Amp/Preamp Asylum

Looking for a new Amp or Preamp? If you're after tubes, post over here.

Return to Amp/Preamp Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Question on stereo/balanced circuits

98.216.185.239
Posted on November 27, 2015 at 15:06:17
Dimitry
Audiophile

Posts: 457
Location: Massachusetts
Joined: January 26, 2006
 I have a balanced SACD player - Oppo 105 - that I would like to tube buffer with a balanced unit. All the balanced tube buffers I see are quite expensive. However, I have several MF 10DV3 SE buffers.

So my question is, can I use a stereo buffer to act as a balanced unit with the right XLR to dual RCA adapters on both input and output? Or will I need to have a phase splitter there as well - which would negate the whole "inexpensive" approach.

I guess it would depend whether standard SE RCA signal is always above ground in voltage potential or is positive/negative. I suspect it is always positive.

 

Hide full thread outline!
    ...
RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 18:02:24
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 An unbalanced AC audio signal alternates between positive and negative relative to ground.

Each leg of a balanced AC audio signal alternates between positive and negative relative to ground. The two legs are 180-degrees out-of-phase with each other.

 

RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 18:42:42
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 Actually not quite correct. In a true balanced set up the signal goes between the plus and minus and not referenced to ground.

From Ralph in an old OTL post -

"But what the standard calls for is that ground should be ignored. This eliminates hum and buzz as well as cable artifacts. But to do that the output of the preamp must occur between pins 2 and 3 of the XLR and have nothing to do with ground (which is pin 1)"

You can do what the OP wants but it will be referenced to gound and one signal must be 180 out of phase.
Dan Santoni

 

RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 19:32:22
Victor Khomenko
Manufacturer

Posts: 55319
Joined: April 5, 2000
 ***Actually not quite correct. In a true balanced set up the signal goes between the plus and minus and not referenced to ground.***

The typical high-end balanced interface does not follow that model, and each leg of signal indeed moves around the ground.


 

RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 20:06:44
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I don't think you are correct. I have a Pass Labs X1 control preamplifier that Pass Labs claims is fully balanced, yet it never looks at the difference between Pins 2 & 3. It carries the signals on Pins 2 & 3 from input to output without ever combining them. In other words, it has four discrete channels -- two for the left stereo channel and two for the right stereo channel. It processes the signal on Pin 2 relative to Pin 1 and the signal on Pin 3 relative to Pin 1 from input to output without ever looking at the difference between pins 2 & 3. Any in-phase information on pins 2 & 3 will be canceled at the differential input of the power amplifier, or with respect to the tape output, at the differential input of my TASCAM DA-3000 digital recorder.

Best regards,
John Elison

PS. Here's what the X1 Owner's Manual says:





 

RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 20:17:15
Dimitry
Audiophile

Posts: 457
Location: Massachusetts
Joined: January 26, 2006
 So,

If I use an XLR to dual RCA adapter and send the in-phase signal to the left channel of the tube buffer and the out-of-phase signal to the right channel, then use the dual RCA to XLR adapter on the output...

Will the output XLR jack have an actual buffered balanced signal? Can I run it safely into a standard balanced preamp input?

 

RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 20:58:20
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 A little complicated, but it will work.


Dan Santoni

 

RE: Question on stereo/balanced circuits, posted on November 27, 2015 at 20:59:17
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 Not disagreeing with you Victor. Just pointing out John's definition was not completely correct.
Dan Santoni

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 07:05:52
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 > In a true balanced set up the signal goes between the plus and minus and not referenced to ground.

I realize that the balanced signal is extracted by taking the difference between Pins 2 and 3, but every circuit I've ever seen has a reference point called circuit ground. Therefore, it is my understand that the individual signals on Pins 2 and 3 are always referenced to circuit ground. Are you suggesting this is not the case?

Thanks,
John Elison

 

Not true, posted on November 28, 2015 at 10:39:50
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 The balanced line has equal impedances to ground.

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 10:42:54
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 You can configure the buffers in the manner that you're describing. It will be a push-pull setup, whereas most tube buffers with balanced inputs will be differential or transformer coupled.

I personally would use the unbalanced outputs of the Oppo if the tube buffer was a necessity.

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 10:47:45
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Again, you need to separate what a balanced cable interface is from what circuit topology is inside a preamp or amplifier.

A balanced cable interface requires equal impedances to ground between positive signal and negative signal. (Note that this can be infinite in the case of a transformer coupled input)

What one company does in its circuit topology inside a preamp or amplifier does not have anything to do with whether something is balanced or not.

You know that it's all marketing when you see the terms "truly balanced" or "fully balanced" being thrown around in product descriptions.


 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 11:29:09
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 In most cases today balanced signals tend to be the 180 deg out of phase referenced to ground type. Same as using a transformer with a center tap. The actual original standard for balanced is signals running between plus and minus with ground ignored. This like a phono cartridge or microphone.
Both work as balanced signals since common mode noise is cancelled. What we're discussing with the OP is the simplest way to implement balanced, with ground referenced. However, where I got that quote I posted is from Ralph Karsten of Atmasphere.
Dan Santoni

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 13:01:34
Dimitry
Audiophile

Posts: 457
Location: Massachusetts
Joined: January 26, 2006
 No chance of DC offset on XLR signal pins?

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 14:28:22
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 Shouldn't have any dc. They're cap coupled are they not.


Dan Santoni

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 16:07:34
Dimitry
Audiophile

Posts: 457
Location: Massachusetts
Joined: January 26, 2006
 Yes, that makes sense. I hope that left/right gain in my MF tube buffers is spot on.

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 17:11:34
Dimitry
Audiophile

Posts: 457
Location: Massachusetts
Joined: January 26, 2006
 My preamp has both SE and balanced inputs... I want to try the balanced ones, but I can't afford a balanced tube buffer.

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 17:13:50
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Why not compare the two without the tube buffer.

 

RE: Question on stereo/balanced circuits, posted on November 28, 2015 at 19:34:09
Dimitry
Audiophile

Posts: 457
Location: Massachusetts
Joined: January 26, 2006
 I will, but I have had an all tube system for 20 years. This is a huge change for me. I have to take it one step at a time.

 

RE: Question on stereo/balanced circuits, posted on November 29, 2015 at 11:14:36
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 If you used a CDP in your prior system, there were solid state components acting on the signal.

 

Paging John Curl, posted on November 30, 2015 at 13:04:32
Inmate51
 Please pick up the nearest courtesy phone.

:)

 

Page processed in 0.030 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]