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.
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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.


ramtubes
ramtubes's avatar
ramtubes OP
460 posts
 
@frogman An extremely generous offer. Thank you.
What is it, from a technical standpoint, that allows good tube amplification to reproduce micro dynamics in a way that is much closer to what I hear in live music? I refer to the ability to reproduce the seamless dynamic gradations in volume (especially very subtle gradations) that give music a sense of aliveness; not simply the ability to play very loudly. I know some will disagree, but to me tube amps generally do a better job of this than solid state. The attributes of tube amplification are often described in terms of tonality, dimensionality, staging, but to me the thing that draws me to tubes more than anything is the way they reproduce dynamics. I generally hear more dynamic nuance (realism) from tubes. Thoughts?


Transistors have a very abrupt turn on. A silicon transistor starts conducting with 0.6 volts on the input (base) and is fully on by 0.7. With MOSFETS the numbers are just as bad 3.1 to 3.5 or so.

Tubes, on the otherhand, have in input range of many volts. A preamp tube might go from -10 to 0 on the input. A power tube -50 to 0. The - sign occurrs because tubes want to be on till you cut them off, so the grid (input) always starts out negative.

So input range has something to do with producing microdynamics and dynamic range as the devices themselves inherently have more range.

One other thing that has drawn me to tubes. Only with tubes can you make a minimal circuit that sound good. Transistors require many stages and lots of feedback. Now feedback is not inherently bad but a lot of feedback gets people in trouble with oscillations (instability). I also like the fact that tubes need no protective circuitry, last long if well treated, are nice to look at.

Transistors don’t last forever and transistor amps are much harder to fix than most tube amps. (not ARC) :(

In the new year, time permitting, I will put up some videos to show people how easy it is to fix a tube amp. The other day I fixed one over the phone in Germany. With proper knowledge and a little advice its not hard.
stereo5's avatar
stereo5
6,569 posts
 
I have a question for you Roger:
What are your thoughts on Class D amps? I have listened to quite a few and always came away unimpressed with my ears aching. I am a Mac guy at heart marrying a Mac solid state amp with a Mac tube preamp. Perhaps I like a more mellower sound?

I heard your tube amps back in the 90’s at Sound II in North Dartmouth, Ma. Leo (RIP) was a huge fan of tubes and carried your line as well as VAC and Audible Illusions. I did a lot of listening and buying in that store.  An added plus was there was a fantastic strip Joint right across the street from the store on Route 6.  Really fun times!
mrdecibel
3,171 posts
 
Roger, thank you for the response. I have to disagree with you as to warm up time of a component ( which is relative to break in time ). For me, 5-10 minutes is never enough. " Don't sound bad when they come up slowly ". For me it takes much more time. I am not talking measurements, I am talking " listening ". I would like to leave it at that, as this, too, could wind up being a very controversial discussion, and not new to Audiogon. Enjoy ! MrD.
ramtubes's avatar
ramtubes OP
460 posts
 
@djones

 I have never owned a tube amp , always used SS and this doesn't come up if it's rated for 8 and 4 Ohm. I have what is I am sure a novice question. My speakers are 6 Ohm and I notice most tube amps have 4 Ohm or 8 Ohm taps and sometimes 2 Ohm. Where would I connect a 6 Ohm speaker?


Here is where experimentation will produce very real and obvious results. Always use the lowest tap that gives you enough volume without distortion (clipping). You will then get the most damping and the speaker will have frequency response as close as possible to the designers voicing. If you want more detail on why that is ask me. Its long.

Also experiment with the taps at low listening levels where clipping will not be an issue. Listen for tonal changes and peaky or mushy bass. The bass is most affected. 

FInd an impedance curve for your speaker and send me a link. Impedance variations are the largest cause of response variations with most tube amps and tap choices.
uberwaltz's avatar
uberwaltz
13,381 posts
 
Welcome Roger and thank you.

Just a point in case this also gets trashed by you know who,s.

The relatively new Insiders Lobby allows you to post a thread and I believe block certain members from adding dross to it.

just a thought n case the worst happens.
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