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
atmasphere's avatar
atmasphere
11,861 posts
 
Ralph, I measured your preamp's RIAA and it was +4 db in the bass. That is not accurate EQ. My RIAA accuracy is +/- 0.2 dB.
.
What interests me is how it came to be thought that preamps are harder. What designer is going around saying that? Im not.
The preamp's math conforms to Stanley Lipshitz's math and the parts are within 1% or better, FWIW.
The thing about a good preamp is that there are so few! In that regard I would say there are a lot more competent amps than there are preamps.

Well, I lied. I have to respond. Ralph-I can't believe that you said that about me after I have done nothing on this Board (in multiple threads) but praise you and after you agreed that preamps are not easier to design (well) than amps.
@fsonicsmith
Sorry- my comment was not aimed at you- I had missed that you had left. I was in fact referring to someone else, who (thankfully) has not posted on this thread at all. I see now that in my haste to get thru all the new posts that I missed several posts somehow and yours was one of them. So I misinterpreted Roger's comment. I apologize- I've no reason to drag your name through the mud!
nitewulf
422 posts
 
@ramtubes I am still a bit hazy on the power versus gain issue.  If you increase the gain, are you not increasing the power output of the amp? So what then affects the power output, the speaker impedance only? In that case, how do we ensure that the amplifier is outputting power within the bandwidth where it has the least amount of distortion? As you stated, and can be seen from measurements, typically harmonic distortions start to increase at the upper and lower limits of the design bandwidths (20HZ and 20KHZ for arguments sake) along with increasing power output. 
fsonicsmith's avatar
fsonicsmith
963 posts
 
Thanks Ralph. That means all the world to me. I know this sounds cheap and tawdry, but when I replace my Ref 150SE, I will be absolutely slanted toward an Atma-Sphere. 
Since I am still here and jabbering, I still maintain that the OP's stated goal of designing an amp for all men and seasons is IMHO misguided. It makes for good marketing but it's not the real world. It may be inconvenient and expensive to buy a new amp when one chooses new loudspeakers but no one said that pursuit of lovely engaging sound is cheap. Though compared to boating and racing cars, it IS cheap. Safer too.
In this holiday season, I too wish to express best wishes for health and happiness to all who contribute to this Board in good faith. Now with that, I am gone from this thread. Not from this Board, but from this thread. 
ramtubes's avatar
ramtubes OP
460 posts
 
@fsonicsmith  Well, I lied. I have to respond. Ralph-I can't believe that you said that about me after I have done nothing on this Board (in multiple threads) but praise you and after you agreed that preamps are not easier to design (well) than amps. Yes, there were a couple typos in my last post due to being busy and typing in haste, but my points should have been clear. I could easily recite ten typos and misspellings in the various posts of Mr. Modjeski, were I to feel the need to resort to that.
It is also shocking to me that Mr. Modjeski criticized the hell out of your M-60's biasing circuit and claimed your RIAA curve in your preamp is not up to snuff and you are doing nothing but kissing his arse
.

hahahahahahahahahahaha.  Honestly this is my first reaction to reading whats above... Thank you, I had a difficult day setting up a strict A/B.  
ramtubes's avatar
ramtubes OP
460 posts
 
@cakyol   I am also looking for a lab/bench symmetric power supply of up to +/- 100 volts DC at about 2 - 3 amps (so about 500 - 600 watts) and having a very difficult time finding it. The very rare ones I have seen are in excess of $1500. I need such a supply for testing purposes. I do not want to build one.

Does anyone know of one around a max of $500 ?


I would just buy two identical supplies, float the grounds and put them in series. Thats what I use on my bench.

You want a lot of watts, 1/2 KW. Most bench supplies are not up to that.  This company made great stuff. This is getting close. www.ebay.com/itm/POWER-DESIGNS-6050A-Variable-Universal-DC-Source-AS-IS-See-Description/292803892089...

Keep looking at ebay. What you want is rather unusual due to the amount of power, heatsinks to manage the drop across the transistors. At the power level you want a linear supply is unlikely. Almost has to be a switcher to manage the losses. Imagine if you are asking for just a few volts at 3 amps. The high side of the regulator has to be above 100 volts so 300 watts are dissipated in a linear regulator. Thats a lot of heat

What I would do is just make a brute force power supply and run it from a variac. Thats what I have done when I need that much power. Its nice, no losses, no heat. 

I do recall that HP made some very high power regulated supplies and handled the dissipation by tracking the regulator with the variac. Again, that is to reduce the heat dissipation. That would be a great and not too difficult project.
More to discover