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.


128x128ramtubes
ct0517's avatar
ct0517
2,041 posts
 
Clio09
@ct0517 - thanks for the response. With the subs in place are you still running the Quads full range, the using the sub fior 60 Hz and under, or are the Quads completely cutoff at 60 Hz?

Hi Clio09
The 57's are full out on the RM10 and in parallel to the subs. The preamp I am using in that room has two direct outputs. One output set going to the L and R 57, the other set going to the L & R sub. The subs are on each side of the listening couch, the opposite room side to the 57's. The Quads are seven feet from the front wall. So they are about a third of the way into the room. 
   
I realize that the way I have set up the Quads (see virtual system pics) and the subs is, well, unorthodox. But that is just one of the aspects of a dedicated room, that allows you to manipulate speaker placement, and affect the way the speaker output and the room gel. The hell with aesthetics. Hey, anyone with Quad 57's isn't into aesthetics anyway - 8^0.  

Room A is my main room, it pressurizes easily due to its shape and the speakers used in there; but Room B is a better room for entertaining due to its size. It's been a lot of fun when people visit and if any are interested in audio, watching them get a grasp that the Quad 57 is actually a speaker. Equally entertaining is when I tell them there are two subs in the room and to tell me where they are as music with a lot of bass plays. They start looking over at the 57's across the room, looking in the corners nearby. When I tell them they are on each side of the couch they are sitting on, one right next to them on the left - they are in disbelief.
Cheers

bdp24's avatar
bdp24
9,866 posts
 
@krelldreams, the "cleaning of a window" is the transparency I was speaking of above. It’s the opposite of the veiled, opaque, translucent sound (a layer of "scrim", as J. Gordon Holt called it) you are trying to rise above. Transparency can and has been achieved via both tubes and transistors, being more a matter of the talent of the design engineer. For instance, though Roger uses primarily tubes, he felt transistors would work better as the input stage of his RM-200 power amp to achieve the performance he was after.
krelldreams
128 posts
 
@bdp24. All understood. Thanks. I guess the trick is to figure out what’s causing it, why it’s happening, and how to fix it. That’s what I’m hoping to learn more about.

 I believe that my speakers, my amplifier, and my vinyl playback system are better able to communicate the music to me than my preamplifier is. I wouldn’t say it’s a “bad” preamp. I just have a sense that it’s not as “good” as the rest of the chain, and is therefore frosting my window, so to speak. 

 I initially joined this conversation to discuss options for using a simpler circuit vacuum tube amplifier in my system, but as I thought more about it, and followed the thread, it occurred to me that my preamplifier may need to be improved before I venture into replacing the amp. 

 It’s helpful to read the opinions and experiences of others, and it’s very valuable to have the perspective of successful component designers (Roger, Ralph, etc.). I appreciate all the contributions (except those added by the trolls... occasionally entertaining, but useless here). 

 I realize Roger is focused on the power amplifier, but he has created well-regarded preamplifiers as well. Ralph currently offers both. They have figured out the “What, Why, & How”. 
bdp24's avatar
bdp24
9,866 posts
 
@krelldreams, if LPs are your main source and focus, one option is to buy as good a phono stage as you have the dough for, along with a relatively inexpensive passive pre. Passives work better in some situations than others, having to do with source gain, output voltage and impedance, along with power amp input sensitivity and impedance. Roger is a proponent of passive pre's, and will make you one. That will leave you more $ for a phono stage.
krelldreams
128 posts
 
@bdp24. 

 I’m thinking that may be exactly the avenue I’d like to explore further. I’m looking at phono preamp options as we speak. I have a very simple passive device, which I did try, but didn’t care for. I am very willing to try other passives though, since the one I have was purchased to provide level control for our kitchen system, where I was using a 1960s HH Scott tube power amp.

 The unit is a Luminous Audio Axiom. When I ordered it they asked what amp it would be used with so they could make one to work specifically with That amp. It is entirely possible that it is a mismatch with my primary amplifier.

 Roger asked for specs... the only spec I know of is “1.2k” hand written on the bottom of the case. This was only a test anyway since I’d need more than the single input this one provides. I was not aware that Music Reference made passive devices (?). 

 I am considering both tubed and solid state phono preamps. Any design parameters that I should be paying attention to? Any designs to avoid? I currently only need one for a high-output MC cartridge (MM gain and loading), but I plan on trying other cartridges in time as well. I’m not opposed to getting a step up device if a cartridge I get in the future needs one. 

Thanks again for the advice!
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