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 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.


ramtubes

Showing 2 responses by alexberger

Hello @ramtubes,

I have a DIY 300B SET.
Input tubes are 6sn7, driver are 6f6 in triod mode.
I use coupling capacitors (Duelund Custom Cu) between input, driver and output tubes.
I use 5K output transformer James Audio.
My speakers Altec 604E ~100dB sensitivity.

I have a number of questions:
1. What is optimal transformer load for 300B? When I don't need extra power with my very sensitive speakers.
2. What do you prefer for inter-stage coupling, transformers or capacitors?
3. I'm thinking to upgrade to Hashimoto output transformers? Do you have experience with Hashimoto?
4. When you design your amplifiers, how do you calculate optimal idle current for input and driver tube stage?
In the past, I increased idle current in both, input and driver tube. And in both cases it gave me a significant improvement in sound.
For example, I increased current in 6sn7 from 4.2mA to 5mA. And I can to increase it let say to 5.5mA. How do I know what is optimal or good enough?
5. What is the best and cost effective way to separate power supply between output tube B+ and driver tube B+?

Regards,
Alex.
Hello @atmasphere ,

Thank you a lot for your reply.

I know some people like to put chokes between output and drivers B+.
It adds better isolation on high frequencies between power supplies.
But what do you think does it have any real effect?

What do you think about separate power  supplies between left and right channels for 300B SET amplifier? Does it do a significant difference?

Regards,
Alex.