[Supperconductor]

Hi Guys,
 
I'm new to balanced headphone drive. I currently have a pair of Sennheiser HD-600's and I want try them out with balanced cables. I also own an Audio Research LS-25 tube pre-amp (with no headphone output) that is part of my main home stereo rig.
 
Is it possible to satisfactorily drive the HD-600's from the balanced pre-amp output of the LS-25? I think the partial answer is not directly since the LS-25 outputs a out-of-phased balanced signal that needs to be summed first before it can drive the headphones, correct?
 
- Kam
 
EDIT:
 
I also have mothballed an Audio Research LS-7 single-ended line stage that I could press into service for this function as well.
 
Links for reference:
 
http://www.audioresearch.com/LS25.html
http://www.arcdb.ws/LS7/LS7.html

 

[El_Doug]

The answer is that this should be entirely possible.  The whole point of balanced headphones is that the ground for each channel is replaced by the inverted phase signal - really a bridged connection.  FYI, summing the two phase signals would result in nothing at all
 
Why dont you plug in and tell us how it sounds?

 

[Supperconductor]

OK, I was just worried about damaging something in the chain. I'll give it a shot and see what happens.
 
- Kam

 

[JB197]

Hi, the first version of LS-25 had cathode follower outputs sitting on current-source field effect transistors. The mk2 version deleted the field effect transistors for marketing reasons and went back to resistor loading of the output followers. Both versions were capacitor coupled.
 
The output source impedance of a LS-25 is around 600 Ohms, and it's not going to like being loaded down by the headphones at all. (It will not cause damage though). I don't know what the current flowing in the output followers is, but I think it's likely to be low because it's designed to feed a 20 K Ohm amp input, so it isn't likely to be great driving headphones.
 
So it's going to have a lot of harmonic distortion and colouration. It's up to you if you like that or not.
 
: )

 

[Supperconductor]

Wow, that's a very helpful assessment of what I'm likely to experience. Thanks for the info. I already have a pair of balanced cables for the HD-600 but the gender is wrong. So I'm going to order some XLR gender changers this week and have a listen.
 
- Kam

 

[Supperconductor]

Well I tried it. And it didn't sound so good 

. The low end sounded fairly neutral, clean, and articulate. The high end got quite messy - very swishy and squishy. So I guess I'll need a headphone amp after all, but that is a matter for a separate thread I think.
 
- Kam