balanced preamp

Not only cost of tubes but they also require more power.

Where are you going with that?? That does not have anything to do with CMRR... and is not accurate. The tubes we use are not expensive, and usually cost less than a set of tubes for a transformer-coupled amp of the same power.

From your other comments though it really sounds like the circuits you are used to measuring have poor CCS circuits. 85 db is not a hard figure to attain.

ZD542
Yes Time for a change I would like to try a good balanced pre, even my phono pre will run balanced... My Question should have asked prior Frist Sound owners where they moved on to (in regards to a new BALANCED preamp) and did they improve their system.

Atmasphere, We were talking about cost of fully balanced gear. I expressed opinion that in order to get fully balanced amp or preamp you pay more and sacrifice CMRR (since you cannot keep gains equal to 0.005%) - whole thing to remove even harmonics that most people don't mind while leaving odd harmonics intact. I suggested to get better standard amp/preamp instead.

As for 85dB being easy to do - please notice that CMRR of line input transformers is shown at 60Hz. 85dB at 20kHz is pretty good number for any instrumentation amp. In addition line input transformers introduce distortions at low frequencies.

OK Kijanki, I will take the other comments as a red herring then.

From your comments it seems to me that you are used to working with balanced gear that uses the ground connection. The ground is supposed to be ignored. But a lot of balanced gear uses it, which degrades their CMRR. I see this all the time in high end. Unfortunately, lots of instrumentation amplifiers have this same design flaw.

However, single ended preamps have no distortion cancelling capacity, and nothing for a CMRR. This is not saying that they can't sound good by any means, but it does mean that they are prone to interactions with the interconnect cable, something that should not happen with balanced operation.

Atmasphere, It seems that fully balanced configuration offers benefit of even harmonics reduction at some expense of CMRR. I can understand that it might be too expensive to manufacture to stay competitive at the lower/medium price range but all your amps are fully balanced (I think).

I often see opinions that XLR cable offers no benefits without fully balanced configuration. Nothing can be further from the truth. Not only that balanced input has common mode noise rejection at the order of 85dB+ (nothing to sneeze at) but also twisted pair (in addition to shielding) has huge rejection especially at audio frequencies (where wavelength is much longer than twist density). In comparison single ended gear has only protection of the shield and, as you stated, zero CMRR.