Little Dot MK2 (Noise) please help (Audio files are provided)

[bikingbuddha]

From a hand full of reviews I read, there was only a minimal amount of hum at high volume. Does it make noise with nothing plugged into it but headphones, and with everything you had plugged into it turned off and disconnected? Did you try setting the dip switches inside to better match your headphone impedance?

Alright... let me be a little clear on this. Sorry if I got you lost and confused!

Gain stage 1 (lowest) - No noise on HD-6XX, others there is noise but very minimal (Not a hiss) (others are iem's and monk plus)
Gain stage 2 - No Noise on HD-6XX until I pass the 80% at least on maximum volume (very minimal). Others have the noise all over the volume range
Gains stage 3 - No noise on HD-6XX until i pass the 70% to 80% Mark (Minimal). Noise in all others (Lower impedance and iems)
Gain stage 4 (Highest Gain settings recommended for High impedance headphones) - Noise all over the volume range even on HD-6XX

* This noise goes up and down with volume controller.
* This noise is there regardless of what is plugged or not...!! just the amp connected to a completely isolated powerline even outside the house next to the main power board meter. The noise is there.

 

[bikingbuddha]

Here is the update.

Last night I got all my audio equipment together and figured out that this noise is coming from the electricity not the amplifier. Yesterday when I pulled up my gear to listen to some music, the noise was higher. This effects only tube amplifiers...! it doesn't effect solid-state stuff like FX Audio DAC-X6. Now I'm looking for a cheap and easy solution to get rid of this.

 

[Dandy]

I wonder whether an isolation transformer would work? It's a useful bit of kit to have anyway, if you work on valve equipment.

 

[Lavane]

Get a power conditioner?

 

[macaltec]

I have the Little Dot MKII with HD650 cans. Very quiet piece of gear. If Im not mistaken it is an OTL design. It is a great sounding piece. Hope you get it sorted.

 

[bikingbuddha]

At the moment I am waiting for the 100ohm resistors to arrive so I can build an artificial center tap to see if that could help. I will update soon as I see some light at the end of this buzzing noise tunnel.

 

[bikingbuddha]

First of all, I want to thank all of you who helped me to solve this problem with my little dot mkII, without your suggestions and advice I could have never done this.

I was right about it. Today I go the 100ohm resistors and what I did was solder a resistor to each of the filament pins of gain tubes (in my case Mullard C8100 and grounded them). It works 98% successful and that's all I need.

Now I can run any headphone on Gain setting 4 (highest) without any buzzing or hum. Here are the test results.

HD6XX there is no noise at all (100% Succesful in all gain settings)

V.E Monk Plus (98% Successful. Absolutely no noise unless I put gain settings to 4 and crank the volume to the highest end) This is unnecessary since it is unbearably loud at 5% volume in high gain settings.

V.E Bonus IEM (Same story as Monk Plus)

KZ ZS5 - This is also 100% successful, zero noise, zero buzzes, and hiss. Completely black background in all volume levels. (Unbelievable since it is a hybrid of Dynamic and balance amateurs )

The above stuff is based on my hearing. Not from graphs or any other things because I don't need that accuracy plus if it doesn't bother me, that's all that matters.

Conclusion & Solution.

"Artificial Center Tap" with 100ohm resistors work flawlessly.