Balanced headphone out question.

[dcham]

I noticed that there is audio on both the balanced and unbalanced outputs at the same time. The balanced and unbalanced switch just has slightly different level with the unbalanced position sounding a bit more open. I had the amp built for me by my studio's tech. Did he wire something wrong? Should not there be no audio out the balanced output when single ended unbalanced is selected, and vice versa? Likewise HiZ and LoZ outs have only a subtle difference. I am using a Sennheiser HD800 wired for balanced 4 pin operation, HiZ and my Westone 4 to listen unbalanced LoZ.

Please kindly let me know if this is normal. Thanks!

[Paul Birkeland]

Yes, there will be signal voltage present on the unbalanced output when the switch is set to balanced operation.

In this instance, however, if you use an unbalanced pair of headphones with the switch set to balanced, you only use half of the secondary winding on each output transformer, leading to less power, and unusual frequency response (but no harm to your headphones or Mainline).

-PB

[Paul Joppa]

PB is absolutely right.

When I designed the switching arrangement, I made sure that both outputs would at least provide a signal in all cases. The balanced/unbalanced switch just optimizes performance for that particular case. In other words, it's feature, not a bug!  :^)

[dcham]

Thanks guys. Very happy with the amp. Running it with an HD800 and the only mod I did with it was to replace the single ended plug with a 4 pin Neutriks XLR. Sounds great with none of the harshness people say the HD800 has.

[Loquah]

I know this thread is a little old, but hopefully someone will see this...

I'm currently finalising my comparison of the Crack, S.E.X. and Mainline over on Head-Fi and for the Mainline review I'd really like to know if switching to Unbalanced will deliver an unbalanced signal via the XLR socket? In other words, can I listen to the difference between balanced and unbalanced just by throwing the switch while connected to the XLR socket?

[Paul Joppa]

Not as easy as you'd think.

Yes, throwing the switch to unbalanced will ground the negative pin of the XLR.

However, I understand that some people feel the audible difference is due to the separate ground-or-negative wires in the cable for each channel, instead of the shared ground in normal unbalanced wiring. Using the XLR connector won't change the cable wiring.

[Loquah]

Interesting. Let me see if I understand...

My T1s are wired to a 4-pin XLR. For unbalanced setups I use a 4-pin to 6mm fly lead. Are you suggesting that this type of wiring (where the ground leads share a common earth in the 6mm jack) is different to shorting the XLR -ve pins?

[Paul Joppa]

Wow - so sorry this nover got responded to. I use the "show unread posts" function, but it's been really unreliable the last month or two, at least for me. I'm trying to go through each sub-forum looking for unread posts and just saw this one today.

I'm not at all up to speed on headphone wiring schemes, so I'm just responding to this in hopes someone who does know will join in.

[mcandmar]

Interesting. Let me see if I understand...

My T1s are wired to a 4-pin XLR. For unbalanced setups I use a 4-pin to 6mm fly lead. Are you suggesting that this type of wiring (where the ground leads share a common earth in the 6mm jack) is different to shorting the XLR -ve pins?

With the amp in unbalanced mode it should be exactly the same.  Only difference is instead of the two - lines being joined together in the TRS connector of your adapter, they are joined together internally at the switch.  Or in the case of my SEX amp at the impedance switch boards.

Have a read of this thread http://www.bottlehead.com/smf/index.php/topic,5043.0.html as it helped me get my head around how the output transformers are wired for balanced/unbalanced operation.  AFAIK the mainline is the same except the switches are on the top panel vs the impedance switch boards. i.e. theory is the same.

[Lambert]

It is a pretty old thread but it triggers my curiosity. I did a test on both balanced and unbalanced inputs with my HD800.

1. Unbalanced Input- The sound was more open when I switched to unbalanced mode of the amp. If the switched was turned to BAL, volume was dropped a bit and the sound stage diminished.
2. Balanced Input - I did not really notify any audible differences between BAL and UNBAL setting. Volume was the same regardless of the switch. Is it normal?

By the way, Can I put in 2 headphones, one in balanced and one in unbalanced input at the same time? I dare not try it because I am afraid it would draw too much current and ruin the output transformer.

[Paul Birkeland]

It is a pretty old thread but it triggers my curiosity. I did a test on both balanced and unbalanced inputs with my HD800.

1. Unbalanced Input- The sound was more open when I switched to unbalanced mode of the amp. If the switched was turned to BAL, volume was dropped a bit and the sound stage diminished.
2. Balanced Input - I did not really notify any audible differences between BAL and UNBAL setting. Volume was the same regardless of the switch. Is it normal?

Is this balanced inputs or outputs?  On which amplifier?  If it's a SEX amp with the switch kit, the balanced setting is not intended to be used with the unbalanced headphone jack.

By the way, Can I put in 2 headphones, one in balanced and one in unbalanced input at the same time? I dare not try it because I am afraid it would draw too much current and ruin the output transformer.

Depends on the amp and the headphones.  It won't be an issue of stressing the output transformer, but more likely that several different headphones will play with very different output levels when connected to the same amplifier.  Again, if this is a SEX amp, it's not intended to do this.

[Lambert]

Hi PB,

I am testing the HD800 with Mainline.

1. I plugged HD800 into the Unbalanced output of Mainline and tested the sound with both BAL or UNBAL setting. It's seemed to me that the volume and sound stage was lower when the switch was turned to BAL.

2. I plugged HD800 into balanced output of Mainline then. I didn't find any audio differences regardless of the position of the BAL/UNBAL switch. Is it normal? Or there is audio differences that my ear could not figure out.

As what you said, I can put in 2 headphones into Mainline at the same time through balance and unbalance output respectively. The drawback is only different output levels, isn't it?

[Paul Birkeland]

1. I plugged HD800 into the Unbalanced output of Mainline and tested the sound with both BAL or UNBAL setting. It's seemed to me that the volume and sound stage was lower when the switch was turned to BAL.

That shouldn't be surprising.  The balanced switch setting moves the ground connection, and when using the unbalanced jack, you've given up on a bunch of the copper on the secondary winding.

2. I plugged HD800 into balanced output of Mainline then. I didn't find any audio differences regardless of the position of the BAL/UNBAL switch. Is it normal? Or there is audio differences that my ear could not figure out.

It will be more subtle on that jack.

As what you said, I can put in 2 headphones into Mainline at the same time through balance and unbalance output respectively. The drawback is only different output levels, isn't it?

You'll want to leave the amp set as unbalanced, then yes, you'll just have unequal output levels.  If both headphones are very low impedance, you may also end up with a bit more distortion than you'd like.

-PB

[Lambert]

Thanks PB. At least I know a new feature to support 2 headphones by the Mainline.