Mainline: Simultaneous Output from both Headphone jacks

aarumugham · 1071

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Offline aarumugham

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Hello all.

Quite frankly, I am absolutely shocked that the Mainline kit works at all. I have ZERO experience with electronics and soldering, but thanks to the excellent instructions, I was able to pull off a successful build and I am extremely pleased with it. I think it sounds great.  Hats off to the Bottlehead engineers for creating a well thought out kit with idiot proof instructions for people like me!

Here's my issue: I have two headphones plugged in simultaneously - one into the balanced jack, the other into the unbalanced. Strangely, there is sound output from both at the same time regardless of which way the switch is toggled. If I select balanced, the balanced headphone will sound a bit louder and vice versa.

So, is there something wrong with my wiring? All voltage and resistance measurements were spot on when testing. All tubes light up.

While the volume is loud enough for me, it seems that it is a bit low - for my turntable, I am on the 0dB on the coarse and for my CD player, I am on the -3dB - so towards the higher levels. These are not loud - just comfortable volumes.

I wonder if there is some sort of crosswiring but I can't seem to find it.

I am using Focal Clear headphones on the balanced output and some old cheap audiotechnica ath-m20x ( which sound surprisingly good on this amp)

Thanks in advance for any advice.



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Reply #1 on: January 13, 2019, 05:24:22 AM
Hi AA - Congrats on the build!

How is the volume with only one set of headphones plugged in? I wonder whether asking the amp to drive two sets at the same time isn't sucking up all the power output capacity of the amp - just a uneducated guess on my part.

Offline Paul Birkeland

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Reply #2 on: January 13, 2019, 06:28:42 AM
If you have both headphones plugged into the amp at the same time, you will load the amp down more than just having one plugged in at a time.  This is especially true with the two pairs of headphones you have, which are both around 50 ohms.  The Mainline should sound quite a bit better if you only plug one pair of headphones in at a time, and there should be a bit more gain.

The switch is functions to move the ground reference depending on which jack you use, but the amp is not designed to have both jacks used at once.   

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline aarumugham

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Reply #3 on: January 13, 2019, 04:26:21 PM
Thanks, guys, for the quick reply.

The volume with both plugged in doesn't really change, although there is a difference in the sound - a bit flatter, perhaps?

At any rate, it seems the amp is working as it should. I unplugged the old ones and just keep the focal clears in the balanced input.


Offline adydula

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Reply #4 on: January 14, 2019, 05:29:12 AM
How do you like the Focal Clears with the Mainline?
Do you have any other cans you use with the Mainline as well?

Interesting to hear your experience.