2. amps-preamps
  3. 140029-80294

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.


128x128ramtubes
ct0517's avatar
ct0517
2,041 posts
 
Clio09
I am curious how you settled on the 60 Hz cutoff and what other levels you may have experimented with.


Clio09
atter much experimentation I found the 57's positioned the way they are in my space to be the most room filling and linear top to bottom - down to about 50-55 hz. Still, to get the bottom octave and bass impact (it's a large room) I needed to add subs. I used to have a big HSU set up in nearfield next to me. It was fine as long as you were sitting in one spot. But if one uses the room - walks around, and sits in different spots around the room;  multiple subs are the answer to eliminate the bass nodes. Adding the two 12" Dynaudio subs improved on the single large HSU. Keeping the HSU as a slave would have been interesting, but my son took it. 8^0
The lowest crossover point on the Dynaudio BM12s is 60 hz. So that is where they are set. I have tried higher settings in the past with other subs and felt it interfered with the 57's bass too much. 


utrak
20 posts
 

I just want to say thank you Roger. With respect to tube amp output impedance selection, I had never heard that you should “Always use the lowest tap that gives you enough volume without distortion (clipping)”. I have a pair of Kef LS50s in an acoustically treated room (16’ x 11’ x 10’) that I’m driving with a pair of ASL DT200 hurricane mono-blocks (100 watts per channel). I’m not worried about clipping. I immediately tried your suggestion by switching the LS50s from the 8 ohm tap to the 4 ohm tap. And, just like you said, the bass tightened up, so much so that it shifted the tonal balance of the system up. This caused the system to actually sound a little strident. Well, I had used a parametric equalizer to boost frequencies around 10KHz a few decibels to offset the acoustically treated room, I thought. I removed the boost and Voila’, things are noticeably better all the way around.

I have another set of tube mono-blocks that use 4 EL34s each. I think that these are more sonically pure than the Hurricanes but they don’t seem to be able to control the bass on the LS50s to an acceptable level. I can’t wait to try the 4 ohm tap on those. Thanks again for sharing this knowledge with us.
fsonicsmith's avatar
fsonicsmith
962 posts
 
I said I was done in this thread and once again, I lied. I swear this question is in good faith and not meant to challenge or make a point. While looking over at Tungsol's website I saw this; 

Engineers and musicians have long debated the question of tube sound versus transistor sound. Conventional methods of frequency response, distortion, and noise measurement have always assumed linear (clean) operation of the test amplifier and have shown that no significant difference exists. In actual operation most amplifiers are often severely overloaded with signal transients. Under this condition there is a major difference in the harmonic distortion of tube and transistor circuits. 
http://www.tungsol.com/html/faqs14.html

RM or RK, there has been this overriding premise (by RM) that most of us have more power and overhead in our amps than we really need. What is your response to the premise above (and everything else in the link provided)? I can find the link if you like, but in one of Charley Hansen's last interviews with Stereophile he stated that after thinking throughout most of his engineering career that tube-o-philes' preferences were largely imagined, he had come around to the thinking that it is in fact extremely difficult to engineer a solid state amp that captures the same magic that a tube amp can have (and in the meantime Charley acknowledged that he had come around to believing that there is in fact a certain tube magic) and that he thought his latest amp design had captured that magic. I only bring up Charley's arguably unrelated "epiphany" because it may or may not be related to the premise of Tungsol that most amps are severely overloaded in actual operation. So what do you say about this? I happen to have 150 watts of glorious tube power (actually more) with my ARC 150SE matched to very efficient and easy to drive loudspeakers-DeVore O/93's-and I have no problems with audible hum and I am very happy with how my system sounds. 
analogluvr
859 posts
 
That article is from a guitar amp perspective where it’s more common to overdrive. 
ramtubes's avatar
ramtubes OP
460 posts
 
I said I was done in this thread and once again, I lied. I swear this question is in good faith and not meant to challenge or make a point. While looking over at Tungsol's website I saw this;

Engineers and musicians have long debated the question of tube sound versus transistor sound. Conventional methods of frequency response, distortion, and noise measurement have always assumed linear (clean) operation of the test amplifier and have shown that no significant difference exists. In actual operation most amplifiers are often severely overloaded with signal transients. Under this condition there is a major difference in the harmonic distortion of tube and transistor circuits.
http://www.tungsol.com/html/faqs14.html

Please be aware that this paper was not written by any Tungsol engineers who are long gone as well as their factory and any tribal knowledge. 

This is the work of New Sensor who has taken over the name, probably with no resistance, and making the tubes in Russia. Im not saying these are bad tubes but they are not Tung Sol of America.  The KT series apperars to be good and I have tested the 120s and 150s. The data sheet for the 150 is in Tungsol style but not of Tung Sol quality. No plate curves, Gm seem too high. Not informative as in the good old days. I have offered to help them.

Also keep in mind that New Sensor sells to the guitar amp market by 100 to 1. Nothing wrong with that. Thanks to the guitar guys for keeping the demand for tubes going. We audio users are a drop in the bucket. 


More to discover