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.
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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 http://berkeleyhifischool.com/ 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.


128x128ramtubes
ramtubes   I poorly wrote that line about the EAR 912-  My pre-amp has subminiature tubes rated for 100,000 hours, the EAR 912 can use 7DJ8s or 6DJ8s rated for 10,000 hours as you stated.  My old EAR 864 NOS 12AX7s and 12AU7s only lasted about 3,000 hours before replacement.  However the EAR Acute has 6DJ8s at over 7,000 hours and going strong.  Depends on the tube and design of course.  My Audio Research gear back in the 90s had power tubes last about 2,000 hours or less, not really good but better than my Dynaco IIIs which lasted about 9 months, 1,000 hours or less.
I would look into Electra-Print output trannys and talk with Jack.  Nice output trannys for sure. 
I've got another question for the tube amp designers.  Does it matter whether the filament supply is AC or DC?  I've heard arguments both ways.  I think that it would be great if one could get away with an AC filament supply because it requires less current from the power transformer and reduces cost to build.

Thanks  
I asked the same question a little back here. Roger said AC is good as long as it is quiet.....😊 Perhaps he has more to add.....

I am upgrading and reassembling an amp with AC fils. Dead quiet.

I also wonder about rectification. My amp has an 5U4 that I am thinking of converting over to a full bridge SS rectifier. I seem to prefer the sound of tube amps and preamps that are SS rectified. My amp is only 13 watts channel/EL86 based and may be low enough power to like tube rectification just fine. I prefer SS rectification in more powerful tube amps, but am not totally sold on their value in lower wattage tube amps ..... say under 10-15 watts. I think I may like SS rectification more in these low power amps, but need to experiment more. I find SS rectification to be more dynamic while delivering much better bass. One can also beef up the supply with more capacitance and very robust Pi filters.