2. amps-preamps
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Dual Differential / Balanced?

Hey all I’ve got that itch to upgrade power amps, and was wondering how valid the dual differential aka "balanced" monoblock or dual mono design is in terms of increasing fidelity compared to a conventional SE amp. note my preamp is also fully balanced

how much noise is avoided by using a fully balanced system?

right now I use 2 haflers horizontally biamping NHT 3.3. using mogami gold XLR
p4000 200wpc mids/highs p7000 350wpc lows

from what I’ve read it only matters if both the preamp and power amp are both truly balanced

I have a nice Integra Research RDC 7.1 fully balanced pre/pro, it was a collab with BAT, I would go for the matching RDA "BAT" amp but its pretty much unobtanium

So far I’ve looked at classe ca200/201, older threshholds, older ksa krell, as fully balanced monoblocks/ dual mono stereo

I was also told to look at ATI amps, they look very impressive but expensive

I’m looking to spend 1500-2500 preferably used products, I dont have an issue with SE amps I just want to exploit the fact my pre is fully balanced, and perhaps get better sound. If anyone has recommendations for awesome dual differential power amps. the NHT 3.3 are power hungry so at least 150wpc, class A/AB

I’ve also come across the emotiva XPA-1 monoblock, I can get a good deal on one of them I wonder if its worth picking this up and praying for a lone one to come on classifieds on ebay- note this is the older model in the silver chassis 500wpc 8ohm / 1000 4ohm

for context prior to the realization that I should use a fully balanced system I was looking at brystons and mccormack amps.. thanks
nyhifihead
charles1dad's avatar
charles1dad
10,236 posts
 
Thank Al, 
So very specific requirements are necessary in order for Ralph's point to be valid,  I appreciate the clarification. This would explain the findings of my friend's Atma-Spheres and his various balanced cables. 
Charles, 
bdp24's avatar
bdp24
9,510 posts
 
I don't know about advantages (if any) provided by a true differential balanced circuit, but EAR-Yoshino designer Tim de Paravacini (who does a lot of work in the pro recording field) chooses to use single-ended circuits, with balanced inputs and outputs provided by a transformer.
philipwu
214 posts
 
"Checkout VAC SigMKIIa SE and above or Atmasphere MP-1 if looking for transformer coupled preamps " by knghifi

dear Ralph, 
is your preamps transformer coupled? (or is it in the signal path or stages?) 
btw, may i ask if your preamps are designed with absolute no local, no global feedback in power supply & audio circuit? if the info is something proprietary to you, then just ignore the questions. Thanks & regards, 
-phil
swampwalker's avatar
swampwalker
5,138 posts
 
As is usually the case in audio, how good the results are depends less on the design approach that is chosen, and more on how well the chosen approach is implemented.

Yes, yes, a thousand times yes!  I nominate this as verse 1 in the Audiophile's gospel, to be said aloud, immediately upon arising in the morning, and before retiring at night!  J/K.  Not really... ;-)

atmasphere's avatar
atmasphere
11,633 posts
 
 I can see a problem with fully balanced audio amp design that has no reference to ground.  Both outputs can be floating together since without output current or voltage difference feedback won't react to that.  It needs ground reference somewhere or some kind of servo on common mode.

Ignoring ground and having a floating circuit are two very different things! Our circuits are referenced to ground but are designed to otherwise ignore it.

BTW if a transformer is used at an input or output (for example to allow a balanced input or output for otherwise single-ended operation) the best way to do it is to not have a center tap, with the winding of the transformer simply tied to pins 2 and 3 of the XLR (the signal pins). Pin 1 is then usually tied to chassis ground. This gets the best Common Mode Rejection Ratio (CMRR). The use of a center tap for ground will degrade the CMRR.

dear Ralph,
is your preamps transformer coupled? (or is it in the signal path or stages?)
btw, may i ask if your preamps are designed with absolute no local, no global feedback in power supply & audio circuit
Our preamps are not transformer coupled- instead they have a direct-coupled output that is balanced and differential. Any DC Offsets are controlled by a simple servo circuit (we went through quite a bit of effort to prevent the servo from being a feedback mechanism in its own right). We obtained a patent regarding this operation. We do not use feedback in our audio circuits (loop feedback or degenerative feedback) although the power supply regulation does.
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