Bottlehead Forum

Bottlehead Kits => Mainline => Topic started by: Loquah on October 11, 2013, 02:09:29 PM

Title: Fully balanced setup
Post by: Loquah on October 11, 2013, 02:09:29 PM

Hi all,

Does the stock design of the Mainline allow for input from a balanced source or only single ended? I was wondering if the 2 sets of SE RCAs combine to accept a balanced signal when the switch is set to balanced.

Title: Re: Fully balanced setup
Post by: Doc B. on October 11, 2013, 02:26:24 PM

Mainline's line level input is single ended. That balanced/single ended switch is for the output to the headphones. You would have to customize the amp by installing input transformers to used balanced input cabling.

Title: Re: Fully balanced setup
Post by: Loquah on October 11, 2013, 03:46:53 PM

OK. Thanks Doc.

Happy to stay single ended on the input because I'm not modding the Mainline. I have a balanced DAC coming so was going to make up an XLR-RCA lead if there was any benefit.

Title: Re: Fully balanced setup
Post by: Tubejack on October 12, 2013, 07:35:37 AM

A few years ago I built a RCA to XLR "box" that basically allowed me to go XLR to RCA, either in or out, or even RCA/RCA or XLR/XLR with a DPDT switch in each channel to allow me to play with the 'phase' of the signal - I wanted to experiment with 'absolute phase' of various input sources, etc.  I would have to look-up which Lundahl's I used.  It's a tool that has paid for itself over the years as DIY pieces moved in and out of the system, taking into account impedance, etc.

Title: Re: Fully balanced setup
Post by: 4krow on October 12, 2013, 10:35:17 AM

Although I am intrigued by the box you have made, it is a little beyond my understanding. The part that I am unsure of is the use of transformers to produce a balanced output. I assume that they are a 1 to 1 winding ratio, but how does impedance play into the mix?

Title: Re: Fully balanced setup
Post by: Paul Birkeland on October 13, 2013, 07:16:21 AM

Balanced and Unbalanced interfaces with transformers (http://www.jensen-transformers.com/an/an003.pdf)

Title: Re: Fully balanced setup
Post by: 4krow on October 13, 2013, 08:11:11 AM

Paul,

 WOW  that is a keeper. I saved it to my info files for reference. Guys, this is why I stick around. Few sites offer the experience/knowledge rather than just an offhand opinion. I continue to value the BH site.

Title: Re: Fully balanced setup
Post by: Tubejack on October 16, 2013, 02:38:29 AM

I looked in my files and that's the AN that prompted me to build the box in 2009.  Great catch, Paul.  Thanks for the reminder. 

And I fully agree with 4krow's comment.