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.

Yes. I used a cheater plug and the hum in the speakers went away. I know it isn’t safe that way and was hoping the hum x product would work. It actually did work but evidently the Classé has too much power for it.
I am getting some ground loop noise from my Classé 5300 amp.
I wired studios with 1000's of interconnections. We never used cheater plugs. E V E R !!  Solve the problem, don't bandaid it. Sometimes it involved fixing the gear's internal wiring.

Are you using balanced or unbalanced inputs? If balanced, remove the screen connection on the amp end. In a balanced system, the screen should be lifted on all the driven ends.

Get some shorting plug and start with just the amp connected to the speakers. Add in each component back from the amp. When the hum starts, solve the problem there and continue.

@almarg Many Thanks!

In your case, both your VAC and Pass amps are capable of producing 32w I presume. What gave XA25 an edge over the VAC amp with your speakers? Does XA25 have less distortion due to its class A operation in the first 25 watt?


Hum is coming from the center and surround speakers and am using unbalanced cables.  
I apologize for my lack of knowledge, but could you explain what shorting plugs are?