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
bdp24's avatar
bdp24
9,874 posts
 

@ramtubes, I finally got around to reading the review by Herb Reichert of the Cary SLI-100 in the December Stereophile. Damn, what a piece of junk! Cary specs the amp at 100w/ch from a pair of KT150 power tubes per channel; John Atkinson, using 1% THD and noise as the definition of clipping, measured the amp’s output from the 8 ohm tap into an 8 ohm load as a mere 3.2 watts! Out of a pair of KT150’s! You have to work REALLY hard to make an amplifier that bad. Whomever designed this boat anchor should find a new line of work; amplifier design is obviously beyond his abilities. 3.2 watts/ch for $5995? Not a "very good value" ;-) .

And what does this tell us about Herb Reichert, who very much likes the sound the amp produces? That Herb apparently likes distortion, I would say. You are now justified in completely disregarding anything and everything Reichert has to say about hi-fi. If one "likes" a power amp this bad, what doesn’t one like?

RM: "He (Harry Pearson) was an idiot." At an instore talk in the 1980’s at a S. California hi-fi shop to introduce a new product, Bill Johnson told this story about Pearson: Bill had sent Harry a new pre-amp for evaluation and review, and soon received a call from HP, saying the pre was defective. Bill had Pearson return the pre to ARC, where it was tested and found to be operating perfectly. A phone call and questions revealed the source of the problem; Harry had installed shorting plugs, not into the pre’s unused input jacks, as they are intended to be used, but into it’s output jacks. Well duh! Should anyone that ignorant really be considered a "reviewer", and empowered as such?

cakyol's avatar
cakyol
940 posts
 
Hi ramtubes,

About your variac suggestion :-)  Funny you mentioned that since I also came to the exact same conclusion.  I have rectifiers & capacitors already lying around with which I can build an un-regulated variac based power supply.  All I have to do is add 2 voltage meters to it and an enclosure and voila, it works.  I dont need extreme regulation anyway so it would be fine.

For isolation also, I have a 1000VA toroidal  with 2 x 50 volts ac lying around which will use.  This will easily give me 2 x 70 - 75 volts DC.  It will be a bit heavy but will successfully work with gobs of spare power.  I will have to add an inrush current limiter too  unless I turn the variac down before I turn the power on, every time.

I also play around with DC motors too, so this supply could also easily be used to test them.

Thanks


teo_audio
2,197 posts
 
They left shaking their heads because when they compare the same preamps one at a time they "think" they hear big differences.

They do hear big differences at home. No doubt about it.

Long term listening does reveal bigger differences than short term listening of unfamiliar complex systems, rooms, etc.

Especially unstressed at home ---long term differences being notable -- with the entire home package being a familiar.

Anything else being paraded about....is well, horsepuckey of the most damaging kind.

Read up on listening tests and the human ear. It’s not a machine, it’s biological, and is individual and has learning curves, and these aspects take time. the ear is a living moving changing variable. and different in every single person. Seven billion different sets of hearing.

It even possesses intelligence and capacities levels like minds and IQ. Yet most people don’t mention these entirely obvious realities. Like your eyes, and mind, they come with a almost totally blank page, and you build it out from some very basic starter forms.. You learn your way to hearing, with your individual package that has as much variation in individuals as does IQ.

Bamboozling them with a test that no one can pass, without adequate amount of time spent in front of it, does not substitute for hearing knowledge and skill.
jdjohn's avatar
jdjohn
39 posts
 
Any thoughts on kits like this modeled after the Dynaco ST-70?  http://www.tubes4hifi.com/bob.htm#ST70  This isn't a mod or upgrade for stock ST70s, but a kit for building a brand-new amp.  Some of the design changes are listed under 'ST70 amplifier features' if you scroll down the page a bit.
ramtubes's avatar
ramtubes OP
460 posts
 
@tomic601  Also on the subject of heat.... this is NOTHING compared to creating a beast like the 787
stick to principles, there are different approaches to solving problems

i like the emerging theme from Eric ( Bdp24 ), Ralph and RM about early audio experiences, and especially mentors. I find that very useful and also a good mentor / mentee relationship benefits both.
for what it’s worth my mentor is Richard Vandersteen, a guy I greatly respect.
but can and certainly will learn from others.
great thread
jim


Thanks Jim, I liken this thread to conversations I had with my mentors. We talked about physics, acoustics, amplifier design all the way down to why I should put chokes in my RM-9  mkII. Bruce DePlama got me onto that one. 

Everyone was nice, no headbanging or harshness. We just shared information. We shared that we knew to be true from our own experience. DePalma also turned me on to the 100watt one pair EL-34 application. This application is always challenged when I bring it out. It is in the data sheets I went over in my Burning Amp presentation. http://berkeleyhifischool.com/having-fun-at-burning-amp-2018/

Anyone who does not believe you can get 100 watts out of ONE PAIR of EL-34s had better have a look. 


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