2. amps-preamps
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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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baranyi's avatar
baranyi
719 posts
 
Roger,
          Thank you for the comments about Beveridge speakers. Could you also make some mention about the power transformer of these direct drive amps?  Should it be so difficult to find a source to rewind these transformers making the amplifiers operational again? I have had 4 amps where this is an issue (in both Beveridge 2 and 2sw amps.) My original pair model 2’s had this issue upon purchase (long story.)

This power transformer issue and panel issues seem to be what keep these speakers from being more highly coveted today. Thanks again for your generous participation on this thread. 
c1ferrari
464 posts
 
Re: Beveridge
Hi, Roger,
You'd worked on the Bev DD amps for my Model II's when you were situated in Santa Barbara.  Unfortunately, Rick was unable to complete the restoration process and my panels require attention.  Can you assist?
Thanks for the attention.
Vbr,
Sam
rollintubes
84 posts
 
Roger, thanks for your time.
Some of the technical talk on this thread is way over my head so I’ll have to bone up on my tube electronics, which I learned over 50 years ago in college, then became a computer jock so I forgot about them until recently.
I am sold on tubes for analogue audio but am confused by all of the information on power. I see from many posts that tube power need not be very high or as high as the speaker manufacturer claims as a requirement, i.e. a 200 WPC SS amp is needed to drive a speaker with 85db sensitivity (the manufacturer requires a minimum of 75 WPC, but likes at least 100 WPC), yet I have used a tube power amp with 40 WPC on the speakers and it sounds terrific. I have read that it is in the output transformers and SS amps are generally direct coupled.
Will you please explain this phenomenon?

Thanks. Rollin
4krow
80 posts
 
Well, that just figures, doesn't it? Living way out here in Wyoming, my chances of having a conversation about this is more than rare. Then in the last few weeks, I have an opportunity to tap into 3 different audio engineers, electronic engineer, amp designer. It's funny how that can be.
  So here is something that probably has been asked before, but there are just too many pages for me to go through. Why shouldn't decent tone controls, and maybe even loudness controls come back in fashion? For it is simply that I need them at times, being 61. Now, mind you, I have bought many a product in the past that had such controls that were not worth the solder. Then, I got ahold of a low cost Yamaha integrated that changed my mind about such things. When it came to a loudness control, they chose NOT to increase the bass/treble, but instead to reduce the midrange. Cool idea. Other companys were spot on in the thinking tone controls whose turn over frequency for that particular control could switched to a more desirable frequency to start the correction. So if you were to use the bass control, you might have a choice of adjustment starting at either 100 hz or lower, at 60 hz, for example. The fact that these could be switched out of circuit when not needed, is enough for me to buy such a product.

  Your thoughts...
clio09
3,360 posts
 
I hope that Roger will step in at some point and address some more questions but currently there are a couple projects occupying a lot of his time. So he’s had to take a little break from here.

@4krow - Roger has often talked to me about the difficulty in doing tone controls right. I know there are some C4 preamps of his out there with tone controls that owners have found very useful. He was often asked how to use the controls and his stock response was use the setting that sounds best to you.

In addition, Roger designed and for a while offered the two knob EQ for speakers that lack bass in the 320, 160 or 80 Hz range. You could choose between these frequencies and dial in exactly how much you want to boost, up to + 6 dB if I recall. Roger designed it in part because he listens to a lot of Leon Redbone and noticed the vocals never quite sounded right on most of the speakers he listened to. So the EQ corrected for that. He’s one of the few people I know that consistently uses the bass control on his RM3 crossover. Me, I’m set it and forget it with my RM3, but Roger fiddles with his to get the sound to his liking.

@c1ferrari (it’s been a while Sam, we met at Newport in my room there as you had interest in demoing the Lightspeed attenuator). I will talk to Roger about your situation and see what we can do to help (same for you Baranyi). We do stock the mylar for the panels if you need some.
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