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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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. 


ramtubes's avatar
ramtubes OP
460 posts
 
@teo_audio  
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/


There was no bamboozling and nothing like the pseudoscience you propose on your website.  http://www.teoaudio.com/technical/

I ran into you on the cable threads. This thread is about answering questions. 

Please leave us alone. 


ramtubes's avatar
ramtubes OP
460 posts
 
@jdjohn   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.


Looks good. I like to see the 3 tube driver board. Do they have a schematic?

The original single  7199 tube driver was flawed by tube to tube variations. Some good 7199 would bias up in a region that actually produced a lot of distortion and reduced power. There are many 3 tube drivers. I would like to know more about theirs. 

The kit looks good and priced well. 
ramtubes's avatar
ramtubes OP
460 posts
 
@cakyol I am therefore using 1800 VA toroidal and a 270 amp rectifier. Caps are 4 x 47,000 uF but s I mentioned, at 85 degrees C the caps are rated at 2000 hours. Therefore they are the weakest links in the amp. I saw some Nichicons with 105 degrees C at 10000 hours but they were about $250 EACH (phew). The rectifier, altho likely to be used for welding applications, has soft switch characteristics AND it is quit fast, so would be suitable for audio.


Electrolytic cap life is much longer than the ratings. Im not sure why they are being so conservative. Perhaps thats all they want to guarantee. They all do it. I was surprised by it too when I first saw the short lifetime. My experience was that the life was much longer.  

I have nice nichcon caps in my RM-9s that ate 35 years old and just fine. They probably run at 150 F.. The thing that kills lytics is the loss of moisture over time. If the moisture stays in the caps go on forever.

So you dont need to spend $250 each. Those older caps on eBay will suit you fine, expecially if they are NOS. If one fails, no biggie since you know what to do. Please fuse accordingly with the lowest current slow blow that will get you past the inrush or come up with an inrush limiting device.


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