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.


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atmasphere's avatar
atmasphere
11,901 posts
 
Also, while I don’t recall the exact numbers, Ralph has stated in some past threads that he has observed remarkably high levels of energy emanating from LOMC cartridges at ultrasonic or RF frequencies.
@almarg
The Hagerman site shows a 30db(!) peak. I can confirm that.

About 35 years ago I used to subscribe to the cartridge-needing-a-load theory. I set out to build a device that would come up with the correct loading so as to eliminate guesswork on the part of the user, which I was hoping to build and sell.

What I found when ringing the cartridges was that they really didn't ring until you got to some very high frequencies well past audio! This is easy to understand- if you pass a squarewave through one, there isn't much inductance to mess with the squareware at audio frequencies.

So if the brightness of an unloaded cartridge isn't due to ringing, what is doing it? I was lucky- a serendipitous event caused me to realize that the preamp played the bigger role.  At that point it became a simple engineering task to insure that a phono preamp design would be resistant to this sort of problem.
In a way, I did get what I set out to achieve- being able to sort out the correct load, which for all LOMC cartridges is 47K. What is needed is a preamp that is unperturbed by a 30 db peak 100KHz or above into the low MHz.... Not that hard once you know what's afoot.
ptss
1,964 posts
 
@ OP. How do you feel about Spectral Audio designing amps with extreme bandwidth? Are there benefits for solid state amps?
ptss
1,964 posts
 
I feel one of the great benefits of tube products is the limited bandwidth eliminates susceptibility to much of the higher frequency ac noise. Comments?
atmasphere's avatar
atmasphere
11,901 posts
 
Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless.
Dr Herbert Melcher showed that there are tipping points in the brain. Normally music is processed by the limbic system. But when things audio go amiss, the processing is unconsciously transferred to the cerebral cortex. At that point the music 'subjectively' loses its 'soul'. For this reason, its really important to know how the ear/brain system perceives sound, so as not to violate its perceptual rules (if you want the gear to be emotionally involving). Once you know that, it becomes and engineering task that is fairly mundane.
He made excellent equipment and I can see from JAs measurements he did a good job on the three major characteristics of a good amplifier, one that would drive a wide variety of speakers well. On this I am in complete agreement with Charley. Im not sure why I need to listen to his amps, I am confident they sound find. Charley and I are on the same page with what is important.
Charles made **zero feedback** amps and IMO his are some of the best solid state amps made. What I like about his approach is that he solved the issue of an amp that acts as a voltage source while also lacking the usual coloration of brightness caused by the distortion of added feedback. The industry needs this sort of diversity and he is missed.

atmasphere's avatar
atmasphere
11,901 posts
 
I feel one of the great benefits of tube products is the limited bandwidth eliminates susceptibility to much of the higher frequency ac noise. Comments?
You can have plenty of bandwidth and not have noise problems. Noise is best handled by proper power supply design and good grounding technique. I find also that fully balanced differential circuits are handy for noise rejection as well. This means that you can have a wide bandwidth tube amplifier and have it be very quiet, even though it may not be shielded by a chassis.
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