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SUPPORT FORUMS FOR ZKITS >> ZKIT 1 Support forum >> Completed ZKIT...With Questions about hum !
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Message started by nipsy on 02/22/22 at 07:09:20

Title: Completed ZKIT...With Questions about hum !
Post by nipsy on 02/22/22 at 07:09:20

A big thank you to all who have come before, asked, answered, and commented upon questions posed here. Starting as a complete novice, I've built my first functioning amplifier and I'm quite pleased with the sound and what I assume it is when people speak about the hologram.

I'd like to add the anniversary mods, but am not sure how to find space for them given my current configuration. Eventually I'd like to put it into a box, but at the moment that's way beyond my design and execution skill set.

After nearly 20 or so hours in, I'm noticing 2 sources of minor hum. Sitting in a chair 10+ feet from the speakers and 15+ feet from the amplifier, I hear no hum at all, just pure, sweet music.

First hum is evident in the area of the PCB and transformers. This is a buzzing, electrical energy type hum. I've heard something similar standing beneath high voltage wires in a field somewhere in Ohio.

It's obvious when I'm flipping a record, but seems nearly non existent when I'm 5 feet away...except I *know* it's there.

2nd hum is more of a true hum and it comes out of the speakers. It is faint and I have to put my ear next to the speaker to hear it. At 3-4 feet it becomes inaudible. An input attached or unattached does not affect the presence of the hum.

Once music is playing, I hear nothing but the music, but again, I *know* those hums are there.

I have a couple of hypotheses.

First: I left all wires coming from the input and output transformers quite long as I'll be making structural changes to the mounting. Might this be causing some interference ?

Second: grounding of the potentiometer case. There were instructions to do this, but I'm wondering if I did it correctly.

Thanks in advance for any ideas y'all might have.

Title: Re: Completed ZKIT...With Questions about hum !
Post by nipsy on 02/22/22 at 07:10:45

Picture of build:

Title: Re: Completed ZKIT...With Questions about hum !
Post by Lin on 02/22/22 at 15:00:04

Twisting the power transformer wires might help and it wouldn't hurt to twist the speaker output wires since it looks like they go under the circuit board.

Title: Re: Completed ZKIT...With Questions about hum !
Post by nipsy on 02/22/22 at 17:56:54

Thank you, Lin. I'll give that a try this afternoon.

Title: Re: Completed ZKIT...With Questions about hum !
Post by Core32 on 02/22/22 at 19:00:13

I think the transformer hum is mechanical in nature (winding vibration?) and will be nearly impossible to completely remedy.
I use the Edcor transformers too and even with grommets for the mounting holes I still get the slightest bit of hum when I place my ear near those. My understanding is some vibration is normal.
Shortening and twisting the transformer wiring may eventually help your hum coming from the speakers.
If you twist the power transformer wiring do not twist the AC input wires with the output wiring.
The AC from the wall is likely a big source of noise and you do not want to couple that with the output wiring.
For sure I had major hum caused by improper grounding of the RCA input jacks.

Title: Re: Completed ZKIT...With Questions about hum !
Post by nipsy on 02/23/22 at 07:08:34

Braided the wires and neatened everything up a bit. I bought miflex capacitors for the anniversary mod, but they are way too big so I'll not install them at least on this presentation. No change to speaker or transformer hum.

I did notice that the transformer him increases with proximity to the tone arm and cartridge. I've tried to separate them as much as I can, but those two lovebirds can't be apart. .

Since I can't hear any hum from where I sit and the ringing in my ears is louder than the hum in any event, I'll just "hang it up and see what tomorrow brings."

And with that, another side of a record !

Title: Re: Completed ZKIT...With Questions about hum !
Post by ArtMan on 02/23/22 at 19:34:00

I did notice that the transformer him increases with proximity to the tone arm and cartridge.

I had the same problem many years ago with my VPI Aries tonearm and Grado cartridge. The hum was related to the proximity of the turntable motor to the cartridge. I ended up buying a flywheel to put between the motor and the chassis. That pretty much eliminated the hum via the additional distance between the two.