P5 & A21 & Pangea Audio AC9 MKII Power Cord between amp & wall, Pangea Audio AC 14SE MKII Power cable between 851D & wall & P5 regular power cord into Furman PL-Plus C. (Nothing fancy)

Hum was not present when I first added the P5 into the system. When P5 is removed from chain with no other changes, hum is gone. 851D operating as DAC/Preamp directly into A21 has no hum at any volume.
To me the problem is the P5 (purchased new in October) & I should call Parasound, wadya think?

motorhead43026

If you remove the 851D with the P5 still in the chain does the hum disappear also?

JPete

I don't think a ground loop hum would increase or decrease with volume adjustment on the preamp.. Maybe wrong there, but I've encountered a few "hums" but nothing that changed with volume. Is it really a hum or a maybe a hiss??

Dennis Gardner

If the hum increases with volume, then it is getting into your system at or prior to the preamp. You need to hook up just the amp and speakers.....no hum, then add the P5....if no hum then add the 851......if no hum add the source.

This will help determine the exact point of entrance into your system.

ukcolin99

Thanks guys 'going home to play with everything. I (my son) changed the hd to ssd last weekend in the Macpro (where iTunes lives) which froze yesterday, as skip, mhead & DG say I need to finish connecting & checking combinations find the source/cause. I did have new AC system installed couple of weeks ago.....

erniejade

How are they plugged in? If I have my amp plugged into the power conditioner, I get s hum but strait to the wall, no hum ( crazy right?.)

Is it all in a strip outlet, a conditioner? Both?
What source? For a while I had a hum issue of my laptop was turned on. With the laptop off, all was quiet.

Emlyn

Is the ground lift switch activated on the back of the A21 amp?

westmassguy

Sounds like a ground plane differential. Try daisy-chaining a single, 20-22 gauge wire from a chassis screw to each component.

ukcolin99

Thanks for the feedback, appears source of the hum is at least connected to the USB out of the MacPro. Suspect it may be related to me changing HD to SDD, not removing the old Hard Drive and/or connections in the Mac or a Ground issue in the Mac.
Temporarily(?) using Toslink into the 851D into the P5 sounds great to me.

erniejade

Glad you are on the right track and got it almost hammered out!

ken brydson

erniejade wrote: »

Glad you are on the right track and almost hammered!

Story of my night right there...