[JaymzN]

Hi there,
 
I recently purchased a Littledot MK V. Only has about 20 hours burn-in with my DT-880's but I'm absolutely loving it!
 
Chain is;
 
PC USB--->X-Fi Surround (Optical/SPDIF out)--->HR Ultra Micro DAC--->LittleDotMKV--->DT880's (250ohm)
 
 
Now the problem is when I try use my HFI-700's. Apparently, the MKV is rated for 32ohm-600ohm and my HFI-700's are 75ohm. So that's well within recommendations. But I get loads of hiss when using them. The hiss is definitely from the MKV, I get it when they're plugged into it regardless of whether it has signal or not and regardless of what level the volume is at.
 
Is 75ohm too low for the MKV? With my DT-880's I can barely hear the hiss which makes me believe it's an impedance issue.

 

[john57]

[size=medium]Is the noise a buzz or a hiss? Do get the hiss when you disconnect the RCA cables in the back of the amp on both input one and two?[/size]

 

[JaymzN]

Quote:

[size=medium]Is the noise a buzz or a hiss? Do get the hiss when you disconnect the RCA cables in the back of the amp on both input one and two?[/size]

 
I would class it as a hiss. Still present when RCA cables are disconnected (no difference) and present on both channels. Only stops when I turn the amp off.
 
Again, it's almost inaudible on my DT880's. But it's quite high on my HFI-700's.

 

[john57]

 
[size=12pt][size=12pt]On what setting the volume control is at? It seems that your HFI-700 is more efficient and therefore you would hear the hiss more. On many amps you would normally hear some noise at 90 to 100 percent of the gain control and this will vary depending on gain factor of the amp and the efficiency of the device that is connected to the output. You are more likely to hear hiss with an in the ear type headphones because of greater efficiency and with the extra gain of outboard amps. If you hear the hiss at the normal operating range of the gain or volume control I would try to carry the amp and headphones in another room to see if any interference can be rule out.   [/size][/size]
 
 
 

 

[JaymzN]

It doesn't matter where the volume knob is, I hear the hissing at the exact same volume from 0 all the way up to about 80+. From there on I hear some more hissing, but I can tell that's actually gain noise which is different and understandable.
 
Since I posted last I've noticed something though. My Mk V came with this odd looking 1/8 to 1/4 adapter (has two parts and exposed wires). If I use that, there's no hissing anymore. Is it some sort of impedance adapter???

 

[john57]

[size=12pt][size=12pt]I did some research and you are right the Little Dot Mk V which  is a solid state amp from my understanding and may have a 120 ohm impedance adapter. [/size][/size]
 

 

[JaymzN]

That explains it!
 
I'll just use the adapter for when I'm using the HFI-700's or anything with lower impedance then. Cheers for the help!