Does anyone care to ask an amplifier designer a technical question? My door is open.

I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.

I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.

I like to tell true stories of my experience with others in this industry.

I have started a school which you can visit at There you can see some of my presentations.

On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.

I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.

Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.

Hey, do you have a link to the complete review? I got 29 hits for Leben. A lot of mention for a poorly performing amplifier.

JA does make mention of the ultrasonic resonance, but "maybe" because they're an advertiser, didn't make too big a deal of it.

Cheers George

John Lennon: "All I want is the truth, just give me some truth".

Amen, brother! "High End" reviewers like Harry Pearson convinced lots of audiophiles that the measured performance of an amplifier and that amp’s sound are unrelated. That making a "good" sounding amp was more art than science. Yes, the race for as-low-as-possible static-measured distortion did lead to bad audio engineering, but good designers understand that, and perform bench tests that reveal the dynamic behavior of their designs.

I can’t count the number of times I have heard an audiophile (or even hi-fi retailer), when presented with evidence of the poor engineering of a component the audiophile likes (or the retailer sells), or worse owns, defend that component by saying something like "Well, it’s the sound that matters". If a poor design, showing obvious performance weaknesses, sounds "good", something is very wrong somewhere.

In the mid-80's I was in a hi-fi shop, and the owner was playing a system for a potential customer. I knew the following about that system's components: the tube pre-amp have a pretty high output impedance, and the interconnect cables very high capacitance, especially at the 30' length of the pair in use (from the pre at one end of the room to the mono power amps at the other). I couldn't stop myself from commenting that the combination of those two factors was obviously creating roll off starting at an audible frequency. The retailer responded by saying, you guessed it, "Well, it sounds good". It didn't to me, sounding, predictably, soft and dark. Cymbals were missing their brassiness and sheen, strings lacking life. I slowly learned some consumers, even "High End" ones, believe whatever they're told. The pre-amp was considered Class A, as was the interconnect. How could they not sound good together?
If an amplifier is class A/B implementation does it not matter to mention the Class A bias i.e how many first watts are class A. Does crossover distortion matter?. If not why and if yes what do Class A/B designers do to make it go away or mitigate it. 

Generally reading around good Class A/B amps that have high bias seem to be well reviewed. Again interested to learn more about this.
What is the difference between high current and high watt per channel amps. Some amps seem to advertise high watt output but don't have much current it gets confusing.
Keep in mind just because a unit has a XLR input that is no assurance that the input is balanced.
A balanced input is no guarantee of better sonics. The devil is in the details.
Every audiophile should read Bill Whitlock's AES paper
"An Overview of Audio System Grounding and Interfacing" 
available here