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.

Fe8c8cab 4117 4c51 b1aa 6b134ad0dca6ramtubes
Love the idea of a switchbox to test various power cords and fuses!
@atmasphere   Roger, you might want to do some reading at the links I posted in my prior post. Most of this post (except perhaps the comments about subjective listening) is incorrect. As I pointed out earlier, the load is not for the cartridge's benefit- its about the preamp.

Please explain. Im all ears.

There's plenty of old school audio electronics that used the 6SN7. As you know, its geometry is similar to that of the 6CG7/12BH7 and 12AU7 (the latter being the same as the 12BH7 but with the entire structure sawed in half)

My dad built the WM-2 in 1956 so I am very aware of 6SN7, as was Heathikit who used them everywhere they could. Are you aware that most of their early products were built largely from WWII surplus of which there was tons. They would buy tons of surpus and then figure out what to do with it. 6SN7 were in great abundance. I think a 6SL7 might have made a better choice and I snuck one in a Williamson, changed a few resistors, and really liked it . Much more linear tube (low distortion). Why, because it was made for audio, not B&W television.

There are some great books on the history of Heath written my people who were there.  

This other stuff about sawing tubes in half make no sense. Ive taked to tube designers and they dont talk that way... at all.

As to it being lower in microphonics, the tone is of course different as the structure is different. But I would not say they are less microphonic than a modern 6922.  But this is just my experience of testing over twenty thousand 6922s
@ramtubes. I’d like to personally thank you for taking the time to sift through all these messages and provide your input on many of them. There’s a lot of valuable information here. I’d like to thank @atmasphere as well! Differing viewpoints gives us all a variety of things to consider. One should never stop seeking knowledge. 

First, the concept of your building the type of switch box I mentioned is very intriguing.  I'm not sure the idea still fits well with my system, which has become more complex (I'm introducing subwoofers, crossover etc).But I will certainly cogitate on the idea.

Also, love your idea for building switch boxes to text cables etc!  If the timing were right financially for me, I'd likely take you up on that (just out of my own interest.  I'm far from sold on the worth of high end cables, but I do have access to a bunch and it would be fun to test under more ergonomic circumstances, fast switching, etc).
I’ve tried a dozen 6SN7s for my amps’ cathode followers. What a huge range of sound characteristics.

The worst (thinnest,brightest) were Russian 80s or 90s ones under the Sovtek label, which looked identical to the Counterpoint branded ones and an English branded one. NOS GEs were generally noisy/distorted sounding.

The best were Raytheons for my amps, with the older VT-231 my favorite for its huge dynamics and warmth. Raytheons from the GT era can be more neutral sounding and harmonically thinner than the VT-231.

Sylvania’s Chrome dome had too tipped up sound for my amps but very clean and dynamic too.

RCAs, for decades of production, were warm sounding but less dynamic. My amp manufacturer uses 60's RCAs to great effect in the same amps but with very different speakers.

Ken-Rad was similar to VT-231s.

Any of the NOS tubes are superior to the 80s/90s Russian made tubes. I haven’t tried the latest tubes. In my application, the tubes can last possibly 10,000 hours (I know it’s lasted 5,000 hours already).

Maybe microphonics are not an issue with cathode followers.

I just don’t understand VAC using only 6SN7s in all their current amplifiers if they are worse than 6SL7s.